A colloid thruster is a type of thruster which uses electrostatic acceleration of charged liquid droplets for propulsion. It is closely related to electrospray ionization and other hydrodynamic spraying processes. In a colloid thruster charged liquid droplets are produced by an electrospray process and then accelerated by a static electric field. The liquid used for this application tends to be a low volatility ionic liquid.
Like other ion thrusters its benefits include high efficiency, thrust density, and specific impulse; however it has very low total thrust, on the order of micronewtons. It provides very fine attitude control or efficient acceleration of small spacecraft over long periods of time.