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August 1956 Popular ElectronicsTable of Contents
People old and young enjoy waxing nostalgic about and learning some of the history of early electronics. Popular Electronics was published from October 1954 through April 1985. All copyrights are hereby acknowledged. See all articles from Popular Electronics.
The Semi-Automatic Ground Environment (SAGE) system was designed and built to monitor the flights of both intercontinental ballistic missiles and hostile aircraft - if they were ever to occur, which, thankfully, they did not. Nuclear bombs were of particular interest since they could be launched not just from the USSR, which was the only other nuclear power in 1956, but also from offshore aircraft carriers and submarines. This was the beginning of the era when school kids participated in practice drills of getting under their desks in the event of an attack. I remember doing it in the mid 1960s while in grade school. Some of the equipment described here represents the earliest computerized digital technology, including magnetic core memory.
By E. D. Morgan
Plunging through the enemy line of aerial and atomic attack, SAGE is ready to make a touchdown for national defense
Direction center and computer are housed in this windowless, reinforced concrete blockhouse at Lincoln Laboratory - the nerve center of the SAGE system. Department of Defense Photos
The destructive power of atomic warfare coupled with the growing array of aerial weapons which could reach our shores raises frightening misgivings. A swift and efficient defense must be instantly available to counter an attack if we are to survive. Fortunately, the same brand of ingenuity that developed these offensive means has been working to give us the weapons and organized control of them that a defense requires.
The task of assignment and control of interceptors, ground-to-air guided missiles, and anti-aircraft guns - the means by which we must defend ourselves - has led to the development of a huge electronic quarterback called the "SAGE" system. The name "SAGE" is derived from its more formal title, the Semi-Automatic Ground Environment system.
Directing Defense. One of the world's largest, fastest and brightest electronic computers is the heart of this fantastic system. It relieves men of the hopeless task of sorting, weighing and evaluating the thousands of pieces of information our radar networks and other detection means can supply. It determines the best assignments of our defensive means to cope with the situation. Then, it directs these aerial weapons until the attacking plane or missile is downed.
Memory unit of computer, made up of three-dimensional array of ferrite cores, receives a constant stream of flight data.
The first of these fabulous systems is centered at Lincoln Laboratory in Lexington, Mass. At this secret laboratory, operated by the Massachusetts Institute of Technology, the system was conceived and developed for the military forces. In all, 32 similar systems will be constructed, protecting our borders with the largest electronic defensive system ever constructed.
At the outer boundaries of the system is a ring of radar detection stations. Long-range surveillance radars and height finders are included, as well as smaller gap-filler radars to detect low-flying planes trying to slip beneath the skirts of the longer range detection systems.
The edge of the system is not confined to coverage from land stations, however; "Texas Towers" constructed far from the shore extend the coverage seaward. These man-made islands are huge platforms standing on legs which reach to the ocean floor. Their name comes from a technique used successfully for offshore oil well rigs in the gulf of Mexico.
Other seaward defensive lines are manned by radar picket ships and AEW (Airborne Early Warning) planes carrying powerful radars. Constant patrols insure that the system remains on the alert.
Interpreting Signals. The mass of information provided by these surveillance systems is transmitted continuously and automatically by either telephone lines or ultra-high-frequency radio networks to a direction center.
Also pouring into this direction center is additional data from other sources: flight plans of friendly aircraft to aid in their identification, up-to-date weather data vital to the successful interception of an enemy, reports from the Ground Observer Corps, data on the readiness of our defensive weapons, etc.
This constant stream of courses, speeds, altitudes and locations is continually digested by the computing facilities. The direction center is located in a windowless concrete blockhouse. It houses the dual-channel computer built by IBM. One channel is on a standby basis, but all the pertinent information is fed into it so that it is immediately ready for action if necessary.
The computer busily compares reports and compiles, sorts and processes the input information. Composite pictures of the air situation are displayed on 30" cathode-ray tubes in a television-like manner. Locations of all aircraft and their identifications can be observed. In addition, the computer weighs all the possible means of eliminating enemy planes or missiles and indicates them. The different weapons that might be used, and the time and place of the interception, are all available to the men making the tactical decisions.
When a particular type of defensive strategy is decided upon, the computer continues its work. It can direct an interceptor or missile until it contacts the enemy. If radio data links and automatic pilots are in an interceptor, it actually flies the plane to its destination. After the kill has been made, the computer continues its task to bring the plane back to its home base.
If the air battle nears the boundary of a particular system, it transfers the problem to the computer in the adjacent sector. With its speed, accuracy and capacity, it can handle many intercepts simultaneously while continuing its function of surveillance.
Over-All Picture. The immensity of the task has involved the cooperation of companies like Western Electric, IBM, Bell Labs, Burroughs and Rand along with Lincoln Laboratory.
The computer contains 25,000 vacuum tubes and covers 10,000 square feet. While it is supervised and monitored by men, it releases them from the overwhelming task of coping with thousands of details. This frees them for the more important job of making tactical decisions. Even in this category, they are guided and aided by the electronic machines.
SAGE changes the basic building block in our defense picture from a single radar and its operator to an entire geographical area treated as a unit. The capacity and efficiency of this technique serve to keep our defensive ability in step with the growing offensive might which may someday be directed against us.
Posted October 28, 2016