Non-paywall version, direct from NASA: [1] [ http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/2014001... ] It's a neat idea. It's really a pulsed fission reactor, pumped by a fusion stage that's below breakeven but produces a lot of neutrons that can ignite fission. It runs on U-238, depleted uranium, which won't fission by itself but can be pumped into fissioning. This is somewhat similar to the process that occ…
Is the proposed use of Tritium practical in terms of supply? It's very expensive to produce.
Also, there are significant impacts on space-borne science observation missions from nuclear reactors in space [1]. It would be a shame if the outcome was to render large sections of space opaque to observatories.
[1] http://www.calpoly.edu/~dhafemei/SciAm_June_1991_NuclearPowe...