Flywheel energy storage for vehicle propulsion

A propulsion system (10) includes a prime mover (14) for providing primary power to propel a vehicle (12); a flywheel energy storage device(18) for providing secondary power to propel the vehicle(12) when primary power is not being provided, wherein the flywheel energy storage device (18) stores power provided by the prime mover (14); and a controller (34) for commanding the prime mover (14) on and off.