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The reaction speed of such a missile must be almost instantaneous to blast off the ground, intercept and, through a precisely timed nuclear blast, destroy enemy missiles coming in at 17,000 miles an hour. "Traffic handling" refers to a system that prevents a flock of U.S. anti-missile missiles from blowing up each other as they climb to find enemy weapons. "Decoy discrimination" is a system that keeps the ABM from exploding harmlessly on contact with phony missiles and other chaff shot along with an attack. "Blackout effects" are caused by nuclear explosions of ABMs attacking an enemy bombardment, disrupt sound and electronic impulses in the gear that is tracking the incoming missiles.
As McNamara said, work on most of these problems could be carried out without the atmospheric atomic tests that would be banned by the treaty. Atmospheric tests would surely be useful in perfecting a warhead for an antimissile missile, but McNamara insisted that satisfactory progress could also be achieved with the underground tests that the treaty permits. As for solving the blackout problem, which cannot be duplicated without actual atmospheric testing, McNamara only said lamely: "We will be able to design around the remaining uncertainties."
Caveat to Cheaters. But what might be the effect upon today's U.S. nuclear superiority of Russian treaty cheating? McNamara argued that the U.S. could almost certainly detect any Russian nuclear tests of a size worth conducting. He conceded that the Soviets might get away with a test in deep space—20 million or more miles away from the earth —but such tests "would involve years of preparation, plus several months to a year of actual execution, and they could cost hundreds of millions of dollars per successful experiment." Anyway, he said, the U.S. plans to launch within two months twin satellites under the Vela-Hotel program (TiME, Aug. 9). These space-snooping detectors are designed to spot unshielded nuclear blasts 200 million miles away from the earth.
The U.S. is also considering ordering more high-flying U-2 aircraft for scooping radioactive debris out of the air, more acoustic and pressure-sensing devices for feeling the pressure waves of a nuclear blast, more sensitive radio devices for detecting a shift in radio signals caused by 10,000-mile-high blasts, more instruments for spotting fluorescence caused when X rays from a nuclear explosion in space excite nitrogen in the ionosphere.
Still, what if the Soviets suddenly abrogated the treaty and started testings without attempt at concealment? McNamara, again, was reassuring: "The consensus is that the Soviets could not in a single series of tests, however carefully planned, achieve a significant or permanent lead in the strategic field, much less a 'superweapon' capable of neutralizing our deterrent force." More important, McNamara promised that the U.S. would maintain "the vitality of our weapons laboratories" and "the administrative and logistic capabilities required to conduct a test series in any environment."