after meditating on what’s been gleaned and slopped into the wikipedia article,
http://en.wikipedia.org/wiki/VASIMR#Research_and_development
i’m thinking i may have overestimated the refrigeration requirements for the magnets, by as much as a factor of 8. so with four engines, that reduces the coolant problem to only 16 times too much. :-/
ideas:
liquid N2 maybe gives a bit more head room, there?
further progress on high Tc superconductors?
make use of a thermal mass, (such as solid CF4 or propane?) and pulse the thing?
