A propulsion system includes an engine and a rotating member rotatably engaging the engine. The rotating member comprises a plurality of drive members positioned around the circumference of the rotating member. Each of the drive members has an unlocked state in which the drive members apply substantially no torque to the rotating member, and a locked state, in which the drive members apply substantially a torque to the rotating member. At a selected time, a first set of the drive members are in the unlocked state and a second set of the drive members are in the locked state to provide a propulsive force.