Geoff Landis has a paper out on novel approaches to space solar power systems.

One of the reasons I’m skeptical of lunar He3 for fusion as a viable space based business is the competition from SPS. If you can put enough infrastructure on the moon to process the enormous quantities of regolith needed to extract He3, you can just as easily churn out huge numbers of SPS satellites. Unless there is some unforseen showstopper with SPS (and the only one I can think of is possible long term environmental effects due to the microwave beam, but that seems unlikely), then SPS construction will win over He3 fusion. We can do SPS with current technology. We’re not even close to being able to do fusion with He3, and we won’t be for probably two decades. That’s just fusing the He3, not doing it cheaply enough to compete with other power sources.

I’m slowly churning through a detailed piece on fusion which will hopefully clarify a lot of these issues, but I’m a having trouble making the piece not suck, so don’t hold your breath. Hopefully I’ll get unstuck soon.