Justice and Public Safety

A SAGE Invention

An air defense system in the mid-1950s laid the foundation for the Internet Age.

by / May 11, 2004 0
When military planners built the Semi-Automatic Ground Environment (SAGE), a computer-based command and control system to thwart potential bombing attacks by the former Soviet Union, they had no idea the project would lay the framework for the Internet Age.

Most people today would be surprised to find that SAGE was a precursor to the Internet. It is commonly acknowledged that the Internet Age began in 1969 when the U.S. Department of Defense implemented the Advanced Research Projects Agency Network (ARPANET), whose purpose was to demonstrate how communications between computers could promote cooperative research among scientists.

But the foundation for ARPANET, and the Internet Age, actually began forming in 1954 with the development of SAGE, said Jim Ray, who worked on the SAGE project as a programmer from 1966 to 1969.

"SAGE laid the foundation for the entire Internet Age," he said. "The Internet is based on a number of inventions made over the years, including the ARPANET, but if you trace them all back as far as they could go, you'll find the earliest patents for things like modems, memories and interactive displays trace back to SAGE."

SAGE emerged as a product of Cold War fears. Twenty-three concrete hardened bunkers across the country (and one in Canada) were linked by a real-time, command and control computer system that would detect Soviet bombers carrying atomic bombs and guide American interceptors to destroy them.

"It was a network system, and it worked interactively with the users and had, in a crude sort of way, all the basic kinds of characteristics of an Internet system," Ray said.

The first of the 23 "Direction Centers" came online in 1959, and comprised two Whirlwind computers. Each center took more than 100 people to operate.


The Whirlwind
In 1944, the Whirlwind computer originated as a general purpose flight simulator that was part of the Navy's Airplane Stability and Control Analyzer project. The computer was developed at the Massachusetts Institute of Technology (MIT) and marked one of the first applications of magnetic core memory. It also landed MIT professor Jay Forrester in the Inventors' Hall of Fame.

It was nearly dumped by the Defense Department because of cost, but was salvaged by the Air Force to support the SAGE project. A little-known company called IBM built the AN/FSQ-7 computer, a military-grade version of Whirlwind. Each AN/FSQ-7 weighed 250 tons, required a 3,000 kW power supply and needed more than 49,000 vacuum tubes to operate.

In its original form, Whirlwind was an analog computer, but in the late 1940s, Forrester decided converting to digital would allow for more functions than flight simulation. Forrester's bold move resulted in the first real-time, general-purpose digital computer.

Relying on vacuum tubes when building the computer represented something less than a bold initiative, however, and their use rendered the SAGE project pretty much obsolete the day it was activated in 1958 -- although SAGE endured for 25 years until the Air Force ended the SAGE program in 1983.

"It might still be around today if they'd chosen to build it with transistors instead of vacuum tubes," Ray said, noting that at the time, transistors weren't as fast or accurate as vacuum tubes. "They made the judgment that transistors were risky technology, and they decided to avoid the risk. If they'd taken the risk, today we'd be saying, 'Wow, that was a smart decision.' They didn't."

Though the computer was originally built to use vacuum tubes, it could have been rebuilt to use transistors, Ray said.


A Breakthrough
SAGE was a breakthrough system for many reasons. "It didn't have some of the refinements that [computer systems] had later on, but there were the beginnings of multitasking and a lot of artificial intelligence notions," Ray said, noting that the computers could be programmed to make decisions based on characteristics they detected, but were often not programmed to do so.

"They didn't want to take operations out of the hands of operators," he said. "They wanted the controllers, surveillance people and identification people to make some decisions on their own."

Each SAGE center could track as many as 400 airplanes, and differentiate the enemy from friendly planes by keeping track of flight plans.

The modem's invention allowed each of the 23 Direction Centers to share pertinent data. What was called COMPOOL, an area in system memory that could be shared by various subroutines, was invented and later became a key concept in COBOL.

The SAGE hardware at each center weighed about 250 tons, and SAGE ran 500,000 lines of code. In all, it took six years to develop the SAGE system. That amounted to 7,000 person years of programming and $61 billion.

SAGE employed digitized radar data, long distance data communications via landlines and ground-to-air radio links, and featured a large collection of interactive display terminals. SAGE gathered information over telephone lines from as many as 100 radar and observation stations, processing the information on cathode-ray tube screens. Technicians used "light guns" to track information just as we use a mouse today. The phone bill was around $1 million per month.

Not only was SAGE ahead of its time technologywise, but it also helped pave the way for the programmer profession. Initially scientists worked on SAGE, but there weren't enough of them, so programmers had to be trained.

"When SAGE started out, there weren't many programmers around," Ray said. "They went out and recruited school teachers, taxi drivers, anyone who would take their test, and if they passed it, they would train them to be a programmer."

The project was responsible for training more than 10,000 programmers in the 1950s, and many later worked for ARPANET and the Defense Advanced Research Projects Agency (DARPA).

This eventually led to the organization of the RAND Corp., which spun off of Systems Development Corp. (SDC) to develop SAGE. SDC trained thousands of programmers and sent them into the work force, and many computer engineers from both SDC and IBM started their own firms with the knowledge they gained working on the SAGE project.

The project also helped fatten IBM, which built 56 computers for SAGE, earning more than $500 million. More than 7,000 IBM employees worked on the project at one time.

SAGE technology also contributed to the Sabre airline reservation system, which later became the backbone of the airline industry.

SAGE was much more than a defense system to thwart a bombing attack that thankfully never came.

"It was one of the engineering marvels of the century," Ray said. "If it had looked better, it might have been ranked with the Eiffel Tower, the Saturn Rocket or the Golden Gate Bridge for engineering accomplishment."
Jim McKay, Justice and Public Safety Editor Justice and Public Safety Editor