As for fusion reactors on airplanes, I just wonder about the amount of lead that has to surround a reactor to keep the x-ray from coming out. That is going to be a lot of weight, I would think. Eric would have the answers, but if you look at the schematics for a FF reactor, you have cooling, transformers, all sorts of stuff that have to be accounted for. You could make a lot of stuff from lightweight materials, but… I just can’t see it.