Space Elevator

[Big John]

Scientist Sees Space Elevator in 15 Years

By CARL HARTMAN, Associated Press Writer

WASHINGTON - President Bush (news - web sites) wants to return to the
moon and put a man on Mars. But scientist Bradley C. Edwards has an
idea that's really out of this world: an elevator that climbs 62,000
miles into space.

Edwards thinks an initial version could be operating in 15 years, a
year earlier than Bush's 2020 timetable for a return to the moon. He
pegs the cost at $10 billion, a pittance compared with other space
endeavors.

"It's not new physics — nothing new has to be discovered, nothing new
has to be invented from scratch," he says. "If there are delays in
budget or delays in whatever, it could stretch, but 15 years is a
realistic estimate for when we could have one up."

Edwards is not just some guy with an idea. He's head of the space
elevator project at the Institute for Scientific Research in Fairmont,
W.Va. NASA (news - web sites) already has given it more than $500,000
to study the idea, and Congress has earmarked $2.5 million more.

"A lot of people at NASA are excited about the idea," said Robert
Casanova, director of the NASA Institute of Advanced Concepts in
Atlanta.

Edwards believes a space elevator offers a cheaper, safer form of
space travel that eventually could be used to carry explorers to the
planets.

Edwards' elevator would climb on a cable made of nanotubes — tiny
bundles of carbon atoms many times stronger than steel. The cable
would be about three feet wide and thinner than a piece of paper, but
capable of supporting a payload up to 13 tons.

The cable would be attached to a platform on the equator, off the
Pacific coast of South America where winds are calm, weather is good
and commercial airplane flights are few. The platform would be mobile
so the cable could be moved to get out of the path of orbiting
satellites.

David Brin, a science-fiction writer who formerly taught physics at
San Diego State University, believes the concept is solid but doubts
such an elevator could be operating by 2019.

"I have no doubt that our great-grandchildren will routinely use space
elevators," he said. "But it will take another generation to gather
the technologies needed."

Edwards' institute is holding a third annual conference on space
elevators in Washington starting Monday. A keynote speaker at the
three-day meeting will be John Mankins, NASA's manager of human and
robotics technology. Organizers say it will discuss technical
challenges and solutions and the economic feasibility of the elevator
proposal.

The space elevator is not a new idea. A Russian scientist, Konstantin
Tsiolkovsky, envisioned it a century ago. And Arthur C. Clarke's novel
"The Foundations of Paradise," published in 1979, talks of a space
elevator 24,000 miles high, and permanent colonies on the moon,
Mercury and Mars.

The difference now, Edwards said, is "we have a material that we can
use to actually build it."

He envisions launching sections of cable into space on rockets. A
"climber" — his version of an elevator car — would then be attached to
the cable and used to add more lengths of cable until eventually it
stretches down to the Earth. A counterweight would be attached to the
end in space.

Edwards likens the design to "spinning a ball on a string around your
head." The string is the cable and the ball on the end is a
counterweight. The Earth's rotation would keep the cable taut.

The elevator would be powered by photo cells that convert light into
electricity. A laser attached to the platform could be aimed at the
elevator to deliver the light, Edwards said.

Edwards said he probably needs about two more years of development on
the carbon nanotubes to obtain the strength needed. After that, he
believes work on the project can begin.

"The major obstacle is probably just politics or funding and those two
are the same thing," he said. "The technical, I don't think that's
really an issue anymore."
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Posted by

Big John

[Ross Oliver]

Big John > wrote:
>Scientist Sees Space Elevator in 15 Years
>
>By CARL HARTMAN, Associated Press Writer
>
>WASHINGTON - President Bush (news - web sites) wants to return to the
>moon and put a man on Mars. But scientist Bradley C. Edwards has an
>idea that's really out of this world: an elevator that climbs 62,000
>miles into space.


The space elevator concept is "discovered" by all the non-SF-reading
journalists about once per decade. Hey, isn't the sunspot cycle
11 years long? Hmm.....

My favorite variation was describe in (IIRC) Scientific American
a while back. Rather than being attached to the ground, this
elevator would rotate in orbit like a huge two-armed windmill.
As one end descended into the upper atmosphere, about 50,000 ft
AGL, an aircraft would dock with the free end (hey, if they can
catch falling satellites...) and be hauled up into space. This
variant has the advantages needing no ground facilities, avoiding
terrestrial storms, and the capability of serving many different
points on the globe.

[Felger Carbon]

"Big John" > wrote in message
...
>
> Arthur C. Clarke's novel
> "The Foundations of Paradise," published in 1979, talks of a space
> elevator 24,000 miles high, and permanent colonies on the moon,
> Mercury and Mars.

"The Fountains of Paradise". Not Foundations.

[Ron Wanttaja]

Space Elevators are obvious, but how does a Space Trim Tab work? :-)

Ron Wanttaja

[Tim Ward]

"Ron Wanttaja" > wrote in message
...
> Space Elevators are obvious, but how does a Space Trim Tab work? :-)
>
> Ron Wanttaja

I dunno, but this seems as good a time as any to bring up a stupid,
complicated idea of mine for access to space.

First, you should be familiar with the Kelly Aerospace idea of towing the
spaceship to altitude. If not, Google for "Eclipse project", NASA, and
perhaps F106.

They towed an idling F106 behind a C141 as a proof of concept project.

Second, you should be aware of the "payout winches" used to ground launch
hang gliders. These just pay the line out at a constant tension, rather
than reeling them in at a high rate of speed, as in sailplane launches.

So here's the scheme:
You build a tow plane about the size of a 747. The payout winch is mounted
such that it "pays out" from the CG of the airplane, on top. You have
somewhere around 100,000 lbs of Vectran tow rope (several tens of
kilometers) on the payout device. This is within the cargo capability of a
747, though you may want to throw on a couple of extra engines because of
the additional drag.

The spacecraft has a CG hook on the bottom.

You take off, and climb as high as you can, while paying out the tow line.
The spacecraft pilot basically controls the pay out. Pitch up, and a little
more line pays out. Pitch down, and it stops.

If the spacecraft can maintain a 45 degree angle behind the towplane, it
will be 70% of the towrope's length higher than the towplane.

At some point, the true airspeed of the tow plane will not provide enough
airspeed for the spacecraft to continue to climb. So the towplane starts to
turn, and the spacecraft maneuvers to the outside of the turn. Now it's
just like playing "crack the whip". The air-breathing booster is down in
the (relatively speaking) thick atmosphere at 50,000 feet, while the
spacecraft is above most of the atmosphere at say, 100,000 feet.

That's when the spacecraft releases and fires its rockets.
Because the atmosphere is so much thinner, and the spacecraft is going
faster than it would be at lower altitudes, the increase in peak altitude
achievable should be much higher than just the 50,000 ft altitude difference
between the tow plane and the spacecraft.

After the spacecraft releases, the towplane also releases the towline, and
it descends under a parachute, separately.

There, I feel better.

Tim Ward

[[email protected]]

You should post this on sci.space.tech

It is a moderated news group and the signal to nise ration is high.





im Ward" > wrote:

>
>"Ron Wanttaja" > wrote in message
...
>> Space Elevators are obvious, but how does a Space Trim Tab work? :-)
>>
>> Ron Wanttaja
>
>I dunno, but this seems as good a time as any to bring up a stupid,
>complicated idea of mine for access to space.
>
>First, you should be familiar with the Kelly Aerospace idea of towing the
>spaceship to altitude. If not, Google for "Eclipse project", NASA, and
>perhaps F106.
>
>They towed an idling F106 behind a C141 as a proof of concept project.
>
>Second, you should be aware of the "payout winches" used to ground launch
>hang gliders. These just pay the line out at a constant tension, rather
>than reeling them in at a high rate of speed, as in sailplane launches.
>
>So here's the scheme:
>You build a tow plane about the size of a 747. The payout winch is mounted
>such that it "pays out" from the CG of the airplane, on top. You have
>somewhere around 100,000 lbs of Vectran tow rope (several tens of
>kilometers) on the payout device. This is within the cargo capability of a
>747, though you may want to throw on a couple of extra engines because of
>the additional drag.
>
>The spacecraft has a CG hook on the bottom.
>
>You take off, and climb as high as you can, while paying out the tow line.
>The spacecraft pilot basically controls the pay out. Pitch up, and a little
>more line pays out. Pitch down, and it stops.
>
>If the spacecraft can maintain a 45 degree angle behind the towplane, it
>will be 70% of the towrope's length higher than the towplane.
>
>At some point, the true airspeed of the tow plane will not provide enough
>airspeed for the spacecraft to continue to climb. So the towplane starts to
>turn, and the spacecraft maneuvers to the outside of the turn. Now it's
>just like playing "crack the whip". The air-breathing booster is down in
>the (relatively speaking) thick atmosphere at 50,000 feet, while the
>spacecraft is above most of the atmosphere at say, 100,000 feet.
>
>That's when the spacecraft releases and fires its rockets.
>Because the atmosphere is so much thinner, and the spacecraft is going
>faster than it would be at lower altitudes, the increase in peak altitude
>achievable should be much higher than just the 50,000 ft altitude difference
>between the tow plane and the spacecraft.
>
>After the spacecraft releases, the towplane also releases the towline, and
>it descends under a parachute, separately.
>
>There, I feel better.
>
>Tim Ward
>
>
>

[Howard Eisenhauer]

On Fri, 25 Jun 2004 22:42:15 -0700, Richard Riley
> wrote:

>On Fri, 25 Jun 2004 20:47:03 -0500, Big John >
>wrote:
>
>:Scientist Sees Space Elevator in 15 Years
>:
>:By CARL HARTMAN, Associated Press Writer
>:
>:WASHINGTON - President Bush (news - web sites) wants to return to the
>:moon and put a man on Mars. But scientist Bradley C. Edwards has an
>:idea that's really out of this world: an elevator that climbs 62,000
>:miles into space.
>
>OK, so you use a whole lotta solar power beamed at your cart to climb
>62,000 miles straight up (without becoming a crispy critter, but
>that's another topic).
>
>Where are you going to get the mass and energy to accelerate yourself
>laterally to reach orbital velocity? Aren't you just going to
>decelerate the beanstalk and send it whipping to the west as the earth
>rotates beneath you, winding the beanstalk along the equator like an
>earth sized yo-yo?


At 24,000 mile you're at geosynchronis orbit, ready to float free. If
you want an orbit lower down you just burn a little rocket fuel (that
you brought up with you) to slow down & drop lower.

The other 38000 miles of line wants to pull away from the Earth so
acts as a counter weight keeping the whole thing pulling straight up.
If you keep going past the 24,000 mark before cutting loose you start
picking up the velocity you need to get to the Moon, as well as many
other fun spots around the system :).

Any deflection caused by sending payloads up gets cancelled out by
stuff coming back down, i.e "My Parents Went to Jupiter & All They Got
Me Was This Cheap T-Shirt" x 10-6.

H.

[Anthony]

"Tim Ward" > wrote in message
...
>
> "Ron Wanttaja" > wrote in message
> ...
> > Space Elevators are obvious, but how does a Space Trim Tab work? :-)
> >
> > Ron Wanttaja
>
> I dunno, but this seems as good a time as any to bring up a stupid,
> complicated idea of mine for access to space.
>
> First, you should be familiar with the Kelly Aerospace idea of towing the
> spaceship to altitude. If not, Google for "Eclipse project", NASA, and
> perhaps F106.

<Snip>

Why not resurrect project Orion and ride the wake of nuclear blasts into
space.

Tony

[Tim Ward]

"Anthony" > wrote in message
...
>
> "Tim Ward" > wrote in message
> ...
> >
> > "Ron Wanttaja" > wrote in message
> > ...
> > > Space Elevators are obvious, but how does a Space Trim Tab work? :-)
> > >
> > > Ron Wanttaja
> >
> > I dunno, but this seems as good a time as any to bring up a stupid,
> > complicated idea of mine for access to space.
> >
> > First, you should be familiar with the Kelly Aerospace idea of towing
the
> > spaceship to altitude. If not, Google for "Eclipse project", NASA, and
> > perhaps F106.
>
> <Snip>
>
> Why not resurrect project Orion and ride the wake of nuclear blasts into
> space.
>
> Tony

Cost?
Even if the hardware was free, the infrastructure to support a surface
launch would be awfully expensive. I know Niven & Pournelle had something
like that in Lucifer's Hammer, but that was an effort to throw off alien
conquerors.

I thought Orion was space-to-space transportation.

The system I've proposed wouldn't be cheap, but it could conceivably take
off and land from a regular airport.

Tim Ward

[Bill Daniels]

"Howard Eisenhauer" > wrote in message
...
> On Fri, 25 Jun 2004 22:42:15 -0700, Richard Riley
> > wrote:
>
> >On Fri, 25 Jun 2004 20:47:03 -0500, Big John >
> >wrote:
> >
> >:Scientist Sees Space Elevator in 15 Years
> >:
> >:By CARL HARTMAN, Associated Press Writer
> >:
> >:WASHINGTON - President Bush (news - web sites) wants to return to the
> >:moon and put a man on Mars. But scientist Bradley C. Edwards has an
> >:idea that's really out of this world: an elevator that climbs 62,000
> >:miles into space.
> >
> >OK, so you use a whole lotta solar power beamed at your cart to climb
> >62,000 miles straight up (without becoming a crispy critter, but
> >that's another topic).
> >
> >Where are you going to get the mass and energy to accelerate yourself
> >laterally to reach orbital velocity? Aren't you just going to
> >decelerate the beanstalk and send it whipping to the west as the earth
> >rotates beneath you, winding the beanstalk along the equator like an
> >earth sized yo-yo?
>
>
> At 24,000 mile you're at geosynchronis orbit, ready to float free. If
> you want an orbit lower down you just burn a little rocket fuel (that
> you brought up with you) to slow down & drop lower.
>
> The other 38000 miles of line wants to pull away from the Earth so
> acts as a counter weight keeping the whole thing pulling straight up.
> If you keep going past the 24,000 mark before cutting loose you start
> picking up the velocity you need to get to the Moon, as well as many
> other fun spots around the system :).
>
> Any deflection caused by sending payloads up gets cancelled out by
> stuff coming back down, i.e "My Parents Went to Jupiter & All They Got
> Me Was This Cheap T-Shirt" x 10-6.
>
> H.

This space elevator thing is elegant in a Newtonian sort of way but I
suspect that there is a lot more to it that hasn't been completely thought
out.

They say put it on the equator where the winds are low. Well, they are low
most of the time but there is always the occasional typhoon.

Then there are the electrical effects. A carbon nanotube cable will conduct
electricity pretty well. Some claim it's a room temperature superconductor
candidate. A tropical lightning strike can be several million amps and this
cable will be a pretty good lightning rod. There's the induced voltages
too. The normal atmospheric potential gradient is several million volts per
meter.

What about tidal effects? Twice each day the Moons gravity will pull on the
structure.

Bill Daniels

[Howard Eisenhauer]

On Sat, 26 Jun 2004 23:15:26 GMT, "Bill Daniels" >
wrote:

>
>"Howard Eisenhauer" > wrote in message
...
>> On Fri, 25 Jun 2004 22:42:15 -0700, Richard Riley
>> > wrote:
>>
>> >On Fri, 25 Jun 2004 20:47:03 -0500, Big John >
>> >wrote:
>> >
>> >:Scientist Sees Space Elevator in 15 Years
:
*Snip*

>>
>> H.
>
>This space elevator thing is elegant in a Newtonian sort of way but I
>suspect that there is a lot more to it that hasn't been completely thought
>out.

You may well be right- not really my field but I've heard the math is
the same as applies to suspension bridges, thats to say well
understood.
>
>They say put it on the equator where the winds are low. Well, they are low
>most of the time but there is always the occasional typhoon.

True, but anything with the kind of strength we're talking about here,
under that amount of tension ain't gonna be much bothered by the
occaisional blow.
>
>Then there are the electrical effects. A carbon nanotube cable will conduct
>electricity pretty well. Some claim it's a room temperature superconductor
>candidate. A tropical lightning strike can be several million amps and this
>cable will be a pretty good lightning rod. There's the induced voltages
>too. The normal atmospheric potential gradient is several million volts per
>meter.

Last I checked deltaV/m was more liket ~200V. I heard the speculation
about nanotubes being superconductors a few years ago back before they
were able to produce them in decent quantities but haven't heard
anything since, If they really are I think somebody would have noticed
by now. To bad though, a superconducting space elevator would be a
neat way to generate "free" power, a-la the NASA/Italian experiment
with a tether a few years back. :).
>
>What about tidal effects? Twice each day the Moons gravity will pull on the
>structure.
>
>Bill Daniels

Yes, it will. Geosync satellites get pulled around quite a bit by the
moon (& sun's) gravity. Then they get pulled back again., Not a
biggie.


H.

[pacplyer]

"Tim Ward" > wrote
>
> I dunno, but this seems as good a time as any to bring up a stupid,
> complicated idea of mine for access to space.
>
> First, you should be familiar with the Kelly Aerospace idea of towing the
> spaceship to altitude. If not, Google for "Eclipse project", NASA, and
> perhaps F106.
>
> They towed an idling F106 behind a C141 as a proof of concept project.
>
> Second, you should be aware of the "payout winches" used to ground launch
> hang gliders. These just pay the line out at a constant tension, rather
> than reeling them in at a high rate of speed, as in sailplane launches.
>
> So here's the scheme:
> You build a tow plane about the size of a 747. The payout winch is mounted
> such that it "pays out" from the CG of the airplane, on top. You have
> somewhere around 100,000 lbs of Vectran tow rope (several tens of
> kilometers) on the payout device. This is within the cargo capability of a
> 747, though you may want to throw on a couple of extra engines because of
> the additional drag.

Pac sez:
I like this idea. A 747-200F can carry 250,000 lbs of fuel and 250,000
of cargo at the same time. But at that weight 820,000 lbs it could
only make ~FL280. It would have to leave most of the gas behind: no
sweat there. Since it burns a rough average of 25,000 lbs an hour a
t/o fuel load could be as low as around ~50,000lbs of fuel for
twenty-nine minutes of ascent plus return and skinny reserves so, you
would have good rate of climb to the service ceiling of FL450 (45,000
ft.) The combined tow weight of OrbitOne plus fuel and Colonauts
could be easily be greater than 200,000 lbs if all your tow apparatus
could handle it. So figure a total Mojave t/o weight of ~650,000lbs.
These numbers are off the top of my head, I could look up the exact
ones if you want me to. Don't know if this would be cheaper than a
Vandenberg launch, but Rutan would control it all, and stay away from
gov turd interference. **** I like it. You should email this idea to
Scaled Composites Tim. Bet you a nickle Burt is already considering
it. Evergreen in Oregon is already using 74's for fire fighting.
This might be the next great role for that old queen of the sky.

pacplyer

>
> The spacecraft has a CG hook on the bottom.
>
> You take off, and climb as high as you can, while paying out the tow line.
> The spacecraft pilot basically controls the pay out. Pitch up, and a little
> more line pays out. Pitch down, and it stops.
>
> If the spacecraft can maintain a 45 degree angle behind the towplane, it
> will be 70% of the towrope's length higher than the towplane.
>
> At some point, the true airspeed of the tow plane will not provide enough
> airspeed for the spacecraft to continue to climb. So the towplane starts to
> turn, and the spacecraft maneuvers to the outside of the turn. Now it's
> just like playing "crack the whip". The air-breathing booster is down in
> the (relatively speaking) thick atmosphere at 50,000 feet, while the
> spacecraft is above most of the atmosphere at say, 100,000 feet.
>
> That's when the spacecraft releases and fires its rockets.
> Because the atmosphere is so much thinner, and the spacecraft is going
> faster than it would be at lower altitudes, the increase in peak altitude
> achievable should be much higher than just the 50,000 ft altitude difference
> between the tow plane and the spacecraft.
>
> After the spacecraft releases, the towplane also releases the towline, and
> it descends under a parachute, separately.
>
> There, I feel better.
>
> Tim Ward

p.s. I wonder what Dr. "Moonraker" (Ron W.) thinks of this idea? Too
revolutionary? Not expensive enough? ;-)

pac

[Brian Whatcott]

On Sat, 26 Jun 2004 09:03:02 -0700, "Tim Ward" >
wrote:
//
>I dunno, but this seems as good a time as any to bring up a stupid,
>complicated idea of mine for access to space.
///
>somewhere around 100,000 lbs of Vectran tow rope (several tens of
>kilometers) on the payout device. This is within the cargo capability of a
>747
//
>There, I feel better.
>
>Tim Ward

Possible practical objection:
there is a limiting length of a line hanging freely downwards.
For the strongest engineering material per unit mass known it's
about 15 miles as I recall. That just to carry its own weight: thick
at the top, thin at the foot.

So less than 24 km. But you want it to tow a spaceplane
so that limiting length goes way shorter....

Feel free to correct this....

Brian W

[Felger Carbon]

"Tim Ward" > wrote in message
...
>
> I know Niven & Pournelle had something
> like that in Lucifer's Hammer, but that was an effort to throw off
alien
> conquerors.

The book was "Footfall", not "Lucifer's Hammer". In the fictional
account, the city of Bellingham WA was scragged by the Orion-engined
takeoff.

BTW, "Orion spacevehicle" and "aviation.homebuilt" are not a close
match. ;-)

[Tim Ward]

"pacplyer" > wrote in message
om...
<snippage>
> Pac sez:
> I like this idea. A 747-200F can carry 250,000 lbs of fuel and 250,000
> of cargo at the same time. But at that weight 820,000 lbs it could
> only make ~FL280. It would have to leave most of the gas behind: no
> sweat there. Since it burns a rough average of 25,000 lbs an hour a
> t/o fuel load could be as low as around ~50,000lbs of fuel for
> twenty-nine minutes of ascent plus return and skinny reserves so, you
> would have good rate of climb to the service ceiling of FL450 (45,000
> ft.) The combined tow weight of OrbitOne plus fuel and Colonauts
> could be easily be greater than 200,000 lbs if all your tow apparatus
> could handle it. So figure a total Mojave t/o weight of ~650,000lbs.
> These numbers are off the top of my head, I could look up the exact
> ones if you want me to. Don't know if this would be cheaper than a
> Vandenberg launch, but Rutan would control it all, and stay away from
> gov turd interference. **** I like it. You should email this idea to
> Scaled Composites Tim. Bet you a nickle Burt is already considering
> it. Evergreen in Oregon is already using 74's for fire fighting.
> This might be the next great role for that old queen of the sky.
>
> pacplyer
>

I think the mission might turn out to be longer than a thirty minute climb.
It's going to take some time to pay out all that tow line -- payout winch
launches are slower than auto tows, and much slower than regular winch
launches.
OTOH, the tow plane doesn't have to _lift_ the spacecraft -- it just has to
overcome the drag.
In fact, once the spacecraft is in high tow, it should be pulling up and
back (or up and out, in the slingshot portion of the flight). If things are
going right, in high tow, the spacecraft is always lifting the weight of the
tow cable that's extended, so as the tow line gets longer, the payload that
the 747's wing is lifting gets smaller. At peak altitude, the 747's wing
should only "see" the remaining fuel as a load. If the tow cable is pulling
down, then you haven't got enough tension in the tow cable. If you can't
increase the tension, then you've got too much line out.
But I expect the drag is going to be considerably higher than a stock 747.
20 km of cable an inch or so in diameter is going to be quite a bit of drag,
even at altitude. Thus my suggestion that some more engines (and higher
fuel burn) might be in order. Or do you need to throttle back a 747 at
altitude to keep the speed in limits?

I'm sure that after the publicity of the SpaceShip1 flight, Rutan is getting
all the hare-brained ideas that he can use via email, snail mail and
telephone. As I mentioned in the first post, Kelly Aerospace is working on
a tow-to-altitude and launch scheme, so some of the idea isn't new, anyway.

I wonder about the flight dynamics of a 20 km tether. I don't think anyone
has modeled anything like that. Why would they?

But a reusable 747 "first stage" that could get the "second stage" to
100,000 feet, albeit only at a little below Mach 1 (I think the drag would
go WAY up if the tether went supersonic!) is certainly cool to think about.

Tim Ward

[anonymous coward]

On Sat, 26 Jun 2004 09:03:02 -0700, Tim Ward wrote:

>
> "Ron Wanttaja" > wrote in message
> ...
>> Space Elevators are obvious, but how does a Space Trim Tab work? :-)
>>
>> Ron Wanttaja
>
> I dunno, but this seems as good a time as any to bring up a stupid,
> complicated idea of mine for access to space.
>
> First, you should be familiar with the Kelly Aerospace idea of towing the
> spaceship to altitude. If not, Google for "Eclipse project", NASA, and
> perhaps F106.
>
> They towed an idling F106 behind a C141 as a proof of concept project.
>
> Second, you should be aware of the "payout winches" used to ground launch
> hang gliders. These just pay the line out at a constant tension, rather
> than reeling them in at a high rate of speed, as in sailplane launches.
>
> So here's the scheme:
> You build a tow plane about the size of a 747. The payout winch is mounted
> such that it "pays out" from the CG of the airplane, on top. You have
> somewhere around 100,000 lbs of Vectran tow rope (several tens of
> kilometers) on the payout device. This is within the cargo capability of a
> 747, though you may want to throw on a couple of extra engines because of
> the additional drag.
>
> The spacecraft has a CG hook on the bottom.
>
> You take off, and climb as high as you can, while paying out the tow line.
> The spacecraft pilot basically controls the pay out. Pitch up, and a little
> more line pays out. Pitch down, and it stops.
>
> If the spacecraft can maintain a 45 degree angle behind the towplane, it
> will be 70% of the towrope's length higher than the towplane.
>
> At some point, the true airspeed of the tow plane will not provide enough
> airspeed for the spacecraft to continue to climb. So the towplane starts to
> turn, and the spacecraft maneuvers to the outside of the turn. Now it's
> just like playing "crack the whip". The air-breathing booster is down in
> the (relatively speaking) thick atmosphere at 50,000 feet, while the
> spacecraft is above most of the atmosphere at say, 100,000 feet.
>
> That's when the spacecraft releases and fires its rockets.
> Because the atmosphere is so much thinner, and the spacecraft is going
> faster than it would be at lower altitudes, the increase in peak altitude
> achievable should be much higher than just the 50,000 ft altitude difference
> between the tow plane and the spacecraft.
>
> After the spacecraft releases, the towplane also releases the towline, and
> it descends under a parachute, separately.
>
> There, I feel better.

I'm fascinated by this idea, but I'm still not sure if I've got my head
round it.

One thing that worries me, is that stubby little planes like the
space-shuttle or spaceship 1 need to be flying very fast in order to stay
up at high altitudes. For example, the U2 cruised at this speed near
100,000 feet (unladen). If the 747 was to tow a spaceplane up to this
altitude in straight and level flight, I expect it would need to look like
an U2 and might have problems during re-entry.

Imagine the 747 was flying in 1km (radius) circles; if the spaceship flew
concentric 4km circles the ratio of its speed to that of the 747 would be
4:1. At it began to approach this speed maybe it could ascend above the
747? If the 747 could reduce the turning circle down to 0.5km radius,
you'd be up to 8 times its velocity - well on the way to orbit. I think
this is a fair simplification of your 'crack the whip' - but this is what
I'm not sure of.

3KM of 1cm wide costlium wire would have 30M^2 of frontal area which
doesn't sound unmanageable, but perhaps it would cause more drag than
that suggests. But presumably it would get quite toasty...

If our 747 is flying 0.5km radius circles at 500kph, acceleration on it
will be V^2/r = (500000/3600)^2/500 = 38.5 M/S - about 4 G's

If our spaceship is flying 4km radius circles at 8*500kph it will be
pulling (8*500000/3600)^2/4000 = about 30 G's.

