The long and the short of it is bouncing microwaves around in a specially shaped closed container produces thrust in a particular direction. About .15 grams of thrust per kilowatt pumped in.
Is there anything radio waves can’t do?
I’m not sure about the conversion — Isn’t 1.2 millinewtons about 0.0012 grams of thrust? Or have I got the units wrong?
I heard it uses a cone. If you had two cones opposed to each other, then if you shot microwaves into one and the second would act as a collector to channel the reflected energy (the reaction ) back to the main gun.