Home TECHNOLOGY “On Guard: The Story of SAGE” 1956 IBM

“On Guard: The Story of SAGE” 1956 IBM

‘”Protection comes high…sky high. Today we must be on guard in the sky when it comes to protecting our resources…the national resources that are so precious to us.” Cut to a shot of children playing at the school playground…
On Guard! introduces the SAGE (Semi-Automatic Ground Environment), a heavily computerized early warning system designed to guard against enemy aircraft. For its time, this was novel technology — room-sized computers and giant “Displayscopes” — and the film seeks to humanize it to a technologically unsophisticated public…’

The AN/FSQ-7 Combat Direction Central (colloq. Q7) was a computerized command and control system for Cold War ground-controlled interception used in the USAF Semi-Automatic Ground Environment (SAGE) air defense network. The largest computer system ever built, each of the 24 installed machines weighed 250 tons and had two computers. The AN/FSQ-7 used a total of 60,000 vacuum tubes (49,000 in the computers) and up to 3 megawatts of electricity, performing about 75,000 instructions per second for networking regional radars… https://en.wikipedia.org/wiki/Semi-Au…

The Semi-Automatic Ground Environment (SAGE) was a system of large computers and associated networking equipment that coordinated data from many radar sites and processed it to produce a single unified image of the airspace over a wide area. SAGE directed and controlled the NORAD response to a Soviet air attack, operating in this role from the late 1950s into the 1980s. Its enormous computers and huge displays remain a part of cold war lore, and a common prop in movies such as Dr. Strangelove and Colossus.

The processing power behind SAGE was supplied by the largest computer ever built, the AN/FSQ-7. Each SAGE Direction Center (DC) housed an FSQ-7 which occupied an entire floor, approximately 22,000 square feet, of the massive concrete blockhouse, not including supporting equipment. The upper two floors contained offices, operator stations, and a single two-story radar display visible to most of the DC’s personnel. Information was fed to the DC’s from a network of radar stations as well as readiness information from various defence sites. The computers, based on the raw radar data, developed “tracks” for the reported targets, and automatically calculated which defences were within range. Subsets of the data were then sent to the many operator consoles, where the operators used light guns to select targets onscreen for further information, select one of the available defences, and issue commands to attack. These commands would then be automatically sent to the defence site via teleprinter. Later additions to the system allowed SAGE’s tracking data to be sent directly to CIM-10 Bomarc missiles and some of the US Air Force’s interceptor aircraft in-flight, directly updating their autopilots to maintain an intercept course without operator intervention. Each SAGE DC also forwarded data to a Combat Center (CC) for “supervision of the several sectors within the division” (“each combat center [had] the capability to coordinate defense for the whole nation”). Connecting the various sites was an enormous network of telephones, modems and teleprinters.

SAGE became operational in the late 1950s and early 1960s at a combined cost of billions of dollars. It was noted that the deployment cost more than the Manhattan Project, which it was, in a way, defending against. Throughout its development there were continual questions about its real ability to deal with large attacks, and several tests by Strategic Air Command bombers suggested the system was “leaky”. Nevertheless, SAGE was the backbone of NORAD’s air defence system into the 1980s, by which time the tube-based FSQ-7’s were increasingly costly to maintain and completely outdated. Today the same command and control task is carried out by microcomputers, based on the same basic underlying data…



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