SAGE Introduction

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SAGE System (1957-1983) - The Semi-Automatic Ground Environment (SAGE) System was a United States Air Defense System designed to protect the United States against nuclear attack by Soviet bombers. The system was designed and put into place starting in 1957 before the ICBM threat materialized and kept in place to manage any air breathing threat until 1983.

Hancock SAGE Direction Center DC-03 (Left) and Hancock SAGE Combat Center CC-01 (Right)
SAGE System Data Flow

The system required a nationwide system of radar sites for detection, a set of 23 direction centers to track incoming targets and direct interceptor aircraft to the incoming bombers and a network of combat centers to direct any resulting air battles. The system was expanded to include warning radars across Canada and came to control not only aircraft interceptors but Bomarc long range interceptor missiles and short range NIKE anti-aircraft missiles, the later versions of both were nuclear armed.

The technology of the day was 1st generation (vacuum tube) and the concept of real time computing was not deemed viable. The SAGE system overcame these challenges and produced possibly the largest computer system ever built for the SAGE Direction Centers (FSQ-7) and the SAGE Combat Centers (FSQ-8). It took a four story concrete blockhouse to house the direction center and a powerhouse with five diesel generators to power it.

The cost of the system was enormous and by the mid 1960s the system was constricting and being constantly reconfigured as radar sites and direction centers closed. The SAGE System was replaced in 1983 with newer computers and a network of joint use FAA/USAF radar sites referred to as the JSS System.


  • Cornett, Lloyd H. & Johnson, Mildred W., A Handbook of Aerospace Defense Organization (1946-1980), Office of History ADC, Peterson AFB, Colorado, 31 Dec 1980, 179 pages, Pdf.
  • Winkler, David F., Searching the Skies: the Legacy of the United States Cold War Defense Radar Program, USAF Hq Air Combat Command, 1997, 192 pages, Pdf.
  • Grometstein, Alan A., Editor, MIT Lincoln Laboratory:Technology in Support of National Security, Copyright 2011, MIT Lincoln Labratory, ISBN 978-0-615-42880-2, 570 pages, Pdf.

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