SCOTT@GACVAX1.BITNET (Scott Hess) (04/04/89)
What with all of the speculation on this new cold-fusion, I was thinking
of its applications to space. Beyond using it for power while in orbit,
and on the ground, I was wondering on ways to use it in launching. I can
think of a bunch of ways: atomic ramjets, launching tracks (accelerate it
up to escape velocity, and let it go), vertical launching tracks (same idea,
but tracks pointing up instead of horizontally - requires alot more
acceleration), one of those solid elevator things from Arthur C. Clarke's
"Fountains of Paridise". One device I've read about in Jerry Pournelle's
"High Justice" used lasers. It seems that a powerful ground-based laser
is fired into a cavity at the bottom of the spacecraft. It is pulsed on
and off, at a high speed. The cavity is vented in such a way that it draws
in air. The laser heats the air very quickly, so the air pushes out the
bottom, propelling the craft. Then more air is brought in ... Basically
a ramjet with half the engine ground-based. I believe that I read elsewhere
that Pournelle is on an advisory commitee to the president, and the original
proposal for SDI called for large ground-based lasers, and orbiting mirrors.
Besides being simpler and easier to maintain, this setup could be used with
the above scheme to launch.
My basic question is this: Does this work? I think that an upward force
can be exerted, but is it enough? This only can work where there is enough
atmosphere, so it would have to be able to aquire a pretty good acceleration.
In the book it seems the acceleration was 10G, for about 30s. I don't know
if that's enough. Also, unmanned pods got something like 30G. This seems
a bit high, to me.
Scott Hess,
<Scott@gacvax1.bitnet>
henry@utzoo.uucp (Henry Spencer) (04/04/89)
In article <Added.sYBzIGy00UkT8Q409X@andrew.cmu.edu> SCOTT@GACVAX1.BITNET (Scott Hess) writes: >... One device I've read about in Jerry Pournelle's >"High Justice" used lasers. It seems that a powerful ground-based laser >is fired into a cavity at the bottom of the spacecraft. It is pulsed on >and off, at a high speed. The cavity is vented in such a way that it draws >in air. The laser heats the air very quickly, so the air pushes out the >bottom, propelling the craft. Then more air is brought in ... Basically >a ramjet with half the engine ground-based... >My basic question is this: Does this work? ... In principle it ought to, although arranging for the laser to heat the centimeters of air in the cavity but *not* the kilometers of air in the rest of the beam path is a bit tricky. The US has a small research program on laser launchers, although they're currently focusing on rockets rather than air-breathing systems. It is hoped that SDI will develop the necessary lasers and optics. It looks both feasible and promising. In particular, with short-pulse lasers, it scales down well. Launching capsules weighing tons takes formidable power sources and lasers, but if you're willing to settle for something smaller, the system (and its budget) gets much more manageable. -- Welcome to Mars! Your | Henry Spencer at U of Toronto Zoology passport and visa, comrade? | uunet!attcan!utzoo!henry henry@zoo.toronto.edu