🚀 go-pugleaf

In article <C0Jv2M.74z.1@cs.cmu.edu> rcs@cs.arizona.edu (Richard Schroeppel) writes:

> Since fusing protons is so hard, why not use deuterons?
> They fuse at a lower temperature, and the reaction only
> requires regrouping the nucleons, rather than invoking the
> weak force to transmute p->n.  The Earth's d/p ratio is ~.0001.
> Perhaps the ramscoop collector could selectively enrich d,
> by selecting for atoms having a magnetic moment.


Or, better yet, why fuse anything at all?  One can do the following:
decelerate the incoming material a bit producing some power.  Now,
accelerate some on-board reaction mass using this power, so that the
two streams are now at the same speed.

Done properly, the thrust from the second part exceeds the drag from
the first part.  The decelerated interstellar material needn't even be
laterally compressed.

This scheme seems counterintuitive, but it violates conservation of
neither energy nor momentum.  The kinetic energy of the vehicle
does not increase with time, it only gets concentrated in less
and less mass.

All these schemes suffer because the local ISM is so damned thin.  The
solar system appears to lie inside a bubble of very thin, hot gas,
perhaps the result of some "recent" supernovae in our neighborhood.

	Paul F. Dietz
	dietz@cs.rochester.edu