Dean Drive

The Dean drive was a mechanical device built and promoted by American engineer Norman Lorimer Dean, who lived from 1902 to 1972, and which gained wide publicity during the 1950s and 1960s as a claimed reactionless drive capable of generating a one directional force in free space. Dean argued the device could revolutionize transportation and space travel by producing thrust without expelling any propellant, a claim that would have violated Newtons third law of motion. Multiple analyses concluded that the apparent forward motion the device displayed on a surface came from asymmetrical frictional resistance between the mechanism and that surface rather than any new form of propulsion, and a 2006 NASA memorandum noted that such devices still required a connection to the ground to produce any net motion at all. No working model of the Dean drive was ever independently verified, and Dean never published a rigorous theoretical justification for how it was supposed to work.