Hmm...

To keep that down to 7G's at 4000kph I get 20km of cable required
80KM for 8000kph

Escape velocity is about 40,000kph

If people are seriously considering cables strong enough for
space-elevators, maybe there could be something in this. If you can
tolerate higher G-forces then you can use much more feasible lengths of
cable - perhaps it would be a practical way of launching freight into
orbit, even if it wasn't suitable for people.

Maybe you could fix one end of the cable to a mountain-top, and send
electrical power through the cable to a prop-unit mounted part of the way
along it.

AC

[Richard Lamb]

They ran this all over the sci.space groups for a while.

Somebody made up a neato web site with clever animations
showing how well it worked.

When people started pointing out some of the more obvious
problems, thing got a bit heated.

It's BAAAck...

One of my posts from back then.......................................


All you have to do is demonstrate that this thing _can_ actually work.

I'd settle for a simple math description of the transfer mechanics
and mechanical reactions, but a couple of small tethers playing catch
with a base ball would convince almost everybody.

(Mom is a die hard skeptic)


Animations are useful for visually describing something.
Ok, you've got that.

Next step up the ladder is a 'simulation'.
A 'scale model'.
Either physical - or computer code.

It will take EVERYTHING into account.

How the ractions occur when you release mass.
What happens (and how?) when you capture mass.

(Including such minor problems as rotation of the mass you
intend to capture? That's energy too.)

How the C.G. of the whole thing changes during capture and release.
Or, while 'hauling' something 'up' the tether?
(that's where I have my own doubts.)

How the tether structure will react to all that...

What the orbital reactions are when gaining and expending energy?

Get a good SIMULATION up and running, you'll get R&D money and a
launch schedule.

And we'll just put a couple of small test toys in orbit and toss a
baseball back and forth...

Until then?

All you have is an idea that can't be tested.

Or a LOT of work to do...

[Anthony]

"Tim Ward" > wrote in message
...
> >
> > Why not resurrect project Orion and ride the wake of nuclear blasts into
> > space.
> >
> > Tony
>
> Cost?
> Even if the hardware was free, the infrastructure to support a surface
> launch would be awfully expensive. I know Niven & Pournelle had something
> like that in Lucifer's Hammer, but that was an effort to throw off alien
> conquerors.
>
> I thought Orion was space-to-space transportation.
>
> The system I've proposed wouldn't be cheap, but it could conceivably take
> off and land from a regular airport.
>
> Tim Ward

You really need to see the history channel show on Project Orion. I can't
do it justice here. The team on the project expected to be to Mars buy 1965
if their funding hadn't been dropped.

Tony

[anonymous coward]

On Sun, 27 Jun 2004 05:38:59 +0000, Anthony wrote:

>
> "Tim Ward" > wrote in message
> ...
>> >
>> > Why not resurrect project Orion and ride the wake of nuclear blasts into
>> > space.
>> >
>> > Tony
>>
>> Cost?
>> Even if the hardware was free, the infrastructure to support a surface
>> launch would be awfully expensive. I know Niven & Pournelle had something
>> like that in Lucifer's Hammer, but that was an effort to throw off alien
>> conquerors.
>>
>> I thought Orion was space-to-space transportation.
>>
>> The system I've proposed wouldn't be cheap, but it could conceivably take
>> off and land from a regular airport.
>>
>> Tim Ward
>
> You really need to see the history channel show on Project Orion. I can't
> do it justice here. The team on the project expected to be to Mars buy 1965
> if their funding hadn't been dropped.

There's a good book on it by Dyson too.

AC

[Dillon Pyron]

On Sun, 27 Jun 2004 01:32:51 GMT, "Felger Carbon" >
wrote:

>"Tim Ward" > wrote in message
...
>>
>> I know Niven & Pournelle had something
>> like that in Lucifer's Hammer, but that was an effort to throw off
>alien
>> conquerors.
>
>The book was "Footfall", not "Lucifer's Hammer". In the fictional
>account, the city of Bellingham WA was scragged by the Orion-engined
>takeoff.

Jerry later said that, had he known what the future would bring, they
would have chosen Redmond. :-)

>
>BTW, "Orion spacevehicle" and "aviation.homebuilt" are not a close
>match. ;-)
>
>

I've seen video of a proof of concept vehicle. Esentially a large
hemispherical plate of steel, maybe 200 kilos. They had some sort of
device to load the explosives into the fireing chamber. They used
half sticks of dynamite and lofted it to over 1000 feet. Really quite
impressive, although I think RUN would be the order of the day when it
quit being a flying machine and turned into a heavy slab of metal.
--
dillon

When I was a kid, I thought the angel's name was Hark
and the horse's name was Bob.

[pacplyer]

"Tim Ward" > wrote in message >...
> "pacplyer" > wrote in message
> om...
> <snippage>
> > Pac sez:
> > I like this idea. A 747-200F can carry 250,000 lbs of fuel and 250,000
> > of cargo at the same time. But at that weight 820,000 lbs it could
> > only make ~FL280. It would have to leave most of the gas behind: no
> > sweat there. Since it burns a rough average of 25,000 lbs an hour a
> > t/o fuel load could be as low as around ~50,000lbs of fuel for
> > twenty-nine minutes of ascent plus return and skinny reserves so, you
> > would have good rate of climb to the service ceiling of FL450 (45,000
> > ft.) The combined tow weight of OrbitOne plus fuel and Colonauts
> > could be easily be greater than 200,000 lbs if all your tow apparatus
> > could handle it. So figure a total Mojave t/o weight of ~650,000lbs.
> > These numbers are off the top of my head, I could look up the exact
> > ones if you want me to. Don't know if this would be cheaper than a
> > Vandenberg launch, but Rutan would control it all, and stay away from
> > gov turd interference. **** I like it. You should email this idea to
> > Scaled Composites Tim. Bet you a nickle Burt is already considering
> > it. Evergreen in Oregon is already using 74's for fire fighting.
> > This might be the next great role for that old queen of the sky.
> >
> > pacplyer
> >
>

Whoops, I forgot the weight of the cable and winches! 100,000 lbs.
So figure t/o weight at ~750,000lbs (including glider/orbiter weight.)
No sweat for t/o but now getting to FL450 is going to be tough. We
may need some JATO bottles to get to FL450 with the -200 tow plane.
The gross on the -400 is 875,000lbs, may have to take that old KLM
bird sitting out in the desert instead.

> I think the mission might turn out to be longer than a thirty minute climb.
> It's going to take some time to pay out all that tow line -- payout winch
> launches are slower than auto tows, and much slower than regular winch
> launches.
> OTOH, the tow plane doesn't have to _lift_ the spacecraft -- it just has to
> overcome the drag.

Yeah, figure an hour climb with all the drag. I think we're back in
business with the 747-200F though. The NASA 747-100 is an old
American Airlines bird with P&W JT9D-7F engines IIRC (about 50,000 lbs
thrust ea. engine and it pulls the drag of the space shuttle orbiter
O.K.) vs. 67,000 ea. engine for our 747-200 freighter with dash 7Q
engines.) So we're good to go again adding another 20,000lbs for the
new normal 1 hr clmb total and return plus reserves. If you don't
count the weight of the lifting body/orbiter we're back to a t/o
weight of 570,000lbs. That's a rocket ship in 747 land. We just need
to figure out the drag of your Kevlar/Carbon Fiber tow lanyard. Maybe
you can weave it like a kite with horizontal stablizers flaps so that
it too produces lift as you pay it out? Naw dumb idea, too draggy,
forget that part.

> In fact, once the spacecraft is in high tow, it should be pulling up and
> back (or up and out, in the slingshot portion of the flight). If things are
> going right, in high tow, the spacecraft is always lifting the weight of the
> tow cable that's extended, so as the tow line gets longer, the payload that
> the 747's wing is lifting gets smaller. At peak altitude, the 747's wing
> should only "see" the remaining fuel as a load. If the tow cable is pulling
> down, then you haven't got enough tension in the tow cable. If you can't
> increase the tension, then you've got too much line out.
> But I expect the drag is going to be considerably higher than a stock 747.
> 20 km of cable an inch or so in diameter is going to be quite a bit of drag,
> even at altitude. Thus my suggestion that some more engines (and higher
> fuel burn) might be in order. Or do you need to throttle back a 747 at
> altitude to keep the speed in limits?

As Han Solo freighter Captain said to Ben Obiwan Kenobi: "She's fast
enough for you old man."

Empty, we flew the -249 model to FL430 one day, kept it at MCT power
and had to pull it back to keep it from busting through the MMO limit
of .92 Mach. I saw .94 on the Capt's Mach at one point. The mach
tuck was tremendous over .88. The a/p mach cruise trim motor took off
like a horse. Think about that for a minute. An airplane that big
that will cruise at .92 mach. It's now the fastest transport in the
world. That's why I laughed when the (now sacked) Boeing CEO Condit
introduced the Sonic Cruiser. What a dull machine. It wasn't really
any faster than a stock 747 (abeit empty at MCT.) No you want a 747
for this. C5's can't go as fast or as high and can't approach the
load. The AN-124 has more power but again is slow and draggy.

>
> I'm sure that after the publicity of the SpaceShip1 flight, Rutan is getting
> all the hare-brained ideas that he can use via email, snail mail and
> telephone. As I mentioned in the first post, Kelly Aerospace is working on
> a tow-to-altitude and launch scheme, so some of the idea isn't new, anyway.

Don't discount this idea. Rutan picked up a lot of his crew from guys
who mailed in hair-brained ideas. John Ronz (sp?) corrected Burt on
his selection of laminar airfoils via mail and became a fixture at
Scaled. If you pointed something like this out at Nasa as a junior
engineer they'd probably laugh in your face and stick you on designing
space toilets for daring to upstage the gov turds who are entrenched
there. In the wake of SS1 the NASA Administrator O'Keef or something,
is completely reorganizing the agency to foster the kind of ingenuity
that SS1 has. Watched it on the NASA channel a couple of days ago.
They are reeling from the SS1 success. But moving desks around is not
going to make Nasa like Scaled IMHO.

>
> I wonder about the flight dynamics of a 20 km tether. I don't think anyone
> has modeled anything like that. Why would they?
>
> But a reusable 747 "first stage" that could get the "second stage" to
> 100,000 feet, albeit only at a little below Mach 1 (I think the drag would
> go WAY up if the tether went supersonic!) is certainly cool to think about.
>
> Tim Ward

It's more than cool Tim. It's the way to open a commercial spaceport
with private ships bound for the New World. I think you're on to
something here. We should ask Dave Hyde or somebody (does he do aero
equations?) to get his buddies to model the drag on a 20km tether. If
the data is good, I know an engineer at scaled that will look at it.

Cheers,

pacplyer

[Ron Webb]

Arthur C Clarke said that the space elevator would be built "about 20 years
after everyone stops laughing." I think we
have a while to wait yet (heh heh).


My concerns are also practical. The things I have read sound like a bunch of
folks who have the theory analyzed, but
don't really want to confront the real world details. The math has been
worked out in great detail by a cadre of folks
who have been working on this for many years. Just because something is
impossible doesn't stop folks from designing it.
http://www.space.com/businesstechnology/technology/space_elevator_020327-1.html


> anything with the kind of strength we're talking about here,
> under that amount of tension ain't gonna be much bothered by the
> occaisional blow.


The tensions are unimaginably high at the hub, but at ground level (at the
ends of the tether), they are zero. A typhoon
would be a BIG problem.


> >Then there are the electrical effects. A carbon nanotube cable will
conduct
> >electricity pretty well. Some claim it's a room temperature
superconductor
> >candidate. A tropical lightning strike can be several million amps and
this
> >cable will be a pretty good lightning rod. There's the induced voltages
> >too. The normal atmospheric potential gradient is several million volts
per
> >meter.
>
> Last I checked deltaV/m was more liket ~200V.

A dV/dM of 200V per meter, in anything approaching a superconductor could
give nearly infinate
current (I=V/R as R approachs 0 --- Ohms law). That is what burned the
Italian tether. I have not seen
any data on how they plan to avoid this fate. I am sure they have a plan - I
just haven't seen it.

Lightening would do bad things to it I am sure.


> I heard the speculation about nanotubes being superconductors a few years
ago back before they
> were able to produce them in decent quantities but haven't heard anything
since, If they really are I
> think somebody would have noticed by now.

I agree. It probably isn't a superconductor, although there might be a way
to make it into one.


>To bad though, a superconducting space elevator would be a
> neat way to generate "free" power, a-la the NASA/Italian experiment
> with a tether a few years back.

The power is there, using it to power the tram would be downright elegant,
but you sure can't ignore it - ask the Italians.

And the next detail is bullistic damage. It forms a ribbon, very thin but a
meter or so wide (tapering). If a piece of
space debris were to blow a hole in it half way up, sufficiently large to
cause a failure, the consequences
would be amazing, as the upper part went winging off into space, and the
lower part came crashing to
earth with a lot of mass and residual velocities of up to 17,000 mph.



Bottom line - the advances in carbon nanotube manufacture show promise. It
used to be said that this thing needed to be made
from "unobtainium" - now it is not quite so unobtainable (but still not
exactly available either.) but there are still many problems,
and more than one look to me to be showstoppers for now.

[Mike Beede]

In article >, Ron Webb > wrote:

> The tensions are unimaginably high at the hub, but at ground level (at the
> ends of the tether), they are zero. A typhoon
> would be a BIG problem.

Huh? There'd be no reason to make a system with zero tension at the ground,
and a lot of reasons not to. I'd assume the tension would be quite large for
purposes of stability as well as so the loads going up don't pull the whole thing
down. Certainly one engineering consideration would be making sure the
largest conceivable typhoon would be a non-issue.

From a standpoint of aviation, the biggest concern would be finding enough
red lights so you could put three of them at each hundred foot level, and hiring
enough guys to keep changing them. I make that 9.9 million bulbs.

Of course, they could change the lighting regulations, but if it only takes twenty
years to build the elevator, they might have to put them on anyway....

Mike Beede


Mike Beede

[Richard Lamb]

pacplyer wrote:
>
> Whoops, I forgot the weight of the cable and winches! 100,000 lbs.
> So figure t/o weight at ~750,000lbs (including glider/orbiter weight.)
> No sweat for t/o but now getting to FL450 is going to be tough. We
> may need some JATO bottles to get to FL450 with the -200 tow plane.
> The gross on the -400 is 875,000lbs, may have to take that old KLM
> bird sitting out in the desert instead.
>
> Cheers,
>
> pacplyer

I think somebody may have overlooked the effect of that 'snap the
whip' manouver on the tow plane too.

I'd almost expect the sudden increase in drag to stall the 747...

Richard

[Tim Ward]

"pacplyer" > wrote in message
om...
> "Tim Ward" > wrote in message
>...
> > "pacplyer" > wrote in message
> > om...
> > <snippage>
<yet more snippage>

> Whoops, I forgot the weight of the cable and winches! 100,000 lbs.
> So figure t/o weight at ~750,000lbs (including glider/orbiter weight.)
> No sweat for t/o but now getting to FL450 is going to be tough. We
> may need some JATO bottles to get to FL450 with the -200 tow plane.
> The gross on the -400 is 875,000lbs, may have to take that old KLM
> bird sitting out in the desert instead.
>
> > I think the mission might turn out to be longer than a thirty minute
climb.
> > It's going to take some time to pay out all that tow line -- payout
winch
> > launches are slower than auto tows, and much slower than regular winch
> > launches.
> > OTOH, the tow plane doesn't have to _lift_ the spacecraft -- it just has
to
> > overcome the drag.
>
> Yeah, figure an hour climb with all the drag. I think we're back in
> business with the 747-200F though. The NASA 747-100 is an old
> American Airlines bird with P&W JT9D-7F engines IIRC (about 50,000 lbs
> thrust ea. engine and it pulls the drag of the space shuttle orbiter
> O.K.) vs. 67,000 ea. engine for our 747-200 freighter with dash 7Q
> engines.) So we're good to go again adding another 20,000lbs for the
> new normal 1 hr clmb total and return plus reserves. If you don't
> count the weight of the lifting body/orbiter we're back to a t/o
> weight of 570,000lbs. That's a rocket ship in 747 land. We just need
> to figure out the drag of your Kevlar/Carbon Fiber tow lanyard. Maybe
> you can weave it like a kite with horizontal stablizers flaps so that
> it too produces lift as you pay it out? Naw dumb idea, too draggy,
> forget that part.

I'd settle for a stable low-drag shape. But I think we're stuck with round.

According to http://www.neropes.com/techdata/v12.htm
16mm Vectran rope has a tensile strength of 49000 lbs and weighs 13.6
lbs/100 ft
Assuming tensile strength and weight per unit length scales with cross
section, a 200,000 lb tensile strength would be about 24mm and weigh 54
lbs/100 feet

So, for 100,000 lbs of 200,000 lb tensile strength tether, we can get
(100,000/54.4) x 100 ft length :
183000 ft = 55 km? Yow! That's probably more than we can reasonably use.
Still, at least it means it's not unobtainium, and a 10 to 20 km tapered
length might even have some safety factor.

<even more snippage>

> As Han Solo freighter Captain said to Ben Obiwan Kenobi: "She's fast
> enough for you old man."
>
> Empty, we flew the -249 model to FL430 one day, kept it at MCT power
> and had to pull it back to keep it from busting through the MMO limit
> of .92 Mach. I saw .94 on the Capt's Mach at one point. The mach
> tuck was tremendous over .88. The a/p mach cruise trim motor took off
> like a horse. Think about that for a minute. An airplane that big
> that will cruise at .92 mach. It's now the fastest transport in the
> world. That's why I laughed when the (now sacked) Boeing CEO Condit
> introduced the Sonic Cruiser. What a dull machine. It wasn't really
> any faster than a stock 747 (abeit empty at MCT.) No you want a 747
> for this. C5's can't go as fast or as high and can't approach the
> load. The AN-124 has more power but again is slow and draggy.

Well, it wouldn't be a stock 747, anyway. The vertical fin is going to be
in the way. A conventional tow is just off the tail of the airplane, but
this scheme needs to be able to pull from the CG of both aircraft so they
stay controllable.

> >
> > I'm sure that after the publicity of the SpaceShip1 flight, Rutan is
getting
> > all the hare-brained ideas that he can use via email, snail mail and
> > telephone. As I mentioned in the first post, Kelly Aerospace is working
on
> > a tow-to-altitude and launch scheme, so some of the idea isn't new,
anyway.
>
> Don't discount this idea. Rutan picked up a lot of his crew from guys
> who mailed in hair-brained ideas. John Ronz (sp?) corrected Burt on
> his selection of laminar airfoils via mail and became a fixture at
> Scaled. If you pointed something like this out at Nasa as a junior
> engineer they'd probably laugh in your face and stick you on designing
> space toilets for daring to upstage the gov turds who are entrenched
> there. In the wake of SS1 the NASA Administrator O'Keef or something,
> is completely reorganizing the agency to foster the kind of ingenuity
> that SS1 has. Watched it on the NASA channel a couple of days ago.
> They are reeling from the SS1 success. But moving desks around is not
> going to make Nasa like Scaled IMHO.

>
> >
> > I wonder about the flight dynamics of a 20 km tether. I don't think
anyone
> > has modeled anything like that. Why would they?
> >
> > But a reusable 747 "first stage" that could get the "second stage" to
> > 100,000 feet, albeit only at a little below Mach 1 (I think the drag
would
> > go WAY up if the tether went supersonic!) is certainly cool to think
about.
> >
> > Tim Ward
>
> It's more than cool Tim. It's the way to open a commercial spaceport
> with private ships bound for the New World. I think you're on to
> something here.

Well, I'm gratified by your enthusiasm, but it's just an idea to noodle
around. I've seen way too many posts with the Final Ultimate Solution to
Some Problem, that have pretty obvious faults. I won't be terribly
surprised if someone points out some reason why this won't work.
Embarrassed, maybe, but not surprised.

One poster pointed out that the G's get really high as the speed
differential goes up, but I think he thought I intended this scheme to get a
substantial fraction of orbital velocity. I don't, but it is something I
hadn't considered. Still, with a 20 km towline and low speed ratios, I
think it's manageable, though not negligible.

Temperature of the towrope is another potential problem. Vectran keeps it's
strength with temperature better than Spectra -- but it's still not what
you'd call a high-temperature material.

> We should ask Dave Hyde or somebody (does he do aero
> equations?) to get his buddies to model the drag on a 20km tether. If
> the data is good, I know an engineer at scaled that will look at it.

Apparently Al Bowers and Jim Murray of Dryden Flight Research have done some
modelling of shorter tethers. The tether they flew was 1000 feet of Vectran
with some nylon webbing in the middle to damp oscillations.
You could read about it (and see some really cool pictures) here:
http://www.nasatech.com/Briefs/July98/DRC9833.html

Their analysis assumed the tow line was a straight line, which would be
nowhere near true for
a long line. They found some significant limits in position to stability.
The simulation was a little conservative, but apparently the limits were
there in flight test as well.

OTOH, neither of the aircraft had the towline attached near the CG.
In my proposed scheme, the payout winch is supposed to damp oscillations,
but eventually you come to the end of the line. There, I would expect the
oscillations to have a very long period.

So, as is usually the case, I dunno.

Tim Ward

[BlakeleyTB]

Why don't we just pile the cash up and burn it...wouldn't that be much
cheaper???

What kind of idiots would give them 2.5 million dollars to research this and
NASA gave 1/2 a million.

I wish NASA and congress would take about 10% ofNASA's budget and invest in
researching affordable alternative energy uses that EVERYONE can afford!!!
Solar, etc type of "stuff"......wouldn't you love to be able to fly your RV-6
on the energy of, heck, from the stars??? Solars cells that can pik up energy
from the stars, not to mention our sun. Or affordable batteries for vehicle
that will run your car, aircraft, boat for 800 miles or more at speeds we know
today. I know, I know...this is some BIG pipe dream...but heck, we've gone to
the moon and we perform body transplants EVERYDAY..in fact, I have both
transplanted corneas......if we can do stuff like this..why can't we take some
of what I believe is wasted money and research something that ALL OF US can
utilize and especially afford??? I want to say "SCREW YOU" to OPEC, etc and
just get out in my car and go anywhere I want in something that's not
polluting our skies.

Oh well, just an idea...I can dream, can't I.

[C.D.Damron]

"BlakeleyTB" > wrote in message
...
> Why don't we just pile the cash up and burn it...wouldn't that be much
> cheaper???
>


This weekend, my father, a retired Naval Officer and aerospace industry
contractor, said that if it were up to him, NASA would consist of six people
and all the projects would be privatized.

[Howard Eisenhauer]

On Sun, 27 Jun 2004 10:22:24 -0800, "Ron Webb"
> wrote:

>Arthur C Clarke said that the space elevator would be built "about 20 years
>after everyone stops laughing." I think we
>have a while to wait yet (heh heh).
>
>
>My concerns are also practical. The things I have read sound like a bunch of
>folks who have the theory analyzed, but
>don't really want to confront the real world details. The math has been
>worked out in great detail by a cadre of folks
>who have been working on this for many years. Just because something is
>impossible doesn't stop folks from designing it.
>http://www.space.com/businesstechnology/technology/space_elevator_020327-1.html

Agreed, there are plenty of examples out there supporting your case.
On the other hand, it's been proven time & again that Man Will Never
Fly, rendering this whole newsgroupe & many years of postings a bit of
a waste-

Realisticly there is much research & real world experimentation to be
done before the concept is either proven or disproven. Hopefully
they'll offer me a job helping out with that ;).
>
>
>> anything with the kind of strength we're talking about here,
>> under that amount of tension ain't gonna be much bothered by the
>> occaisional blow.
>
>
>The tensions are unimaginably high at the hub, but at ground level (at the
>ends of the tether), they are zero. A typhoon
>would be a BIG problem.

I don't think they're un-imaginably big, just a number followed by a
lot of zeros. Everything I've read on the subject says that the
ground anchor would be under tension for stability purposes. However,
consider this- Not being sure of the elastic modulus of a Nanotube &
Glop composite cable, I'll make the un-warranted assumtion it's not
much. So even if the anchor is under little or no tension any big
wind that comes along will have to deal with the inertia of the
cable's portion lying outside of the atmosphere before causing a
deflection. Hurricane winds are limited mostly to the troposphere,
~30,,00 feet at the equater if I recall correctly. I'm pretty sure
there are large suspension bridges around with an equivalent wind load
to 30,000 feet of space elevater that withstand typhoons just fine.
>
>
>> >Then there are the electrical effects. A carbon nanotube cable will
>conduct
>> >electricity pretty well. Some claim it's a room temperature
>superconductor
>> >candidate. A tropical lightning strike can be several million amps and
>this
>> >cable will be a pretty good lightning rod. There's the induced voltages
>> >too. The normal atmospheric potential gradient is several million volts
>per
>> >meter.
>>
>> Last I checked deltaV/m was more liket ~200V.
>
>A dV/dM of 200V per meter, in anything approaching a superconductor could
>give nearly infinate
>current (I=V/R as R approachs 0 --- Ohms law). That is what burned the
>Italian tether. I have not seen
>any data on how they plan to avoid this fate. I am sure they have a plan - I
>just haven't seen it.
>
>Lightening would do bad things to it I am sure.
>
>
The potential for high voltage is certainly there, but consider that
the source impedance of the atmospere is rather large untill actual
ionization occurs, which would limit the currents available. Possibly
large, but not unlimited. Also, AFAIK, superconducting effect breaks
down once a certain current desity is reached in the conductor,
another limitation. TANFL.

As for lightening, I'm from the school of thought that says a
conductor stuck up into the atmosphere actually discourages
lightening, drains away all those pesky ions in the neighborhood.
leaving a nice insulating volume of poorly conducting air around it.

>> I heard the speculation about nanotubes being superconductors a few years
>ago back before they
>> were able to produce them in decent quantities but haven't heard anything
>since, If they really are I
>> think somebody would have noticed by now.
>
>I agree. It probably isn't a superconductor, although there might be a way
>to make it into one.
>
>
>>To bad though, a superconducting space elevator would be a
>> neat way to generate "free" power, a-la the NASA/Italian experiment
>> with a tether a few years back.
>
>The power is there, using it to power the tram would be downright elegant,
>but you sure can't ignore it - ask the Italians.

I thought the whole idea of the Italian tether Was to generate power-
wasn't the problem with it a stuck cable reel?
>
>And the next detail is bullistic damage. It forms a ribbon, very thin but a
>meter or so wide (tapering). If a piece of
>space debris were to blow a hole in it half way up, sufficiently large to
>cause a failure, the consequences
>would be amazing, as the upper part went winging off into space, and the
>lower part came crashing to
>earth with a lot of mass and residual velocities of up to 17,000 mph.

Again, I agree with you on the space junk problem, I did hear
recently that the problem has been considered, can't remember what the
take on it was though. But consider this, it wouldn't be just the one
cable, I believe the design would be four or more cables tied
togeather every so often that would tend to minimize the potential
for (hind quarters of a cat mounted on a wooden plaque) from smaller
pieces of junk. The larger pieces' orbits are pretty well defined,
they'd have a good idea of what could cause major damage well ahead of
time. What to do about it? Damned if I know- I guess maybe they're
not gonna give me a job afterall :(.

I do remember from the same article that the problem of a broken
cable coming down isn't thought to be a major concern. Due to the
density of the cable & it's profile in theory once it hit the
atmosphere, instead of falling down @ 17,000 + change MPH as you (& I
as well) thought, it would end up "fluttering" down, coupla feet per
second range. IIRC the simulation showed it would all end up
reasonably close the the anchor site. Still a big mess to clean up
though-
>

>Bottom line - the advances in carbon nanotube manufacture show promise. It
>used to be said that this thing needed to be made
>from "unobtainium" - now it is not quite so unobtainable (but still not
>exactly available either.) but there are still many problems,
>and more than one look to me to be showstoppers for now.
>

You can never tell what's gonna show up & bitechya on the ass when you
start something as new as this, always unforseen problems there are.
Can't say that I see what they are right at the moment though-

Howard.

