THE APOLLO SPACESHIP

Apollo was conceived as a two-part spacecraft. The three-man crew occupied the conical re-entry section, from which they controlled the mission. This command module (CM) carried much of the equipment the crew needed for their flight, and everything they needed for re-entry. Most of their consumables (air, water, power) and their chief means of propulsion and cooling were carried in a cylindrical section attached behind the command module’s aft heatshield. This service module (SM) remained attached to the CM for most of the flight, the two sections acting as one spacecraft under the acronym CSM, for command and service modules. On the return journey the SM was discarded shortly prior to re-entry into Earth’s atmosphere. This distinctive cone-and-cylinder arrangement, with a nozzle sticking out of its aft end, became the archetypal spacecraft in the minds of many children who grew up at this time, fascinated by space flight.

Early plans envisaged taking some arrangement of the CSM all the way to the Moon’s surface as part of a larger vehicle that would sport a set of landing legs to enable the combination to touch down. Although this would have been a rather unwieldy craft to land, the requirement to lift the CSM off the Moon dictated the thrust of the spacecraft’s large main engine.