Retrotechtacular: Wising Up With The SAGE System

The birth of the supersonic jet made the United States’ airstrike defenses look antiquated. And so, during the Cold War, the government contracted a number of institutions and vendors to create and maintain the Semi-Automatic Ground Environment (SAGE) aircraft detection system with Western Electric as project manager.

SAGE was developed at MIT’s Lincoln Laboratory on computers built by IBM. It used the AN/FSQ-7 in fact, which was The Largest Computer Ever Built. SAGE operated as a network of defense sectors that divided the continental U.S. and Canada. Each of these sectors contained a directional center, which was a four-story concrete blockhouse that protected and operated a ‘Q7 through its own dedicated power station. The SAGE computers employed hot standby processors for maximum uptime and would fail over to nearby direction centers when necessary.

Information is fed into each directional center from many radar sources on land, in the air, and at sea. The findings are evaluated on scopes in dimly-lit rooms on the front end and stored on magnetic cores on the back end. Unidentifiable aircraft traces processed in the air surveillance room of the directional center are sent to the ID room where they are judged for friendliness. If found unfriendly, they are sent to the weapons direction room for possible consequences.

Retrotechtacular is a weekly column featuring hacks, technology, and kitsch from ages of yore. Help keep it fresh by sending in your ideas for future installments.

23 thoughts on “Retrotechtacular: Wising Up With The SAGE System

  1. My favorite feature of the SAGE system was the built-in pullout ashtrays on the control console.

    Given that all computers at that time were kept in environmentally controlled rooms with separate air conditioning systems, it always seemed odd to me that smoking would be allowed at all.

    1. Back then, cigarettes were good for you! Probably good for electronics too…

      Some vintage music recording consoles also had ashtrays and automobile-style lighters built in. Nowadays you wouldn’t even think of smoking in a studio.

  2. On that radar system, how did they change the letters and numbers showing up on each hostile aircraft’s position? It looks like a cross between X/Y vector tracing (easily within 1950’s tech) and some clever dynamic, phosphorescent shadow masking for the textual content.

    …Or was this all an elaborate propaganda mock-up to needle the Soviets?

    1. The CRTs were very special: they had an electron gun for vector drawing, and separate guns that used the same technology used for Charactron tubes ( to display alphanumeric data. With the technology of the day, there was no way they could have drawn each individual character with vectors.

      One part of this that IS propaganda is how fast the displays updated. In the film, it only takes a couple of seconds to fully refresh all of the data on the display. In real life (I’ve seen this with my own eyes), it took up to 30 seconds. No way did the Air Force want to show THAT off!

      The strangest thing is that this barely-adequate technology was used up through the mid 1980s. I worked on SAGE radar systems from 1976-1981, and this was the “state of the Ark”, as we called it, at the time.

    1. Tu-95 entered service with the Soviet Union in 1956 and is expected to serve the Russian Air Force until at least 2040 The B-52 has been in active service with the USAF since 1955. As of 2012, 85 were in active service with nine in reserve. Interestingly the BBC referred to the TU-95 as a Russian jet bomber although it is in fact a turbo prop! What goes around keeps going around if it’s a good design.

      1. Gotta live the TU-95, subsonic bomber, supersonic propeller tips. They also made a passenger version of the 95, I believe it wasn’t successful though because the passengers didn’t like be deafened.

        1. I once saw the VIP/passenger version come through Denver once. Interesting craft — they must have WAY soundproofed that thing for President Yeltsen. Its scheduled takeoff was delayed several hours because they loaded fuel for a non-stop trip to Moscow, but it was too warm outside to lift off at that gross weight.

    2. No,
      With the bubble canopy on the top the jets in the video looked like B-47 Stratojet bombers. Bear bombers are turboprops. VERY Russian looking, VERY loud and subsonic but with good range.
      The only purpose for the Bear bombers in real battle would be target practice and nuclear weapon material dispersal (after they were blown up). IMO, they are used for propaganda as a way of rattling the saber blades without causing undue alarm.

      The general spoke of a “network” and they showed a manual telephone switching station. Whatever did they use to communicate between the directional centers??? One scene showed what looked like a teletype and someone manually entering data into a console. Military sneaker-net??

    3. The bombers in the video are in fact American B-47s. The Tu-95 “Bear” was one of the threats, but other threats WERE jet bombers – the Tu-16 “Badger” and M-4 “Bison”.

  3. When there were parts of SAGE at the Computer Museum in Boston (now all relocated to Computer History Museum in Silicon Valley), the most interesting part, to me, was that how they maintained reliability of a TUBE-based computer. Every morning, they would turn up the filament voltage to 125% or so of normal for a few minutes. This accelerated the failure of marginal tubes. After that they would stroll up and down the rows of SAGE with a grocery cart full of tubes, replacing any that had burned out. Then SAGE would be 100% for the rest of the day.

  4. am I the only one who sees sightly movement on the right half of the first picture. I see an effect very similar to the typical optical illusions you can find everywhere.

  5. I have trouble watching this. I switched the resolution to 144p and still only get 1-digit FPS out at >90% CPU usage. The Machine I’m using IS a little dated, but had no trouble with full motion 360p 16:9 video content fullscreen so far (480p lags most the time, but not always). Heck, even my old Pentium 1 MMX could do 240p.

  6. The SAGE building were big concrete blocks. Note they show the power and air conditioning systems, and point to the water coolers outside. But the coolers were just steel tanks- one well placed mortar shell and the cooling would loose its water and soon the building would be toast.

        1. I reported the above post, hoping to add a comment to the report that the link to the Wikipedia article seems broken here. It is highlighted when moused over, but can not be clicked.

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