Computers in Spaceflight: The NASA Experience

- Chapter Three -
- The Skylab Computer System -
[82] The Skylab program demonstrated that careful management of software development, including strict control of changes, extensive and preplanned verification, and the use of adequate development tools, results in quality software with high reliability. Attention to piece part quality in hardware development and the use of redundancy resulted in reliable computers. However, it must be stressed that part of the success of the software management and the hardware development was due to the small size of both. Few programmers were involved in initial program design and writing. This meant that communications between programmers and teams were relatively minimal. The fact that IBM produced just 10 computers and really needed to ensure the success of just 2 of those helped in focusing the quality assurance effort expended on the hardware.
[83] What happened after the manned Skylab program demonstrated the need for foresight and proper attention to storage of mission-critical materials until any possibility of their use had gone away. The dispersal of the verification hardware is understandable, as it is expensive to maintain. However, some provision should have been made for retaining mission-unique capabilities such as actual flight hardware. The destruction of the flight tapes and source code for the software by unknown parties was inexcusable. A single high-density disk pack could have held all relevant material.
Skylab marked the beginning of redundant computer hardware on manned spacecraft. It was also the first project that developed software with awareness of proper engineering principles. The Shuttle continued both these concepts but on a much larger and more complex scale.

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