An attitude jet is a device used to steer some type of
aircraft or
spacecraft by the controlled,
directional emission of gasses, or through
rocket combustion. They operate on the
reaction principle, first described by
Isaac Newton.
Attitude jets require some type of stored fuel to operate, so they are limited in how often they can be used. Aerodynamic control surfaces are better solutions inside our atmosphere but in the vacuum of space or at very high altitudes attitude jets are often chosen.
Attitude jets are rarely solitary, though with steerable rockets they can be. Usually they are grouped to provide control in all three dimensions, with five being a common number. Several groups are studded at appropriate spots on the craft to be controlled. Attitude jet arrays can be easily seen photographs of the Apollo program Command Module and Landing module for a look at a practical system. They can be recognized as a series of cones with the points centered on a small box, with the bases pointed in different directions.
The Space Shuttle uses attitude jets while in orbit, as do all satellites.