Solar electric propulsion
Solar electric propulsion (SEP) typically refers to the combination of solar cells and an ion drive to propel a spacecraft through outer space. This technology has been exploited in a variety of spacecraft by the European Space Agency, the Japanese Space Agency, Indian Space Research Organisation and NASA. SEP is valued for its potential for a high specific impulse, thus allowing less mass for propellant to be launched with a spacecraft and it has been evaluated for mission to Mars.
Solar electric propulsion combines solar panels on spacecraft and ion thrusters, used in tandem. However, there are a number of other types of electrically powered spacecraft propulsion such as arcjet rockets. It may not employ an ion drive, of which there is a variety of types also.
The NASA Solar Technology Application Readiness (NSTAR) ion engine has been used with photovoltaic solar panels, which was tested on the Deep Space 1 mission along with Solar Concentrator Arrays (Launched in 1998 as part of the New Millennium Program) 
SEP has been studied as a technology for a mission to Mars. In particular the high specific impulse of the ion engines could lower overall mass and avoid having to use nuclear technology for power when coupled with solar panels. A 1998 study for SEP for a human mission suggest that a human-sized spacecraft would need 600 to 800 kilowatts of electrical power coupled with ion engines with a specific impulse of 2000 to 2500 seconds.
- BepiColombo mission to Mercury (launched) 
- Dawn asteroids mission (launched)
- Deep Space 1 asteroid and comet mission (launched)
- Hayabusa asteroid mission (launched)
- PSLV-C45 EMISAT Mission (launched)
- Asteroid Redirect Mission (cancelled)
- Lunar Orbital Platform-Gateway (planned)
- Psyche asteroid mission (planned)
Electric propulsion technologies
- Resistojet rocket
- Ion thruster
- Pulsed plasma thruster
- Hall-effect thruster
- Magnetoplasmadynamic thruster
- Field-emission electric propulsion
- Variable Specific Impulse Magnetoplasma Rocket (VASMIR)
- Batteries in space
- Liquid-propellant rocket
- List of spacecraft with electric propulsion
- Nuclear electric rocket
- Solar panels on spacecraft
- Solar sail
- Solar thermal rocket
- Sterling engine
- Mohon, Lee. "Solar Electric Propulsion (SEP)". NASA. Retrieved 2016-04-24.
- Solar Electric Propulsion for Mars Exploration NASA, 2005-01-08.
- "Solar Electric Propulsion: NASA's engine to Mars and Beyond - SpaceFlight Insider". www.spaceflightinsider.com. Retrieved 2018-07-28.
- "NASA Awards Solar Electric Propulsion Flight System Contract".
- "Advanced Electric Propulsion System successfully tested at NASA's Glenn Research Center - SpaceFlight Insider". www.spaceflightinsider.com. Retrieved 2018-07-28.
- "Advanced Technologies". NASA / Jet Propulsion Laboratory. Retrieved 20 November 2016.
- "In Depth | Deep Space 1 – Solar System Exploration: NASA Science". Solar System Exploration: NASA Science. Retrieved 2018-08-08.
- BepiColombo Fact Sheet European Space Agency, 2010-07-05.