[Brian Whatcott]

On 27 Jun 2004 09:39:26 -0700, (pacplyer) wrote:

> ///
> No you want a 747 for this.
> C5's can't go as fast or as high and can't approach the load.
///
>
>pacplyer

Maybe: but did you ever see a 747 do a soft field takeoff?

Brian W

[Brian Whatcott]

On Sun, 27 Jun 2004 12:16:08 -0700, "Tim Ward" >
wrote:

>I'd settle for a stable low-drag shape. But I think we're stuck with round.
>
>According to http://www.neropes.com/techdata/v12.htm
>16mm Vectran rope has a tensile strength of 49000 lbs and weighs 13.6
>lbs/100 ft
>Assuming tensile strength and weight per unit length scales with cross
>section, a 200,000 lb tensile strength would be about 24mm and weigh 54
>lbs/100 feet
>
This looks very promising. You meant the diameter to be 32 mm,
I expect. Their table gives an AVERAGE tensile strength at break.
They warn to derate 2 SDs for a minimum break strength.
Then the boring engineering realities creep in.
Derate a little for wet and contaminated line.
Derate a bit for the UV breakdown which the coating is intended to
reduce.
Then add the factors of safety. They recommend X15 for man rated uses.
For an experimental use, maybe you could use a more generous factor -
as low as X4? That would give say 14 kilometers.
One end would need to support its own weight and any load you might
apply, of course.

>So, for 100,000 lbs of 200,000 lb tensile strength tether, we can get
>(100,000/54.4) x 100 ft length :
>183000 ft = 55 km? Yow! That's probably more than we can reasonably use.
>Still, at least it means it's not unobtainium, and a 10 to 20 km tapered
>length might even have some safety factor.
>

[Darrel Toepfer]

Mike Beede wrote:

> From a standpoint of aviation, the biggest concern would be finding enough
> red lights so you could put three of them at each hundred foot level, and hiring
> enough guys to keep changing them. I make that 9.9 million bulbs.
>
> Of course, they could change the lighting regulations, but if it only takes twenty
> years to build the elevator, they might have to put them on anyway....

Our guvunmit radar balloons, don't have lights on their tethers...
They geaux up something like 15 to 25k'...

[Bob Chilcoat]

According to the newspaper article I read, the proposed fiber is a "tape"
roughly three feet wide and a few thou thick. A flat ribbon is
aerodynamically unstable and will vibrate axially in any wind. This thing
would seem to be the ultimate Tacoma Narrows Bridge. Just my first
impression.

--
Bob (Chief Pilot, White Knuckle Airways)

I don't have to like Bush and Cheney (Or Kerry, for that matter) to love
America

"Howard Eisenhauer" > wrote in message
...
> On Fri, 25 Jun 2004 22:42:15 -0700, Richard Riley
> > wrote:
>
> >On Fri, 25 Jun 2004 20:47:03 -0500, Big John >
> >wrote:
> >
> >:Scientist Sees Space Elevator in 15 Years
> >:
> >:By CARL HARTMAN, Associated Press Writer
> >:
> >:WASHINGTON - President Bush (news - web sites) wants to return to the
> >:moon and put a man on Mars. But scientist Bradley C. Edwards has an
> >:idea that's really out of this world: an elevator that climbs 62,000
> >:miles into space.
> >
> >OK, so you use a whole lotta solar power beamed at your cart to climb
> >62,000 miles straight up (without becoming a crispy critter, but
> >that's another topic).
> >
> >Where are you going to get the mass and energy to accelerate yourself
> >laterally to reach orbital velocity? Aren't you just going to
> >decelerate the beanstalk and send it whipping to the west as the earth
> >rotates beneath you, winding the beanstalk along the equator like an
> >earth sized yo-yo?
>
>
> At 24,000 mile you're at geosynchronis orbit, ready to float free. If
> you want an orbit lower down you just burn a little rocket fuel (that
> you brought up with you) to slow down & drop lower.
>
> The other 38000 miles of line wants to pull away from the Earth so
> acts as a counter weight keeping the whole thing pulling straight up.
> If you keep going past the 24,000 mark before cutting loose you start
> picking up the velocity you need to get to the Moon, as well as many
> other fun spots around the system :).
>
> Any deflection caused by sending payloads up gets cancelled out by
> stuff coming back down, i.e "My Parents Went to Jupiter & All They Got
> Me Was This Cheap T-Shirt" x 10-6.
>
> H.

[pacplyer]

Richard Lamb > wrote
>
> I think somebody may have overlooked the effect of that 'snap the
> whip' manouver on the tow plane too.
>
> I'd almost expect the sudden increase in drag to stall the 747...
>
> Richard

The airplane is op specs limited to +2.5 g's and -1.0g. Not worried
about stalling a 747. There's so much mass the tow rope would break
before any instant degradation would show up on the airspeed
indicator. Airspeed trends take A LONG LONG time to develop on this
bird. It's not like anything you've every flown before. I use the
analogy of surfing on a mountain of metal to describe a visual
approach on the 74 because the previous vector it was on before you
made the change is what it will be on for a number of seconds. By the
time you've pulled off the thrusters because you're too fast, the huge
inertia will keep it accelerating. You must use speed brakes or drop
the gear to arrest the buildup and start a deceleration trend.
(anticipate desired changes big time!) But if you're deep into flaps
already and the wheels are already down; it's a go around if you can't
get below speed for final flaps! Speed brakes can't be used down
here. You need to have this airplane stable at the Outer Marker or
you can get hopelessly out of phase with the airspeed trends in a
hurry. If you think you're headed for a stall, going to full power,
Scottie, will, after a number of seconds delay, start pushing the
mountain faster again. The power to weight of this thing at mid
weights below gross is just incredible. But the shear mass of the
mountain will always delay a desired acceleration direction reversal.

You cruise at Mach .86, typically ~550kts IIRC, stall might be at
about 180kts clean at heavy weights. But you would want a cruise
climb of say mach .82 to mach .84 to conserve fuel and keep a good
buffet boundary margin at higher altitude. What we always did was
stay at max climb power for a while at the target altitude to crawl up
to .86. But in this case, I'd think you'd want to try to get as close
to .92 before release in a turn. You can pull G/A power in this thing
rated anyway, for five minutes. Then you'd have to notch down to MCT.
Very do-able. If there's too much drag on the line, then maybe put
the thing on top like the Space Shuttle?

Anyway I always marvelled at the fact an old 747-100 could carry the
Space Shuttle around on it's back. Maybe that's the real way to go.

pac

[pacplyer]

Brian Whatcott > wrote in message >...
> On 27 Jun 2004 09:39:26 -0700, (pacplyer) wrote:
>
> > ///
> > No you want a 747 for this.
> > C5's can't go as fast or as high and can't approach the load.
> ///
> >
> >pacplyer
>
> Maybe: but did you ever see a 747 do a soft field takeoff?
>
> Brian W

Mojave is a hard surfaced runway. A soft field takeoff is not part of
the equation here. 74's have landed on lakebeds before at lower
weights, however. There is an increased risk of FOD of the inboard
engines compared to the highwing C-5. Since they are five million
dollar engines, you are right, it's role is not soft field.

pac

[Alan Baker]

In article >,
(pacplyer) wrote:

> Richard Lamb > wrote
> >
> > I think somebody may have overlooked the effect of that 'snap the
> > whip' manouver on the tow plane too.
> >
> > I'd almost expect the sudden increase in drag to stall the 747...
> >
> > Richard
>
> The airplane is op specs limited to +2.5 g's and -1.0g. Not worried
> about stalling a 747. There's so much mass the tow rope would break
> before any instant degradation would show up on the airspeed
> indicator. Airspeed trends take A LONG LONG time to develop on this
> bird. It's not like anything you've every flown before. I use the
> analogy of surfing on a mountain of metal to describe a visual
> approach on the 74 because the previous vector it was on before you
> made the change is what it will be on for a number of seconds. By the
> time you've pulled off the thrusters because you're too fast, the huge
> inertia will keep it accelerating.

Read a physics text and then say that again...

> You must use speed brakes or drop
> the gear to arrest the buildup and start a deceleration trend.
> (anticipate desired changes big time!) But if you're deep into flaps
> already and the wheels are already down; it's a go around if you can't
> get below speed for final flaps! Speed brakes can't be used down
> here. You need to have this airplane stable at the Outer Marker or
> you can get hopelessly out of phase with the airspeed trends in a
> hurry. If you think you're headed for a stall, going to full power,
> Scottie, will, after a number of seconds delay, start pushing the
> mountain faster again. The power to weight of this thing at mid
> weights below gross is just incredible. But the shear mass of the
> mountain will always delay a desired acceleration direction reversal.
>
> You cruise at Mach .86, typically ~550kts IIRC, stall might be at
> about 180kts clean at heavy weights. But you would want a cruise
> climb of say mach .82 to mach .84 to conserve fuel and keep a good
> buffet boundary margin at higher altitude. What we always did was
> stay at max climb power for a while at the target altitude to crawl up
> to .86. But in this case, I'd think you'd want to try to get as close
> to .92 before release in a turn. You can pull G/A power in this thing
> rated anyway, for five minutes. Then you'd have to notch down to MCT.
> Very do-able. If there's too much drag on the line, then maybe put
> the thing on top like the Space Shuttle?
>
> Anyway I always marvelled at the fact an old 747-100 could carry the
> Space Shuttle around on it's back. Maybe that's the real way to go.
>
> pac

--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling 4 feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect
if you sit in the bottom of that cupboard."

[pacplyer]

"Tim Ward" > wrote <snip>
>
> So, for 100,000 lbs of 200,000 lb tensile strength tether, we can get
> (100,000/54.4) x 100 ft length :
> 183000 ft = 55 km? Yow! That's probably more than we can reasonably use.
> Still, at least it means it's not unobtainium, and a 10 to 20 km tapered
> length might even have some safety factor.
>
> <even more snippage>
>
> > As Han Solo freighter Captain said to Ben Obiwan Kenobi: "She's fast
> > enough for you old man."
> >
> > Empty, we flew the -249 model to FL430 one day, kept it at MCT power
> > and had to pull it back to keep it from busting through the MMO limit
> > of .92 Mach. I saw .94 on the Capt's Mach at one point. The mach
> > tuck was tremendous over .88. The a/p mach cruise trim motor took off
> > like a horse. Think about that for a minute. An airplane that big
> > that will cruise at .92 mach. It's now the fastest transport in the
> > world. That's why I laughed when the (now sacked) Boeing CEO Condit
> > introduced the Sonic Cruiser. What a dull machine. It wasn't really
> > any faster than a stock 747 (abeit empty at MCT.) No you want a 747
> > for this. C5's can't go as fast or as high and can't approach the
> > load. The AN-124 has more power but again is slow and draggy.
>
> Well, it wouldn't be a stock 747, anyway. The vertical fin is going to be
> in the way. A conventional tow is just off the tail of the airplane, but
> this scheme needs to be able to pull from the CG of both aircraft so they
> stay controllable.
>
>

Maybe not a bad problem. The APU sits between the elevators and could
be either be removed or carry-though stucture could envelop it (better
for CG.) So we'd have a nice long tow hitch/pulley past the sweep of
the vertical stab. The tailplane (THS) is huge and has a massive rage
of trimable positions, so I would think that you could use a
conventional tow, loading the winch and line at the far aft CG limit.
Orbiter+glider wings pulling up on the tail would eliminate tailplane
downloading (which on -100's and -200's is many thousands of pounds)
requiring less power to maintain alt (equals more pwr avail to get up
to .92 mach.) A sudden break however, could result in a severe pitch
up, causing a jet upset, and tumble of tens of thousands of feet. But
this is test pilot stuff and I believe could be managed within
acceptable risk levels.

All things considered: Still a tantalizing idea. :-)

pac

[Richard Lamb]

I think I understand what you were saying, but...?

I was addressing the 'crack the whip' idea that someone thought
might could be used to toss the tow-ee into orbit.

First, the tow line 'can't' break for this maneuver, or the whole
idea 'breaks down' with it. But we'll come back to that after the
commercial.

Next, remember that we want to be as high as practically possible.
VERY high density altitude?

Stall speed at extreme altitude would not the benign 180 knots,
but something appreciably higher (can you help me out with the
high altitude 747 data - actual stall speed at FL 450?).

I believe the OP was suggesting something on the order of 20 kilometers
(!) of cable? (That part I don't even want to think about!)

We are cruising fat and happy at FL 450, pulling a bunch of miles of
cable with a real slick 'kite' on the end.

The kite supplies enough drag to keep the cable tensioned. (?)
(and carries it's half of the cable weigh too!)

That drag reduces the 747's speed by some amount, causing the 747 to
have to fly at a higher angle of attack (AoA) already.

Then the kite starts the pull up maneuver, (which by the way is going
to increase the amount of cable load that _it_ is carrying).

The pitch up increases drag on the kite due to the zoom climb.

THAT will be (eventually - cable stretch?) will be applied to the 747.

And the 747, although massive, WILL decelerate due to the increased
cable load (and probably cable drag too, since the cable is no longer
in trail).

As the angular difference between the two aircraft increases so the
cable load on the 747 increase.

The kite's speed has increased during this maneuver. Sure enough,

But it is PULLING AGAINST the 747, and sure as God made little green
apples, that load will also decelerate the big momma.

So we get to the disconnect point.

ALL the energy transferred to the kite comes from the 747.
All of it.
All of that energy is removed (just as quickly?) from the 747.

And at some critical point, big momma finds herself below critical
flight speed and above critical AoA, and things could get a little
- critical?

Now in reality, all of that could probably be dealt with. Some of
those perimeters would define the limits of this kind of operation.

From a PAWKI standpoint, it's probably cable tensile strength.

But if that held, I'd suspect this event is going to feel a lot like
catching a Three Wire - at FL 450.

Richard

Standard disclaimer:

Take all this with a grain of salt.
If I really knew what I was talking about,
I'd be working for Burt...

Ta, Yaw'll

[Tim Ward]

"Richard Lamb" > wrote in message
...
>
> I think I understand what you were saying, but...?
>
> I was addressing the 'crack the whip' idea that someone thought
> might could be used to toss the tow-ee into orbit.

No, just get the spacecraft part of the way out of the atmosphere

>
> First, the tow line 'can't' break for this maneuver, or the whole
> idea 'breaks down' with it. But we'll come back to that after the
> commercial.
>
> Next, remember that we want to be as high as practically possible.
> VERY high density altitude?

Yep.

> Stall speed at extreme altitude would not the benign 180 knots,
> but something appreciably higher (can you help me out with the
> high altitude 747 data - actual stall speed at FL 450?).

I actually want to fly the 747 pretty fast. If its speed at 45000 feet is
fast enough so that the spacecraft's airspeed at 100000 feet is at the
spacecraft's best rate of climb speed, then the turning maneuver isn't
required.
This is a booster. It just happens to get its oxidizer at 45000 feet. The
assumption is that there is enough excess thrust on the 747 to overcome the
drag on the towline and whatever is attached to it. If that means extra
engines, that's okay with me.

>
> I believe the OP was suggesting something on the order of 20 kilometers
> (!) of cable? (That part I don't even want to think about!)

Ain't imagination great? ;-)

> We are cruising fat and happy at FL 450, pulling a bunch of miles of
> cable with a real slick 'kite' on the end.
>
> The kite supplies enough drag to keep the cable tensioned. (?)
> (and carries it's half of the cable weigh too!)

The kite carries the _entire_ weight of the cable. If it doesn't, the cable
is sagging below the towplane, and you have too much line out. Might as
well shorten it and reduce drag, because it isn't helping the kite get
higher.

>
> That drag reduces the 747's speed by some amount, causing the 747 to
> have to fly at a higher angle of attack (AoA) already.

I would expect it to require quite a lot of additional power. That's why I
originally suggested extra engines on the 747. I wasn't envisioning it as a
dynamic maneuver. More like impedance matching. The 747 is buzzing around
at a relatively low altitude. The spacecraft is up really high (we hope),
and so it's minimum sink speed is probably very high, because there's durn
few air molecules bumping into it. There's a constant force between the two
aircraft, but the spacecraft probably needs to be flying faster. By
turning, the 747 can fly at some reasonable speed, and the spacecraft can
fly at a higher speed.

>
> Then the kite starts the pull up maneuver, (which by the way is going
> to increase the amount of cable load that _it_ is carrying).

No. As originally posted, the kite is constantly trying to climb, pulling
out more and more cable as it does so. And of course you're coupling power
from the towplane into the kite/towline combo. That's the whole point of
the exercise.

> The pitch up increases drag on the kite due to the zoom climb.
>
> THAT will be (eventually - cable stretch?) will be applied to the 747.

Yep -- although it's not a zoom climb. There's a constant tension on the
cable.

>
> And the 747, although massive, WILL decelerate due to the increased
> cable load (and probably cable drag too, since the cable is no longer
> in trail).

All the forces are coupled to the 747 through the tow line. But they're
relatively constant, because of the payout winch.

I never expected the towline to be in trail. Because of sag in the
towline, the towline would probably be nearly horizontal at the towplane,
and nearly vertical at the kite at release.

> As the angular difference between the two aircraft increases so the
> cable load on the 747 increase.

No, there's a constant tension. This is not difficult with a payout winch,
since the mechanism pays out cable above a certain tension, which lowers the
tension, so it slows down the payout, raising the tension... it stays
pretty constant. The line length changes.

>
> The kite's speed has increased during this maneuver. Sure enough,
>
> But it is PULLING AGAINST the 747, and sure as God made little green
> apples, that load will also decelerate the big momma.

It's pulling against the constant tension of the payout winch

This constant tension is additional drag, and will need additional
hrust -- but that's just a higher power setting.

>
> So we get to the disconnect point.
>
> ALL the energy transferred to the kite comes from the 747.
> All of it.
> All of that energy is removed (just as quickly?) from the 747.

No. You have a 747 being slowed by cable tension. (Dammit! the cable has
to carry the aerodynamic drag as tension-- so that _is_ something I
overlooked. I figured on cable weight and the tow force, but the drag on the
cable adds another load.)
The kite's energy is energy of position, which it's already got. When the
cable is released, or breaks, the 747 is going to accelerate, not slow. An
instant additional 100,000 lbs of thrust. (or reduction in drag) It'll
still be a kick in the butt, but it will be speeding the 747 up, not slowing
it down.

> And at some critical point, big momma finds herself below critical
> flight speed and above critical AoA, and things could get a little
> - critical?
> Now in reality, all of that could probably be dealt with. Some of
> those perimeters would define the limits of this kind of operation.
>
> From a PAWKI standpoint, it's probably cable tensile strength.

Probably. This basically puts a limit on how long the towline can be.

>
> But if that held, I'd suspect this event is going to feel a lot like
> catching a Three Wire - at FL 450.

I think it would be more like a cat shot -- though I haven't experienced
either one.
On a commanded release, you could gradually decrease the tension on the
payout winch over a number of seconds prior to cutting loose, and you might
be able to throttle down at a similar rate, but if the line breaks, you're
gonna speed up.

Tim Ward


>
> Richard
>
> Standard disclaimer:
>
> Take all this with a grain of salt.
> If I really knew what I was talking about,
> I'd be working for Burt...
>
> Ta, Yaw'll

[Mark Hickey]

Todd Pattist > wrote:

>The last time I looked at this, the load on a space elevator
>due to its own weight exceeded the load that any other known
>material could carry. I suspect it will pretty damn stiff
>under the required tension. I also suspect they will do an
>aerodynamic analysis that's better than the one done for the
>Tacoma Narrows bridge . In view of aerodynamic
>considerations, I agree it does "seem" like it's a poor
>selection to use a thin tape, but perhaps our "gut feelings"
>are not calibrated for the properties of carbon nanotube
>materials.

And I almost hate to bring it up, but the thing would be the ultimate
terrorist target. Hit it anywhere with just about anything that
flies, and billions of dollars (and whatever's on the other end...)
down the tubes.

Mark Hickey

[pacplyer]

> > The airplane is op specs limited to +2.5 g's and -1.0g. Not worried
> > about stalling a 747. There's so much mass the tow rope would break
> > before any instant degradation would show up on the airspeed
> > indicator. Airspeed trends take A LONG LONG time to develop on this
> > bird. It's not like anything you've every flown before. I use the
> > analogy of surfing on a mountain of metal to describe a visual
> > approach on the 74 because the previous vector it was on before you
> > made the change [control input] is what it will be on for a number of seconds. By the
> > time you've pulled off the thrusters because you're too fast, the huge
> > inertia will keep it accelerating.
>

Alan Baker > wrote

> Read a physics text and then say that again...
>


Inertia: a property of matter whereby it remains at rest or continues
in uniform motion unless acted upon by some outside force.

The uniform motion in my example was acceleration. In this bird it
takes longer for the opposing force: drag to arrest the motion. Due
to it's large Kinetic Energy. Can you be more specific? What part do
you disagree with?

pacplyer

[Alan Baker]

In article >,
(pacplyer) wrote:

> > > The airplane is op specs limited to +2.5 g's and -1.0g. Not worried
> > > about stalling a 747. There's so much mass the tow rope would break
> > > before any instant degradation would show up on the airspeed
> > > indicator. Airspeed trends take A LONG LONG time to develop on this
> > > bird. It's not like anything you've every flown before. I use the
> > > analogy of surfing on a mountain of metal to describe a visual
> > > approach on the 74 because the previous vector it was on before you
> > > made the change [control input] is what it will be on for a number of
> > > seconds. By the
> > > time you've pulled off the thrusters because you're too fast, the huge
> > > inertia will keep it accelerating.
> >
>
> Alan Baker > wrote
>
> > Read a physics text and then say that again...
> >
>
>
> Inertia: a property of matter whereby it remains at rest or continues
> in uniform motion unless acted upon by some outside force.
>
> The uniform motion in my example was acceleration. In this bird it

Acceleration is not uniform motion.

> takes longer for the opposing force: drag to arrest the motion. Due
> to it's large Kinetic Energy. Can you be more specific? What part do
> you disagree with?

That an object will keep accelerating in the absence of an external
force on the object. Inertia will keep it moving at a constant velocity,
but it won't keep it accelerating.

--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling 4 feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect
if you sit in the bottom of that cupboard."

[pacplyer]

Richard Lamb > wrote in message >...
> I think I understand what you were saying, but...?
>
> I was addressing the 'crack the whip' idea that someone thought
> might could be used to toss the tow-ee into orbit.
>
> First, the tow line 'can't' break for this maneuver, or the whole
> idea 'breaks down' with it. But we'll come back to that after the
> commercial.

Sure, you hope for a smooth intentional release. "Can't break?"
Anything can happen in flight test. :-) I believe designing for the
line to break before high momentary loads are transferred through the
aft pressure bulkhead area is an important engineering goal: You don't
want the keel-beam of the aircraft to be pulled apart or
stringers/longerons to stretch and allow the pressure bell to blow
like it did at JAL. They lost all four hydro systems and crashed.
There is no manual reversion system (cables) in the whale. All four
hydro systems run to the elevators in that area.

>
> Next, remember that we want to be as high as practically possible.
> VERY high density altitude?

Same kind of idea: High *Pressure Altitude*. Out of 17,000 (in the
cont.U.S.) everyone switches over to Standard 29.92 so the term
Density altitude is not used (since the pressure part of the equation
is constant.) ISA+/- (non-standard) temperature becomes important for
climb/cruise performance and mach number. Our actual, true altitude
above MSL varies from day to day at the same flight level.

>
> Stall speed at extreme altitude would not the benign 180 knots,
> but something appreciably higher (can you help me out with the
> high altitude 747 data - actual stall speed at FL 450?).

Just cause you asked, I spent an hour digging through boxes and
finally found my "buffet boundry" charts. Initial Low and High Speed
Buffet (standard temp) is dependant on aircraft weight and G
load/bank. But you're right, at FL450 you are up in "coffin corner"
and on the straight and level chart (1G) at 400,000lbs the LSB (low
speed buffet) is like I remembered at 178kts. HSB (high speed buffet)
is VMO/MMO (.92 mach)

Now let's take our theoretical weights (subject to tweaking.)
Empty Weight: ~380,000lbs
Skinny Fuel: ~70,000lbs (30k up, 10 dwn, 10 aprch, 20k res)
Winches and 20km tether: ~100,000lbs
Drag ‘weight' ~30,000lbs (a complete WAG till somebody gives me a
#)
Total 747 T/O WT ~580,000lbs

Orbit One plus fuel and three plastic pax: 200,000 lbs


[note: the space vehicle with swept glider wings really weighs nothing
since Tim Ward promised us that it will lift itself after t/o. ;-)
So we're at the modest t/o weight of 580,000 (lot's of margin here
since the 747 gross is 820,000.)

So we take off with Orbit one in tow and arrive an hour later, fat
dumb and happy at FL450 again. (which must be done in smooth air at
GA thrust since we have no upset margin) The 1G chart yields a Low
Speed Buffet onset of 208kts and a high speed mach buffet of 251. In
other words: we stall outside that range. No sweat.

But you hotdog rocket jocks aren't going to be happy in straight and
level at 1G! You're going to want old "Hand Solo" Cargo Dog here to
do some hair brained "deathwhip" maneuver at a 45 degree bank and risk
my pink little ass in a flat spin if the ****ing cable breaks or if it
pulls the Jesus rivets out of the goddam tail (in which case the cabin
blows taking out all elevator control on the way out! What a ****
poor deal! You rocket jocks get all the glory and I crash and burn.
*******s!

So just for you *******s here's the 45 degree bank chart at FL450 and
1.41G's: XXX to XXX…… **** what does that mean? I'm going to have
little X's in my eyes? I'm going to fall out of the sky and do a
supersonic recovery like China Airlines did at SFO? So we can't do a
45 degree bank over 400,000lbs (that's empty) or else we do the
****ing Hoot Gibson High Dive…Gulp!

Damn we can only do a 30 degree bank at this weight and live; let's go
back to that chart and not embarrass ourselves in front of CNN:
FL450, 500,000lbs max (damn,) 1.15G, 30 degrees bank equals 229kts
low speed stall, and 238kts high speed mach stall. That's only a
nine knot range! I can't do that! I can only hold a tolerance of
about plus or minus one inch on the gauge! You crazy "Jet-eyes" are
trying to get me killed! I quit!

pacplyer – over and out!

[Felger Carbon]

"pacplyer" > wrote in message
om...
>
> Inertia: a property of matter whereby it remains at rest or
continues
> in uniform motion unless acted upon by some outside force.
>
> The uniform motion in my example was acceleration.

Disclaimer: It's 5:30AM. I'm an engineer, not a physicist. BUT...

Acceleration **by definition** is **not** uniform motion! ;-)

[Richard Lamb]

pacplyer wrote:
>
>
> Damn we can only do a 30 degree bank at this weight and live; let's go
> back to that chart and not embarrass ourselves in front of CNN:
> FL450, 500,000lbs max (damn,) 1.15G, 30 degrees bank equals 229kts
> low speed stall, and 238kts high speed mach stall. That's only a
> nine knot range! I can't do that! I can only hold a tolerance of
> about plus or minus one inch on the gauge! You crazy "Jet-eyes" are
> trying to get me killed! I quit!
>
> pacplyer – over and out!

Thanks for the info, Pacman.

And for the correction - Pressure altitude - not density.

Aw heck, the U-2 guys did it tighter than that for hours on end.
Stall at 90 knots (indicated?) and mach buffet sets in at 95 knots???

(Reality really sucks, don't it.)

