SAGE AN/FSQ-7
The computer at the center of the US air defense network of the Cold War, and the largest vacuum-tube computer ever built.
SAGE, the Semi-Automatic Ground Environment, linked radar stations to computers that tracked aircraft and helped controllers guide interceptors. MIT Lincoln Laboratory designed it using Whirlwind research. IBM built the AN/FSQ-7 computers that ran it. Operators used consoles with a light gun to select aircraft on a round display.
The first direction center went into service in 1958 and the network grew to about two dozen sites. Each site used two computers so that one could take over if the other failed. The last SAGE sites closed in the early 1980s.
Why it matters
SAGE taught IBM how to build large, reliable real-time systems and trained a generation of programmers. Its ideas of online terminals, shared data networks and airline-style reservations reached the SABRE system and many later projects.
Key facts
- Each AN/FSQ-7 used roughly 55,000 vacuum tubes.
- Operators pointed a light gun at the display to identify aircraft.
- Computers worked in pairs for reliability.
- The network operated from 1958 into the early 1980s.
Sources
- Campbell-Kelly, Martin, and William Aspray, et al. Computer: A History of the Information Machine. 3rd ed. Westview Press, 2013.
- Edwards, Paul N. The Closed World: Computers and the Politics of Discourse in Cold War America. MIT Press, 1996.
- Redmond, Kent C., and Thomas M. Smith. From Whirlwind to MITRE: The R&D Story of the SAGE Air Defense Computer. MIT Press, 2000.