There's no mystery to producing thrust with microwaves. Photons have a momentum of E/c, so if you make photons with a power P and send them in one direction, yo

There's no mystery to producing thrust with microwaves. Photons have a momentum of E/c, so if you make photons with a power P and send them in one direction, you'll get a thrust of P/c. I think the issue is that they claim to a) not emit anything, and b) claim many orders of magnitude more thrust than could be achieved by just emitting photons.