Hall-effect Thruster (HET)

A Hall-effect thruster is an electric propulsion device used on spacecraft for efficient, low-thrust orbit raising, station keeping, and attitude or orbital maneuvers. It operates by accelerating ions—typically xenon—using an electric field while a magnetic field is applied to trap electrons, creating a plasma discharge.

In a Hall-effect thruster, neutral propellant is injected into an annular discharge chamber where electrons are constrained by a radial magnetic field and ions are accelerated axially by an electric field. The ions exit the thruster at high velocity, producing thrust, while an external cathode supplies electrons to neutralise the exhaust plume. Although the thrust level is low compared with chemical propulsion, Hall-effect thrusters achieve very high specific impulse, resulting in substantial propellant mass savings.

Hall-effect thrusters are widely used on modern communications satellites for station keeping, orbit maintenance, and increasingly for orbit raising from transfer orbit to geostationary orbit. They are also used extensively on small satellites and deep-space missions where high efficiency and long operational life are critical.