A module of a spacecraft that provides the command module with electricity, air, and water. It is also the location of the thrusters used for manoeuvring. It is usually identified with the Apollo missions, which had cylindrical service modules, 7.5 m long and 3.9 m in diameter. The service module was launched sitting above the lunar module and under the command module, to which it remained connected in space to form the command and service modules (CSM). The service module had the only engine power available to return the Apollo astronauts to Earth.
Subjects: Astronomy and Astrophysics.