4 ms·

Depends on your definition of vastly, and superior but: Uranium-235 (fission) ~80,000,000 MJ/kg 1× Coal ~24 MJ/kg ~3.3 million× less Oil ~42 MJ/kg

• ben_w 1y ago
  1. The part I was responding to was in comparison "to every other form of green energy". None of those other things you list are green energy, and your numbers are incorrect for space purposes anyway as they don't include the mass of the oxygen. 2. Energy-density-vs-mass is relevant for the rocket equation when you burn it as a fuel (and, optionally, use as reaction mass), but not vs. PV where you don't burn it and lose it. e.g. ion drives, magnetic sails of various kinds, launch loops/space elevators and similar, space stations/bases/almost all planetary industry (which can be PV powered), nor solar sails which directly use the momentum of light (usually the sun's nearly isotropic emission, but in a grand space empire anywhere from here to K2 all bar the entropy losses can be pumped into a single direction by lasers).