The concept applies to propulsion system operating at a theoretical impulse, with hydrogen, as high as 2200 seconds at a high thrust to power ratio. Microwave energy used to dissociate a continuously flowing gas is transferred to the propellant via three-body-recombination for conversion to kinetic energy. Power absorption by the microwave plasma discharge was in excess of 90 percent over a range of pressures. Gas temperatures showed higher temperatures from microwave heating than from electrothermal heating.