Propulsion is the generation of force by any combination of pushing and/or pulling to modify the translational motion of an object, which is typically a rigid body but may also concern a fluid. A propulsion system is a machine system consisting of at least two core elements: the powerplant, a source of mechanical power; and the propulsor, an actuator mechanism that converts the supplied power into propulsive force; often also with supplementary components such as transmission and control system that enhance the final outcome of the propulsion system.