Abstract: A propulsion system for converting rotary motion into unidirectional motion and consisting of a frame, a pair of counterrotating lower members rotatably mounted to the frame containing damping elements, a pair of upper members containing damping elements rotatably mounted to the frame and positioned above the lower members, each at an angle to the disk so that each contacts a surface of the member below it at a single point, and a motor and drive train for driving the lower members. Each lower member includes a pair of studs mounted at its periphery which engage radially extending posts mounted to its corresponding upper cylinder so that rotation of the lower member causes the upper member to rotate in the same sense damped and at the same angular velocity. The super position of the damped upper members upon the damped lower members generates unbalanced centrifugal forces which result in a constant unidirectional resultant force.