In 1961 when the Apollo program came into being with President Kennedy's challenge, the mini-computer had not emerged, commercial computers filled rooms and aerospace computers had limited computational capacity. Therefore there were no commercial available computers which would be suitable for the guidance application in an Apollo mission. Microprocessors, semiconductor memories or even simple integrated circuits were components of the future. Commercially available transistors were unreliable. Most technologies that were eventually used in the Apollo computer were just emerging from research and development laboratories. The state of the technology and unknown requirements for such a mission was the designer's dilemma.
Even those requirements of the mission which were understood presented a challenge to designers, that is, the need to minimize size, weight, and power consumption and achieve a level of reliable operation beyond any demonstrated behavior of digital computers. But what about computational capacity? The schedule required the computer designers to make assumptions where the functional requirements of the computer were unknown and charge ahead with the design. The first three years were hectic as the mission requirements developed and the computational load became better understood. Two quite similar designs emerged Block I, which could be available early, for the earth orbital missions and Block II with increased computational and control capabilities for the lunar missions.
A set of slides and a movie made in the spring of 1966 for an AGARD lecture tour documented the two computer designs and production processes.
Eldon Hall, The Apollo Moon Mission Guidance Computer, Inventor, receiving The George R. Stibitz Computer Pioneer Award, at the American Computer Museum, 1997.
Last Revised: January 09, 2002
Digital Engineering Institute
Web Grunt: Richard Katz