Could not agree more. (Well in this case the problem is solvable unlike cryogenics or turning sand into fuel). Btw, the Feynman story you referred to is from "Surely, you're Joking, Mr. Feynman", interesting stories about Feynman's adventures: "One guy in a uniform came to me and told me that the army was glad that physicists were
advising the military because it had a lot of problems. One of the problems was that tanks use up
their fuel very quickly and thus can't go very far. So the question was how to refuel them as they're
going along. Now this guy had the idea that, since the physicists can get energy out of uranium,
could I work out a way in which we could use silicon dioxide--sand, dirt--as a fuel? If that were
possible, then all this tank would have to do would be to have a little scoop underneath, and as it
goes along, it would pick up the dirt and use it for fuel! He thought that was a great idea, and that
all I had to do was to work out the details. That was the kind of problem I thought we would be
talking about in the meeting the next day. "