An array of small thrusters on a spacecraft, used for attitude control, altitude, and speed. A space shuttle has 44 thrusters on its nose and tail. The pilot moves hand controllers that instruct computers to fire the thrusters in specific combinations in order to control the shuttle by pitch, roll, and yaw movements.

Out of the 44 thrusters, six are quiet vernier thrusters (two forward and four aft) that move the shuttle slowly; they are normally the only ones required. The remaining 38 are loud primary thrusters (14 forward and 24 aft) that give a strong, rapid movement.