IBM System/4 Pi
 | It has been suggested that IBM AP-101 be merged into this article. (Discuss) Proposed since October 2013. |
The IBM System/4 Pi is a family of radiation hardened avionics computers used, in various versions, on the B-52 Stratofortress bomber, the F-15 Eagle fighter, E-3 Sentry, NASA's Skylab, MOL, and the Space Shuttle, as well as other aircraft. It descends from the System/360 mainframe family of computers.
The Skylab space station employed the model TC-1,[1] which had a 16-bit word length and 16,384 words of memory with a custom input/output assembly.[2]
The top-of-the-line 4 Pi is the AP-101, used in the B-52. The U.S. Navy used a similar variant, the AN/ASQ-155, in the carrier based A-6E/A-6E TRAM medium attack aircraft. The Shuttle is controlled by five AP-101 computers, four of which are arranged in a redundant configuration, with the fifth as backup.
The name of the system is derived from the fact that the angular measure of a complete sphere (solid angle) is 4π steradians,[3] while the angular measure of a complete circle is 360 degrees; hence System/4 Pi and System/360. This implies that System/4 Pi is a version of the IBM System/360 for the three-dimensional world of avionics.
References
- ^ Jenkins, Dennis (April 5, 2001). "Advanced Vehicle Automation and Computers Aboard the Shuttle". NASA History Homepage. NASA. Retrieved 27 October 2013.
- ^ "Skylab Space Station". eoPortal. ESA. Retrieved 27 October 2013.
- ^ Technical Description of IBM System/4 Pi Computers. Owego, NY: Federal Systems Division of IBM. 1967. Retrieved 27 October 2013.
- Computers in Spaceflight: The NASA Experience, Ch.3: The Skylab Computer System – Hardware – From the online version of the NASA report by George Tomayko.
- Olsen, P. F.; R. J. Orrange (September 1981). "Real-Time Systems for Federal Applications: A Review of Significant Technological Developments". IBM Journal of Research and Development. 25 (5): 405–416. doi:10.1147/rd.255.0405.
External links
 | This article about aircraft components is a stub. You can help Wikipedia by expanding it. |
 | This space- or spaceflight-related article is a stub. You can help Wikipedia by expanding it. |