A rocket engine that uses electric current to increase the energy of a propellant prior to exhausting the propellant rather than the more conventional method of combustion or decomposition heating. Typically, electric thrusters, have remarkably high efficiency but poor thrust and operate only in vacuum, making them unsuitable for launch and landing operations.
Goebel, Dan M., and Ira Katz. Fundamentals of electric propulsion: ion and Hall thrusters. Vol. 1. John Wiley & Sons, 2008.