The AFT of the space shuttle is the back end of the spacecraft. It is the section that contains the main engines and the Orbital Maneuvering System (OMS) engines, which are used to control the shuttle's attitude and altitude. The AFT also contains the payload bay doors, which open to allow the payload to be deployed. Additionally, the AFT contains the Reaction Control System (RCS) thrusters, which are used for fine-tuning the shuttle's orientation in space.