Sorry for the previous empty post. My "expand quote" button and my "Send" button are VERY close to one another . . . .

Anyway . . .

I was just reading the wikipedia article on resonant cavity thrusters. While the inventors math does seem to be "hogwash" (he apparently over-simplified a complex formula), there appears to be a couple of things that could be going on which end up not violating known physics. The one I found most interesting was the possibility that the thruster is pushing against a localized plasma-like state of the quantum vacuum. The article acknowledges that (for most practical purposes) quantum vacuum can be treated as [literally] "nothing is there," in certain conditions and for certain durations it definitely has structure.

I read elsewhere that there are physicists which want to call quantum vacuum "ether," but this term has too many negative connotations for modern scientists.

So . . . could it be possible that we've actually invented the "ether propeller" from Space: 1889? :)