Nuclear, or if you want space stuff, build a station at the Lagrange point and sling from there? I don’t need to be an expert in launch solutions to know that we shouldn’t speculate mining the moon till it’s well researched and that we have more accessible options here for the forseeable future with solar as my choice of example, so let’s not jump the gun on another finite resource?
I am referring to commercial speculation, and I literally laid this out in the second sentence, thanks!