EmDrive

The EmDrive is a proposed microwave resonant cavity thruster, a device that its inventor, British engineer Roger Shawyer, claimed in 2001 could generate thrust without expelling any propellant, making it what is called a reactionless drive. Because this claim would violate the conservation of momentum and other fundamental laws of physics, physicists and engineers have generally regarded the EmDrive concept as pseudoscience. Rigorous independent testing, most notably by Martin Tajmar's group at the Dresden University of Technology, concluded in 2021 that its measurements refuted all EmDrive thrust claims by at least three orders of magnitude, showing that the small effects earlier experimenters observed were fully explained by thermal expansion and electromagnetic interference rather than any real propulsion.