Zeroing in on the Silo Busters

Long before the March SALT standoff in Moscow, the central issue in the U.S.-Soviet arms race had become the increasing vulnerability of land-based ICBMS to surprise enemy attack. In recent months, U.S. defense officials and strategic analysts have warned repeatedly that the Soviets were rapidly increasing their ability to destroy American missiles. Meanwhile, although the fact has received surprisingly little publicity, the U.S. is on the verge of taking a big step forward in its own ability to knock out Soviet ICBMS in their steel-and-concrete silos. The startling success of the new program has important implications for the delicate balance of terror between the U.S. and the Soviet Union. The developments are bound to be an important factor when the two nuclear superpowers begin low-key SALT talks next week in Geneva, in an attempt to work out a new agreement to replace the current, stop-gap measure that expires in October.

Even Odds. As it happens, October is also the month when the U.S. is scheduled to begin modernizing its 550 land-based Minuteman III missiles. An improved guidance system will be installed in the final stage of the missile. The system will double the accuracy, or halve the "circular error probability," of each of the 1,650 Minuteman warheads. The current version has a fifty-fifty chance of falling within 1,200 ft. of its target; the new model would be even odds to land within 600 ft. (see diagram).

A second and equally important phase of upgrading the Minuteman III will begin in the fall of 1979, when the missile's Mk-12 warhead will be replaced with the Mk-12A. Using miniaturized arming and fusing components, the new warhead will be able to contain enough payload to double its explosive yield from 170 kilotons to 350 kilotons of TNT. This is still far below the 1 megaton (1,000 kilotons) clout of each of the eight warheads carried in the huge SS-18 that the Soviet Union is already deploying. But, with the improved guidance system, the Mk-12A will be much more accurate than an SS-18 warhead, and as a result will have an 80% plus chance of destroying any hardened target it is aimed at. In contrast, the Soviet warhead has a "hard target kill probability" estimated at less than 60%.

This breakthrough dramatically illustrates American technological superiority over the Russians. But it also poses difficult problems in arms control. The advances add one more complex variable to the equation of mutual deterrence. About 75% of the Soviets' 3,500 warheads are carried by land-based missiles that would be vulnerable to the Mk-12A (in contrast, more than 60% of the 8,500 American warheads are mounted on Poseidon and Polaris missiles in submarines). Understandably, the Soviet Union is concerned about the new American warheads. Last week Georgy Arbatov, head of Moscow's U.S.A. Institute, which analyzes American affairs and advises the Kremlin, was spreading the word in Washington that the upcoming improvements were more worrisome to him than the advanced U.S. ICBM--the M-X-- which still exists only on paper, or the cruise missile, which has yet to be deployed and is too slow to be used in a surprise attack.

The Soviets are not the only people worried about the plans to refit the Minuteman; U.S. officials are also concerned. Paul Warnke, SALT negotiator, and director of the Arms Control and Disarmament Agency, asserts that from the Soviet point of view the arms race is "coming to a very, very dangerous stage" because of the "spectacular increase" in America's hard-target knockout capability. Warnke compares the danger to what happened when the U.S. developed MIRVS (multiple independently targetable re-entry vehicles). Says he: "We are going to be worse off if both sides are MIRVed than we would have been if neither had been. The same is going to be true about hard-target kill capability."

Tentative Basis. The U.S. was hoping to stop a contest to build the biggest and most accurate silo busters when it presented the comprehensive arms control proposal that the Soviets rejected so brusquely in March. Provisions of the plan would have scrapped the improved NS-20 guidance system and the Mk-12A warhead. In turn, the Soviets would have had to stop improving their own silo busters. Explained Zbigniew Brzezinski, President Carter's National Security Adviser: "We felt particularly by concentrating on the land-based ICBMS that are 'MIRVed,' we would take into account the greatest sources of insecurity on both sides."

As the SALT talks begin again on a preliminary and tentative basis, Defense Secretary Harold Brown believes, despite the doubts of some arms experts, that it would be possible for the U.S. and the Soviet Union to sign an agreement before October, when the Minuteman III improvements would begin. Brown thinks--and Carter agrees-- that the new American silo-busting technology serves as both a stick and a carrot to coax the Soviets into taking action. To the Kremlin, the stick is the disquieting knowledge that the refitted Minuteman III could knock out vast numbers of their land-based missiles. The carrot is the promise that by signing an agreement, they could prevent the new, sophisticated gear from being deployed (assuming the treaty solved the vexing problem of creating adequate verification provisions).

Whatever the difficulties, the stakes are so high that both the Soviet Union and the U.S. have good reason to want to go to the bargaining table. Without an agreement banning new silo busters --Soviet as well as American--both nations could well be driven to develop even deadlier and more costly weapons. The arms race would accelerate--and escalate--once again.

This file is automatically generated by a robot program, so viewer discretion is required.