Abstract: A hybrid propulsion system for aerospace and other applications is disclosed in which a thruster is operable to release energy from a propellant, thereby producing an exhaust gas. The thruster is selectable from one of a plurality of thrusters that are different from one another. A plasma fuel engine (PFE) accelerator, which is coupled to the thruster in a tandem arrangement, provides partial ionization of the exhaust gas, an electric field, and a magnetic field. The electric field is aligned to accelerate the partially ionized exhaust gas and the magnetic field is aligned transversely to the electric field. The combination of the electric field and the magnetic field augment the specific impulse of the hybrid propulsion system.