Source: NASA Historical Reference Collection, NASA History Office, NASA Headquarters, Washington, DC.

The Apollo spacecraft is the entire structure atop the launch vehicle. It is 82 feet tall and has five distinct parts: the command module, the service module, the lunar module, the launch escape system, and the spacecraft-lunar module adapter.

The three modules make up the basic spacecraft; the launch escape system and adapter are special purpose units which are jettisoned early in the mission after they have fulfilled their function. The launch escape system is essentially a small rocket which will thrust the command module--with the astronauts inside--to safety in case of a malfunction in the launch vehicle on the pad or during the early part of boost. The spacecraft lunar module adapter serves as a smooth aerodynamic enclosure for the lunar module during boost and as the connecting link between the spacecraft and the launch vehicle.

The basic difference in the two versions was in the addition, in Block II, of some equipment and systems designed specifically for the lunar mission.

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Updated February 3, 2003
Steve Garber, NASA History Web Curator
For further information E-mail histinfo@hq.nasa.gov