Discussion on answer by Rory Alsop: Why don't aircraft use nuclear propulsion?

Christoph

11:51

@RoryAlsop "On a submarine, that's okay - weight can be dealt with" in fact a lot of weight is necessary for a submarine. You want some empty space in it for you know the crew and stuff. So in order to get an average density of around 1 g/cm^3 (so you can actually go under water) you need a lot of materials with a high density.