Rui lost track of time as he grew immersed in fleshing out the theoretical frameworks of the two projects. The many possibilities that existed with Project Muspelheim were, in particular, difficult to parse through.
"Friction is not a bad idea for a heating technique."
In fact, friction was the reason that all mechanical processes yielded heat. It was an extremely natural source of heat and, in some mechanical processes, produced so much heat that extra cooling units needed to be put in place just to ensure that friction did not cause them all to melt.
Back on Earth, in recognition of how great a source of heat it was, there even existed welding methods known as friction welding that used the tremendous heat that friction could generate to heat up two objects and weld them together. It was especially used for metals that had high melting points and was an efficient way of getting them to weld.