John Wohlstetter - Sleepwalking with the Bomb

Missile defense capabilities deployed to date cannot intercept ICBMs, which travel at four miles per second (nearly equal to the five-mile per second orbital velocity of satellites), twice the speed of intermediate-range missiles and about four times the speed of a short-range missile (like the Scud). Such superfast warheads cannot be tracked and intercepted by existing defensive systems.

But the Russians feared that America would be able to surmount missile defense limitations. When U.S. Secretary of Defense McNamara lectured Soviet Premier Alexei Kosygin on the dangers of missile defense at the 1967 Glassboro (New Jersey) Summit, Kosygin countered him with Occam’s Razor (a rule of preference for the simplest explanation): “When I have trouble sleeping, it’s because of your offensive missiles, not your defensive missiles.” McNamara was focused on defensive missiles because he accepted MAD. There is no credible evidence that the Soviets accepted MAD, except, perhaps, as Mainly America’s Destruction. The Soviet Union’s extensive civil defense program indicated a desire to save its population, which is utterly inconsistent with MAD. Even if the shelters would have proven useless, the government’s intention in building them was to protect the very people MAD was supposed to hold at risk. (Nor did America fully accept MAD, as noted in the text.)

As arms talks progressed in the Nixon administration, domestic opposition to ABM—an acronym of Cold War origin that denotes anti-ballistic missiles, still used by many—began to build. Such systems were far more widely known than MIRV, and thus became the primary focus of arms-control attention.

The ABM/MIRV case was a classic example of strategic systems whose development was so closely linked that the “action-reaction” cliché often used by arms controllers—that each side’s programs were primarily driven by similar moves by the other side—held an initial measure of validity. That theory, however, suggested that American restraint would have been reciprocated. By the mid-1970s it became clear that far from emulating American decisions, the Soviets were continuing their massive military buildup despite considerable American restraint, including freezing offensive forces at 1967 numbers. This should not have come as a surprise, in that American and British restraint during the 1920s and 1930s pursuant to the interwar naval treaties did not dissuade Nazi Germany and militarist Japan from rushing pell-mell to build far beyond the limits they had nominally agreed to accept. Nor have the post-1967 proliferators—India, Pakistan, South Africa, North Korea, and nuclear-club wannabe Iran—followed U.S. nuclear restraint.

The 1972 ABM Treaty did not halt development of MIRV. The price of gaining broad support for the first arms-control treaty between the U.S. and USSR included deployment of several modern strategic systems, including those incorporating MIRV. The rationale driving deployment was that as Soviet missiles became more accurate a smaller number of missiles would survive a surprise attack, and these would need enough warheads to be able to fully retaliate and thus preserve deterrence.

While MIRV development continued, ABM development was brought to a virtual standstill. The ABM Treaty permitted each side to deploy 100 missiles to defend a chosen land-based missile-silo basing site and another 100 to defend the national capital city. America deployed its Safeguard ABM in 1974 at the missile base in Grand Forks, North Dakota. Safeguard consisted of a two-layer defense: the Spartan missile designed to intercept ballistic missiles above the atmosphere, and the Sprint missile designed to intercept at low altitude missiles that Spartan missed. The system was never deployed around Washington, D.C., due to very understandable popular resistance to deploying five-megaton warheads close to heavily populated areas. The system at Grand Forks was dismantled in 1976. A 1974 protocol (add-on) to the ABM Treaty limited Russia to 100 ballistic missile interceptors. [57] The Russians had first deployed 64 “Galosh” ABMs around Moscow in 1972.

The systems ultimately deployed by the United States were “dumbed down”—deliberately made less capable of intercepting incoming warheads—in order to conform to arms-control agreements as interpreted by arms controllers. Specifically, radar capabilities and access to satellite tracking data were restricted. Thus when a Scud missile (a short-range, primitive Soviet ballistic missile system sold to several Mideast countries) destroyed a barracks and killed American servicemen in Dhahran, Saudi Arabia, near the end of the Gulf War, the dumbed-down Patriot-3 system failed. It is reasonable to believe, though not definitively provable as it is the road not taken, that unfettered development of missile defense technology would have produced a system able to destroy the Scuds launched during the Gulf War (most landed in Israel). Thus arms agreements already have plausibly prevented deployment of lifesaving defensive systems.

Much of the opposition to missile defense was based upon the sheer infeasibility of defeating a massive missile salvo of the kind the Soviet Union could have launched, using the kinds of systems deployable within arms-control constraints. The uncertainties were similar to those faced by prospective attackers using a large fleet of missiles. Put simply, systems were tested in small numbers, with many tests solo. There is no way for technologists to gauge from such tests how the same systems will perform when used on a large scale. Test trajectories and war trajectories differ, with aim “bias” introduced by asymmetries in the Earth’s magnetic fields. System performance, in a nutshell, may not scale in uniform, linear fashion. Thus offensive system behavior in situations other than those specifically tested cannot confidently be predicted by attacker or defender.

Systems currently deployed intercept missiles either in their final (terminal) phase of flight or in midcourse. Terminal-phase intercept involves separating heavier warheads from lighter decoys in the closing seconds, made possible when warheads encounter friction in the atmosphere, which then separates the two based upon weight and density differentials. But with time so short, taking out a large salvo—even if defense radars were not destroyed, a highly shaky assumption—is a complex task. Midcourse intercept targets ballistic missiles coasting in space on unalterable trajectories (like artillery shells), but where the zero gravity of space makes separating warheads and decoys extremely difficult.

The result is a set of complex trade-offs, well illustrated by Paul Nitze in his memoirs. The early U.S. systems relied on nuclear warheads to destroy warheads with near misses. The altitude at which decoys begin to slow down sufficiently to be separated from actual warheads is about 250,000 feet, just under 50 miles up. Under 100,000 feet—19 miles up—marks a line below which detonating nuclear devices is out of the question when defending cities. This offers some 30 miles in which to engage decoys; below 19 miles, nonnuclear or kinetic-impact missile defense warheads must be used. Silo defense is less demanding, as incoming warheads can be engaged well below 100,000 feet, where lighter decoys are out of the way, and thus genuine warheads will be easier to identify.

Ultimately perhaps more promising, but strongly opposed by the Russians, are boost-phase intercept systems that target missiles shortly after launch. The missile is traveling far more slowly than in space; decoys cannot be released and thus intercept could well work, even on a large scale. But such systems, which employ lasers, have had to compete for funding with other defensive ideas. Because such intercepts would likely take place over the attacker’s territory, potential attackers, including Russia, vigorously oppose their deployment.