 A propulsion system consists of a source of mechanical power, and a "propulsor" (means of converting this power into propulsive force).A technological system uses an engine or motor as the power source (commonly called a powerplant), and wheels and axles, propellers, or a propulsive nozzle to generate the force.Components such as clutches or gearboxes may be needed to connect the motor to axles, wheels, or propellers.