quantum rocket motor: thrust without propellant

smellsofbikes writes: New Scientist is reporting a motor designed by aeronautical engineer Roger Shawyer, that fires microwave radiation into closed, conic tubes, yielding thrust with no emissions whatsoever, not even radiation, relying on unequal force distribution within the conic section. He reports current incarnations produce thrust similar to solar wind but proposed supercooled varieties would yield orders of magnitude more. Spacecraft wouldn't have to carry any propellant, just solar cells. Can this possibly work?