VLSI%DEC-MARLBORO@sri-unix.UUCP (07/06/83)
Someone mentioned David Brin's book "Sundiver" a while back. I read
it and liked it, but am a little unsure of the physics behind it.
Perhaps someone here can say if his machinery would work.
The premise is that people have built a ship to go exploring the sun.
To do this Brin had to think of some way to keep the ship from vaporizing. If a
refrigeration system keeps some area cooler than its environment, it has
to make some other area hotter. The heat removed from the ship's hull
has to go somewhere. Ordinary radiators wouldn't work, because they
would have to be hotter than the 6000 degree plasma outside in order
to dissipate the heat. They would instantly vaporize, and you would back
where you were. The heat could be dumped into some fluid that would
then be ejected from the ship (this is how rocket combustion chambers
keep from burning up), but whatever put the heat into the fluid would
again have to be hotter than the outside.
Brin's solution is to dump the excess heat into an X-ray laser
(xaser?). The laser beams the energy out through the surrounding gas.
A blackbody that emitted its peak energy in the x-rays would have a
temperature in the millions of degrees. The laser, then, is 'hotter'
then the surroundings and so can radiate to them.
This sounds kind of plausible, but my thermodynamics isn't solid enough to
be sure. Can you really cool things off by making them lase? The book has a
lot of other nice ideas (eg. in order to join the galactic federation a species
has to bring another species to sentience. Intelligent chimpanzees and
dolphins figure into the plot.), but I'm not too sure of its physics.
John Redford
DEC Hudson
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