>helium 3 Breakeven D-T fusion has never been demonstrated, at any scale. ITER won't even attempt D-T fusion until 2035, and then you need to figure out how to

>helium 3 Breakeven D-T fusion has never been demonstrated, at any scale. ITER won't even attempt D-T fusion until 2035, and then you need to figure out how to scale the reactor down until it doesn't cost $50 billion and 50 years to build, and also increase the collision energy until it can actually do D-He3 fusion, or even higher, true aneutronic He3-He3 fusion. Yes, yes, Stellarator, Polywell. Neither have been built. Or you can just do solar and batteries. Which exist today. >space based solar Tom Arnold did the best post on SBS back in 2012: https://dothemath.ucsd.edu/2012/03/space-based-solar-power/ https://dothemath.ucsd.edu/2012/03/space-based-solar-power/ Depending on what downlink power density you're willing to tolerate, how big of a transmit dish you can assemble in orbit, and how big of a receive array you want to build on the ground, you only get maybe four times the power density of the sunlight falling on the ground taken up by the rectenna array. Awful lot of work to go to just to get four times more power per square meter on the ground. And if you've got the room for a rectenna array 4 km across for SBS, you might want to just build a regular terrestrial solar array 8km across instead, and save a few dozen billion dollars in launch costs.