🚀 go-pugleaf

In article <HAGERMAN.92Jul20182314@rx7.ece.cmu.edu>,
hagerman@ece.cmu.edu (John Hagerman) writes:
|>In article <76248@ut-emx.uucp> johncobb@ut-emx.cc.utexas.edu (John W.
Cobb) writes:
|>>
|>> Now for fusion you've got to go even
|>> further. Imagine trying to load a TOKAMAK into a spaceship. It's mass
|>> is huge {...}

|>How about using inertial confinement?  What are the heavy components?
|>
Capacitor banks. Look at some of the big Laser systems. They aren't light.
I'm out of my league here (but not as far out as my comments on solar
sailing --- how embarrasing) so maybe people have addressed these issues.
Moreover, the focussing has to be very precise or you don't get ignition.
Imagine trying to damp-out mechanical vibrations on a space ship over
the integrate light path over all optical elements. One usual way is to
add mass and dampers. Well you don't want to just add mass willy-nilly
for a spaceship.

There is another idea that uses lasers. I believe it came out of Livermore
a decade or so ago. The idea is to use ground based lasers. Focus them on
an ablative underbelly of a space-craft and use the thrust generated for
manuevering and perhaps even orbit lifting. The beauty is that your
power source never has to be launched. The difficulty is that you have to
track your craft, focus your beam, and penetrate the atmosphere. The fact 
that you would even consider such a scheme indicates how important it is
to decrease powerplant mass on these high specific impulse systems.

john w. cobb
jwc@fusion.ph.utexas.edu