The two rockets on a space shuttle that lift the craft into orbit, change its attitude while orbiting, and decelerate the spacecraft for re-entry into the upper edge of the atmosphere. The rockets are located on either side of the aft fuselage near the main engines. They have their own hydrazine fuel, oxidized by nitrogen tetroxide. After launching, when the main engines have burned out and the external tank has dropped away, the shuttle is lifted into an elliptical orbit by a 2.5-minute first firing, the OMS-1 burn. As the vehicle reaches the apogee of this orbit, a shorter second ignition, the OMS-2 burn, places it into a circular orbit.