Space Elevator

"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

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/businesstechnol..._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.

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

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

"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) he
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

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.

"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.

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/businesstechnol..._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.

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

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.