Computers in Spaceflight: The NASA Experience

Part One: Manned Spacecraft Computers



[7] In the first 25 years of its existence, NASA conducted five manned spaceflight programs: Mercury, Gemini, Apollo, Skylab, and Shuttle. The latter four programs produced spacecraft that had on-board digital computers. The Gemini computer was a single unit dedicated to guidance and navigation functions. Apollo used computers in the command module and lunar excursion module, again primarily for guidance and navigation. Skylab had a dual computer system for attitude control of the laboratory and pointing of the solar telescope. NASA's Space Shuttle is the most computerized spacecraft built to date, with five general-purpose computers as the heart of the avionics system and twin computers on each of the main engines. The Shuttle computers dominate all checkout, guidance, navigation, systems management, payload, and powered flight functions.
NASA's manned spacecraft computers are characterized by increasing power and complexity. Without them, the rendezvous techniques developed in the Gemini program, the complex mission profiles followed in Apollo, the survival of the damaged Skylab, and the reliability of the Shuttle avionics system would not have been possible.
When NASA began to develop systems for manned spacecraft, general-purpose computers small and powerful enough to meet the requirements did not exist. Their development involved both commercial and academic organizations in repackaging computer technology for spaceflight.

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