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Additional Reading

D.L. Clark, “Early Advances in Radar Technology for Aircraft Detection” (pdf), Lincoln Laboratory Journal, vol. 12, no. 2, pp. 167–180, 2000.

The SAGE Air Defense System

The Semiautomatic Ground Environment (SAGE) Air Defense System is the beginning of MIT Lincoln Laboratory's history of developing innovative technology. The legacy of SAGE is two-fold: computing was transformed and system engineering was born.

Under its initial name of Project Lincoln, the Laboratory was conceived as a research and development enterprise tasked by the Air Force to develop an air defense system that would counter the threat of air attacks launched at the United States.

The system to meet this challenge, SAGE, was designed to collect, analyze, and finally relay data from a multitude of radars, all quickly enough that defense responses could be initiated if needed. The challenges to this system were the transmittal of vast quantities of radar data via telephone lines to a central computer and the computing speed required to interpret and relay the resulting analysis to U.S. air commands and aircraft.

The Whirlwind Computer

The key to this system was a computer that could perform reliably in real time. MIT's Whirlwind computer, built in the 1940s, looked to be a possible candidate for the system. However, the Whirlwind was not reliable or fast enough for the processing needed for analyzing data coming in from dozens of, perhaps even 100, radars. Jay Forrester, an MIT professor instrumental in the development of the Whirlwind, found the breakthrough to enable the computer to achieve outstanding reliability and doubled speed—the magnetic-core memory.

The magnetic-core memory revolutionized computing. Computers became machines that were not just large and fast calculators; their uses for varying applications grew. Industry followed this development closely, adopting the magnetic-core memory that expanded the capabilities of computers. Today's computer technology explosion is the offspring of the SAGE project.

The Cape Cod System

Between 1953 and 1956, the concept of the SAGE system was tested on a small scale in what was called the Cape Cod System. Simulated detection, identification, and interception of air targets of interest were performed using a series of radars existing in the Cape Cod region in conjunction with the SAGE computer operations. The Cape Cod System was a success for Lincoln Laboratory, demonstrating that an automated air defense system could detect and intercept incoming aircraft.

To maintain the Laboratory's mission as a research and development incubator, the building of the SAGE computer centers and the implementation of the system passed to contractors. In fact, the MITRE Corporation was spun off from the Laboratory specifically to become a provider of systems engineering for SAGE. By 1963, more than 20 SAGE computer centers were deployed across the United States, each linked to more than 100 air defense components, such as radars, and all working interoperably.

SAGE's Legacy

In his 1998 book, Rescuing Prometheus, Thomas P. Hughes proposed that SAGE's lasting contribution to technology development was not just the breakthrough computer discoveries but also the demonstration of a systems approach to solving problems. The SAGE success showed the effectiveness of having "scientist-managers" treat a project as an evolving whole composed of distinct but interrelated parts.

 

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