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 (conical section, upper right) housed a crew of three astronauts. The cylindrical Service Module contained scientific instruments, fuel cells, fuel tanks, and propulsion systems, including the Service Propulsion System (seen here) which propelled the craft into and out of lunar orbit. 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 Command Module was then used to re-enter the Earth's atmosphere, with the other sections being jettisoned.