August 1956 Popular Electronics
Table of Contents
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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.
SAGE - Whirlwind Defense Quarterback Goes into Operation
By E. D. Morgan
Plunging through the enemy line of aerial and atomic attack, SAGE is ready to make a touchdown for
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
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.
The computer which forms the nucleus of the SAGE system is known as an AN/FSQ-7.
One of the world's largest and fastest, it contains 25,000 vacuum tubes. Maintenance console is shown
Memory unit of computer, made up of three-dimensional array of ferrite cores, receives a constant
stream of flight data.
Cathode-ray tubes are used to display composite pictures of the changing air situation
in a television-like manner. Locations of all aircraft and their identifications can be observed. The
consoles at the left are part of Whirlwind I, a forerunner of the present computer.
Electronic equipment shown above is installed in one of the gap-filler radar stations
which are located between more powerful long-range search transmitters.
Ground-to-air guided missiles are a key factor in our defense. A "Nike" battery,
shown ready for firing, can locate and destroy enemy aircraft by means of electronic brain. The "Nike"
is the nation's first combat-ready surface-to-air guided missile.
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
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,
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
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
Many radar locations have control centers where the search and height-finding radars
work as a team (right). The information is then relayed to the system's direction center for processing.
Interceptors like this all-weather F-86D Sabre provide one
means of downing enemy
planes. The SAGE computer is
capable of flying the plane to its destination using a u.h.f.
link and automatic pilot. "Mighty Mouse" 2.75 - inch
rockets are fired from a retractable pod beneath
Posted October 28, 2016