Exactly! AFAICT, the trickiest unknown is maintaining plasma stability and not degrading the insides (and then, breaking even on power while doing so.) Wendelst

Exactly! AFAICT, the trickiest unknown is maintaining plasma stability and not degrading the insides (and then, breaking even on power while doing so.) Wendelstein seems to be on track to steady-state operation; they've held plasma for 100s, and their graphite shielding seems to be delivering cleaner plasma streams. The design for the 7-X wasn't feasible until supercomputers got powerful enough. We know how to run those simulations; fusion should get more practical as computers get faster.