starship-design: Staged Fusion Power

["N. Lindberg" <nlindber@u.washington.edu>]

	I was reading some of the numbers for the various engines that
could be used to power a starship, and I noticed that every fusion
reaction shown only used its fuel once.  If a closed powerplant (not
rocket) could be run hot enough, there's no reason I can see not to run
the fuel up to heavier elements instead of just throwing it away after it
turns to helium. Note:  I didn't do any math for this one, it might be
impractical.  Although I realize that a scheme like this would require
reactors far superior to a today's can't-quite-ignite tokamaks, it might
be doable in fifty years. The power from this type of reactor could be
used to power a laser or ion drive, the latter prehaps adding the
reactor exhaust to the Xenon reaction mass. 
	The upshot is, exhaust recycling could reduce the amount of fuel
required by which is one of the major hurdles of starflight.  
Best Regards,
Nels Lindberg