Richard

[Richard Lamb]

Sorry dude, I wasn't refering to the release itself.
Just the problems associated with _getting_ there.

I'll refer you to Pacman's post (and conclusions) with the
gentle reminder that he _does_ know what he's talking about
as opposed to my questionable speculation).

Also, Keith gave us some first hand info on what is actually
involved in tow ops - something I've never even tried to do.

PAWKI is a mean and evil term that stands for "Physics as we know it".

Please don't be too upset with the 'ain't gonna work' mentality
you find here. The guys on this group are a different kind of
dreamer. Fantasy, with a hard dose of reality blended in.

You have to expect that attitude from people who actually BUILD
and FLY their own dreams.

I once heard it said that we don't really build airplanes.
We build bridges - between dreams and reality.

Well, I gotta go clean up my messy shop now.

Later.

Richard

[Tim Ward]

"Richard Lamb" > wrote in message
...
> Sorry dude, I wasn't refering to the release itself.
> Just the problems associated with _getting_ there.
>
> I'll refer you to Pacman's post (and conclusions) with the
> gentle reminder that he _does_ know what he's talking about
> as opposed to my questionable speculation).

Sure. I never really thought a stock 747 would work for an idea as extreme
as this one. I was actually thinking of a 747-sized canard design -- gets
all the control surfaces out of the way, makes hooking to the CG easier --
and so on. From Pac's information, it will probably have to have a lower
wing loading and higher aspect ratio if we want it to tow at FL450.

>
> Also, Keith gave us some first hand info on what is actually
> involved in tow ops - something I've never even tried to do.

Oddly enough, I have. I aerotow my sailplane on weekends. I used to
aerotow and ground launch hang gliders with both straight auto tow (long
line with a tensionmeter), and the payout winch. Out at El Mirage dry lake,
in the 80's, we got six thousand feet of line out one evening.
That was just to see if we could do it. The sag in the line made the
release altitude not as high as you might think. There were diminishing
returns.

>
> PAWKI is a mean and evil term that stands for "Physics as we know it".
>
> Please don't be too upset with the 'ain't gonna work' mentality
> you find here. The guys on this group are a different kind of
> dreamer. Fantasy, with a hard dose of reality blended in.

I'm not upset. But I do find it interesting that some posters have argued
against concepts I never proposed: e.g. 8:1 speed ratios between the towed
and towing aircraft. The use of a stock 747.
Of course PAWKI limits the possible. Right now, we _know_ that it's
possible to tow a smaller aircraft with a 747-sized aircraft. It's been
done six times with a thousand foot tow line.
That gives us one data point. What _are_ the limits imposed by PAWKI? I
doubt that it's a tow line of 1001 feet. How high could you reasonably
expect to get the towed vehicle on a CG to CG aerotow? How much advantage
is that for a rocket launch? I don't know, but it's kind of interesting to
speculate.

Tim Ward

> You have to expect that attitude from people who actually BUILD
> and FLY their own dreams.
>
> I once heard it said that we don't really build airplanes.
> We build bridges - between dreams and reality.
>
> Well, I gotta go clean up my messy shop now.
>
> Later.
>
> Richard

[Bill Daniels]

"Tim Ward" > wrote in message
...

> Sure. I never really thought a stock 747 would work for an idea as
extreme
> as this one. I was actually thinking of a 747-sized canard design -- gets
> all the control surfaces out of the way, makes hooking to the CG easier --
> and so on. From Pac's information, it will probably have to have a lower
> wing loading and higher aspect ratio if we want it to tow at FL450.
>

Heck, if you want to build a million pound homebuilt with, say, eight GE
C-90's with 110,000 pounds thrust each, why not resurrect the Northrop B-49
idea. That way the towrope could be attached exactly on the CG with nothing
behind it.

Fly the tow formation to FL400 and then zoom climb the spacecraft ala a
winch launch as the tug pilot firewalls all eight.

BTW, a million pound breaking strength carbon nanotube tow rope might be
only .250" in diameter so not too much drag there.

Bill Daniels

[Jay]

Depending on how you look at it, your could fly/drive your RV on solar
energy.

Plants store solar energy in 2 forms:
1) Sugars
2) Oils

Put one of new fangled turbo diesels in your RV and go take it out on
plant oils. Or... ferment the sugars, make alcohol, burn it in your
engine and call yourself a kamikazi. Carbon captured, carbon
released.

But we're not out of mineral oils yet, they're still harvesting in
order of cost. Its still cheaper for oil companies to use your tax
money/kids to fight wars to provide cheaper access to more easily
recovered/refined reserves.



(BlakeleyTB) wrote in message >...
> Why don't we just pile the cash up and burn it...wouldn't that be much
> cheaper???
>
> What kind of idiots would give them 2.5 million dollars to research this and
> NASA gave 1/2 a million.
>
> I wish NASA and congress would take about 10% ofNASA's budget and invest in
> researching affordable alternative energy uses that EVERYONE can afford!!!
> Solar, etc type of "stuff"......wouldn't you love to be able to fly your RV-6
> on the energy of, heck, from the stars??? Solars cells that can pik up energy
> from the stars, not to mention our sun. Or affordable batteries for vehicle
> that will run your car, aircraft, boat for 800 miles or more at speeds we know
> today. I know, I know...this is some BIG pipe dream...but heck, we've gone to
> the moon and we perform body transplants EVERYDAY..in fact, I have both
> transplanted corneas......if we can do stuff like this..why can't we take some
> of what I believe is wasted money and research something that ALL OF US can
> utilize and especially afford??? I want to say "SCREW YOU" to OPEC, etc and
> just get out in my car and go anywhere I want in something that's not
> polluting our skies.
>
> Oh well, just an idea...I can dream, can't I.

[pacplyer]

Alan Baker > wrote in message >...
> In article >,
> (pacplyer) wrote:
>
> > > > The airplane is op specs limited to +2.5 g's and -1.0g. Not worried
> > > > about stalling a 747. There's so much mass the tow rope would break
> > > > before any instant degradation would show up on the airspeed
> > > > indicator. Airspeed trends take A LONG LONG time to develop on this
> > > > bird. It's not like anything you've every flown before. I use the
> > > > analogy of surfing on a mountain of metal to describe a visual
> > > > approach on the 74 because the previous vector it was on before you
> > > > made the change [control input] is what it will be on for a number of
> > > > seconds. By the
> > > > time you've pulled off the thrusters because you're too fast, the huge
> > > > inertia will [make it seem like] it's accelerating.
> > >
> >
> > Alan Baker > wrote
> >
> > > Read a physics text and then say that again...
> > >
> >
> >
> > Inertia: a property of matter whereby it remains at rest or continues
> > in uniform motion unless acted upon by some outside force.
> >
> > The uniform motion in my example was acceleration. In this bird it
>
> Acceleration is not uniform motion.
>
> > takes longer for the opposing force: drag to arrest the motion. Due
> > to it's large Kinetic Energy. Can you be more specific? What part do
> > you disagree with?
>
> That an object will keep accelerating in the absence of an external
> force on the object. Inertia will keep it moving at a constant velocity,
> but it won't keep it accelerating.

You're right. It would be *decellerating* abeit at a very slow rate of
decay. My error. Thanks Allen. I've modified above in [brackets] for
clarity. But I swear, when I was brand new in the box it really
seemed like it was accelerating away from my intended Vref speed even
after slamming back to idle! The snickers from the back of the
simulator made it seem to accelerate even more!

pac

[pacplyer]

I missed this post of yours Tim, since I was in the middle of a "High
Anxiety" spiral/flat spin flashback. O.K. I'll come back to work for
you guys if you promise me: no banks over 30 degrees up there in the
tow/tug plane and no ‘walking the dog' type stunts with the cable.
(now I see why Rutan built his own high-G' White Knight "toss"
airplane. He was able to release at up to 90 degrees bank if he
wanted to.) But we're going for Low Earth Orbit here, so getting to
the ‘barber pole' (VMO/MMO; airspeed limit pointer) is probably
important. I figured on a tow plane release weight of 550,000 lbs in
a 30 degree bank, which is 50,000 too heavy to prevent upset (damn.)
Also we only get five minutes of GA thrust to get up to MMO (Mach Max
Operating) after leveling off at FL450 or we may start cooking some
engines. "If I give you any more Captain, she going to blow!"


"Tim Ward" > wrote <the following are excerpts
from his longer post earlier in the thread>

spacecraft's best rate of climb speed, then the turning maneuver isn't
> required.
> This is a booster. It just happens to get its oxidizer at 45000 feet. The
> assumption is that there is enough excess thrust on the 747 to overcome the
> drag on the towline and whatever is attached to it. If that means extra
> engines, that's okay with me.

You may be right about the need for bigger engines (or more of them;
hanging engines will mean re-certifing the airplane; and that's going
to run the cost up by tens of millions.) I don't think a -400's going
to work because; the tailplane is probably smaller; this was a trick
used by later designs to increase range. They pump gas back to the
smaller horz stab to get a more aft CG (equals better range.) It's
closer to upset than a -200 airframe AFAIK.

> > That drag reduces the 747's speed by some amount, causing the 747 to
> > have to fly at a higher angle of attack (AoA) already.
>
> I would expect it to require quite a lot of additional power. That's why I
> originally suggested extra engines on the 747. I wasn't envisioning it as a
> dynamic maneuver. More like impedance matching. The 747 is buzzing around
> at a relatively low altitude. The spacecraft is up really high (we hope),
> and so it's minimum sink speed is probably very high, because there's durn
> few air molecules bumping into it. There's a constant force between the two
> aircraft, but the spacecraft probably needs to be flying faster. By
> turning, the 747 can fly at some reasonable speed, and the spacecraft can
> fly at a higher speed.
>

This methodology sounds very promising. I'm a little worried about
the centrifugal recoil of the cable after release, but maybe the
payout winch will absorb some of it? That lanyard's gotta sling
across down somewhere: "Break left! Cable at Two O'clock!" Don't
need a string tangled up in the Slats or gear on approach either. ;-)

> No, there's a constant tension. This is not difficult with a payout winch,
> since the mechanism pays out cable above a certain tension, which lowers the
> tension, so it slows down the payout, raising the tension... it stays
> pretty constant. The line length changes.
>

Pretty clever. I like it.

> > So we get to the disconnect point.
> >
> > ALL the energy transferred to the kite comes from the 747.
> > All of it.
> > All of that energy is removed (just as quickly?) from the 747.
>
> No. You have a 747 being slowed by cable tension. (Dammit! the cable has
> to carry the aerodynamic drag as tension-- so that _is_ something I
> overlooked. I figured on cable weight and the tow force, but the drag on the
> cable adds another load.)
> The kite's energy is energy of position, which it's already got. When the
> cable is released, or breaks, the 747 is going to accelerate, not slow. An
> instant additional 100,000 lbs of thrust. (or reduction in drag) It'll
> still be a kick in the butt, but it will be speeding the 747 up, not slowing
> it down.
>
> > And at some critical point, big momma finds herself below critical
> > flight speed and above critical AoA, and things could get a little
> > - critical?
> > Now in reality, all of that could probably be dealt with. Some of
> > those perimeters would define the limits of this kind of operation.
> >
> > From a PAWKI standpoint, it's probably cable tensile strength.
>
> Probably. This basically puts a limit on how long the towline can be.
>
> >
> > But if that held, I'd suspect this event is going to feel a lot like
> > catching a Three Wire - at FL 450.
>
> I think it would be more like a cat shot -- though I haven't experienced
> either one.

Not sure it's the same, but a 74 jock in training changes thrust by
nearly 100,000 lbs on empty go-arounds from idle and I'm here to tell
you: it's a frickin earthquake in the air. You commonly bust your
level off altitude as a student, even after you've slammed the thrust
levers to idle. There's just too much power to weight. Those Big
Fans wagg on the pylons like a dog's tail. It scared the **** out of
me riding in the supernumerary area (the hump) while letting the other
student do his bounces in SMF on "MLO" one of our two PAX birds.
Without the weight of 531 other bodies, belly freight and large fuel
load, a go-around is a violent maneuver. Looking down out the window
from the upper deck at the inboard engine: one second you're looking
into the intake, the next you can only see the outer engine cowling,
the next your looking into the engine inlet….. I was just waiting for
a loud SNAP! of the pylon, since I thought: "NO Way would they design
it to do THAT!

So I think the airplane can handle a 100,000lb change in
acceleration/deceleration if you can time release to coincide with
idle pwr, speed brakes and pull up. Actually the aircraft pitch up
from the down moment at the tail attatch point would help in
preventing overspeed stall. Remember at 30 degree bank, I've only got
nine knots to play with.

Think I'll call in sick on that day. Better call Bob Hoover to take
that flight for me! If he's too old than call one of those U2 guys.

> On a commanded release, you could gradually decrease the tension on the
> payout winch over a number of seconds prior to cutting loose, and you might
> be able to throttle down at a similar rate, but if the line breaks, you're
> gonna speed up.
>
> Tim Ward
>

Any way you slice it, it's going to be an interesting ride for both
vehicles. But as Chuck Yeager once said after drinking whiskey the
night before and falling off a horse while drinking and driving and
busting his ribbs and showing up for the mission the next morning and
lighting the candle: "I don't advise it mind you, but it *can* be
done."

pac "no wonder these guys are all on the bottle" plyer

[Corrie]

Richard Lamb > wrote in message >...

> From a PAWKI standpoint, it's probably cable tensile strength.

Naw, using unobtainium cable takes care of that. The real PAWKI issue
is conservation of energy.

> But if that held, I'd suspect this event is going to feel a lot like
> catching a Three Wire - at FL 450.

At least you have some room to recover from the spin....

[Corrie]

"Bob Chilcoat" > wrote in message >...
> According to the newspaper article I read, the proposed fiber is a "tape"
> roughly three feet wide and a few thou thick. A flat ribbon is
> aerodynamically unstable and will vibrate axially in any wind. This thing
> would seem to be the ultimate Tacoma Narrows Bridge. Just my first
> impression.

The problem with the Tacoma bridge was that the materials couldn't
handle the flexing. Lots of materials are designed to vibrate -
saxophone reeds, guitar strings, etc.

So what would the pitch of this critter be, and how many Db?

[Brian Whatcott]

On Tue, 29 Jun 2004 16:48:11 -0400, Bryan Martin
> wrote:
//
>The designers of the Tacoma-Narrows bridge didn't give enough consideration
>to its aerodynamics or stiffness. It shouldn't have been flexing to that
>degree at all. It was a solid road deck built from I-beams in an area known
>for frequent high winds. Modern suspension bridges are usually built from
>steel trusses for stiffness and have open steel grid decking down the middle
>of the span to kill any lift generated by the roadway.


It's not a kind site. The current bridge there gallops too a little,
in high winds.

Brian W

[Richard Lamb]

Just for clarity, how tall is this thing supposed to be?

I saw on proposal that said 62,000 miles!

If that's supposed to be anchored to the Earth, I gotta
belly laugh.

Anybody want to calculate the rotational moment of something THAT
long?????


Richard

[Dillon Pyron]

On 29 Jun 2004 12:44:56 -0700, (Corrie) wrote:

>Richard Lamb > wrote in message >...
>
>> From a PAWKI standpoint, it's probably cable tensile strength.
>
>Naw, using unobtainium cable takes care of that. The real PAWKI issue
>is conservation of energy.
>
>> But if that held, I'd suspect this event is going to feel a lot like
>> catching a Three Wire - at FL 450.
>
>At least you have some room to recover from the spin....

The debris field, however, will be quite immense.
--
dillon

When I was a kid, I thought the angel's name was Hark
and the horse's name was Bob.

[Regnirps]

Brian Whatcott wrote:

>On Tue, 29 Jun 2004 16:48:11 -0400, Bryan Martin
> wrote:
>//
>>The designers of the Tacoma-Narrows bridge didn't give enough consideration
>>to its aerodynamics or stiffness. It shouldn't have been flexing to that
>>degree at all. It was a solid road deck built from I-beams in an area known
>>for frequent high winds. Modern suspension bridges are usually built from
>>steel trusses for stiffness and have open steel grid decking down the middle
>>of the span to kill any lift generated by the roadway.

>It's not a kind site. The current bridge there gallops too a little,
>in high winds.

I have never noticed any motion. My mother cried when the old one went down. It
was back to waiting in line for the ferry. The original design was an upside
down U in cross section with solid sides. It didn't exactly generate lift. It
would flex a bit under a wind load (35 mph made it gallop like crazy) and twist
and dump, twist back with the U slightly facing the wind and do it again. The
real problem was harmonic oscilation. The darn thing had a harmonic mode that
could get pumped up over time with very little wind.

The replacement is all open gridwork with four wind grates in the roadway the
whole length. My brother, who is a ranger in the Tetons (was on Lou Dobbs the
other night about rescue operations), has his arrest ticket framed from the
time he walked the cable from end to end when he was a teenager.

-- Charlie Springer

[Regnirps]

I missed part of the thread, but the whips are an idea of the late brilliant
Robert F. Forward. I think Tether's Inc. is still going.

The idea is that a mass orbits at a reasonable height. Two or three long whips
rotate at such a speed that if they where a wheel, it would be rolling on an
imaginary sphere that matched the globe that would fit the intended intercept
altitude. Just like the wheel of a car, at the lowest point it is not moving
with respect to the Earth. If the end is flyable, the slack or flexibility
allows it to station keep or more on some course and speed to perform the
intercept. The timing has to be good, like 20 or 30 seconds, but lining it all
up is pretty predictable.

The whip is kept powered up by delivering material from space back to Earth.

Forward worked out a series of transfer whips that would allow travel to Mars
without carrying any more than maneuvering fuel. The ship or attachment has to
be able to travel on the whip in order to change angular speed (by moving the
mass closer to or further from the release points. Or delivering the load to
the central mass.)

I can pull out his papers and elucidate if anyone wants more. We exchanged
copies of everything we had published once. I sent some letters to the editors
of journals and tech magazines. He sent a big box of Hughes Research internal
papers, patents, Omni articles, Physical Review papers, etc. (Included is the
famous "Rotating Cylinders and the Possibility of Global Causality Violation.")

Forward thought up a lot of great stuff. NASA uses his space-time flatteners
for micro-gravity research on the Shuttle. He invented the third of the four
basic instruments for testing or measuring gravity, the Rotating Gravity
Gradiometer. (I invented the fourth, which required his as a detector). We used
to talk occasionally. His death from a brain tumor in his 60's was a major
loss.

-- Charlie Springer

[pacplyer]

"Felger Carbon" > wrote in message t>...
> "pacplyer" > wrote in message
> om...
> >
> > Inertia: a property of matter whereby it remains at rest or
> continues
> > in uniform motion unless acted upon by some outside force.
> >
> > The uniform motion in my example was acceleration.
>
> Disclaimer: It's 5:30AM. I'm an engineer, not a physicist. BUT...
>
> Acceleration **by definition** is **not** uniform motion! ;-)


Yeah, I've heard all this before:

"Dammit Jim, I'm a doctor, not an engineer!"

and

"Captain, I cannot change the laws of physics!"

My reply:
I'm getting a little bit tired of my senior crewmembers conspiring
against me! The superstructure can do those things in a jacked-up
simulator, understand? It's aviation, but not as we know it. The
main thing here is the Enterprise Carrier (NASA 747) is the most
capable ship in the fleet and if we can somehow harness the power of
those new GE big fan engines by setting them up on the existing
airframe...
We just might get off this rotten planet! Now get to work on the
tether drag calculations! I don't want to hear any more excuses!

(yeah, something like that'll suffice... After all, this is a high
altitude space thread.) ;-)

pac "suffering from hypoxia" plyer

[Kevin Horton]

On Mon, 28 Jun 2004 20:23:11 -0700, Tim Ward wrote:

>
>> Stall speed at extreme altitude would not the benign 180 knots, but
>> something appreciably higher (can you help me out with the high altitude
>> 747 data - actual stall speed at FL 450?).
>
> I actually want to fly the 747 pretty fast. If its speed at 45000 feet is
> fast enough so that the spacecraft's airspeed at 100000 feet is at the
> spacecraft's best rate of climb speed, then the turning maneuver isn't
> required.

pacflyer gave a 1g speed range for the 747 at 45,000 ft and 580,000 lb of
208 kt to 251 kt. I'm assuming those numbers are in KCAS. If so, that
works out to 444 KTAS to 524 KTAS under standard day conditions.

At 100,000 ft, those same true airspeed values work out to 56 KCAS to 68
KCAS. The equivalent airspeed, which is what the wing sees, is a bit
lower at 52 KEAS to 61 KEAS. That means the orbiter needs to have a very,
very low wing loading, which doesn't seem compatible with a re-entry. And
it has to support the weight of the tether too. I'm not sure this idea
will work, unless we can get a much faster tow aircraft.

--
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://go.phpwebhosting.com/~khorton/rv8/
e-mail: khorton02(_at_)rogers(_dot_)com

[Tim Ward]

"Kevin Horton" > wrote in message
...
> On Mon, 28 Jun 2004 20:23:11 -0700, Tim Ward wrote:
>
> >
> >> Stall speed at extreme altitude would not the benign 180 knots, but
> >> something appreciably higher (can you help me out with the high
altitude
> >> 747 data - actual stall speed at FL 450?).
> >
> > I actually want to fly the 747 pretty fast. If its speed at 45000 feet
is
> > fast enough so that the spacecraft's airspeed at 100000 feet is at the
> > spacecraft's best rate of climb speed, then the turning maneuver isn't
> > required.
>
> pacflyer gave a 1g speed range for the 747 at 45,000 ft and 580,000 lb of
> 208 kt to 251 kt. I'm assuming those numbers are in KCAS. If so, that
> works out to 444 KTAS to 524 KTAS under standard day conditions.
>
> At 100,000 ft, those same true airspeed values work out to 56 KCAS to 68
> KCAS. The equivalent airspeed, which is what the wing sees, is a bit
> lower at 52 KEAS to 61 KEAS. That means the orbiter needs to have a very,
> very low wing loading, which doesn't seem compatible with a re-entry. And
> it has to support the weight of the tether too. I'm not sure this idea
> will work, unless we can get a much faster tow aircraft.
>
> --
> Kevin Horton RV-8 (finishing kit)
> Ottawa, Canada
> http://go.phpwebhosting.com/~khorton/rv8/
> e-mail: khorton02(_at_)rogers(_dot_)com

Ahh... at last someone who did what I was too lazy to do... the numbers.
I knew the indicated airspeed at 100,000 feet would be low.

If I can ask a favor, what is the equivalent airspeed at Mach 1 at 100,000
feet, standard atmosphere?

And hey, I've already figured on dropping 20 km of tether, what's a wing
between friends?

Tim Ward

[Richard Lamb]

Tim Ward wrote:
>
> > >> Stall speed at extreme altitude would not the benign 180 knots, but
> > >> something appreciably higher (can you help me out with the high
> altitude
> > >> 747 data - actual stall speed at FL 450?).
> > >
> > > I actually want to fly the 747 pretty fast. If its speed at 45000 feet
> is
> > > fast enough so that the spacecraft's airspeed at 100000 feet is at the
> > > spacecraft's best rate of climb speed, then the turning maneuver isn't
> > > required.
> >
> > pacflyer gave a 1g speed range for the 747 at 45,000 ft and 580,000 lb of
> > 208 kt to 251 kt. I'm assuming those numbers are in KCAS. If so, that
> > works out to 444 KTAS to 524 KTAS under standard day conditions.
> >
> > At 100,000 ft, those same true airspeed values work out to 56 KCAS to 68
> > KCAS. The equivalent airspeed, which is what the wing sees, is a bit
> > lower at 52 KEAS to 61 KEAS. That means the orbiter needs to have a very,
> > very low wing loading, which doesn't seem compatible with a re-entry. And
> > it has to support the weight of the tether too. I'm not sure this idea
> > will work, unless we can get a much faster tow aircraft.
> >
> > --
> > Kevin Horton RV-8 (finishing kit)
> > Ottawa, Canada
> > http://go.phpwebhosting.com/~khorton/rv8/
> > e-mail: khorton02(_at_)rogers(_dot_)com
>
> Ahh... at last someone who did what I was too lazy to do... the numbers.
> I knew the indicated airspeed at 100,000 feet would be low.
>
> If I can ask a favor, what is the equivalent airspeed at Mach 1 at 100,000
> feet, standard atmosphere?
>
> And hey, I've already figured on dropping 20 km of tether, what's a wing
> between friends?
>
> Tim Ward

I'm not usually intentionally mean to newbies (well, unless they talk
like tort lawyers wanting a cheap helicopter. And that was more for fun
than meanness).

And I'm not being mean now, Tim. Even if it sounds like it...

The only lazy part here is being too lazy to learn the basic subject
matter before pontificating about it.

The _correct_ question would have been, "What the heck does equivalent
airspeed mean, why is it important, and how do I calculate it?"

I had intended to come back to this discussion and ask if you already
knew that your orbiter was a swing wing design.

But Kevin beat me to it. (From the 3 point line - nothin but net!)


Richard Lamb

"Math - It's not just for sissies any more"

[Kevin Horton]

On Thu, 01 Jul 2004 08:02:07 -0700, Tim Ward wrote:

>
> If I can ask a favor, what is the equivalent airspeed at Mach 1 at 100,000
> feet, standard atmosphere?
>

Mach 1 at 100,000 ft is 67 KEAS, rounded to the nearest knot. You
probably need to get to at least Mach 3 to have enough EAS to work with
(201 KEAS), and that is probably even on the low side for speed.
The highly swept shapes that favour reentry generally tend to be quite
draggy at low speed. Just as an example, the Mirage III has a 60 deg
delta wing. It has a speed for min drag of around 300 KEAS at typical
operating weights. It was a real pig at 200 kt. It didn't really start
to fly crisply until you got it up over 400 kt.

--
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://go.phpwebhosting.com/~khorton/rv8/
e-mail: khorton02(_at_)rogers(_dot_)com

[pacplyer]

Kevin Horton > wrote in message >...
> On Mon, 28 Jun 2004 20:23:11 -0700, Tim Ward wrote:
>
> >
> >> Stall speed at extreme altitude would not the benign 180 knots, but
> >> something appreciably higher (can you help me out with the high altitude
> >> 747 data - actual stall speed at FL 450?).
> >
> > I actually want to fly the 747 pretty fast. If its speed at 45000 feet is
> > fast enough so that the spacecraft's airspeed at 100000 feet is at the
> > spacecraft's best rate of climb speed, then the turning maneuver isn't
> > required.
>
> pacflyer gave a 1g speed range for the 747 at 45,000 ft and 580,000 lb of
> 208 kt to 251 kt. I'm assuming those numbers are in KCAS. If so, that
> works out to 444 KTAS to 524 KTAS under standard day conditions.

Goddammit. That's not right. I interpolated backwards on both
numbers. The 1g chart only allows a max weight of 550,000 lbs for low
speed buffet of 218kts and high speed of 242kts. and this being test
pilot land, I was trying to interpolate another 30,000 lbs into the
equation (for total of 580K: which is just outside the envelope.)
Sorry Guys. I should have ADDED the ten knots to the low speed number
and SUBTRACTED nine on the high speed mach buff number. (hence the
term coffin corner; range narrows as you go up.) So 580K at FL450
would be: 228-233 interpolated out of the envelope. Or you can just
go with the stock 550,000 lbs numbers of 218-242.

So could you recalculate the below values Kevin? I promise not to
play test pilot any more!
>
> At 100,000 ft, those same true airspeed values work out to 56 KCAS to 68
> KCAS. The equivalent airspeed, which is what the wing sees, is a bit
> lower at 52 KEAS to 61 KEAS. That means the orbiter needs to have a very,
> very low wing loading, which doesn't seem compatible with a re-entry. And
> it has to support the weight of the tether too. I'm not sure this idea
> will work, unless we can get a much faster tow aircraft.

