Gun launched orbital systems

From: jeff davis (
Date: Sun Oct 21 2001 - 04:21:34 MDT

The threads "BIOTERRORISM: Our heads in the sand...",
and "Humans doomed without space colonies, says
Hawking" give birth to this one.

A google search for babylon gun, from the
"BIOTERRORISM" thread gives



wherein we find launch costs estimated at $600/Kg (in
1990 dollars) for a 200 kg payload. I
believe--someone care to confirm?--that this is
substantially cheaper than than current launch costs
using conventional, ie multistage rockets, methods.

It would seem to me that for any payload capable of
withstanding the rigors of such a launch method--bulk
payloads of food, water, fuel, and building materials
immediately come to mind--the economic advantages of
gun launch present a striking commercial opportunity.
Additionally, and logically, for anyone interested in
more human activity in space, a dual-mode launch
strategy, based on the complementarity of gun and
rocket launch methods, would seem a promising means to
that end.

So I have to ask, "Where's the problem?. Why hasn't
anyone done this?"

Also, sometime back I read that the PV solar panels
for the Internation Space Station generate 65 kw and
cost $500,000,000. Now I can't verify the accuracy of
that number--I no longer remember where I read it--but
I recall thinking that half a billion dollars for 65
kw seemed a bit much, and it got me to thinking about
low-tech power generation in space. Specifically, I
envisioned, as the basis for such a system, a
parabolic dish made of minimum thickness styrofoam
and coated with a film of appropriate reflective

For comparison purposes, at 10% conversion efficiency,
and 1300 watts/sq meter, you can get 65 kw out of a
dish a mere 13m in radius. (And a dish of 100m radius
delivers a healthy 4 mega watts.)

Two immediate obsevations. Weightlessness would seem
to allow an EXTREMELY large dish, and the hard vacuum
of space seems to suggest that the reflective surface
would not be subject to oxidative degradation.

As to size, anyone care to suggest how big is too big
and why?

I envision the dish as spin stabilized to keep it
pointed at the sun, with steam generator, and dual,
counter-rotating turbine/generator units axially
mounted, and the waste heat radiator located in the
shadow behind the dish.

I have a nifty little idea for the design of that
radiator. A conical 'balloon', perhaps
stiffened/stabilized with an axial mast, into which
the exhaust steam is vented. As it condenses, the
spin of the system will send the droplets toward the
inner surface of the balloon where the 'slope' will
cause the liquid to flow back to the rim of the dish
for reinjection to the steam generator.

My engineering background always makes low-tech and
cheap more appealing than high-tech and expensive.

Maybe I'm just talking out my asteroid, but hey, I'm
havin' fun.

Ball's in your court.

Best, Jeff Davis

     "Everything's hard till you know how to do it."
                        Ray Charles

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