Field Emission Electric Propulsion
) is an advanced electrostatic propulsion concept, a form of ion thruster
, that uses liquid metal
(usually either caesium
) as a propellant. A FEEP device consists of an emitter and an accelerator electrode. A potential difference on the order of 10 kV is applied between the two, which generates a strong electric field
at the tip of the metal surface. The field extracts ions, which then are accelerated to high velocities, typically more than 100 km/s. A separate electron source is required to keep the spacecraft electrically neutral.
Due to its very low thrust (in the micronewton to millinewton range), FEEPs are primarily used for microradian, micronewton attitude control on spacecraft.