Detachable 200' U-2 type Glider Wings? ;-) Well U-2's fly at low TAS
speeds up there don't they? Hence my detachable 200 ft glider wing
idea. Let's see if I understand Tim Ward's logic in getting the
vehicle to 100,000 ft. I might be wrong, but isn't the purpose of
this to just get the vehicle out of the "Max Q" area of the
atmosphere? Building up to "Max Q" is were space vehicles burn most
of their propellant from the first stage isn't it? Do we really care
what speed it's at as long as we can initiate Orbiter burn sequence up
high? (I agree, high altitude AND high speed would be better.)

Now if you want high tow plane ground speed so that it takes less
"Orbit One"-fuel for orbital insertion, the old jet adage is: "You
stay down low if you want to go fast." Power, wing performance, and
curvature of the earth is "more better." If we stayed down at FL 350
we'd have to drag another couple of miles of tether cable but: we'd be
able to fly at a 550,000 lb weight AND do a 45 degree bank (1.41g.)
Low speed stall buffet would start below 249kts ind/cas . High speed
mach buffet would not happen until the absolute top certified speed of
the aircraft .92 Mach (I think that's just about 305kts IAS/CAS in
that bank/alt by interpolation; chart only says VMO.) A 90-year-old
woman could hold this range no sweat in the very forgiving 747. So is
that about 518 kts IAS/CAS? (somebody check my math please.) But our
ground speed will be higher down low, right? Isn't that what we are
really after for orbit insertion: high tow-plane ground speed relative
to the earths surface? Having trouble with this cuz computers figure
this out for us all the time now!

So I guess a trade off is going to emerge between tow plane ground
speed/bank advantage at lower altitudes and extra cable length drag.
Now that I've reviewed the charts; it seems like at FL 450 we're at
the extreme limits of the stock 747-200F with P&W Q powered engines.
It appears to me that maybe we need a lot more thrust if we're going
to do this on a routine basis at FL450. Someone mentioned using GE
C-90's, of which one was hung for testing on the 74 already. Four of
those engines would make getting up to .92 mach easy, but I'm sure
they ain't cheap (10 mil ea?). Maybe Burt would do it anyway and just
fly it under experimental rules since no paying passengers are aboard
that vehicle? This would save tens of millions in re-engine
certification costs.

The reason for me obsessing with the 747 is two-fold. The first is
low cost (I want to say about $10,000 an hour is typical op cost in
some fleets. Does that sound right Kevin?) Of course there are a lot
of variables but if Tim's slingshot idea would work, one hour of climb
time has got to be many many millions of dollars cheaper than doing a
bargain launch-pad t/o as Ron W. was suggesting (I think he said it
could be 20 mil.)

The second reason for the using "the whale" is simplicity. There's
almost no development needed of the first stage at all (beyond winch
fab and tst and possible aircraft re-engining. The 747 is a known
commodity and last I kept track, over 2000 have been built. Parts,
engines, crews, mechs, techs are plentiful at LAX and Edwards. This
system could be sold overseas to other governments; so the project is
potentially profitable. At 1g S&L flight at FL350 the 74 can be at
750,000lbs at M.92 (wing limit); so we pay a big capacity price to fly
it at FL450 or in a 45 degree bank at FL350. Down at FL350 level
Straight and Level means big Low Earth Orbit payloads, (since at light
weights: huge power is available to overcome huge drag.) and this
means Mr Allen and his early shareholders may get rich from the
endeavor.

Still waiting for a RAH engineer to take a guess of the drag
coefficient involved.

Scottie… how much longer for an answer! The frog Cling-ons are going
to show up with their bird of commercial prey A380 any minute now! We
have to get off this planet before they start cutting into our
business!

pac "push em till they come apart" plyer

[Dillon Pyron]

On 1 Jul 2004 11:39:07 -0700, (pacplyer) wrote:

>Kevin Horton > wrote in message >...
>> On Mon, 28 Jun 2004 20:23:11 -0700, Tim Ward wrote:

Before we go to much further, I think it would be appropriate for the
OP to send out a dated notebook with original facts, figures and
drawings to someone who can sign it "read and understood on this
date".

It's known as prior art. Also establishes a date certain should you
wish to patent the idea.


--
dillon

When I was a kid, I thought the angel's name was Hark
and the horse's name was Bob.

[pacplyer]

(pacplyer) wrote
> Now if you want high tow plane ground speed so that it takes less
> "Orbit One"-fuel for orbital insertion, the old jet adage is: "You
> stay down low if you want to go fast." Power, wing performance, and
> curvature of the earth is "more better." If we stayed down at FL 350
> we'd have to drag another couple of miles of tether cable but: we'd be
> able to fly at a 550,000 lb weight AND do a 45 degree bank (1.41g.)
> Low speed stall buffet would start below 249kts ind/cas . High speed
> mach buffet would not happen until the absolute top certified speed of
> the aircraft .92 Mach (I think that's just about 305kts IAS/CAS in
> that bank/alt by interpolation; chart only says VMO.) A 90-year-old
> woman could hold this range no sweat in the very forgiving 747. So is
> that about 518 kts IAS/CAS? (somebody check my math please.)

Curses. I meant to ask: is that "about 518 kts TAS?" (somebody check
my math please.) NOT IAS/CAS! I'm helpless without a secretary! And
I'm helpless anymore without a TAS readout on the INS. To answer
Kevin's question on the charts: IIRC, it was explained to me in school
that CAS and IAS through the magic of 747 CADC's (central air data
computers) are pretty much the same numbers. The buffet boundry
tables don't say CAS or IAS; but I'm sure they are designed to be
flown off directly. These tables I'm quoting are generic; they were
compiled for the -100 and -200 airframes and engine types in our
fleet. OTOH, I remember seeing CAS data placards on some 74's under
the wiskey compass. I remember wondering if they were left over from
some previous airline. But Boeing would have more "specific to a
certain model" envelopes to draw from if Rutan ever pursued this idea.

pac - out

[Kevin Horton]

On Thu, 01 Jul 2004 12:39:07 -0700, pacplyer wrote:

> Kevin Horton > wrote in message
> >...
>> On Mon, 28 Jun 2004 20:23:11 -0700, Tim Ward wrote:
>>
>>
>> >> Stall speed at extreme altitude would not the benign 180 knots, but
>> >> something appreciably higher (can you help me out with the high
>> >> altitude 747 data - actual stall speed at FL 450?).
>> >
>> > I actually want to fly the 747 pretty fast. If its speed at 45000
>> > feet is fast enough so that the spacecraft's airspeed at 100000 feet
>> > is at the spacecraft's best rate of climb speed, then the turning
>> > maneuver isn't required.
>>
>> pacflyer gave a 1g speed range for the 747 at 45,000 ft and 580,000 lb
>> of 208 kt to 251 kt. I'm assuming those numbers are in KCAS. If so,
>> that works out to 444 KTAS to 524 KTAS under standard day conditions.
>
> Goddammit. That's not right. I interpolated backwards on both numbers.

Good thing airlines use tabular data so you don't have to interpolate
Vref. Sure hate to go 10 kt the wrong way on that one :)

> The 1g chart only allows a max weight of 550,000 lbs for low speed buffet
> of 218kts and high speed of 242kts. and this being test pilot land, I was
> trying to interpolate another 30,000 lbs into the equation (for total of
> 580K: which is just outside the envelope.) Sorry Guys. I should have
> ADDED the ten knots to the low speed number and SUBTRACTED nine on the
> high speed mach buff number. (hence the term coffin corner; range narrows
> as you go up.) So 580K at FL450 would be: 228-233 interpolated out of the
> envelope. Or you can just go with the stock 550,000 lbs numbers of
> 218-242.
>
> So could you recalculate the below values Kevin? I promise not to play
> test pilot any more!

If you've got 1 g buffet numbers of 228-233 at FL450 at 580,000 lb, you
don't have a practical envelope to do this mission. You'd be in buffet
the first time someone sneezed. So, I'll use 550,000 lb.

218 KCAS at FL450 equals 463 KTAS, which equals 54 KEAS at 100,000 ft.
242 KCAS at FL450 equals 508 KTAS, which equals 60 KEAS at 100,000 ft.

This still isn't anywhere close to a practical envelope for the orbiter.

>>
>> At 100,000 ft, those same true airspeed values work out to 56 KCAS to 68
>> KCAS. The equivalent airspeed, which is what the wing sees, is a bit
>> lower at 52 KEAS to 61 KEAS. That means the orbiter needs to have a
>> very, very low wing loading, which doesn't seem compatible with a
>> re-entry. And it has to support the weight of the tether too. I'm not
>> sure this idea will work, unless we can get a much faster tow aircraft.
>
> Detachable 200' U-2 type Glider Wings? ;-) Well U-2's fly at low TAS
> speeds up there don't they? Hence my detachable 200 ft glider wing idea.
> Let's see if I understand Tim Ward's logic in getting the vehicle to
> 100,000 ft. I might be wrong, but isn't the purpose of this to just get
> the vehicle out of the "Max Q" area of the atmosphere? Building up to
> "Max Q" is were space vehicles burn most of their propellant from the
> first stage isn't it? Do we really care what speed it's at as long as we
> can initiate Orbiter burn sequence up high? (I agree, high altitude AND
> high speed would be better.)

Well, the orbiter needs to have enough speed to be above stall speed. The
drag will be very high if it is too close to stall. So 100,000 ft is way
too high to tow the orbiter, if we have a subsonic tow aircraft.

>
> Now if you want high tow plane ground speed so that it takes less "Orbit
> One"-fuel for orbital insertion, the old jet adage is: "You stay down low
> if you want to go fast." Power, wing performance, and curvature of the
> earth is "more better." If we stayed down at FL 350 we'd have to drag
> another couple of miles of tether cable but: we'd be able to fly at a
> 550,000 lb weight AND do a 45 degree bank (1.41g.) Low speed stall buffet
> would start below 249kts ind/cas . High speed mach buffet would not
> happen until the absolute top certified speed of the aircraft .92 Mach (I
> think that's just about 305kts IAS/CAS in that bank/alt by interpolation;
> chart only says VMO.)

I don't know how position error is handled in the 747 Classic. M0.92 true
works out to 530 KTAS and 318 KCAS at FL350. But there may be a bit of
position error in the machmeter, so your 305 KCAS could be right too.
If you held a 45 deg bank turn, I think your turn radius would be just
under 25,000 ft (if I didn't screw this up - I've just had a couple of
beer). So, if you had a 20 km tether, and the orbiter was at 75,000 ft, I
figure his radius of turn would be about 77,000 ft, and he would be going
about 3.1 times as fast as you, or a TAS of about 1640 KTAS or about 350
KEAS. This might be achievable.

A 90-year-old woman could hold this range no sweat
> in the very forgiving 747. So is that about 518 kts IAS/CAS? (somebody
> check my math please.) But our ground speed will be higher down low,
> right? Isn't that what we are really after for orbit insertion: high
> tow-plane ground speed relative to the earths surface? Having trouble
> with this cuz computers figure this out for us all the time now!
>
> So I guess a trade off is going to emerge between tow plane ground
> speed/bank advantage at lower altitudes and extra cable length drag. Now
> that I've reviewed the charts; it seems like at FL 450 we're at the
> extreme limits of the stock 747-200F with P&W Q powered engines. It
> appears to me that maybe we need a lot more thrust if we're going to do
> this on a routine basis at FL450. Someone mentioned using GE C-90's, of
> which one was hung for testing on the 74 already. Four of those engines
> would make getting up to .92 mach easy, but I'm sure they ain't cheap (10
> mil ea?). Maybe Burt would do it anyway and just fly it under
> experimental rules since no paying passengers are aboard that vehicle?
> This would save tens of millions in re-engine certification costs.
>
> The reason for me obsessing with the 747 is two-fold. The first is low
> cost (I want to say about $10,000 an hour is typical op cost in some
> fleets. Does that sound right Kevin?)

No idea. I work in the flight test world, so I don't have to bother
myself with the bean counters (no FAs or pax complaining if I go over 30
deg of bank either). Fuel cost is fairly easy to calculate, but I don't
know what maintenance and other costs are.


--
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://go.phpwebhosting.com/~khorton/rv8/
e-mail: khorton02(_at_)rogers(_dot_)com

[Tim Ward]

"Dillon Pyron" > wrote in message
...
> On 1 Jul 2004 11:39:07 -0700, (pacplyer) wrote:
>
> >Kevin Horton > wrote in message
>...
> >> On Mon, 28 Jun 2004 20:23:11 -0700, Tim Ward wrote:
>
> Before we go to much further, I think it would be appropriate for the
> OP to send out a dated notebook with original facts, figures and
> drawings to someone who can sign it "read and understood on this
> date".
>
> It's known as prior art. Also establishes a date certain should you
> wish to patent the idea.

Well, as the OP, it's just a goofy idea I had. I'll put my rights to it in
the public domain. Google should archive it well enough.
OTOH, I wouldn't mind attending the launch :-)

Tim Ward

>
>
> --
> dillon
>
> When I was a kid, I thought the angel's name was Hark
> and the horse's name was Bob.

[Morgans]

"pacplyer" > wrote

>
> Detachable 200' U-2 type Glider Wings? ;-) Well U-2's fly at low TAS
> speeds up there don't they? Hence my detachable 200 ft glider wing
> idea. Let's see if I understand Tim Ward's logic in getting the
> vehicle to 100,000 ft. I might be wrong, but isn't the purpose of
> this to just get the vehicle out of the "Max Q" area of the
> atmosphere? Building up to "Max Q" is were space vehicles burn most
> of their propellant from the first stage isn't it? Do we really care
> what speed it's at as long as we can initiate Orbiter burn sequence up
> high? (I agree, high altitude AND high speed would be better.)
>

> pac "push em till they come apart" plyer

A while back in this thread, it was kicked around, about where the tether
should be attached to the tow plane. I think what I am about to say has not
been kicked about, but who knows; so much has been kicked about! <g>

How about taking off with the orbiter on the 747's back, a-la shuttle
transporting? When the duo is at altitude, the tether could start to reel
out, with the orbiter pulling it out. This would do two things; less drag
(no tether) while getting to altitude, and secondly, the wings on the
orbiter could be designed to work best _at altitude_.
--
Jim in NC


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.711 / Virus Database: 467 - Release Date: 6/25/2004

[pacplyer]

"Morgans" > wrote
>
> A while back in this thread, it was kicked around, about where the tether
> should be attached to the tow plane. I think what I am about to say has not
> been kicked about, but who knows; so much has been kicked about! <g>
>
> How about taking off with the orbiter on the 747's back, a-la shuttle
> transporting? When the duo is at altitude, the tether could start to reel
> out, with the orbiter pulling it out. This would do two things; less drag
> (no tether) while getting to altitude, and secondly, the wings on the
> orbiter could be designed to work best _at altitude_.


Geez Morgan,

You are good for something after all! ;-) I think you just earned
your pay for the week. One of the things I didn't want to bring up
was wake turbulence on take off; since I knew it would probably kill
the project. Even heavy jets wait at least two minutes before
following the jumbo on t/o; to give the house-sized wake vortices time
to roll off the runway. Otherwise you wind up on your head if you're
light, and temporarily out of control even if you're a 727. They are
very likely to bounce a glider wing into pieces on the t/o attempt;
but I don't have any experience in glider ops, so I was just living in
fear on that one. Your idea solves that and the initial cable drag
problem, and it solves the cable tether attachment position problem as
well. Now we can pay out Cable near 747 CG through the roof with
élan! With up to three 747 pacs to pressurize with, we could leave a
large hole in the roof, no sweat. O.K Jim, you can ride along in the
jumpseat as a technical advisor.

We're going to have to get the waitress to bring us some more cocktail
napkins to write on…

pac

[pacplyer]

That's why enjoy discussing experimental space solutions on an
un-moderated homebuilt aircraft NG like RAH. I don't think a
moderator could be well versed enough on all the disparate backgrounds
necessary to plan something like this out. He just couldn't make good
decisions on who to post and who to block. Take Tim for example.
This guy has actually taken a TRUCK and surfed behind it, in tow, with
his hang gliders! You just can't buy better real world experience
than that.

So what do we have now? The OrbitOne vehicle on top of the tow
aircraft courtesy Jim Morgan's good idea. It just has to clear the
74 vertical stab at release; but the Space Shuttle "Enterprise" test
vehicle proved that can be done. I like Tim Ward's two wing
component idea: an SS1 type "re-entry" inner wing with a 100ft
swingable detatchable glider wing on each tip to be deployed after
detach from the mother ship?….. Both these RAH built wings would be
shed upon reaching 75,000-100,000 ft. And Kevin Horton calculated
that we can get over 3 times the steady state speed with Richard
Lamb's snap-whip maneuver (a 45 degree bank initiated by the 747
towship at .92mach; ~310TAS at FL350….) This gives Orbit One at
>75,000ft a leg up on escape velocity as it blows the cable and lights
the Orbital Insertion rocket engine….

There just may be enough brain power on this NG to put together a
computer model!

Here's the 680k t/o weight 747 tow-ship vertical profile as I see it
so far: V2 + 10 to 1000ft agl, clean up accel to 3000ft agl, call for
climb power, accel to 250, IAS hold to 10,000msl, alt hold, accel to
best rate of climb about 320kts is a good guess unless that exceeds
glider/OrbitOne "piggyback stability" speeds, then continue climb up
to 24,500 ft, switch over to Mach .82 climb and hold that with Mach
Hold, and call for MCT (max continuous thrust) power when rate of
climb drops off, then call for G/A (go around) thrust (five minute
limit) when rate of climb drops off, and level off at FL410 (since an
[up to] 250,000 lb space vehicle is now riding on our back we can't
make FL450.) Note we will be at about a 650,000 joined vehicle weight
upon reaching FL410 in this senerio. Detach OrbitOne with
coordinated push over maneuver and descend 747 tow aircraft back down
to FL350 accelerating to MMO .92 mach in the descent (pull back to MCT
power.) Pay out cable and let OrbitOne/glider ascend as high as
possible (75,000-100,000 ft.) Level towship at FL350, call for G/A
thrust and enter 45 degree bank, bracing for possible cable break and
resultant pitch down and overspeed. When Colonauts release the cable
(coordinated,) slam to idle 747 power, deploy full speedbrakes, level
wings, pull up with authority, and recover from resultant mach buffet.

Ya know, I hate to say it guys: but this Rube Goldberg type solution
may just be nothing short of brilliant. It IS, as described above,
from a preliminary perspective, all just barely within the
capabilities of a stock B747-200F with JT9D-Q or -70A engines and more
importantly: does not require superior ****ing airmanship skills on
the part of the tow ship PIC.

We need to further explore several tow tether candidates like Tim's
"Vetron" rope. 1: We need to calc the tension involved using Kevin
Horton's 3 to 1 speed slingshot target (77,000ft radius.) 2. We need
to calculate a drag number for this 24km tether at a selected average
thickness.

Well, what you are waiting for? An engraved invitation? Get to work
and make some engineering decisions! I'm just a towship driver. I
don't know how to calculate the tether load we're going to experience
in the 45 degree bank…

pacplyer

> Not a bad idea, even for a much shorter towline, and not too far different
> from truck towing with a payout winch and a hang glider. There, the
> basebar is sitting in a bracket and the nose is tied down to about the right
> angle. You lay proned out in your harness, and when the truck has 25 or 30
> mph airspeed, you pull the nose release, and start pulling out line.
> When I first tried it, I thought the turbulence off the truck cab would
> make those first few feet exciting, but it's a non-issue.
>
> But the disadvantage is you need the infrastructure to mate the two. One
> advantage the Kelly Air and Space idea (of just a straight tow to altitude)
> is that you could launch from any airport with a long enough runway. No
> special equipment. Just roll 'em out, hook 'em up and wag the rudder.
>
> Tim Ward

[Regnirps]

(pacplyer) wrote:

>So what do we have now? The OrbitOne vehicle on top of the tow
>aircraft courtesy Jim Morgan's good idea. It just has to clear the
>74 vertical stab at release; but the Space Shuttle "Enterprise" test
>vehicle proved that can be done.

There were two SR-71s that could cary a high speed drone on top and release
them to streak across enemy teritory. One is hanging at the Museum of Flight at
Boeing Field. The other was destroyed in a fatal test that ended the program.

-- Charlie Springer

[pacplyer]

Whoops I was looking at the wing tables only, the 747 wing can fly
O.K. at a 650K combined vehicle weight (piggyback) at FL410 1g but the
67,000 lbs thrust class stock -200F engines may or may not get us up
to FL410. I don't seem to have a pure climb capability chart, since
my tabular tables assume you will pull climb power and then throttle
back to a Cruise thrust limit at ISA+10. You can *maintain* only
38,000ft at that weight throttled back to Cruise thrust. And that's
not what we're planning on. I'm planning on MCT at 100ft/min until we
crawl up as high as she will go and then going to the absolute limit
in thrust up there which is G/A EPR for five minutes. However, I'm
not considering the drag of this attached space vehicle! Better get
partner Bill Gates to float us a loan for four C-90 class engines!

pac "little engines that could" plyer

[Tim Ward]

"pacplyer" > wrote in message
m...
> That's why enjoy discussing experimental space solutions on an
> un-moderated homebuilt aircraft NG like RAH. I don't think a
> moderator could be well versed enough on all the disparate backgrounds
> necessary to plan something like this out. He just couldn't make good
> decisions on who to post and who to block. Take Tim for example.
> This guy has actually taken a TRUCK and surfed behind it, in tow, with
> his hang gliders! You just can't buy better real world experience
> than that.

Don't make more out of that than it is. Truck towing is a very popular way
to launch hang gliders. LOTS of hang glider pilots launch that way. After
twenty years, it ain't exactly bleeding edge technology.

>
> So what do we have now? The OrbitOne vehicle on top of the tow
> aircraft courtesy Jim Morgan's good idea. It just has to clear the
> 74 vertical stab at release; but the Space Shuttle "Enterprise" test
> vehicle proved that can be done. I like Tim Ward's two wing
> component idea: an SS1 type "re-entry" inner wing with a 100ft
> swingable detatchable glider wing on each tip to be deployed after
> detach from the mother ship

No, viewed from the front, the "joined wing" looks like a big diamond. It
attaches under the nose and at the top of the rudder. In the dismount, the
front wing pivots down, away from the orbiter, around the rear attach
point -- which can just slide out backwards.

>
> There just may be enough brain power on this NG to put together a
> computer model!
>
> Here's the 680k t/o weight 747 tow-ship vertical profile as I see it
> so far: V2 + 10 to 1000ft agl, clean up accel to 3000ft agl, call for
> climb power, accel to 250, IAS hold to 10,000msl, alt hold, accel to
> best rate of climb about 320kts is a good guess unless that exceeds
> glider/OrbitOne "piggyback stability" speeds, then continue climb up
> to 24,500 ft, switch over to Mach .82 climb and hold that with Mach
> Hold, and call for MCT (max continuous thrust) power when rate of
> climb drops off, then call for G/A (go around) thrust (five minute
> limit) when rate of climb drops off, and level off at FL410 (since an
> [up to] 250,000 lb space vehicle is now riding on our back we can't
> make FL450.) Note we will be at about a 650,000 joined vehicle weight
> upon reaching FL410 in this senerio. Detach OrbitOne with
> coordinated push over maneuver and descend 747 tow aircraft back down
> to FL350 accelerating to MMO .92 mach in the descent (pull back to MCT
> power.)

No, once you've released OrbitOne, rather than pull power, you add line
tension to slow down. Remember the 747 engines are our booster. We want
them running as at high a power as we can all the stinkin' time. We recover
some of the 747's potential energy that way.

Pay out cable and let OrbitOne/glider ascend as high as
> possible (75,000-100,000 ft.) Level towship at FL350, call for G/A
> thrust and enter 45 degree bank, bracing for possible cable break and
> resultant pitch down and overspeed. When Colonauts release the cable
> (coordinated,) slam to idle 747 power, deploy full speedbrakes, level
> wings, pull up with authority, and recover from resultant mach buffet.
>
> Ya know, I hate to say it guys: but this Rube Goldberg type solution
> may just be nothing short of brilliant. It IS, as described above,
> from a preliminary perspective, all just barely within the
> capabilities of a stock B747-200F with JT9D-Q or -70A engines and more
> importantly: does not require superior ****ing airmanship skills on
> the part of the tow ship PIC.
>
> We need to further explore several tow tether candidates like Tim's
> "Vetron" rope. 1: We need to calc the tension involved using Kevin
> Horton's 3 to 1 speed slingshot target (77,000ft radius.) 2. We need
> to calculate a drag number for this 24km tether at a selected average
> thickness.

That's Vectran. Bill Daniel's suggestion of carbon nanotube fiber would be
great -- if it existed.

> Well, what you are waiting for? An engraved invitation? Get to work
> and make some engineering decisions! I'm just a towship driver. I
> don't know how to calculate the tether load we're going to experience
> in the 45 degree bank.

With the payout winch, until you run out of line, the tension in the line is
whatever the payout winch is set for.

Drag on the line: not only at the selected thickness, but there's a big
altitude difference as well. Fortunately, the thick end of the line is up
where the air is thinner.
When you're doing the turning maneuver, the speed continuously varies from
one end to the
It's non-linear with line length because of the caternary in the tow line.

What happens if the tow line goes supersonic? I suspect the drag goes way
up because of the shock wave, but are there instabilities as a result?


> pacplyer

Tim Ward

[Morgans]

"pacplyer" > wrote

One of the things I didn't want to bring up
> was wake turbulence on take off; since I knew it would probably kill
> the project. Even heavy jets wait at least two minutes before
> following the jumbo on t/o; to give the house-sized wake vortices time
> to roll off the runway. Otherwise you wind up on your head if you're
> light, and temporarily out of control even if you're a 727.

Most likely not a show stopper, since most of the energy is out at the tips,
which will be behind the C.G. Our orbiter will be ahead of the main
turdulance. Plus the fact that the vortcies descend as the are formed and
linger.
--
Jim in NC


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[pacplyer]

"Morgans" > wrote in message >...
> "pacplyer" > wrote
>
> One of the things I didn't want to bring up
> > was wake turbulence on take off; since I knew it would probably kill
> > the project. Even heavy jets wait at least two minutes before
> > following the jumbo on t/o; to give the house-sized wake vortices time
> > to roll off the runway. Otherwise you wind up on your head if you're
> > light, and temporarily out of control even if you're a 727.
>
> Most likely not a show stopper, since most of the energy is out at the tips,
> which will be behind the C.G. Our orbiter will be ahead of the main
> turdulance. Plus the fact that the vortcies descend as the are formed and
> linger.

I'm speaking of tow ops on the runway. I wonder where a 250,000 lb
vehicle would break ground in tow behind the 747? Engines of that
size alone put out bad turb 1500 feet behind them. How far back would
it be behind the towship at brake release? And if you have a ten knot
or so crosswind it can blow a wing-tip vorticie back up onto the
runway centerline and ruin your whole day. Ten knot crosswinds are
80% of Mojave days. Nasa and SS1 avoided this with the piggyback
schemes. Maybe also the vehicle on top can be designed to provide
part of the combined lift liberating more power for getting to target
altitude. Data exists and is pubic about NASA's 747 carrier aircraft;
so flight test development cost might be low. I like this
roofmount/payout on cable idea better. Is the payout cable tension
adjustable in flight? At vehicle split you'd want the payout cable
resistance to be low for a few seconds right? So you'd get a positive
clearance on the 74 vert stab?

pac

[Morgans]

"pacplyer" > wrote



> I'm speaking of tow ops on the runway.

***I see. You were talking about before we put it up top.

I wonder where a 250,000 lb
> vehicle would break ground in tow behind the 747?

