The History of the

Semi Automatic Ground Environment (SAGE)




SAGE had a fundamental impact on the development of computers and the computer industry. When the program began, work on the first digital computer, MIT's Whirlwind, was in progress. Key to the success of SAGE was the development of a production version of MIT's prototype Whirlwind computer. A little known company called IBM won the contract to design and build the Whirlwind II, otherwise known as AN/FSQ-7, for the proposed new air defense system. When complete, the AN/FSQ-7 weighed 250 tons, and required a 3,000kW power supply and over 49,000 vacuum tubes. When SAGE became fully operational, it relied on 24 AN/FSQ-7s; they remained in service until the Air Force ended the SAGE program in 1983.

In this way, the Q-7 was the computer that built IBM.

In the 1950's MITRE's founders played a key role in the development of the Semi-Automatic Ground Environment (SAGE) system, the first major real-time, computer-based command and control system. Designed as a new air defense system to protect the United States from long-range bombers and other weapons, the SAGE system sent information from geographically dispersed radars over telephone lines and gathered it at a central location for processing by a newly designed, large-scale digital computer. As the system evolved, SAGE broke new ground in radar, communications, computer, information display, and computer programming technologies.


The SAGE system was fully deployed in 1963; the 24 SAGE Direction Centers and three SAGE Combat Centers were spread throughout the U.S.  Bill became involved when he returned from Korea late in 1960  He was assigned to the Seattle Air Defense Sector (SEADS) at Mc Chord Air Force Base, just south of Tacoma, Washington.

SAGE Workstations
The Tech in the foreground is pointing to the display with a "Light Gun," which detects the time in the cycle when a particular icon is desplayed to select it for the operation he has inserted in the control panel. The Interceptor Director to his left appears to be controlling an interceptor. If this is in 1960, quite possibly an F-86D, the radar equipped version which fired Folding Fin Aereal Rockets (FFAR) from a "chin mounted" rocket pod.

SEADS, 25th AD and GeneratorsThe three buildings in the graphic are SEADS on the right, 25th Air Division on the left and the generator building at the bottom.


The antique aircraft in the upper left corner seems to be a retired Interceptor on display at the old SAGE center which was first operational about 1958.

IBM's massive SAGE (Semi-Automatic Ground Environment) system for air-defense radar processing helpd calm '50s societal hysteria over the possibility of a renegade Russian bomber. A replacement for the grease-pencil plotting of radar blips - far too slow to be effective against supersonic planes - SAGE kept vigil for Red nukes screaming over the North Pole. Yet it was fooled more than once, says Computer Museum curator Dag Spicer, by flocks of birds soaring above Newfoundland.

During its design, some 7,000 programmers had their hands on SAGE. By 1963, the system had evolved into 23 windowless blast-resistant centers around North America, each with a 250-ton computer powered by 49,000 vacuum tubes. Via modem, the machines spoke to one another, to ground and shipboard radar, and to weather stations, and kept tabs on legit air traffic.

Operators stationed in blue-lit rooms interacted with their screens using light guns. Judging by the messages penciled on the backs of removable knobs on the pictured model - "Get me out of here!" and "I want a pizza!" - the work was tedious. Energy boosts came from cigarettes, ignited from lighters built into the console, and snuffed out into onboard ashtrays. Rare moments of intensity were quickly quelled, recounts Spicer, once it was determined that "attacks" were simulations generated by training tapes accidentally left playing.

This view of the computer room should start to give you an idea of the scle of the machine. Each of those white handles is connected to and can pull out a panel of vaccum tubes each of which has its own duct to direct air conditioning over its

The Computer Room surface.  The panel fronts each are about 4 inches high and 30-40 inches wide.

There were two complete computers, one currently controlling the Air Defense of the Sector, the other in stand by and except when maintenance was being performed was in a continuous loop of self tests.  One part of the self test was to copy a complete data base of the current situation from the active computer so that the standby could assume that role without skipping a beat.


The room was incredibly cold but the vacuum tubes demanded it. There was a constant warbling sound that helped the operators detect any problem. The engineers had rigged an audio amplifier on a particular bit in the accumulator so that the cycling programs could be "listened to."  When we were learning to program the computer (in binary) one game we played was to learn how to make the speakers play musicAn added challenge was to control the user consoles.  We drew a hula dancer whose hips moved just right.  Then we blended it with the computer playing Aloha Oye and when we used the light gun on her navel the skirt fell off.
SAGE Memory
One of my favorite stories to illustrate the advance of technology is to remember when we got our second 8k of memory.  Here is a photo of the first 8k with a blurb from the MITRE Corp. documentation.


" FSQ-7 magnetic core memory. Central computer was a binary parallel machine with an 8892-word core memory and a speed of roughly 75,000 single-address instructions/second. To facilitate processing, numbers representing positional data were stored and processed as vectors with two 16-bit components."

That rack is 4 foot square and 8 feet tall.  It contanis 8k of core memory.  The cores are tiny donuts of ferrite with wires strund back-and-forth and up-and-down.  We used to say "they were strung in our Hong Kong Core House."  :-)  
:-)   :-)   :-)   :-)

Both the computers and the display equipment were housed in massive concrete buildings.  This Illustration shows a typical Direction CenterDirection Center Floor Plan.  At McChord, there was a Division Control Center next door. See aerial photo above.  A CC coordinated and commanded a number of adjacent DCs.  Here is the MITRE blurb that explained this graphic:
Typical 4-story SAGE Direction Center. 1st floor: Air cooling and ducting equipment plus telephone frames, cables, and equipment to maintain communication and radar data flow. Power house attaches to operations part of building by a common wall. 2nd floor: The SAGE FSQ-7 duplex computers. 3rd floor: Service area for the operation room above plus office and storage space, the subsector command post, and the Kelvin-Hughes projector and air-situation display screen. 4th floor: Operational areas where Air Force staff supervised each major air defense function (weapons direction, identification, air surveillance, etc.) from separate areas


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