Thrusters (spacecraft)

Thruster is a propulsive device used by spacecraft for station keeping, attitude control, in the reaction control system, or long-duration, low-thrust acceleration. A vernier engine or gimbal engine is a particular case used on launch vehicles where a secondary rocket or other high thrust device is used to control the attitude of the rocket while the primary thrust engine (generally also a rocket engine) is fixed to the rocket and supplies the principal amount of thrust.
Some devices that are used or proposed to use as thrusters are: