BALL!
[!0.987]2015-12-25

Whatever happened to that plan of mining helium three on the moon?

It was never really practical.

Half the Deuterium-deuterium reactions produce helium three as a byproduct. Helium three requires a higher temperature to fuse, so very little gets consumed in the plasma. It's easier to make helium three than it is to mine it. Are you ready to throw the ball again?

I expect this is the kind of conversation someone would have if they ever went water skiing with Einstein.

Color by George Peterson

Indeed, the D-D reaction has a cross-section only slightly smaller than the D-He reaction³. If the second can be ignited  -it will not be difficult to start the first one as well. In the meantime, our as yet unreached goal is the D-T reaction. (KALDYH)
Perhaps this strip is a reference to the film Iron Sky(namely/keywords -mining for helium-3 on the moon).
Or to a film Moon (There's also the same amount of emotion expressed by the robot as there is by Clippy).