Whys and Why Nots of Dense Pack

Putting all of America's MX eggs in one basket seems to defy common sense. But there is a certain logic to Dense Pack that can only be understood in terms of the strange and fearsome technology involved. The closer the Soviet missiles come to the 21-sq.-mi. Wyoming strip, the closer they come to each other. When the first finally explodes just above its target, its apocalyptic power is turned against fellow Soviet missiles. Its blast, and those of any succeeding warheads that manage to detonate, would cause mutual missile annihilation known in the lexicon of strategic warfare as Fratricide.

The initial Soviet H-bombs would create powerful shock waves (throwing warhead guidance systems off course), searing temperatures (high enough on the periphery of the fireball to incinerate other warheads) and a flood of radiation (highenergy gamma and X rays, plus neutrons, which would wreck a warhead's electronics). The blast would also produce the deadly vacuum characteristic of all thermonuclear explosions, destroying almost all the atmosphere in an incoming warhead's path and effectively ending its maneuvering ability. Any warheads surviving these multiple perils would probably be burned up by frictional heat as they plunged earthward at more than 5,000 m.p.h. through dust and debris. Under its worst-case scenario, the Pentagon figures at least 70 of the MXs would survive in their superhardened silos.

The underground communications centers, housing the vital electronics for firing and controlling the MXs, would be similarly shielded, relying on fiber optics and lasers rather than conventional wiring to resist the devastating effects on electrical circuits known as electromagnetic pulse (EMP) from nuclear blasts. To clear the way for the missiles, giant, hydraulically powered blades would rise out of the silos and sweep away obstructing rubble. Once launched, the MXs would be traveling much slower than the incoming Soviet missiles. Thus, as they rose through the cloud of dust and debris, the buildup of heat on their exteriors would not be disabling. Says Under Secretary of Defense Richard DeLauer: "We can fly the MX out before he [the Soviets] can fly his missiles in."

As sound as Dense Pack may seem in the Pentagon's hard sell, many scientists believe it is fatally flawed. Says IBM Physicist Richard Garwin: "Fratricide may well be true, but it is irrelevant because it can be defeated." The Soviets, for example, could avoid Fratricide by dropping a single warhead at a time, beginning with the southern end of the Wyoming strip, at a rate of one every 20 to 40 sec. Strategists call such a barrage Slow Walk. The Pentagon says that the first detonations would leave so many particles in the atmosphere that the incoming warheads would still burn up before they could do any damage.

The Soviets might resort to another ploy known as Pindown. By repeatedly exploding missiles high above the silos for several hours, they would create a blanket of floating debris, thermal shocks and high radiation that would keep the American missiles trapped in their silos. But the Pentagon replies that even if Pindown worked, which it doubts, the MXs could eventually be launched.

Critics say the Soviets might try to develop missiles that bury themselves in the ground and explode in what the planners call Earth Penetrator. Or the Soviets could try to detonate them simultaneously right over the targets. The Pentagon retorts that incredibly precise timing would be needed: the missiles would have to explode within a millionth of a second of one another to avoid Fratricide--a capability, U.S. intelligence sources optimistically estimate, that will not be achieved by the Soviets for at least ten years. Says Berkeley Physicist Charles Townes, a key Pentagon adviser: "The Soviets are resourceful guys, fully capable of developing ways to counter Dense Pack sooner than anybody expects."

Dense Pack depends on many calculations and assumptions, most of them untested and untried, perhaps happily so. If only one of them proved wrong (for example, that the U.S. can build silos and subterranean communications centers able to withstand the effects of a nuclear blast), Dense Pack might fall apart like a house of cards. And scientists are all too familiar with that law of Mr. Murphy: if anything can go wrong...

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