Space Elevator

(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

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

"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

"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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"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

"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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"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

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?

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.

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

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.

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