"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