But but but!...
IF we were able to get all that He3, we’d have to do *something* with it!
Until controlled fusion is demonstrated (and I’m fairly sure it won’t be), there’s no reason to bring back He3. Depending on the actual yield, it will probably remain uneconomical to fetch it from the Moon using chemical propulsion, and in fact, as we move into methane/reformer fuel cell technology for electrical power generation and get the methane from the hydrates and clathrates on the sea floor, fusion research is likely to become more and more a tough sell.