Apollo spacecraft. Cutaway illustration of the Command/Service Module (CSM) spacecraft, used during the Apollo programme which landed astronauts on the Moon. The Command Module (CM, conical section, upper right) housed a crew of three astronauts. The cylindrical Service Module (SM) contained scientific instruments, fuel cells (upper compartment) with oxygen and hydrogen gas tanks below, and propulsion systems. Propulsion was provided by a rocket engine, and four sets of thrusters with fuel tanks (gold) which allowed control of the spacecraft's orientation. Once at the Moon, two astronauts used the Lunar Module (not shown) to descend to the Moon's surface and return to the CSM. The CM was then used to re-enter the Earth's atmosphere, with the other sections being jettisoned.