Harlan E. Anderson

by Harlan E. Anderson

S.A.G.E. stands for Semi Automatic Ground Environment. The computers that were part of  it were the largest ever built and had 60,000 vacuum tubes in each.  Each consumed 3 megawatts of power and  weighed 250 tons. It was the largest electronic military sytem ever built and the total cost was estimated to be between 8-12 billion dollars. There were 24 direction centers and 3 combat centers located throughout the United States and Canada, each housing two of these monster computers in hardened bomb proof buildings. It became operational in 1963 and continued for over 20 years.  It was operated by NORAD which at the time stood  for North American Air Defense Command. NORAD headquarters also had a sysem which was inside of  Cheyenne Moutain outside of Colorado Springs, Colorado.     

Its military purpose was to detect enemy bombers and present graphical information about all of the airplanes in the sky to miliary operators who could decide what to do.  The aircraft data was collected from 100 radar sites, which also had computers  to convert the analog radar signals to digital and send the information over telephone lines to the nearest direction center. There were  150 CRT display consoles in each center and it took 100 persons to operate each center. Military operators could decide what to do,  including  scrambling intercept fighters and automatically providing continusously updated vector heading information to create a successful intercept of the incoming aircraft.

This concept and the demonstration of  its feasibility were develped at M.I.T. Lincoln Lab, where  I had my first computer engineering job out of college in 1952.  IBM built the production versions of the computers. What a thrill to be a small part of such a gigantic project.  Many of the new concepts of  how to use computers were pioneered at M.I.T.  Among these were data communications to computers over telephone lines,  graphical presentation of computer data,  man machine interaction in real time, networking and many others. 

These new technologies had a strong influence on Ken Olsen and me when we  started Digital in 1957. We, of course, had the advantage that transistors for computer were becoming available by that time. We had no particular military application in mind when we started building the PDP-1.  Fortunately, there were lots of  talented customers, many of whom were in scientific work who valued these characteristics and the low cost and speed of our computers. They pioneered many new applications for computers that we benefited from.