Id answer this in 2 ways: First. Let's say we have a trillion people in space stations/multiple planets. Fusion is a energy source that can plausibly power th

Id answer this in 2 ways: First. Let's say we have a trillion people in space stations/multiple planets. Fusion is a energy source that can plausibly power them. Second. fission works close to other sources, but is so hampered by regulation that it hasn't gotten to be affordable. This may be fixed in the future. micro-reactors solve the biggest economy of scale issues and a renewed bipartisan interest in nuclear could help it be politically viable. If fission works in theory, fusion definitely works in theory (as the energy output is much higher).