Question: Would nuclear engines be a good idea for now or the future, possibly like one of the main robots in the film Pacific Rim?

Ellen Gill answered on 16 Jun 2016:

Nuclear fission reactors would be completely impractical for pacific rim sized robots. We currently use small fission reactors to power submarines, but size vs. output is a real limiting factor. Nuclear *fusion* on the other hand has potential. Unfortunately we don’t have fusion at the point where we can use it to generate power but I sincerely hope we get to see awesome giant fighting robots in our lifetimes, or at the very least, everyone realises that Pacific Rim was better than Transformers.