One of the pleasant side-effects of the unpleasant fact that the US pulled out of the nuclear non-proliferation treaties is that NASA is now free to restart research into nuclear thermal rockets. For those not familiar with the concept, a lightweight gas (helium or hydrogen) gets passed through a "combustion chamber" which doesn't combust anything. Instead of oxodizer and fuel getting burnt to raise it to high temperatures and pressures, it merely sucks the heat out of a nuclear reactor and gets accelerated through a standard converging/diverging nozzle. The main upside is that nuclear rocket motors provide two to three times as much thrust as conventional rockets, enabling much faster transit times. Another plus is the capability to siphon off heat which can be converted to electricity, providing the potential for large missions to the outer planets where solar cells don't cut it. What does everyone think about the possibility of us building one of these? It's a nuclear reactor, and the guys at NASA would be the ones flying it... still, the potentials are huge if all goes well.