High Quality Content by WIKIPEDIA articles! The Dean drive is a device intended to be a reactionless thruster that was invented by Norman L. Dean. Dean claimed that it was able to generate a uni-directional force, in violation of Newton`s Third Law of Motion. Such a violation is generally considered to be impossible in physics. While it is theoretically possible for a mass that moves in one direction to have its momentum balanced by something other than a reaction mass (e.g. see Nuclear photonic rocket), there is no known theoretical mechanism for a mass to be moved one way while nothing moves the other way, at least in a flat spacetime.