Space Elevator

"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

"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

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

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

"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

"Tim Ward" wrote in message ...
"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.

That's 84,000 ft at "Slingshot" maneuver. I'll take it! That's a
free cold one for you for this fine bit of cocktail napkin work.


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

Good post Tim. I didn't want to half to hang six: ten million dollar
motors on the tugplane anyway! Four is do-able. Six means major
headaches with new pylon engineering... ugghh.

Talked to my NASA friend last night. She's heavy into a project at
work right now, but says she'll get me some answers on max altitude
for the Shuttle transport and hopefully some drag figures. Gotta
remember that NASA doen't like the latest turn of manned flying
events. SS1 made em' look kinda bad!

pac

On 17 Jul 2004 14:45:30 -0700, (pacplyer) wrote:

"Tim Ward" wrote in message ...
"pacplyer" wrote in message
om...
snip

Talked to my NASA friend last night. She's heavy into a project at
work right now, but says she'll get me some answers on max altitude
for the Shuttle transport and hopefully some drag figures. Gotta
remember that NASA doen't like the latest turn of manned flying
events. SS1 made em' look kinda bad!

pac
Well, no kidding. They've been sitting on DCX for years, until 18
months ago thought the Shuttle was the "be all, end all" and had no
real goals beyond Fred.

Now people are asking what they are getting for their billions when a
bunch of amateur airplane builders can get into space (ignoring for a
moment just how "amateur" Scaled really is, but you get the point).
--
dillon

When I was a kid, I thought the angel's name was Hark
and the horse's name was Bob.