***Not soon enough! <g>

Maybe also the vehicle on top can be designed to provide
> part of the combined lift liberating more power for getting to target
altitude.

***Yes. Otherwise you could get a negatibe AOA, and have a "Voyager takeoff
wingtip droop", which most people think is a bad thing. I still cant
believe Burt blew it on that one. Oh well, no harm, no foul.

Gotta be careful, not to get too much AOA, or the high indicated airspeed
down low, could pull those long wings right off. We had better make the
mount to have an adjustable AOA, so we can crank in some more AOA when we
start to get up high, to help out more in getting up there. I like that.
Another thing that would do is reduce development time; getting the AOA just
right. Another good thing that would do is get the orbiter to pop off the
roof quick, to get away from boundary flow, and clear the vertical stab.


> Is the payout cable tension adjustable in flight? At vehicle split >you'd
want the payout cable resistance to be low for a few seconds right? So
you'd get a positive clearance on the 74 vert stab?


***Yes. More tension would be like more thrust, to get higher AOA right
off, to get that high angle of climb. Also, once we get lots of cable out,
we want to slow the cable, and stop it, so we can crack the whip with the
cable locked.

The thing that has me most concerned is cable aero drag. I think we better
make that cable streamlined, and *real* thin, or drag could spell an end,
right off.
--
Jim in NC


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[pacplyer]

"Tim Ward" > wrote in message <snips throughout >...

> No, viewed from the front, the "joined wing" looks like a big diamond. It
> attaches under the nose and at the top of the rudder. In the dismount, the
> front wing pivots down, away from the orbiter, around the rear attach
> point -- which can just slide out backwards.

Good. A single piece so that you can't get asymmetrical detachment.
How would it be recovered I wonder? Remote fly down? probably it
would flutter end over end until a chute deployed? Sorry but unlike
gov ops this mission has to be profitable!

> > Here's the 680k t/o weight 747 tow-ship vertical profile as I see it
> > so far: V2 + 10 to 1000ft agl, clean up accel to 3000ft agl, call for
> > climb power, accel to 250, IAS hold to 10,000msl, alt hold, accel to
> > best rate of climb about 320kts is a good guess unless that exceeds
> > glider/OrbitOne "piggyback stability" speeds, then continue climb up
> > to 24,500 ft, switch over to Mach .82 climb and hold that with Mach
> > Hold, and call for MCT (max continuous thrust) power when rate of
> > climb drops off, then call for G/A (go around) thrust (five minute
> > limit) when rate of climb drops off, and level off at FL410 (since an
> > [up to] 250,000 lb space vehicle is now riding on our back we can't
> > make FL450.) Note we will be at about a 650,000 joined vehicle weight
> > upon reaching FL410 in this senerio. Detach OrbitOne with
> > coordinated push over maneuver and descend 747 tow aircraft back down
> > to FL350 accelerating to MMO .92 mach in the descent (pull back to MCT
> > power.)
>
> No, once you've released OrbitOne, rather than pull power, you add line
> tension to slow down. Remember the 747 engines are our booster. We want
> them running as at high a power as we can all the stinkin' time. We recover
> some of the 747's potential energy that way.

Hopefully we won't be slowing down! :-) Once you get the whale on
the step you'd like to leave her there. It's damn hard to recover
lost cruise speed below .84 mach when you're heavy up there. That's
my reason for splitting the vehicles as high as we can, and then going
downhill on the payout: heading for thicker air for the bank maneuver.
MCT (max continuous thrust) in the descent is almost full power
(sometimes they're the same EPR (engine pressure ratio) setting. We
have to throttle back a scoash to this after five minutes of Go-Around
thrust (the highest setting) or else bad thermodynamics in the engine
start happening. Also Blade creep is possible – a very expensive
boo-boo. But I see what you're saying. When I get to MMO (Mach Max
Op) of .92m, don't pull back any power, just add line tension. Thanks
Tim. I didn't understand that part of the scheme. That being the
case, the towship pilot needs a tether line payout tension control. I
envision this to be used just like a throttle lever. The flight
engineer will keep max power going all the time, while the pilot
controls overspeed after split by varying the line tension with his
line tension lever. Used like a throttle the same way the Shuttle
guys use the bellybrake lever. Very do-able. I like it.

>
> With the payout winch, until you run out of line, the tension in the line is
> whatever the payout winch is set for.

So you'd raise the payout winch tension up against max line tether
strength just prior to the bank maneuver?

>
> Drag on the line: not only at the selected thickness, but there's a big
> altitude difference as well. Fortunately, the thick end of the line is up
> where the air is thinner.
> When you're doing the turning maneuver, the speed continuously varies from
> one end to the
> It's non-linear with line length because of the caternary in the tow line.

Looks like this post got cut off. Could you elaborate some more on
this for me? Talk more about "caternary" for me and the dynamics of
this line.

>
> What happens if the tow line goes supersonic? I suspect the drag goes way
> up because of the shock wave, but are there instabilities as a result?
>
>
> Tim Ward

Good question. That hadn't occured to me. There's only one man who
has enough design confidence to find out: Burt da man.

Well it's been a fun thread everybody. Good posts by all.

pacplyer

[Richard Lamb]

Morgans wrote:
>
>
> The thing that has me most concerned is cable aero drag. I think we better
> make that cable streamlined, and *real* thin, or drag could spell an end,
> right off.
> --
> Jim in NC
>

Based on some very shakey assumptions...

Looking for drag per killometer of cable....

1) Using EAS for speed (already corrected for temperature and pressure
at cruise altitude)
218 K EAS = 250 MPH

2) that makes Q = 160 (.00256 * V^2 where V in MPH)

3) RN = 7657 Million (that's for 1 KM chord - in line with slipstream)
Viscosity effects predominate onthe part of thecable in trail!
But I have no clue how to calculate the drag on that part...

4) For the part of the cable that is _perpendicular_ to the
slipstream...

Dp = Cd S Q
Cd = .02 ?? for a round cross section
Cable diameter guessed at 2 inches diameter
S = 546 sq feet per Km of cable length

Dp = 1750 pounds per Km of cable exposed perpendicular to the stream.


Well?

[pacplyer]

Richard Lamb > wrote
>
> Based on some very shakey assumptions...
>
> Looking for drag per killometer of cable....
>
> 1) Using EAS for speed (already corrected for temperature and pressure
> at cruise altitude)
> 218 K EAS = 250 MPH
>
> 2) that makes Q = 160 (.00256 * V^2 where V in MPH)
>
> 3) RN = 7657 Million (that's for 1 KM chord - in line with slipstream)
> Viscosity effects predominate onthe part of thecable in trail!
> But I have no clue how to calculate the drag on that part...
>
> 4) For the part of the cable that is _perpendicular_ to the
> slipstream...
>
> Dp = Cd S Q
> Cd = .02 ?? for a round cross section
> Cable diameter guessed at 2 inches diameter
> S = 546 sq feet per Km of cable length
>
> Dp = 1750 pounds per Km of cable exposed perpendicular to the stream.
>
>
> Well?

Nice formula Richard. If you don't mind I'm going to email it to my
friend at Scaled tomorrow. Don't worry; it's just for grins. I spoke
with him briefly last night and asked him Tim's question about the
line speed when the tow plane banks and gives a 3 to 1 speed advantage
to the Orbiter. He says the line going supersonic is no problem; "it
just Zings" he told me. There are no stability problems with the line
at Mach numbers. Edwards has lots of experience with supersonic tow
lines.

Just for my education, what was your source and method for calculating
your Reynolds Number? What pressure altitude did you use? I'm
thumbing through my old "Theory of Wing Sections" by Abbott and Von
Doenhoff, but it's not making much sense to me!

So if we double your drag per km number, just for ballpark
"do-abiltiy" wag calcs, and call it 3500 lbs of drag per Km of cable
exposed perpendicular to the stream, since it'll be semi-vertical just
prior to towship 45 degree bank maneuver, that yields: 84,000lbs of
drag for 24km of line.

Let's see: four engines producing 67,000lbs of thrust at SL… [note:
we don't know yet what it is at FL 410 but, P&W has those charts and
we can guess it's pretty high since we can pull 1.71 normal climb EPR
at FL410 which is only .02 off the max value on the table.] Four
engines pulling 67,000lbs plus 5,000 lbs of thrust from the APU
chugging out the tail (no I'm not making this up) gives us 273,000
lbs of potential pounds of thrust (minus minor alt effects) to
overcome the line drag coefficient with. Now most of this is going to
be used just getting the mated vehicles to 41,000 ft. But once I get
that 150,000 lb OrbitOne off my back (I keep forgetting about the
100,000lbs of winch and cable so the OrbitOne wt limit is 150,000lbs),
I'll have 190,000 lbs of thrust avaiable for aircraft speed control
above whats required to overcome the line drag. That is, when the
line's pulled out all the way 24km out the roof (84,000lbs of drag.)
But at vehicle split the line will still be short so the drag from it
is negligible, and I can accelerate up to .92 mach, in a shallow
descent. Once I get down to FL350 (where the 747 was designed to
make money,) and pay out all that heavy cable in the process (say
75,000 lbs of Vetran) I'm lighter than **** at 445,000 lbs [380k
empty wt+40Kgas remaining+25k winch pallet wt] so will 84,000 lbs of
line drag have me struggling to hold MMO .92? Don't know, lets go try
it. :D

Let's see: 100million a launch, or $100,000 a launch? (10,000 per hr
for 747, plus OrbitOne prep and support costs guessed at 90K.) Look
out NASA, this SpaceSlingShot thing is worth exploring further since
on paper it's 100 times cheaper to launch payloads and people into
orbit than the shuttle. ;-)

Cheers,

pac "beautiful dreamer" plyer

stay tuned for more wild numbers

[Richard Lamb]

pacplyer wrote:
>
> Richard Lamb > wrote
> >
> > Based on some very shakey assumptions...
> >
> > Looking for drag per killometer of cable....
> >
> > 1) Using EAS for speed (already corrected for temperature and pressure
> > at cruise altitude)
> > 218 K EAS = 250 MPH
> >
> > 2) that makes Q = 160 (.00256 * V^2 where V in MPH)
> >
> > 3) RN = 7657 Million (that's for 1 KM chord - in line with slipstream)
> > Viscosity effects predominate onthe part of thecable in trail!
> > But I have no clue how to calculate the drag on that part...
> >
> > 4) For the part of the cable that is _perpendicular_ to the
> > slipstream...
> >
> > Dp = Cd S Q
> > Cd = .02 ?? for a round cross section
> > Cable diameter guessed at 2 inches diameter
> > S = 546 sq feet per Km of cable length
> >
> > Dp = 1750 pounds per Km of cable exposed perpendicular to the stream.
> >
> >
> > Well?
>
> Nice formula Richard. If you don't mind I'm going to email it to my
> friend at Scaled tomorrow. Don't worry; it's just for grins. I spoke
> with him briefly last night and asked him Tim's question about the
> line speed when the tow plane banks and gives a 3 to 1 speed advantage
> to the Orbiter. He says the line going supersonic is no problem; "it
> just Zings" he told me. There are no stability problems with the line
> at Mach numbers. Edwards has lots of experience with supersonic tow
> lines.
>
> Just for my education, what was your source and method for calculating
> your Reynolds Number? What pressure altitude did you use? I'm
> thumbing through my old "Theory of Wing Sections" by Abbott and Von
> Doenhoff, but it's not making much sense to me!
>
> So if we double your drag per km number, just for ballpark
> "do-abiltiy" wag calcs, and call it 3500 lbs of drag per Km of cable
> exposed perpendicular to the stream, since it'll be semi-vertical just
> prior to towship 45 degree bank maneuver, that yields: 84,000lbs of
> drag for 24km of line.
>
> Let's see: four engines producing 67,000lbs of thrust at SL… [note:
> we don't know yet what it is at FL 410 but, P&W has those charts and
> we can guess it's pretty high since we can pull 1.71 normal climb EPR
> at FL410 which is only .02 off the max value on the table.] Four
> engines pulling 67,000lbs plus 5,000 lbs of thrust from the APU
> chugging out the tail (no I'm not making this up) gives us 273,000
> lbs of potential pounds of thrust (minus minor alt effects) to
> overcome the line drag coefficient with. Now most of this is going to
> be used just getting the mated vehicles to 41,000 ft. But once I get
> that 150,000 lb OrbitOne off my back (I keep forgetting about the
> 100,000lbs of winch and cable so the OrbitOne wt limit is 150,000lbs),
> I'll have 190,000 lbs of thrust avaiable for aircraft speed control
> above whats required to overcome the line drag. That is, when the
> line's pulled out all the way 24km out the roof (84,000lbs of drag.)
> But at vehicle split the line will still be short so the drag from it
> is negligible, and I can accelerate up to .92 mach, in a shallow
> descent. Once I get down to FL350 (where the 747 was designed to
> make money,) and pay out all that heavy cable in the process (say
> 75,000 lbs of Vetran) I'm lighter than **** at 445,000 lbs [380k
> empty wt+40Kgas remaining+25k winch pallet wt] so will 84,000 lbs of
> line drag have me struggling to hold MMO .92? Don't know, lets go try
> it. :D
>
> Let's see: 100million a launch, or $100,000 a launch? (10,000 per hr
> for 747, plus OrbitOne prep and support costs guessed at 90K.) Look
> out NASA, this SpaceSlingShot thing is worth exploring further since
> on paper it's 100 times cheaper to launch payloads and people into
> orbit than the shuttle. ;-)
>
> Cheers,
>
> pac "beautiful dreamer" plyer
>
> stay tuned for more wild numbers

Oh great! There goes my chance at getting hired!


One thing I already know about is that the Cd increases (a lot)
in the transonic range, and again (even more) for supersonic.

Problem is, the drag bill gets paid before anything else does.

So it's entirely likely that the 'zing' is gonna 'fizzle'...

Still, it will be interesting to see what the cool guys say.
(a little kissing up might keep them from laughing so hard?)

Richard

[Richard Lamb]

RN = 778 C V
Where C = chord in inches
V = speed in MPH

I used your EAS numbers (the lowest one too) assuming that would include
the corrections for pressure altitude and temperature. That may or
may not be correct, but it was all I could find at the moment.

Cd of .02 for a round cross section may also be ridiculously low.
But that's a moot point.

Recall that in straight and level flight drag equals thrust.

So I'll SWAG that the 747 total drag at cruise is 273,000 pounds.

That takes up ALL of the avaliable engine thrust.

Oh bloody oops!


Richard

[Kevin Horton]

On Sun, 04 Jul 2004 13:25:10 -0700, pacplyer wrote:

> So if we double your drag per km number, just for ballpark "do-abiltiy"
> wag calcs, and call it 3500 lbs of drag per Km of cable exposed
> perpendicular to the stream, since it'll be semi-vertical just prior to
> towship 45 degree bank maneuver, that yields: 84,000lbs of drag for 24km
> of line.
>
> Let's see: four engines producing 67,000lbs of thrust at SL… [note: we
> don't know yet what it is at FL 410 but, P&W has those charts and we can
> guess it's pretty high since we can pull 1.71 normal climb EPR at FL410
> which is only .02 off the max value on the table.] Four engines pulling
> 67,000lbs plus 5,000 lbs of thrust from the APU chugging out the tail (no
> I'm not making this up) gives us 273,000 lbs of potential pounds of
> thrust (minus minor alt effects) to overcome the line drag coefficient
> with. Now most of this is going to be used just getting the mated
> vehicles to 41,000 ft. But once I get that 150,000 lb OrbitOne off my
> back (I keep forgetting about the 100,000lbs of winch and cable so the
> OrbitOne wt limit is 150,000lbs),
> I'll have 190,000 lbs of thrust avaiable for aircraft speed control
> above whats required to overcome the line drag. That is, when the line's
> pulled out all the way 24km out the roof (84,000lbs of drag.) But at
> vehicle split the line will still be short so the drag from it is
> negligible, and I can accelerate up to .92 mach, in a shallow descent.
> Once I get down to FL350 (where the 747 was designed to make money,) and
> pay out all that heavy cable in the process (say 75,000 lbs of Vetran) I'm
> lighter than **** at 445,000 lbs [380k empty wt+40Kgas remaining+25k
> winch pallet wt] so will 84,000 lbs of line drag have me struggling to
> hold MMO .92? Don't know, lets go try it. :D
>

But, jet engine thrust falls of quite a bit with altitude. Don't be
fooled by that EPR. EPR is Exhaust Pressure Ratio. An EPR of 1.71 just
means that the total pressure in the engine exhaust is 1.71 times as high
as the total pressure in the inlet. But, the total pressure at altitude
is a lot lower than the total pressure at sea level, so the absolute
values of the inlet total pressure and the exhaust total pressure are much
lower than sea level.

Jet engine thrust varies with Mach too. High bypass engines make less
thrust the faster you go. I don't have the rules of thumb at hand, as my
text books are at work, but a quick look at a couple of web pages suggest
that thrust at FL410 might be on the order of 1/3 to 1/4 of sea level
thrust.

http://adg.stanford.edu/aa241/propulsion/tvshv.html
http://www.aerospaceweb.org/design/ucav/propulsion.shtml

I think the drag from the orbiter, plus the drag from the tether will be
too high to allow it to be towed at anything over the mid-thirties, and
that might well be optimistic. More thrust Scottie :)

--
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://go.phpwebhosting.com/~khorton/rv8/
e-mail: khorton02(_at_)rogers(_dot_)com

[pacplyer]

Kevin Horton > wrote in message >...
> On Sun, 04 Jul 2004 13:25:10 -0700, pacplyer wrote:
>
> > So if we double your drag per km number, just for ballpark "do-abiltiy"
> > wag calcs, and call it 3500 lbs of drag per Km of cable exposed
> > perpendicular to the stream, since it'll be semi-vertical just prior to
> > towship 45 degree bank maneuver, that yields: 84,000lbs of drag for 24km
> > of line.
> >
> > Let's see: four engines producing 67,000lbs of thrust at SL? [note: we
> > don't know yet what it is at FL 410 but, P&W has those charts and we can
> > guess it's pretty high since we can pull 1.71 normal climb EPR at FL410
> > which is only .02 off the max value on the table.] Four engines pulling
> > 67,000lbs plus 5,000 lbs of thrust from the APU chugging out the tail (no
> > I'm not making this up) gives us 273,000 lbs of potential pounds of
> > thrust (minus minor alt effects) to overcome the line drag coefficient
> > with. Now most of this is going to be used just getting the mated
> > vehicles to 41,000 ft. But once I get that 150,000 lb OrbitOne off my
> > back (I keep forgetting about the 100,000lbs of winch and cable so the
> > OrbitOne wt limit is 150,000lbs),
> > I'll have 190,000 lbs of thrust avaiable for aircraft speed control
> > above whats required to overcome the line drag. That is, when the line's
> > pulled out all the way 24km out the roof (84,000lbs of drag.) But at
> > vehicle split the line will still be short so the drag from it is
> > negligible, and I can accelerate up to .92 mach, in a shallow descent.
> > Once I get down to FL350 (where the 747 was designed to make money,) and
> > pay out all that heavy cable in the process (say 75,000 lbs of Vetran) I'm
> > lighter than **** at 445,000 lbs [380k empty wt+40Kgas remaining+25k
> > winch pallet wt] so will 84,000 lbs of line drag have me struggling to
> > hold MMO .92? Don't know, lets go try it. :D
> >
>
> But, jet engine thrust falls of quite a bit with altitude. Don't be
> fooled by that EPR. EPR is Exhaust Pressure Ratio. An EPR of 1.71 just
> means that the total pressure in the engine exhaust is 1.71 times as high
> as the total pressure in the inlet. But, the total pressure at altitude
> is a lot lower than the total pressure at sea level, so the absolute
> values of the inlet total pressure and the exhaust total pressure are much
> lower than sea level.

Yeah, I was grinning even as I typed "minor alt effects" in the above
post. Line pilots don't deal in lbs of thrust much. I vaguely
remembered back in 88' calculating lbs of thrust in ground school, and
that it dropped off badly with altitude but you have to remember what
my job is: To sell this idea first; worry about the details later!

Just like the Jim Bede battle cry: "First sell them the airframe.
Worry about supplying engine thrust later!" ;-) Just kidding.
Thanks for keeping me honest Kevin. As you said airlines ops use
weight capability tables and EPR charts. But I didn't remember
that the drop-off in pounds of thrust is so severe! So you guys may
be right; we may be in deep do-do drag wise with stock engines. One
third of 273K lbs thrust at Sea Level is 91,000 lbs of thrust
available! Subtract our line drag guess of 84,000lbs for a two inch
dia line and that gives us 7,000 lbs to overcome 747 vehicle drag
with. Not going to work.

However, before we abandon ship like the rest of the world, I think
maybe we're being too conservative on the drag figures. Tim
calculated a 24mm line which is 0.944882 Inches wide. So Richard
you need to recalculate your formula using numbers for a *one inch*
line instead.

>
> Jet engine thrust varies with Mach too. High bypass engines make less
> thrust the faster you go. I don't have the rules of thumb at hand, as my
> text books are at work, but a quick look at a couple of web pages suggest
> that thrust at FL410 might be on the order of 1/3 to 1/4 of sea level
> thrust.
>
> http://adg.stanford.edu/aa241/propulsion/tvshv.html
> http://www.aerospaceweb.org/design/ucav/propulsion.shtml
>
> I think the drag from the orbiter, plus the drag from the tether will be
> too high to allow it to be towed at anything over the mid-thirties, and
> that might well be optimistic. More thrust Scottie :)

Dang. Bet you're right. Not only that, but getting our hands on a
-200F is going to be impossible. Everybody loves that thing. What's
a C-90 engine worth? Ten mil each? Re-engine program (experimental
category only: no pax's) would be what another ten –twenty million?
So say it costs 60 million to re-engine one of those old -200
Continental birds that my brother used to fly that are sitting out at
Mojave. He says they are in good shape with all the section 41, 43
etc mods done, and new pylons and fuse pin work done, but that they
parked them because of the fuel consumption. He remembers them at
about 780,000 lbs gross (smaller landing gear than my old -200F
freighter.) We could pick one up for about 50 million. What kind of
TBO do you think we could get out of one of those C90's running it
hard all the time? If we could only get say 240 one hour cycles out
of a new engine, we could afford to burn up about one million in total
tailpipe & total operations cost per slingshot and still break even at
60 slingshots (sell the engines and airframe after retiring in
Tahiti.) That's still cheaper than twenty million on the launch pad
every time at Vandenburg. 20X60 is... hmmmmm One point Two Billion
dollars over at Vandenberg with conventional rockets cost after 60
launches. ...minus our 110 mill cost for aircraft and re-engine-ing
equals one billion ninety million in tow-ship company savings (like my
math?) Let's say we price it for half what Nasa can, and put the
rest in our pocket as shear old profit... 60 shots a year... Yeah, I'm
willing to fly five slingshots a month... Half a billion dollars
tow-ship company profits per year... One percent rah "space-slingshot"
thread-member's fee, Jesus, there's gold in them there slingshots! :^D

Christ! I think I see our ship coming in! Dammit Richard! Give me
some new drag numbers based on a one inch line! Kevin find out how
much thrust in pounds a C-90 can put out at FL410! :-O

pacplyer

up periscope!, damn the torpedoes, full speed ahead! (you guys are
going to need big hangars to put all you're new toys in!) ;-)

[Richard Lamb]

pacplyer wrote:
>
>
> However, before we abandon ship like the rest of the world, I think
> maybe we're being too conservative on the drag figures. Tim
> calculated a 24mm line which is 0.944882 Inches wide. So Richard
> you need to recalculate your formula using numbers for a *one inch*
> line instead.
>
> > pacplyer
>
> up periscope!, damn the torpedoes, full speed ahead! (you guys are
> going to need big hangars to put all you're new toys in!) ;-)


It won't help, Pac.
The cable is not the problem.

The only thing that counts is _excess_ thrust.
That's what ever is left over after the airframe is straight and level.

Then, there is the _second_ airframe! Strangely enough, at the same
speed and altitude, the second ship will have perty near the same
drag as the tow plane.

A simple way to tell (real rough estimate) how high this rig can go
might be to pull all four go levers back to half power.
Whatever altitude you finally stabalize at is gonna be right near the
service ceiling of the combined lash up.

Just for grinn and giggles, check with NASA and see how high the
747/Shuttle piggyback arrangement cruises. 22K maybe?

And that would be balls to the wall, barely hanging in the air!

When the glider _starts_ to manouver, we goin' _down_. Fast.

Other than that, Mr. Lincoln, how was the play?

Richard

[pacplyer]

Richard Lamb > wrote

> Oh great! There goes my chance at getting hired!
>
>
> One thing I already know about is that the Cd increases (a lot)
> in the transonic range, and again (even more) for supersonic.
>
> Problem is, the drag bill gets paid before anything else does.
>
> So it's entirely likely that the 'zing' is gonna 'fizzle'...

Good One Richard. Sorta of a "dirty string," that's going to break in
half and wrap me up like a mummy? But wait, cranking into a turn's
going to put Mr Newton and his centrifugal force to work against that
drag, right?
>
> Still, it will be interesting to see what the cool guys say.
> (a little kissing up might keep them from laughing so hard?)
>
> Richard

Well I chickened out in sending it to him until we massage the numbers
a little more! But I'll email the thread link to him for comic relief
later tonight after I've had a couple beers! They're going to laugh
no matter what, but hey, If you can't be good: Be Colorful! (That was
Pete Conrad's battle cry, as I understand it, and he became the third
man on the moon.)

Anyway, My pal at scaled suggested what Bill D. did here: hang four GE
C90's on it. "But the wing is the thing," here as far as I am
concerned and it can do it at FL350. It's just a matter of Kevin
coming up with enough power. He's the steely-eyed jet engine man
here. If Big Fans can't cut it; then dammit, well mount some SRB's
between the inboards and the fuselage...

pac "don't wantta hear no more excuses" plyer

[Tim Ward]

"pacplyer" > wrote in message
om...
> "Tim Ward" > wrote in message <snips throughout
>...
>
> > No, viewed from the front, the "joined wing" looks like a big diamond.
It
> > attaches under the nose and at the top of the rudder. In the dismount,
the
> > front wing pivots down, away from the orbiter, around the rear attach
> > point -- which can just slide out backwards.
>
> Good. A single piece so that you can't get asymmetrical detachment.
> How would it be recovered I wonder? Remote fly down? probably it
> would flutter end over end until a chute deployed? Sorry but unlike
> gov ops this mission has to be profitable!

Spoilsport. If you want it to be profitable, you probably don't do manned
missions.
<snippage>
> >
> > With the payout winch, until you run out of line, the tension in the
line is
> > whatever the payout winch is set for.
>
> So you'd raise the payout winch tension up against max line tether
> strength just prior to the bank maneuver?
>
> >
> > Drag on the line: not only at the selected thickness, but there's a big
> > altitude difference as well. Fortunately, the thick end of the line is
up
> > where the air is thinner.
> > When you're doing the turning maneuver, the speed continuously varies
from
> > one end to the
> > It's non-linear with line length because of the caternary in the tow
line.
>
> Looks like this post got cut off. Could you elaborate some more on
> this for me? Talk more about "caternary" for me and the dynamics of
> this line.

Caternary is just the six dollar word for the sag in the line. It seems to
me calculating the drag on the line has a number of variables -- variation
of density with altitude, taper of the line, and probably other stuff I
don't know about. Then the vary the curve depending on the tension, and my
head spins.



Tim Ward

<snip>

[Felger Carbon]

"Richard Lamb" > wrote in message
...
>
> Other than that, Mr. Lincoln, how was the play?

