Electrostatic & Hall-Effect Ion Thruster

Electric spacecraft propulsion system ionizing xenon or krypton gas and accelerating cations to 20–50 km/s via electric fields.

Specifications & Metrics

type: Space & Hydraulic Propulsion
working principle: Electron-bombardment or Hall-current ionization followed by electrostatic Coulomb grid or radial-magnetic-field acceleration and cathode beam neutralization
operating regime: In-space high-vacuum continuous low-thrust propulsion (25–500 mN at 1–100 kW electrical input)
efficiency or isp: Specific impulse I_sp = 1,500–5,000+ s; propulsive electrical efficiency 65–80%
originator: Robert Goddard (1906–1920), Hermann Oberth (1929), Harold R. Kaufman (NASA SERT-1, 1959/1964) & AI Morozov (Hall thruster)

Built in gridded electrostatic form by NASA's Harold R. Kaufman in 1959 (flown on SERT-1 in 1964) and in Hall-effect form in the Soviet Union, ion thrusters bypass the Carnot thermal limit of chemical rockets by accelerating ionized propellant atoms directly with electric fields.
With exhaust velocities of 20 to 50 km/s (specific impulse 2,000–5,000 seconds, roughly ten times chemical bipropellants), NASA's Dawn spacecraft achieved a record 11.5 km/s post-launch delta-v to orbit both Vesta and Ceres while consuming only 425 kg of xenon.
An external hollow-cathode neutralizer injects electrons into the exiting positive ion beam so the spacecraft does not accumulate a negative charge that would draw the ions back and cancel thrust; today thousands of Hall-effect thrusters maintain orbits on Starlink satellites and the Tiangong space station.