Start here: https://en.wikipedia.org/wiki/Aneutronic_fusion https://en.wikipedia.org/wiki/Aneutronic_fusion (TLDR version: proton-boron fusion is a less energe

Start here: https://en.wikipedia.org/wiki/Aneutronic_fusion https://en.wikipedia.org/wiki/Aneutronic_fusion (TLDR version: proton-boron fusion is a less energetically efficient alternative to 3He fusion, but with the howlingly significant advantage that boron -- the fuel -- is lying around in heaps and drifts on Earth, rather than being so exotic a substance that annual global production is measured in single-digit kilograms and a significant energy economy would require mining it from the Lunar regolith. It's not as well-known as 3He fusion, though, because the space cadets don't see the point -- there are no Moon colonies required. Advantages of 3He or B + p fusion over D-T fusion: it doesn't produce a surplus of neutrons, so there's less radioactive waste created as a by-product of the process.)