Space Elevator

"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.