(I-am-not-an-aerospace-engineer) I was thinking the fundamental difference would come from viewing rocket vs prop from the mass perspective you outlined in your

(I-am-not-an-aerospace-engineer) I was thinking the fundamental difference would come from viewing rocket vs prop from the mass perspective you outlined in your previous comment. In a rocket, and also in the various derivatives of a jet engine, forward thrust is generated by the expansion and acceleration of mass away from you. Either fuel + oxidizer in the former, or fuel + compressed air taken from the atmosphere in the latter. And the corresponding effect of that fuel+ acceleration on your mass. In a prop, forward thrust is generated by linking a powerplant to a blade that interacts with air. The exhaust mass from the powerplant burning fuel in this isn't directly connected to the forward thrust. In that, if you had a non-propeller method of propulsion, you could hook the powerplant to that and still have effectively the same system.