Chuck Taylor, Principal Investigator, NASA Langley Research Center, Hampton, VA

Chuck Taylor: Solar Electric Propulsion is a form of spacecraft propulsion used in space. It relies on the acceleration of ions using electricity generated by solar arrays instead of the chemical energy stored in the propellant itself. It is attractive because by using the Sun’s energy in the process we can bring considerably less propellant mass into orbit; this reduces our launch mass and cost. An SEP system is usually considered to consist of the large arrays that generate electric power, the power processing units or PPUs that convert this power, and the thruster which uses the electric power to ionize the inert propellant and accelerate it out of the spacecraft to generate thrust.