Abstract: A thruster system for use in a spacecraft includes a microwave source, a resonant cavity coupled to the microwave source, wherein the microwave source is configured to generate a standing wave field in the resonant cavity, a nozzle provided at one end of the resonant cavity; and at least one injector configured to inject propellant into the resonant cavity so as to create a rotating circumferential flow. The standing wave field raises a temperature of the injected propellant to provide thrust by way of a hot gas exiting the resonant cavity via the nozzle.