If I wasn't dead, Richard, - I was assassinated just a few minutes
ago - I'd be happy to provide a short review. Why not ask my wife?
;-)

[Richard Lamb]

Tim Ward wrote:
>
>
> Caternary is just the six dollar word for the sag in the line. It seems to
> me calculating the drag on the line has a number of variables -- variation
> of density with altitude, taper of the line, and probably other stuff I
> don't know about. Then the vary the curve depending on the tension, and my
> head spins.
>
> Tim Ward
>

Which is exactly why all I tried to address was the portion
of the cable perpendicular to the slip stream.



Stick sharply forward, opposite rudder.
When the spin stops, recover from the dive... :)


Richard

[Richard Lamb]

pacplyer wrote:
>
> Richard Lamb > wrote
>
> > Oh great! There goes my chance at getting hired!
> >
> >
> > One thing I already know about is that the Cd increases (a lot)
> > in the transonic range, and again (even more) for supersonic.
> >
> > Problem is, the drag bill gets paid before anything else does.
> >
> > So it's entirely likely that the 'zing' is gonna 'fizzle'...
>
> Good One Richard. Sorta of a "dirty string," that's going to break in
> half and wrap me up like a mummy? But wait, cranking into a turn's
> going to put Mr Newton and his centrifugal force to work against that
> drag, right?

If the cable breaks, it could easily go _thru_ the airframe.
That's going to be one massive piece of 'string'.

As the toe-ee swings out and up, I think IT will feel an increaded
portion of of the cable drag. At least initially.

The cable will feel the added forces, but look where it's anchored.
Newton will definately have his way with the tow plane...



> > Still, it will be interesting to see what the cool guys say.
> > (a little kissing up might keep them from laughing so hard?)
> >
> > Richard
>
> Well I chickened out in sending it to him until we massage the numbers
> a little more! But I'll email the thread link to him for comic relief
> later tonight after I've had a couple beers! They're going to laugh
> no matter what, but hey, If you can't be good: Be Colorful! (That was
> Pete Conrad's battle cry, as I understand it, and he became the third
> man on the moon.)


Tell them, 'color me green' - with envy!


> Anyway, My pal at scaled suggested what Bill D. did here: hang four GE
> C90's on it. "But the wing is the thing," here as far as I am
> concerned and it can do it at FL350. It's just a matter of Kevin
> coming up with enough power. He's the steely-eyed jet engine man
> here. If Big Fans can't cut it; then dammit, well mount some SRB's
> between the inboards and the fuselage...
>
> pac "don't wantta hear no more excuses" plyer

Ok, I'll come around and try to help some (for a change).

Put the nose down (WAY down!) before the sling manouver starts.
Then wait for the 'colorful' language to commence!
Shouldn't take long.


Richard
(colorful enough?)

[Richard Lamb]

Felger Carbon wrote:
>
> "Richard Lamb" > wrote in message
> ...
> >
> > Other than that, Mr. Lincoln, how was the play?
>
> If I wasn't dead, Richard, - I was assassinated just a few minutes
> ago - I'd be happy to provide a short review. Why not ask my wife?
> ;-)

I think she had the good sense to stay on the ground for this one...

But I take your point. ;)


Richard

[anonymous coward]

On Tue, 29 Jun 2004 08:02:51 -0700, Tim Ward wrote:

>
> "Richard Lamb" > wrote in message
> ...
>> Sorry dude, I wasn't refering to the release itself.
>> Just the problems associated with _getting_ there.
>>
>> I'll refer you to Pacman's post (and conclusions) with the
>> gentle reminder that he _does_ know what he's talking about
>> as opposed to my questionable speculation).
>
> Sure. I never really thought a stock 747 would work for an idea as extreme
> as this one. I was actually thinking of a 747-sized canard design -- gets
> all the control surfaces out of the way, makes hooking to the CG easier --
> and so on. From Pac's information, it will probably have to have a lower
> wing loading and higher aspect ratio if we want it to tow at FL450.
>
>>
>> Also, Keith gave us some first hand info on what is actually
>> involved in tow ops - something I've never even tried to do.
>
> Oddly enough, I have. I aerotow my sailplane on weekends. I used to
> aerotow and ground launch hang gliders with both straight auto tow (long
> line with a tensionmeter), and the payout winch. Out at El Mirage dry lake,
> in the 80's, we got six thousand feet of line out one evening.
> That was just to see if we could do it. The sag in the line made the
> release altitude not as high as you might think. There were diminishing
> returns.
>
>>
>> PAWKI is a mean and evil term that stands for "Physics as we know it".
>>
>> Please don't be too upset with the 'ain't gonna work' mentality
>> you find here. The guys on this group are a different kind of
>> dreamer. Fantasy, with a hard dose of reality blended in.
>
> I'm not upset. But I do find it interesting that some posters have argued
> against concepts I never proposed: e.g. 8:1 speed ratios between the towed
> and towing aircraft.

Sorry if I was putting words into your mouth - I thought this was what you
meant by the 'whiplash' effect, and I was just trying to work it out in my
own mind.

> The use of a stock 747.
> Of course PAWKI limits the possible. Right now, we _know_ that it's
> possible to tow a smaller aircraft with a 747-sized aircraft. It's been
> done six times with a thousand foot tow line.
> That gives us one data point. What _are_ the limits imposed by PAWKI? I
> doubt that it's a tow line of 1001 feet. How high could you reasonably
> expect to get the towed vehicle on a CG to CG aerotow? How much advantage
> is that for a rocket launch? I don't know, but it's kind of interesting to
> speculate.

This is a question I've been asking myself too. My understanding is that
the primary problem in getting to space isn't flying high - it's flying
fast. Hence my assumption that you were looking to get a large dV from the
'whiplash' effect.

A few of the threads on Spacship One have said that the advantages of an
air-launch were to do with keeping the weight of the landing gear down,
and optimising the rocket engine to work at high-altitude rather than sea
level. There may be other things too - for example is skin-heating
more of a problem at low-altitude, or does reduced drag mean that you get
disproportionate gains in efficiency if you start at 100kf rather than sea
level?

I don't know the answers to these questions, but it seems to me that it
would be useful to answer them. For example, perhaps getting to 60,000
feet gives 90% of the advantage of getting to 100,000 feet. What would
the cost:benefit ratio be for different altitudes?

AC

>
> Tim Ward
>
>> You have to expect that attitude from people who actually BUILD
>> and FLY their own dreams.
>>
>> I once heard it said that we don't really build airplanes.
>> We build bridges - between dreams and reality.
>>
>> Well, I gotta go clean up my messy shop now.
>>
>> Later.
>>
>> Richard

[pacplyer]

Richard Lamb > wrote
>
> It won't help, Pac.
> The cable is not the problem.
>
> The only thing that counts is _excess_ thrust.
> That's what ever is left over after the airframe is straight and level.
>
> Then, there is the _second_ airframe! Strangely enough, at the same
> speed and altitude, the second ship will have perty near the same
> drag as the tow plane.
>
> A simple way to tell (real rough estimate) how high this rig can go
> might be to pull all four go levers back to half power.
> Whatever altitude you finally stabalize at is gonna be right near the
> service ceiling of the combined lash up.
>
> Just for grinn and giggles, check with NASA and see how high the
> 747/Shuttle piggyback arrangement cruises. 22K maybe?

Damn good ideas Richard.


>
> And that would be balls to the wall, barely hanging in the air!
>
> When the glider _starts_ to manouver, we goin' _down_. Fast.
>
> Other than that, Mr. Lincoln, how was the play?
>
> Richard



Sorry Richard my friend, but the show must go on!

Bones! Quick! Get over here and treat Mr Lincoln! You space actors
aren't getting out of this Ford Theater production this easily!

Actors! They drop the ball every time someone gets shot in the VIP
box…

John Wilks Booth is a drag, no doubt about it. But a huge drag may
not kill us yet…

Anyway I called a friend of mine at NASA. He's out on a motorcycle
trip to Alaska, but his wife works there as well and is going to try
to come up with some data, including talking to one of the 747-100
pilots there.

So before you guys bury this 747 towship thing under the sounds of
"TAPPS," somebody ought to check for a 21st century pulse.

Hey Tim and Richard, here's what my friend at Scaled said:



************************************************** ***************************

Most interesting. Hmmm....I wonder just how much drag a 10 mile tow
cable will create at Mach 1. Let's see Cd=1.0, Diameter = 0.5",
dynamic pressure at Mach 1 is somewhere between 69 psf at 50,000 ft
and 16 at 100,000 ft....call it average at 75,000 ft where it's 51 psf
and we get:

D = 50,000 * 0.5/12 * 51 * 1.0 = 106,250 lbs!

Not scientific but certainly within an order of magnitude or so. Need
to apply a little higher order calculus to narrow the uncertainty down
a bit.

Anyway, ya might just need (4) GE-90s on that 747--eh?

Do-able ? Yeah, Maybe!

************************************************** ******************************

in message >...
> pacplyer wrote:
> >
> >
> > However, before we abandon ship like the rest of the world, I think
> > maybe we're being too conservative on the drag figures. Tim
> > calculated a 24mm line which is 0.944882 Inches wide. So Richard
> > you need to recalculate your formula using numbers for a *one inch*
> > line instead.
> >
> > > pacplyer
> >
> > up periscope!, damn the torpedoes, full speed ahead! (you guys are
> > going to need big hangars to put all you're new toys in!) ;-)

[Tim Ward]

"pacplyer" > wrote in message
m...
<snippage>
> Hey Tim and Richard, here's what my friend at Scaled said:
>
>
>
>
************************************************** **************************
*
>
> Most interesting. Hmmm....I wonder just how much drag a 10 mile tow
> cable will create at Mach 1. Let's see Cd=1.0, Diameter = 0.5",
> dynamic pressure at Mach 1 is somewhere between 69 psf at 50,000 ft
> and 16 at 100,000 ft....call it average at 75,000 ft where it's 51 psf
> and we get:
>
> D = 50,000 * 0.5/12 * 51 * 1.0 = 106,250 lbs!
>
> Not scientific but certainly within an order of magnitude or so. Need
> to apply a little higher order calculus to narrow the uncertainty down
> a bit.
>
> Anyway, ya might just need (4) GE-90s on that 747--eh?
>
> Do-able ? Yeah, Maybe!
>
>
************************************************** **************************
****

Well, he certainly sounds optimistic on the size of the tow line! I was
figuring more than twice that thick, but of course that was for a commercial
12-strand braid.
A jacketed line instead of braid would probably be a little smaller, but I
can't see half the diameter.

Now you're talking about lowering the 747 altitude, which will increase the
drag even more.

The tow line has to carry _all_ the drag force as well as its own weight, so
between the weight and the drag, it's not clear that at breaking tension (or
braking tension, with the winch) we're going to have much residual force at
the high end of the line to apply to the spacecraft to overcome its drag.

Tim Ward

[Bill Daniels]

"Tim Ward" > wrote in message
...
>
> "pacplyer" > wrote in message
> m...
> <snippage>
> > Hey Tim and Richard, here's what my friend at Scaled said:
> >
> >
> >
> >
>
************************************************** **************************
> *
> >
> > Most interesting. Hmmm....I wonder just how much drag a 10 mile tow
> > cable will create at Mach 1. Let's see Cd=1.0, Diameter = 0.5",
> > dynamic pressure at Mach 1 is somewhere between 69 psf at 50,000 ft
> > and 16 at 100,000 ft....call it average at 75,000 ft where it's 51 psf
> > and we get:
> >
> > D = 50,000 * 0.5/12 * 51 * 1.0 = 106,250 lbs!
> >
> > Not scientific but certainly within an order of magnitude or so. Need
> > to apply a little higher order calculus to narrow the uncertainty down
> > a bit.
> >
> > Anyway, ya might just need (4) GE-90s on that 747--eh?
> >
> > Do-able ? Yeah, Maybe!
> >
> >
>
************************************************** **************************
> ****
>
> Well, he certainly sounds optimistic on the size of the tow line! I was
> figuring more than twice that thick, but of course that was for a
commercial
> 12-strand braid.
> A jacketed line instead of braid would probably be a little smaller, but I
> can't see half the diameter.
>
> Now you're talking about lowering the 747 altitude, which will increase
the
> drag even more.
>
> The tow line has to carry _all_ the drag force as well as its own weight,
so
> between the weight and the drag, it's not clear that at breaking tension
(or
> braking tension, with the winch) we're going to have much residual force
at
> the high end of the line to apply to the spacecraft to overcome its drag.
>
> Tim Ward
>
>
Take a look at the pull vector of the cable at the glider/spacecraft. The
weight of the cable and its drag will create a huge sag. The pull vector is
likely to be nearly straight down.

Winch launching gliders works very well but the height achieved is due to
the lift of the glider's highly efficient wings. If the spacecraft doesn't
have the L/D of a sailplane, this may not work as well as you think.

Bill Daniels

[Dillon Pyron]

On Mon, 12 Jul 2004 02:16:50 GMT, "Bill Daniels" >
wrote:

>
>"Tim Ward" > wrote in message
...
>>
>> "pacplyer" > wrote in message
>> m...
>> <snippage>
>> > Hey Tim and Richard, here's what my friend at Scaled said:
>> >
>> >
>> >
>> >
>>
>************************************************** **************************
>> *
>> >
>> > Most interesting. Hmmm....I wonder just how much drag a 10 mile tow
>> > cable will create at Mach 1. Let's see Cd=1.0, Diameter = 0.5",
>> > dynamic pressure at Mach 1 is somewhere between 69 psf at 50,000 ft
>> > and 16 at 100,000 ft....call it average at 75,000 ft where it's 51 psf
>> > and we get:
>> >
>> > D = 50,000 * 0.5/12 * 51 * 1.0 = 106,250 lbs!
>> >
>> > Not scientific but certainly within an order of magnitude or so. Need
>> > to apply a little higher order calculus to narrow the uncertainty down
>> > a bit.
>> >
>> > Anyway, ya might just need (4) GE-90s on that 747--eh?
>> >
>> > Do-able ? Yeah, Maybe!
>> >
>> >
>>
>************************************************** **************************
>> ****
>>
>> Well, he certainly sounds optimistic on the size of the tow line! I was
>> figuring more than twice that thick, but of course that was for a
>commercial
>> 12-strand braid.
>> A jacketed line instead of braid would probably be a little smaller, but I
>> can't see half the diameter.
>>
>> Now you're talking about lowering the 747 altitude, which will increase
>the
>> drag even more.
>>
>> The tow line has to carry _all_ the drag force as well as its own weight,
>so
>> between the weight and the drag, it's not clear that at breaking tension
>(or
>> braking tension, with the winch) we're going to have much residual force
>at
>> the high end of the line to apply to the spacecraft to overcome its drag.
>>
>> Tim Ward
>>
>>
>Take a look at the pull vector of the cable at the glider/spacecraft. The
>weight of the cable and its drag will create a huge sag. The pull vector is
>likely to be nearly straight down.
>
>Winch launching gliders works very well but the height achieved is due to
>the lift of the glider's highly efficient wings. If the spacecraft doesn't
>have the L/D of a sailplane, this may not work as well as you think.
>
>Bill Daniels
>

Well, one solution might be, as someone else has already suggested, to
have a two part vehicle. Part of it would be the actual space
vehicle, the other part a sailplane type configuration to get the
needed altitude. Let the sailplane glide home on it's own.

Plenty of holes in the theory, anybody care to put plugs in the Swiss
cheese or at least tell me what they are?

--
dillon

When I was a kid, I thought the angel's name was Hark
and the horse's name was Bob.

[Bill Daniels]

"Dillon Pyron" > wrote in message
...
> On Mon, 12 Jul 2004 02:16:50 GMT, "Bill Daniels" >
> wrote:
>
> >
> >"Tim Ward" > wrote in message
> ...
> >>
> >> "pacplyer" > wrote in message
> >> m...
> >> <snippage>
> >> > Hey Tim and Richard, here's what my friend at Scaled said:
> >> >
> >> >
> >> >
> >> >
> >>
>
>************************************************** *************************
*
> >> *
> >> >
> >> > Most interesting. Hmmm....I wonder just how much drag a 10 mile tow
> >> > cable will create at Mach 1. Let's see Cd=1.0, Diameter = 0.5",
> >> > dynamic pressure at Mach 1 is somewhere between 69 psf at 50,000 ft
> >> > and 16 at 100,000 ft....call it average at 75,000 ft where it's 51
psf
> >> > and we get:
> >> >
> >> > D = 50,000 * 0.5/12 * 51 * 1.0 = 106,250 lbs!
> >> >
> >> > Not scientific but certainly within an order of magnitude or so. Need
> >> > to apply a little higher order calculus to narrow the uncertainty
down
> >> > a bit.
> >> >
> >> > Anyway, ya might just need (4) GE-90s on that 747--eh?
> >> >
> >> > Do-able ? Yeah, Maybe!
> >> >
> >> >
> >>
>
>************************************************** *************************
*
> >> ****
> >>
> >> Well, he certainly sounds optimistic on the size of the tow line! I
was
> >> figuring more than twice that thick, but of course that was for a
> >commercial
> >> 12-strand braid.
> >> A jacketed line instead of braid would probably be a little smaller,
but I
> >> can't see half the diameter.
> >>
> >> Now you're talking about lowering the 747 altitude, which will increase
> >the
> >> drag even more.
> >>
> >> The tow line has to carry _all_ the drag force as well as its own
weight,
> >so
> >> between the weight and the drag, it's not clear that at breaking
tension
> >(or
> >> braking tension, with the winch) we're going to have much residual
force
> >at
> >> the high end of the line to apply to the spacecraft to overcome its
drag.
> >>
> >> Tim Ward
> >>
> >>
> >Take a look at the pull vector of the cable at the glider/spacecraft.
The
> >weight of the cable and its drag will create a huge sag. The pull vector
is
> >likely to be nearly straight down.
> >
> >Winch launching gliders works very well but the height achieved is due to
> >the lift of the glider's highly efficient wings. If the spacecraft
doesn't
> >have the L/D of a sailplane, this may not work as well as you think.
> >
> >Bill Daniels
> >
>
> Well, one solution might be, as someone else has already suggested, to
> have a two part vehicle. Part of it would be the actual space
> vehicle, the other part a sailplane type configuration to get the
> needed altitude. Let the sailplane glide home on it's own.

One problem with the glider carrier aircraft concept is that a sailplane
configuration has a low MMO - probably no more than .5 Mach. (Research the
Perlan high altitude pressurized sailplane project.) On the other hand, a
supersonic or transonic airframe will have a much lower L/D.

Another problem is that aeroelastic flutter is proportional to true airspeed
so the Vne, expressed as IAS, will be lower at extreme altitudes unless
strong measures are taken to contain flutter. High aspect ratio
sailplane-like wings are prone to flutter.

The idea still has merit if the payoff sought is merely altitude and you can
accept low speeds. The airtow/winch launch approach could get a booster to
70 - 80 thousand feet fairly cheaply by keeping the tow aircraft lower in
the atmosphere where the engines produce more thrust - and the towing TAS
can be kept low to match the needs of the sailplane carrier aircraft at high
altitude.

One need take care that the pull on the tow line doesn't upset the towing
aircraft. If the tow line is long enough, the sag will have the pull vector
at the tug nearly horizontal.

Notwithstanding the above, you probably wouldn't encounter any problems
finding glider pilots willing to take the ride.

All-in-all, I'm inclined to think that a flyback, air-breathing first stage
ala Scaled Composites "White Knight" is the best solution. There is no
reason to think that it couldn't deliver a second stage booster to the same
altitude and airspeed as the winch launch method could. It would be
operationally simpler too.

Bill Daniels

[Tim Ward]

"Bill Daniels" > wrote in message
news:o9oIc.58807$MB3.890@attbi_s04...

> One problem with the glider carrier aircraft concept is that a sailplane
> configuration has a low MMO - probably no more than .5 Mach. (Research
the
> Perlan high altitude pressurized sailplane project.) On the other hand, a
> supersonic or transonic airframe will have a much lower L/D.
>
> Another problem is that aeroelastic flutter is proportional to true
airspeed
> so the Vne, expressed as IAS, will be lower at extreme altitudes unless
> strong measures are taken to contain flutter. High aspect ratio
> sailplane-like wings are prone to flutter.

Yep. The conceptual idea currently being kicked around is a "joined wing",
where an aft-swept forward wing is joined at the tip by a forward-swept aft
wing. Structurally, this allows them to torsionally stabilize each other a
bit.

> The idea still has merit if the payoff sought is merely altitude and you
can
> accept low speeds. The airtow/winch launch approach could get a booster
to
> 70 - 80 thousand feet fairly cheaply by keeping the tow aircraft lower in
> the atmosphere where the engines produce more thrust - and the towing TAS
> can be kept low to match the needs of the sailplane carrier aircraft at
high
> altitude.

Yep, altitude before rocket ignition was the original idea.

> One need take care that the pull on the tow line doesn't upset the towing
> aircraft. If the tow line is long enough, the sag will have the pull
vector
> at the tug nearly horizontal.

Yep, that's why the tow line is attached near the CG of the towplane.

>
> Notwithstanding the above, you probably wouldn't encounter any problems
> finding glider pilots willing to take the ride.
>
> All-in-all, I'm inclined to think that a flyback, air-breathing first
stage
> ala Scaled Composites "White Knight" is the best solution. There is no
> reason to think that it couldn't deliver a second stage booster to the
same
> altitude and airspeed as the winch launch method could. It would be
> operationally simpler too.

> Bill Daniels

Tim Ward

[pacplyer]

"Tim Ward" > wrote
> Well, he certainly sounds optimistic on the size of the tow line! I was
> figuring more than twice that thick, but of course that was for a commercial
> 12-strand braid.
> A jacketed line instead of braid would probably be a little smaller, but I
> can't see half the diameter.
>
> Now you're talking about lowering the 747 altitude, which will increase the
> drag even more.

Yeah, I think maybe you're right. Good point Tim. My friend at
Scaled doesn't want to be down there either. Well, I used FL350 about
half for stock engine thrust considerations and half for my little
pink ass to have a nice wing margins at heavier weights. You gotta
remember that I see things from a conservative line pilot perspective,
and these guys are pushing new envelopes. Also I was trying to give
you max speed. Now that we are using not quite double the power with
GE-90's we may be able, in our hypothetical carrier towship model to
get up in a mated configuration to about 50,000 ft. according to my
pal at Scaled. Now that's outside the certified ceiling of the 747
airframe but these guys are not worried about that at all. Gulp. 8-/
Guess we'll have to raise the **** out of the cabin altitude (at
least keep a pressure differential of below 9.2 psi) At 9.4 psi diff,
there's a couple of man-hole sized overpressure relief circles on the
port side that will blow, so we gotta run in semi-auto or manual valve
mode, so we have to have a good engineer. Trust me; you don't want
this max diff to happen. Don't ask how I know. First blood runs out
of your ears; then it get real cold down there on the main deck aft of
the L-1 door. I mean reeeeeallllll cold.

So let's see where that demon lives.
Let's plan to operate at FL500 in a 30 degree bank so we can avoid
some line drag, and sling this puppy up to some partial speed before
disc and lightoff. Extrapolating up out of the top of my Buffet
Boundry table says I have to put this bird on an low-carb weight
reduction program and get it down to 400,000 lbs max in-flight weight
to sling the line. Now I think I know now why NASA uses a 747-100
airframe: Although it has smaller engines and it can't carry as much
on t/o, the structure is lighter weight; hence the BOW (basic op wt;
kinda like empty wt) is much lighter also at 323K. I figured a BOW on
the -200 airframe at 340k plus 40k in structural mods (horizontal
tailplane stabilizers and carry-through floor structure for a total
BOW "empty wt" of 380K) But it's clear that's just too much heavy
crap. So now I'll use the data for our old 747-132SF (ex Pam Am
bird.) We're going to have to pull the end of the tether from the
winch pallet sitting on the main deck through the ceiling , and just
tie the other end of the spool off around the titanium spar through a
hole in the floor near CG. We can loose some more weight by tearing
out the upper deck lav, galley, and supernumerary (hump) seats and
flooring. (Oh, the humanity!) We can ditch the APU in back (real
heavy,) the center tank, weather radar, about half the avionics, the
aux "tip" tanks, All the hot wing garbage, the jumpseats, and the
biggest weight savings of all: jettison all the paperwork! (Hey I
think I'm going to like this job after all!)

In flight weight at ‘slingshot' event is now:
BOW 323K
Winch pallet 20k
Fuel remaining 57k

Total in flight wt (sans OrbitOne) at FL500: 400K


Back to buffet speeds in a 30degree 1.15g bank: we're going to have
to hold 230kts IND/CAS plus or minus 4kts is as good a guess as any.
Forget about a 45 degree bank up here. Forget about top end speeds.
So a little flight test is in order unless Boeing has 1969 graphs on
this (which I bet they do.)

>
> The tow line has to carry _all_ the drag force as well as its own weight, so
> between the weight and the drag, it's not clear that at breaking tension (or
> braking tension, with the winch) we're going to have much residual force at
> the high end of the line to apply to the spacecraft to overcome its drag.
>
> Tim Ward

So we wouldn't shed the 200 ft swing wing glider "diamond" till the
last second before we start slingshot-ing; since it's kiting almost
*ALL*? the weight of the near vertical portion of the line? Right?
And is the line drag number split between the two ships?

Line drag's a lot less at FL500. Thrust is 110K, lbs x 4 = 440K (at
sea level :-) I wonder if Kevin Horton can give me max thrust in lbs
in the high 40's for a GE C-90 engine?

This whole thing reminds me of water skiing when I was a kid, and
finding myself at incredible speeds near-even with the driver in a
turn.

pacplyer

[Dillon Pyron]

On Mon, 12 Jul 2004 04:08:52 GMT, "Bill Daniels" >
wrote:

>
>"Dillon Pyron" > wrote in message
...
>> On Mon, 12 Jul 2004 02:16:50 GMT, "Bill Daniels" >
>> wrote:
>>
>> >
>> >"Tim Ward" > wrote in message
>> ...
>> >>
>> >> "pacplyer" > wrote in message
>> >> m...
>> >> <snippage>
>> >> > Hey Tim and Richard, here's what my friend at Scaled said:
<snippage>.
>
>One problem with the glider carrier aircraft concept is that a sailplane
>configuration has a low MMO - probably no more than .5 Mach. (Research the
>Perlan high altitude pressurized sailplane project.) On the other hand, a
>supersonic or transonic airframe will have a much lower L/D.
>
>Another problem is that aeroelastic flutter is proportional to true airspeed
>so the Vne, expressed as IAS, will be lower at extreme altitudes unless
>strong measures are taken to contain flutter. High aspect ratio
>sailplane-like wings are prone to flutter.
>
>The idea still has merit if the payoff sought is merely altitude and you can
>accept low speeds. The airtow/winch launch approach could get a booster to
>70 - 80 thousand feet fairly cheaply by keeping the tow aircraft lower in
>the atmosphere where the engines produce more thrust - and the towing TAS
>can be kept low to match the needs of the sailplane carrier aircraft at high
>altitude.
>
>One need take care that the pull on the tow line doesn't upset the towing
>aircraft. If the tow line is long enough, the sag will have the pull vector
>at the tug nearly horizontal.
>
>Notwithstanding the above, you probably wouldn't encounter any problems
>finding glider pilots willing to take the ride.
>
>All-in-all, I'm inclined to think that a flyback, air-breathing first stage
>ala Scaled Composites "White Knight" is the best solution. There is no
>reason to think that it couldn't deliver a second stage booster to the same
>altitude and airspeed as the winch launch method could. It would be
>operationally simpler too.

Simple? Who said we were looking for simple? We want something
complex to stimulate our brains. It doesn't have to work, although
we'll likely all pay to see someone else try it. :-)

>
>Bill Daniels

--
dillon

When I was a kid, I thought the angel's name was Hark
and the horse's name was Bob.

