Apollo Guidance Computer

Apollo Guidance Computer
Apollo Guidance Computer and DSKY
Invented byCharles Stark Draper Laboratory
      ManufacturerRaytheon
      IntroducedAugust 1966 (1966-08)
      DiscontinuedJuly 1975 (1975-07)
      Type
      • Avionics
      • Guidance computer
      ProcessorDiscrete silicon integrated circuit (IC) chips (RTL based)
      Frequency2.048 MHz
      Memory
      PortsDSKY, IMU, Hand Controller, Rendezvous Radar (LM), Landing Radar (LM), Telemetry Receiver, Engine Command, Reaction Control System
      Power consumption55 W[2]: 120 
      LanguageAGC Assembly Language
      Weight70 lb (32 kg)
      Dimensions24 in × 12.5 in × 6.5 in (61 cm × 32 cm × 17 cm)

      The Apollo Guidance Computer (AGC) was a digital computer produced for the Apollo program that was installed on board each Apollo command module (CM) and Apollo Lunar Module (LM). The AGC provided computation and electronic interfaces for guidance, navigation, and control of the spacecraft.[3] The AGC was the first computer based on silicon integrated circuits (ICs).[4][5] The computer's performance was comparable to the first generation of home computers from the late 1970s, such as the Apple II, TRS-80, and Commodore PET.[6] At around 2 cubic feet (57 litres) in size, the AGC held 4,100 IC packages.[5]

      The AGC has a 16-bit word length, with 15 data bits and one parity bit. Most of the software on the AGC is stored in a special read-only memory known as core rope memory, fashioned by weaving wires through and around magnetic cores, though a small amount of read/write core memory is available.

      Astronauts communicated with the AGC using a numeric display and keyboard called the DSKY (for "display and keyboard", pronounced "DIS-kee"). The AGC and its DSKY user interface were developed in the early 1960s for the Apollo program by the MIT Instrumentation Laboratory and first flew in 1966.[7] The onboard AGC systems were secondary, as NASA conducted primary navigation with mainframe computers in Houston.[8]

      1. ^ Programmer's Manual, Block 2 AGC Assembly Language, retrieved 2018-08-27
      2. ^ Cite error: The named reference Hall-1996 was invoked but never defined (see the help page).
      3. ^ Interbartolo, Michael (January 2009). "Apollo Guidance, Navigation and Control Hardware Overview" (PDF).
      4. ^ "1962: Aerospace systems are the first applications for ICs in computers". Computer History Museum. 2025. Retrieved March 13, 2025.
      5. ^ a b tluong (2019-07-17). "Silicon Chips Take Man to the Moon". CHM. Retrieved 2025-03-31.
      6. ^ "How did the Apollo flight computers get men to the moon and back ?". 11 March 2017.
      7. ^ James E. Tomayko (1988). "The Apollo guidance computer: Hardware". Computers in Spaceflight: The NASA Experience. NASA. Archived from the original on December 29, 2023.
      8. ^ Cite error: The named reference :1 was invoked but never defined (see the help page).
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