The command and service modules (CSM) made up the main part of the Apollo spacecraft, the other part being the lunar module (LM). They remained mated together for most of the trip to and from the Moon. The command module (CM) was cone-shaped and provided accommodation for three astronauts. At the tip was a docking probe for linking up with the LM, and at the base a heat shield. The atmosphere was low-pressure oxygen. The service module (SM) had a powerful engine for in-space acceleration and braking. Among other equipment, it carried liquid hydrogen and liquid oxygen tanks to feed the fuel cells that provided the CSM with electrical power. At lift-off the CSM sat on top of the launching rocket, with the LM underneath; it was surmounted by a rocket-powered escape tower for use in an emergency. En route for the Moon, the astronauts carried out manoeuvres to dock 'nose to nose' with the LM, allowing them to enter. They returned from the Moon in the CSM, the SM being jettisoned prior to the 40,000 km/h re-entry. After parachute braking, the CM splashed down at sea.
