Space Elevator

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

"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


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.716 / Virus Database: 472 - Release Date: 7/5/2004

"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

"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


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.716 / Virus Database: 472 - Release Date: 7/6/2004

"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

"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.

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

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

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 su 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

"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