[Leica] Another in the Computer History Museum series

[kanner at acm.org (Herbert Kanner)]

In the early 1950's, there what was called the "Cold War". With the 
realization the that Soviet Union had nuclear weapons and bombers capable of 
getting here via the North Pole without refueling, some kind of defense 
system became mandatory. The SAGE (Semi Automatic Ground Environment) 
System, a multi-billion dollar system was developed. It had twenty one main 
sites. The computers, which received radar information and then directed 
fighter places, had forty-nine thousand vacuum tubes. Because this system 
was to be operational 24/7, each site had two such computers, and the 
magnetic drum memory units in the two were updated often enough so that they 
could switch computers and the guys on what looked like radar displays 
wouldn't know that they had switched. Here is the console of one computer.

http://gallery.leica-users.org/v/herbk1/L1002792.jpg.html

Here is a typical display unit that simulates a radar. If you look large at 
the left side of the desk, you will see an ashtray and a socket for a 
cigarette lighter (sign of the times--they didn't want the soldier to leave 
the console for a cigarette break).

http://gallery.leica-users.org/v/herbk1/L1002795.jpg.html

There are several ironic facts about this muliti-billion dollar project. 
First, the last of these units was decommissioned in 1983. For several years 
prior, the threat was not bombers; it was intercontinental ballistic 
missiles, for which this system was useless. Well before 1983, the West was 
not manufacturing vacuum tube; every thing was transistorized. Guess where 
we got the replacement tubes. From the Soviet bloc!

The next image shows a tiny fraction of a computer at MIT called Whirlwind. 
It was the progenitor of SAGE. It also has an interesting story, which is 
all about a remarkable guy named Jay Forrester. He was not only an inventor, 
but an incredible project manager an negotiator. It all started around 1946 
when the Navy wanted a flight simulator to use as a pilot trainer for planes 
that had not yet been built, but that were on the drawing boards. They 
believed they knew the flight characteristics. Because the only existing 
digital computer was much too slow, it was clear that it had to be driven by 
an analog computer. But those are hideously difficult to program, and soon 
Forrester realized that the task was impossible. It had to be a digital 
computer, but the several existing ones were still much too slow. So 
Forrester set himself the task of speeding up digital computers by reducing 
the word size and performing many operations in parallel that used to be 
performed serially. I saw this computer--my best guess was in 1953. It was 
imposing. Three of the four walls of the room were filled with panels 
plugged with vacuum tubes. There was a very large cathode ray display tube 
on which "real-time" displays could be seen. A favorite demo was the display 
of the path of a bouncing ball. The image below was cooked up by the Museum 
to show the front of a few panels and their vacuum tubes, and the rear, 
showing components and wiring.

http://gallery.leica-users.org/v/herbk1/L1002818.jpg.html 

Whirlwind initially had a memory consisting of a bank of cathode ray tubes 
(William's Tubes), a fast but unreliable memory. Someone called to 
Forester's attention a new thingy called a "magnetic core," being used to 
temporarily store bits in something called a "shift register" in a computer 
at Harvard. Forrester disappeared into his lab for about eight months, and 
came up with core memory. This became the standard computer memory for the 
next twenty years until semi-conductor memory was invented.

When the Navy lost interest in flight trainers, Forrester persuaded them 
that Whirlwind was the prototype for a Command and Control computer, aka 
"Combat Information Center". There was a new contract. When that petered 
out, he persuaded the Air Force that the computer could be an air defense 
device. The tipping point was the "Cape Cod Experiment". There were enough 
radars around that area to permit a demonstration where bombers would 
"attack" Cape Cod and Whirlwind operators, using radar information, would 
direct fighters to the bombers. This demonstration was so successful that it 
launched the development of SAGE. IBM was the prime contractor; this put IBM 
solidly in the computer business. 

Herbert Kanner
kanner at acm.org
650-326-8204

Question authority and the authorities will question you.