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Mid-Canada Line. With SAC bombers warned and on their way, electronically guided elements behind the DEW lines —interceptor fighters and guided missiles, already in place—would take on NORAD's second function, the interception and destruction of the attackers. Some 600 miles south of the Arctic DEW line, -the mid-Canada line's double fence of warning stations would pick up the invaders, plotting information on course for their interception in the air north of settled areas. Aircraft control and warning stations of the Pinetree system along both sides of the U.S.-Canadian border would be brought into action, pinpointing the targets in the sky with their radar, and directing their destruction by antiaircraft fire, guided missiles or interceptor planes, now in the process of being armed with nuclear-warhead rockets. Behind the Pine-tree posts, watching for breakthroughs or for flank attacks from the sea, are a host of additional AC&W units, including lines of offshore picket ships, Air Force RC-121 Super Constellations, Navy ZPG-2W blimps and, in the Atlantic off Cape Cod, a Texas Tower (two others are under construction, off Nantucket and New Jersey).
Helping to speed interception are newly developed SAGE (SemiAutomatic Ground Environment) system units, now being installed at direction centers of Air Divisions into which Canada and the U.S. are divided for defensive action. Into SAGE computers will be fed information about aircraft anywhere within the Air Division's radar area. This information will instantaneously be translated into symbols on TV-like picture tubes, showing current air situations, and automatically calculating correct employment of defense weapons.
As air battle commanders watch the picture, they can direct interception by remote control, automatically ordering "scrambles" by interceptor planes at nearby bases, or fire from antiaircraft and Nike guided-missile batteries in the area. In either case, the interceptors or missiles will be steered to the targets by directions from SAGE. As the battle moves, information will be automatically transferred to computers and picture tubes in the adjacent Air Division area.
All of this deterrence to a manned bomber attack must have a raising of sights against missiles. Columbia University's Electronics Research Laboratories and the Air Force have developed a 3,000-mile, anti-missile radar-detection system, but huge appropriations and long months of testing are needed before it can be superimposed on NORAD's present defenses. Nike-Zeus and Wizard anti-missile missile systems, and an Air Force Special Weapons Center's proposal to use nuclear explosions as defense weapons against ICBMs in outer space, are similarly far from test stage. "The new system, the one we must have," says General Partridge, "will embrace the basic principles of the present system, but we will have to speed it up from minutes to three, four or five seconds."