"Tim Ward" wrote

I dunno, but this seems as good a time as any to bring up a stupid,
complicated idea of mine for access to space.

First, you should be familiar with the Kelly Aerospace idea of towing the
spaceship to altitude. If not, Google for "Eclipse project", NASA, and
perhaps F106.

They towed an idling F106 behind a C141 as a proof of concept project.

Second, you should be aware of the "payout winches" used to ground launch
hang gliders. These just pay the line out at a constant tension, rather
than reeling them in at a high rate of speed, as in sailplane launches.

So here's the scheme:
You build a tow plane about the size of a 747. The payout winch is mounted
such that it "pays out" from the CG of the airplane, on top. You have
somewhere around 100,000 lbs of Vectran tow rope (several tens of
kilometers) on the payout device. This is within the cargo capability of a
747, though you may want to throw on a couple of extra engines because of
the additional drag.

Pac sez:
I like this idea. A 747-200F can carry 250,000 lbs of fuel and 250,000
of cargo at the same time. But at that weight 820,000 lbs it could
only make ~FL280. It would have to leave most of the gas behind: no
sweat there. Since it burns a rough average of 25,000 lbs an hour a
t/o fuel load could be as low as around ~50,000lbs of fuel for
twenty-nine minutes of ascent plus return and skinny reserves so, you
would have good rate of climb to the service ceiling of FL450 (45,000
ft.) The combined tow weight of OrbitOne plus fuel and Colonauts
could be easily be greater than 200,000 lbs if all your tow apparatus
could handle it. So figure a total Mojave t/o weight of ~650,000lbs.
These numbers are off the top of my head, I could look up the exact
ones if you want me to. Don't know if this would be cheaper than a
Vandenberg launch, but Rutan would control it all, and stay away from
gov turd interference. **** I like it. You should email this idea to
Scaled Composites Tim. Bet you a nickle Burt is already considering
it. Evergreen in Oregon is already using 74's for fire fighting.
This might be the next great role for that old queen of the sky.

pacplyer


The spacecraft has a CG hook on the bottom.

You take off, and climb as high as you can, while paying out the tow line.
The spacecraft pilot basically controls the pay out. Pitch up, and a little
more line pays out. Pitch down, and it stops.

If the spacecraft can maintain a 45 degree angle behind the towplane, it
will be 70% of the towrope's length higher than the towplane.

At some point, the true airspeed of the tow plane will not provide enough
airspeed for the spacecraft to continue to climb. So the towplane starts to
turn, and the spacecraft maneuvers to the outside of the turn. Now it's
just like playing "crack the whip". The air-breathing booster is down in
the (relatively speaking) thick atmosphere at 50,000 feet, while the
spacecraft is above most of the atmosphere at say, 100,000 feet.

That's when the spacecraft releases and fires its rockets.
Because the atmosphere is so much thinner, and the spacecraft is going
faster than it would be at lower altitudes, the increase in peak altitude
achievable should be much higher than just the 50,000 ft altitude difference
between the tow plane and the spacecraft.

After the spacecraft releases, the towplane also releases the towline, and
it descends under a parachute, separately.

There, I feel better.

Tim Ward

p.s. I wonder what Dr. "Moonraker" (Ron W.) thinks of this idea? Too
revolutionary? Not expensive enough? ;-)

pac