RF resonant cavity thruster

An RF resonant cavity thruster is a proposed new type of electromagnetic thruster. Unlike conventional electromagnetic thrusters, they are designed to use no reaction mass, and to emit no directional radiation. Their design principles seem to be not scientific, because they violate the fundamental law of momentum conservation.A few variations on such thrusters have been proposed. Aerospace engineer Roger Shawyer designed the EmDrive in 2001, and has persistently promoted the idea since then through his company, Satellite Propulsion Research.Chemical engineer Guido Fetta designed the Cannae Drive, based on similar principles. If they were found to work as claimed, providing thrust without consuming a propellant would have important applications to all areas of propulsion, from spacecraft to other vehicles.A few independent teams of physicists, notably a team at Xi'an's Northwestern Polytechnical University (NWPU), one at NASA's Eagleworks laboratories, and another at the Dresden University of Technology in Germany, have built prototypes of these designs. Some of their tests have tentatively observed a small net thrust from those prototypes. A small thrust has also been observed in devices deliberately built to not produce thrust. This experimental work has been published in university journals, conference proceedings, and some local Chinese peer-reviewed journals. Research is in progress to see if these effects are caused by some as-yet-unknown phenomenon, or artifacts due to experimental error, particularly because the observed results are small, and there are otherwise no compelling explanations for the apparent violation of the law of conservation of momentum. Claims of such a surprising result would need especially thorough efforts to rule out sources of error.