[Bill Daniels]

"Dillon Pyron" > wrote in message
...
> >All-in-all, I'm inclined to think that a flyback, air-breathing first
stage
> >ala Scaled Composites "White Knight" is the best solution. There is no
> >reason to think that it couldn't deliver a second stage booster to the
same
> >altitude and airspeed as the winch launch method could. It would be
> >operationally simpler too.
>
> Simple? Who said we were looking for simple? We want something
> complex to stimulate our brains. It doesn't have to work, although
> we'll likely all pay to see someone else try it. :-)

> dillon

Why not visit the nearest glider operation launching gliders with a winch
and get a ride. It's not a space launch but it will feel like one.

Bill Daniels

[pacplyer]

Good post Bill.

"Bill Daniels" > wrote <snip>

> One problem with the glider carrier aircraft concept is that a sailplane
> configuration has a low MMO - probably no more than .5 Mach. (Research the
> Perlan high altitude pressurized sailplane project.) On the other hand, a
> supersonic or transonic airframe will have a much lower L/D.

Well, in the magic kingdom of drafting tables and simulators, we can
keep that 200 ft glider wing (100 per side) swept until the 747 tow
ship levels at FL500 straight and level, puts out flaps 10
electrically (since it's outside the 20,000 ft hydro flap limitation,)
slows to 150kts CAS/IND (a wag of just above VsFo 10 stall at altitude
since I can't find that chart,) and releases the still semi-swept
OrbitOne+glider wing assembly "cocoon" vehicle along it's tether line.
OrbitOne+glider then ‘unsweeps' going into high aspect ratio mode
pulling up with authority to avoid exceeding Vne/MMo of say .5 Mach.
The payout winch will spit out enough line to make up for the
difference in speed of the two vehicles. Then at when OrbitOne
reaches > FL750, OrbitOne sheds its glider cocoon, and 747Towship goes
into a 30 degree bank to achieve max slingshot speed before
intentional release or line failure, whichever occurs first! Then,
OrbitOne lights the candle for Orbital Insertion.

There, I feel better. Burt and shareholders split up the 15 million
dollar profit.

Then we all live happily ever after.

>
> Another problem is that aeroelastic flutter is proportional to true airspeed
> so the Vne, expressed as IAS, will be lower at extreme altitudes unless
> strong measures are taken to contain flutter. High aspect ratio
> sailplane-like wings are prone to flutter.
>
> The idea still has merit if the payoff sought is merely altitude and you can
> accept low speeds. The airtow/winch launch approach could get a booster to
> 70 - 80 thousand feet fairly cheaply by keeping the tow aircraft lower in
> the atmosphere where the engines produce more thrust - and the towing TAS
> can be kept low to match the needs of the sailplane carrier aircraft at high
> altitude.

Exactly.

>
> One need take care that the pull on the tow line doesn't upset the towing
> aircraft. If the tow line is long enough, the sag will have the pull vector
> at the tug nearly horizontal.

Man, you're full of all kinds of good news. So the Russian AN-124
with dual tails may be better suited to prevent cable/tail fouling
after all.

>
> Notwithstanding the above, you probably wouldn't encounter any problems
> finding glider pilots willing to take the ride.
>
> All-in-all, I'm inclined to think that a flyback, air-breathing first stage
> ala Scaled Composites "White Knight" is the best solution. There is no
> reason to think that it couldn't deliver a second stage booster to the same
> altitude and airspeed as the winch launch method could. It would be
> operationally simpler too.
>
> Bill Daniels

You're probably right Bill. But "Big Fans" and "smooth bores" that
I'm familiar with, piddle out in the 40's – Low 50's even at the low
transport weights were talking about here. So I'm not sure how you
would deliver a second stage booster to the same altitude and airspeed
as the winch method could. Unless you built a massive U-2 ("Black
Knight"?) with ten U-2 turbojet engines (as opposed to high-bypass
turbofan engines) designed for those altitudes? I'm not sure you'd
have large money-making payload capabilities beyond the carrier ship
though since the air's so thin. Even though you have plenty of excess
thrust to get up there with your Black Knight/OrbitOne combo, the
wing's operating in a five knot speed range empty. Even a little
weight increase beyond the empty weight, pilot and fuel of the carrier
may exceed buffet boundries at 75,000ft and put you into a Gary Powers
high dive. Incidentally, he was not shot down. They were shooting at
him, but he panicked and broke out of the five knot range . The
tumble flamed out the engine. After he recovered much lower, but not
low enough to be in the relight envelope, the battery on the ADI was
only good for three minutes at the time, he knew it, and tried to get
out of Russian airspace. Three minutes later, right on schedule, the
battery croaked, the ADI (attitude directional indicator) went "tits
up" along with his nav, so all he had was airspeed and the sun on his
wingtip for directional reference to try and get back to friendly real
estate. But he was concentrating so much on the wingtip that he
punched through VNE and tore the tail off, and... the rest is history.

(Another old roommate who flew tst for most of his career told me the
U-2 is the hardest plane he's ever flown.) That's the beauty of
having a towship down in the thicker air. Omitting the heavy engines
at FL750 can equate to more second stage oxidizer for Orbit riding on
the same size wing. That's assuming we don't tear our line apart from
all the drag. Feel free to argue for a Black Knight type solution
though, since, as you correctly pointed out: it is a lot simpler!

BTW hope you guys enjoyed my "fictional" U-2 story above.

pacplyer

[Morgans]

"pacplyer" > wrote

> And is the line drag number split between the two ships?

Nope, I would think the tow ship will have the drag of the horizontal
portion of the line, with the tow ship and kite sharing the vertical part.
Trick is, once the zoom/slingshot occurs, the kite wil start picking up more
drag, as more of the line goes vertical, and more weight, to pick up the
line from horizontal.
>

> This whole thing reminds me of water skiing when I was a kid, and
> finding myself at incredible speeds near-even with the driver in a
> turn.
>
> pacplyer

Zactly. But you gotta hate the broke ribs, when you catch a tip and fall
broadside, into the waves, at that speed. DAMHIK!
--
Jim in NC


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[Tim Ward]

"pacplyer" > wrote in message
om...
<snippage>
> So we wouldn't shed the 200 ft swing wing glider "diamond" till the
> last second before we start slingshot-ing; since it's kiting almost
> *ALL*? the weight of the near vertical portion of the line? Right?
> And is the line drag number split between the two ships?

I think the joined wing would have a redline, and as you approached this,
you'd have to release and fire the rocket (or the reverse). The towed
aircraft can control its airspeed somewhat by turning nearer (slow down) or
away from (speed up) the towplane.

The 747 has to handle all the drag because it has all the power. That
includes the drag of the towed vehicle.

The towed vehicle has to handle the weight of the towline, because it and
the towline are above the 747, and it's really hard to push with a rope.

If the towed vehicle isn't seeing the towline as thrust, then the exercise
is pointless.

In the case where the towline is not doing anything (there's just enough
tension to balance the weight and drag of the towline), the line should be
vertical at the towed vehicle (if it was forward it would be adding thrust,
and if it was backward, it would be adding drag), and horizontal at the
towplane (if it was above horizontal, there's more tension in the line than
necessary to overcome its weight, and if it's below horizontal, there's not
enough tension.

> Line drag's a lot less at FL500. Thrust is 110K, lbs x 4 = 440K (at
> sea level :-) I wonder if Kevin Horton can give me max thrust in lbs
> in the high 40's for a GE C-90 engine?
>
> This whole thing reminds me of water skiing when I was a kid, and
> finding myself at incredible speeds near-even with the driver in a
> turn.

I never skiied behind a boat, but there was this thing called the "Cable
Skiway".
They had a cable up in the air, running in a square around four pulleys,
that they could drive at 25 mph or so. The cable had bumps swaged onto it
at regular intervals. You'd sit on their little dock, at one corner of the
square canal that ran beneath the cable, and they'd drop a fork attached to
a towline over the cable, and when the next bump came along, BANG! you were
going 25 mph too.

I managed to stay up after a couple of tries, and then I came to the first
corner. The pulleys were about two feet in diameter. Instead of staying on
the outside of the turn, I cut the corner. So the towline has to go out to
the pulley, and around it, of course... a much longer path than I was
taking, so the line went slack and I slowed down. As I slowed, I sank.
Finally the towline got back out in front of me, and once again, BANG! I was
going 25mph. But the skis were about eighteen inches under water at that
point. I held on to the towline, and I got jerked completely out of the
water. The skis didn't. Well, there didn't seem to be much point to being
dragged through the water without skis, so I let go. I did make it all the
way around, though. Eventually.


> pacplyer

Tim Ward

[Morgans]

"pacplyer" > wrote

If the tow line is long enough, the sag will have the pull vector
> > at the tug nearly horizontal.
>
> Man, you're full of all kinds of good news. So the Russian AN-124
> with dual tails may be better suited to prevent cable/tail fouling
> after all.
>
> pacplyer

I figured on a split tail, all along. Need more tail for stability, anyway,
for when orbit 1 is piggyback, plus when slingshot starts, we want plenty of
positive yaw margin, as the line starts jerking the tow plane all over the
sky. Spins suck, and plenty of rudder will help to pick up that low wing.

That's the beauty, though. We can slap bigger engines on, and chop tail off
and make separate tails, cause the whole thing is going to be
EXPERIMENTAL!!! All we gotta do is convince the FAA that the thing is
airworthy, then go play.

Can we sacrifice a little weight on the tow, and put a section of the roof
with explosive chord, and some ejection seats? I think I might want to
leave with my jumpseat, if things head the wrong way! <g>
--
Jim in NC


---
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[pacplyer]

"Morgans" > wrote
> I figured on a split tail, all along. Need more tail for stability, anyway,
> for when orbit 1 is piggyback, plus when slingshot starts, we want plenty of
> positive yaw margin, as the line starts jerking the tow plane all over the
> sky. Spins suck, and plenty of rudder will help to pick up that low wing.
>
> That's the beauty, though. We can slap bigger engines on, and chop tail off
> and make separate tails, cause the whole thing is going to be
> EXPERIMENTAL!!! All we gotta do is convince the FAA that the thing is
> airworthy, then go play.
>
> Can we sacrifice a little weight on the tow, and put a section of the roof
> with explosive chord, and some ejection seats? I think I might want to
> leave with my jumpseat, if things head the wrong way! <g>

No.

I threw your jumpseat out to get the weight down to 400K! You're now
sitting on the floor strapped down with some lightweight plastic
Rosary beads, freezing to death since we stripped out all the
insulation and heating ducts. An ejection seat wouldn't help you
anyway since you couldn't pull the handles up with your frozen hands.
Looks like you'll have to stick with the PIC (and he always goes down
with the ship!) <g>

Besides, I kinda get a warm fuzzy having the designers ride along with
me. Years ago, the USAF was experiencing a bad rash of KC-135
accidents attributable to sloppy maintenance. The Wing Commander's
answer to this was to require the crew chief signing off the work to
ride in the aircraft for at least two legs. The maintenance problems
immediately disappeared!

pac "ride em on in to the ground" plyer

[pacplyer]

"Tim Ward" > wrote
> <snippage>
>
> The 747 has to handle all the drag because it has all the power. That
> includes the drag of the towed vehicle.
>
> The towed vehicle has to handle the weight of the towline, because it and
> the towline are above the 747, and it's really hard to push with a rope.
>
> If the towed vehicle isn't seeing the towline as thrust, then the exercise
> is pointless.

pac then stumbles around these numbers:

SSS - Space Sling Shot feasibility wags using a ONE INCH line:

(devil's advocates get one free beer for each correction substantiated
by some sort of rough data.
Nanotube rope discoverer gets free Johnny Walker Blue – 60year old
Scotch)

I. Subsonic Line Operation FL750.

Vectran towrope Assumptions:

Length: 10sm's long or 52,800 ft
Dia: One in or 24mm
Avrg. Tensile strength: 200,000 lbs?
Cd 1.0
1" Line Drag at.82M: 143,333lbs (D = 50,000*1.0/12*34.4*1.0=143.333)
Deployed 10sm Wt: 54.4lbs/100ft. +28,723lbs (52,800/100(54.4)= 28,723)
Total tension on the 1" line: 172,056? (line sees its wt plus drag
wt?)
Allowable Space Vehicle Drag: 27,944 (derived from 200,000 limit)

Thrust Assumptions:
6 GE C90s:

Thrust at S.L: 110,000 lbs * 6 engs = 660,000 total thrust at
S.L.
Thrust at FL500 (1/4 of S.L va.): 165,000 lbs

Thrust at dismount: 165,000
Line Drag at Mach .82 -143,333
Residual thrust available for vehicles 21,667
Thrust needed for 747 only -40,000 (whoops shortfall of 20k here!)
Available for OrbitOne vehicle none: (I think we need 747
SRB's)



II. Supersonic Line Operation at FL750:

Vectran towrope Assumptions:

1" Line Drag at Mach 1: 212,499 lbs (D = 50,000 * 1.0/12 * 51 * 1.0 =
106,250 lbs)

Thrust Assumptions:
GE C90s:

Thrust at S.L: 110,000 lbs * 6 engs = 660,000 total thrust at
S.L.
Thrust at FL500 (1/4 of S.L.): 165,000 lbs

Thrust at dismount: 165,000
1" Line Drag at Mach 1.0: -212,499
Residual thrust available for vehicles Mayday, Mayday, Mayday!
Thrust needed for 747 only: -40,000
Available for OrbitOne vehicle: Forget it, can't even fly the 1" line
by itself at mach 1.0

Note: Towship is a stripped-down 747-132SF. These supersonic line
calcs are for 10-15 seconds only in 30 degree towship bank.
You may have noticed I had to hang six GE C90 engines on this thing.
(maybe we'll have to call the Russians on this, they built one right?)

Conclusion: This Vectran Boat Rope just isn't going to cut it. To
overcome 10sm drag at Mach numbers I feel like we can not exceed a
half inch line. The one inch line weighs about 28,000lbs on the
glider assymbly and produces 143,333 lbs of drag in M.82 flight *just
for the line*. Richard Lamb was right: "He's dead Jim, dead Jim,
dead."

So I guess we would have augered in with a stock 747-200.
As Clint Eastwood used to say: "A man's just gotta-know his
limitations."

pacplyer

p.s. fun exercise though, I'll rework the numbers with a half inch
line of unobtainium on the following post.

[Richard Lamb]

pacplyer wrote:
>
> Richard Lamb was right: "He's dead Jim, dead Jim,
> dead."
>
> So I guess we would have augered in with a stock 747-200.
> As Clint Eastwood used to say: "A man's just gotta-know his
> limitations."
>
> pacplyer
>

Not THAT'S something that doesn't happen every day!


The problem here is that the 747 was designed to LIFT stuff, not
pull it.

How about let's get a fresh napkin and work out what's really needed
for the job?

Richard

[pacplyer]

Senerio #2 Optimum:

SSS - Space Sling Shot feasibility wags with A HALF INCH LINE


Unobtainium towrope Assumptions:

I. Subsonic Line Operations at FL750.

Length: 10sm's long or 52,800 ft
Dia: .5 in or 12mm
Avrg. Tensile strength: Needs to be 200,000 lbs. not Vectran's
24,500lbs!

Cd 1.0
Line Drag at .82 Mach clb: 71,667 (D = 50,000 * 0.5/12 * 34.4 * 1.0
= 71666.6 lbs)
Deployed Wt: 7.7lbs/100ft. 4065 lbs (Vectan #'s) (52,800/100=528,
528(7.7)=4065.6

Thrust Assumptions:
6 GE C90s:

Thrust at S.L: 110,000 lbs * 6 engs = 660,000 total thrust at
S.L.
Thrust at FL500 (1/4 of S.L.): 165,000 lbs

Thrust at dismount: 165,000
Line Drag at Mach .82 -71,667
Residual thrust available for vehicles 93,333
Thrust needed for 747 only -40,000
Available for OrbitOne vehicle 53,333 lbs thrust

Hmmmmmm, this looks very Do-able.



II. Supersonic Line Operation at FL750:

Line Drag at Mach 1: 106,250 lbs (D = 50,000 * 0.5/12 * 51 * 1.0 =
106,250 lbs)

6 GE C90s:

Thrust at S.L: 110,000 lbs * 6 engs = 660,000 total thrust at S.L.
Thrust at FL500 (1/4 of S.L.):165,000 lbs

Thrust at dismount: 165,000
Line Drag at Mach 1.0: -106,250
Residual thrust available for vehicles 58,750
Total 747 thrust need: -40,000
Available for OrbitOne vehicle: 18,750

Hmmmmm, just do-able.

Note: Towship is a stripped-down 747-132SF. These supersonic line
calcs are for 10-15 seconds only in 30 degree towship bank.

Summary: We need some newer technology tether material that allows us
to weave it into a half inch thickness (so that line drag is
reasonable.) We need to stay with a six engine 747 if we're going to
do the slingshot maneuver. A twin tail might get fouled since the
tether is attached to the tugship CG near the main wing stations.
Durring bank the OrbitOne is going to pitch out to the side with the
line taunt. Right? So turn must be made opposite side that tether
runs by tail.

This drag bill Richard warned us about is a ****er!

pac

[pacplyer]

Richard Lamb > wrote in message >...
> pacplyer wrote:
> >
> > Richard Lamb was right: "He's dead Jim, dead Jim,
> > dead."
> >
> > So I guess we would have augered in with a stock 747-200.
> > As Clint Eastwood used to say: "A man's just gotta-know his
> > limitations."
> >
> > pacplyer
> >
>
> Not THAT'S something that doesn't happen every day!
>
>
> The problem here is that the 747 was designed to LIFT stuff, not
> pull it.

True enough. Even the NASA carrier transport, is a misapplication of
the original design. What's attractive is that 747's are plentifully
available and rather cheap compared to the cost of engineering a whole
new machine of that size, or plunking down 20mil each launch over at
Vandenberg. Buying an old 747-100 for 30 million and re-engining for
another 60mil breaks even in about five launches. Also Burt and Co.
could focus more on building the Orbiter itself. My guess is Burt may
wind up building a massive "Black Knight" in the next couple of years
(but what's that going to cost?) He could use the existing White
Knight Cockpit design, but if he uses the same type of construction,
the thing might be bigger than the Voyager! The 747 is about 199
lbs/ft wing loading IIRC. It has a massive Titanium spar that can do
amazing lifting feats: and that's initially what we are after, to lift
the thing to FL500. Turning it into a towplane after we get up there
has never been done before, and that's why we will get bragging rights
and free launch passes when it is done. ;-)

One thing is for sure: the ability to escape all the costs and weight
of the conventional first stage renting a government facility is the
name of the game here. It costs Burt virtually NOTHING to use Mojave,
since it is a public airport with no landing fees.

>
> How about let's get a fresh napkin and work out what's really needed
> for the job?
>
> Richard

I was just doing a super wag (wild ass guess) exercise to convince
myself that it was worth further inquiry. I think my friend at
Scaled is right though. We cannot exceed a half inch average line
width or we're doomed. In my mind we need to find something that
average width that has a 200,000lb tensile strength. So Richard,
here's a new stack of napkins, all I ask is that you explain the math
to me. :-) Meanwhile, I'm on a search for unobtanium tether cable.

pac

[Tim Ward]

"pacplyer" > wrote in message
om...

> SSS - Space Sling Shot feasibility wags using a ONE INCH line:
>
> (devil's advocates get one free beer for each correction substantiated
> by some sort of rough data.
> Nanotube rope discoverer gets free Johnny Walker Blue - 60year old
> Scotch)
>
> I. Subsonic Line Operation FL750.
>
> Vectran towrope Assumptions:
>
> Length: 10sm's long or 52,800 ft
> Dia: One in or 24mm
> Avrg. Tensile strength: 200,000 lbs?
> Cd 1.0
> 1" Line Drag at.82M: 143,333lbs (D = 50,000*1.0/12*34.4*1.0=143.333)
> Deployed 10sm Wt: 54.4lbs/100ft. +28,723lbs (52,800/100(54.4)= 28,723)
> Total tension on the 1" line: 172,056? (line sees its wt plus drag
> wt?)
> Allowable Space Vehicle Drag: 27,944 (derived from 200,000 limit)
>
> Thrust Assumptions:
> 6 GE C90s:
>
> Thrust at S.L: 110,000 lbs * 6 engs = 660,000 total thrust at
> S.L.
> Thrust at FL500 (1/4 of S.L va.): 165,000 lbs
>
> Thrust at dismount: 165,000
> Line Drag at Mach .82 -143,333
> Residual thrust available for vehicles 21,667
> Thrust needed for 747 only -40,000 (whoops shortfall of 20k here!)
> Available for OrbitOne vehicle none: (I think we need 747
> SRB's)

<snip supersonic stuff>
> Note: Towship is a stripped-down 747-132SF. These supersonic line
> calcs are for 10-15 seconds only in 30 degree towship bank.
> You may have noticed I had to hang six GE C90 engines on this thing.
> (maybe we'll have to call the Russians on this, they built one right?)
>
> Conclusion: This Vectran Boat Rope just isn't going to cut it. To
> overcome 10sm drag at Mach numbers I feel like we can not exceed a
> half inch line. The one inch line weighs about 28,000lbs on the
> glider assymbly and produces 143,333 lbs of drag in M.82 flight *just
> for the line*. Richard Lamb was right: "He's dead Jim, dead Jim,
> dead."
>
> So I guess we would have augered in with a stock 747-200.
> As Clint Eastwood used to say: "A man's just gotta-know his
> limitations."
>
> pacplyer

It may not be as bad as we think.
On page 138 of Warner and Johnston's "Aviation Handbook" I came across a
graph of "Effect of inclining wires into wind". And so I did a little more
sophisticated drag analysis by pulling numbers from that place which such
numbers are usually pulled from.
I divided the line into 8 sections, and decided arbitrarily, that the first
line section was at 10 degrees, the 2nd at 20 degrees, and so on, up to the
eighth, which was at 80 degrees.
The graph shows the percentage of the maximum drag for the wire vs the wire
inclination
So,
10 .05
20 .1
30 .2
40 .35
50 .5
60 .7
70 .85
80 .9
Sum 3.46
Now, each of those segments is only 1/8 of the total line drag, so divide
that total by 8, and the drag is only about .46 of the previously
calculated "worst case". That lowers the drag for the one inch cable down
to 66000 pounds. There being no free lunch, with this particular sag
schedule, we only get about 65% of the line length as altitude, so the towed
vehicle is only about 34000 feet higher than the towplane.

With yet more sophisticated analysis, the drag might get better yet. The
high drag parts of the line are up where the air is a little thinner.

Tim Ward

[pacplyer]

"Tim Ward" > wrote in message >...
> "pacplyer" > wrote in message
> om...
>
> > SSS - Space Sling Shot feasibility wags using a ONE INCH line:
> >
> > (devil's advocates get one free beer for each correction substantiated
> > by some sort of rough data.
> > Nanotube rope discoverer gets free Johnny Walker Blue - 60year old
> > Scotch)
> >
> > I. Subsonic Line Operation FL750.
> >
> > Vectran towrope Assumptions:
> >
> > Length: 10sm's long or 52,800 ft
> > Dia: One in or 24mm
> > Avrg. Tensile strength: 200,000 lbs?
> > Cd 1.0
> > 1" Line Drag at.82M: 143,333lbs (D = 50,000*1.0/12*34.4*1.0=143.333)
> > Deployed 10sm Wt: 54.4lbs/100ft. +28,723lbs (52,800/100(54.4)= 28,723)
> > Total tension on the 1" line: 172,056? (line sees its wt plus drag
> > wt?)
> > Allowable Space Vehicle Drag: 27,944 (derived from 200,000 limit)
> >
> > Thrust Assumptions:
> > 6 GE C90s:
> >
> > Thrust at S.L: 110,000 lbs * 6 engs = 660,000 total thrust at
> > S.L.
> > Thrust at FL500 (1/4 of S.L va.): 165,000 lbs
> >
> > Thrust at dismount: 165,000
> > Line Drag at Mach .82 -143,333
> > Residual thrust available for vehicles 21,667
> > Thrust needed for 747 only -40,000 (whoops shortfall of 20k here!)
> > Available for OrbitOne vehicle none: (I think we need 747
> > SRB's)
>
> <snip supersonic stuff>
> > Note: Towship is a stripped-down 747-132SF. These supersonic line
> > calcs are for 10-15 seconds only in 30 degree towship bank.
> > You may have noticed I had to hang six GE C90 engines on this thing.
> > (maybe we'll have to call the Russians on this, they built one right?)
> >
> > Conclusion: This Vectran Boat Rope just isn't going to cut it. To
> > overcome 10sm drag at Mach numbers I feel like we can not exceed a
> > half inch line. The one inch line weighs about 28,000lbs on the
> > glider assymbly and produces 143,333 lbs of drag in M.82 flight *just
> > for the line*. Richard Lamb was right: "He's dead Jim, dead Jim,
> > dead."
> >
> > So I guess we would have augered in with a stock 747-200.
> > As Clint Eastwood used to say: "A man's just gotta-know his
> > limitations."
> >
> > pacplyer
>
> It may not be as bad as we think.
> On page 138 of Warner and Johnston's "Aviation Handbook" I came across a
> graph of "Effect of inclining wires into wind". And so I did a little more
> sophisticated drag analysis by pulling numbers from that place which such
> numbers are usually pulled from.
> I divided the line into 8 sections, and decided arbitrarily, that the first
> line section was at 10 degrees, the 2nd at 20 degrees, and so on, up to the
> eighth, which was at 80 degrees.
> The graph shows the percentage of the maximum drag for the wire vs the wire
> inclination
> So,
> 10 .05
> 20 .1
> 30 .2
> 40 .35
> 50 .5
> 60 .7
> 70 .85
> 80 .9
> Sum 3.46
> Now, each of those segments is only 1/8 of the total line drag, so divide
> that total by 8, and the drag is only about .46 of the previously
> calculated "worst case". That lowers the drag for the one inch cable down
> to 66000 pounds. There being no free lunch, with this particular sag
> schedule, we only get about 65% of the line length as altitude, so the towed
> vehicle is only about 34000 feet higher than the towplane.

That's 84,000 ft at "Slingshot" maneuver. I'll take it! That's a
free cold one for you for this fine bit of cocktail napkin work.

>
> With yet more sophisticated analysis, the drag might get better yet. The
> high drag parts of the line are up where the air is a little thinner.
>
> Tim Ward

Good post Tim. I didn't want to half to hang six: ten million dollar
motors on the tugplane anyway! Four is do-able. Six means major
headaches with new pylon engineering... ugghh.

Talked to my NASA friend last night. She's heavy into a project at
work right now, but says she'll get me some answers on max altitude
for the Shuttle transport and hopefully some drag figures. Gotta
remember that NASA doen't like the latest turn of manned flying
events. SS1 made em' look kinda bad!

pac

[Dillon Pyron]

On 17 Jul 2004 14:45:30 -0700, (pacplyer) wrote:

>"Tim Ward" > wrote in message >...
>> "pacplyer" > wrote in message
>> om...
<snip>
>
>Talked to my NASA friend last night. She's heavy into a project at
>work right now, but says she'll get me some answers on max altitude
>for the Shuttle transport and hopefully some drag figures. Gotta
>remember that NASA doen't like the latest turn of manned flying
>events. SS1 made em' look kinda bad!
>
>pac
Well, no kidding. They've been sitting on DCX for years, until 18
months ago thought the Shuttle was the "be all, end all" and had no
real goals beyond Fred.

Now people are asking what they are getting for their billions when a
bunch of amateur airplane builders can get into space (ignoring for a
moment just how "amateur" Scaled really is, but you get the point).
--
dillon

When I was a kid, I thought the angel's name was Hark
and the horse's name was Bob.