This type of electric propulsion uses magnetic or electric fields to accelerate heavy ions, usually xenon or krypton, out of a nozzle. While the absolute thrust is extremely low compared to chemical rockets, the exhaust velocity is incredibly high. This allows a spacecraft to continuously accelerate for months or years, ultimately reaching massive speeds while consuming very little propellant.
Heard on the job
The main ion engine is firing nominally, and we expect it to run continuously for the next three hundred days.
Insider tip
Because the thrust is so gentle, ion engines are useless for launching off a planet and are only fired once the vehicle is already in the vacuum of space.