Here's a new and interesting design for a nuclear reactor which I've never seen before: http://www.rbsp.info/rbs/RbS/PDF/aiaa05.pdf [Broken] It's harvesting the kinetic energy of fission fragments via magnetic fields, converting it directly into electrical energy. They say that past obstacles over heat build-up are addressed by having the fuel as a dusty plasma, which has high enough surface area to alleviate heat build-up through thermionic emission. I wonder if this could somehow be adapted to a nuclear rocket design? Perhaps instead of the magnetic fields converting the fission fragment kinetic energy into electricity, the magnetic fields could instead somehow directly transfer the kinetic energy of the fission fragments to a propellant flowstream. If you create a perturbation in a magnetic field, is it possible to have it propagate to something else also in that field? If you have these fission fragments shooting through a magnetic field, can their kinetic energy be transposed onto other objects (particles) via that magnetic field? If so, then I wonder what the conversion efficiency would be? I've also read about conjectured fission-fusion hybrid designs, and presumably they too would benefit from some mechanism to directly convert the fission fragment kinetic energy more into kinetic energy of hydrogen for fusion purposes.