Thread:IceBite/@comment-2001921-20120922211421

Hi! I have become aware of a planned fusion/helium fission system for starships. I am guessing this is based on hydrogen fusion (4p to He-4) and then the fission of the produced helium.

Unfortunately, fission of helium requires far more energy than it releases in binding energy. The principle of fission is to release the binding energy of the nucleus by subdividing a larger nucleus into smaller parts. To initiate it, you take large nuclei and hit them with high-energy neutrons. Naturally, this only works with certain elements, as they're the only ones which can self-sustain fission by releasing their own neutrons as a fission byproduct. You know their names :P

Elements lighter than iron release energy than they require by fusion, and those heavier than iron would release less energy than they require by fusion. Vice versa for fission.

Hope that helps :) 