Nation: An ABM Primer

Four months ago, President Nixon announced his decision to go ahead with deployment of an anti-ballistic-missile system called Safeguard. This week the issue is scheduled to come before the Senate, probably for more of the acrimonious debate that has divided scientific experts, politicians and laymen. The essence of the argument:

What is Safeguard supposed to do?

The system proposed by the President and Defense Secretary Melvin Laird is designed primarily to protect U.S. offensive missiles against surprise attack, and also to provide a measure of defense for U.S. cities if an enemy should launch a few missiles at them by accident or by design. Strategically, the argument for the project is that if an ABM defense guaranteed the survival of enough missiles to inflict prohibitive damage on an attacker’s homeland, the aggressor would be deterred from risking the first strike.

The Safeguard system has four key elements. PAR (perimeter acquisition radar) detects an enemy ICBM at long range some time after it has been launched, calculates its path, and then passes the missile track along to the less powerful but much more complex MSR (missile site radar). MSR then directs two types of ABMs against the incoming warheads. The long-range Spartan is designed to make an intercept above the atmosphere, at altitudes between 200 and 400 mi. The smaller Sprint would seek out and destroy warheads that penetrated the Spartan screen by intercepting them within 40 miles of the target.

Is it necessary?

In March, speaking of Soviet intentions, Secretary Laird said flatly: “They are going for a first-strike capability [the ability to so devastate the American arsenal that the U.S. could not retaliate]. There is no question about that.” That statement flew in the face of testimony by Pentagon intelligence experts only a few months before, contending that the Russians were doing no such thing. Laird’s assertion drew charges that ABM advocates have altered intelligence estimates and used classified information that helps their case, while downplaying data that damages it. Laird has since modified his March statement; he now says that the Russians are developing S59 missiles with multiple warheads that would give them the capacity for a first strike against U.S. Minuteman and Titan II ICBMs —but not against Polaris submarines.

The U.S. has other nuclear delivery systems, which include both B-52 and B58 bombers as well as smaller fighter-bomber aircraft.

The distinction is important, because a crucial point in the argument is just how many deliverable H-bombs the U.S really needs to make retaliation a sufficiently convincing threat to the Russians. The “optimum” retaliatory force, according to former Defense Secretary Robert McNamara, consists of 400 one-megaton warheads delivered to their assigned targets, destroying an estimated 30% of Russia’s population and 76% of its industry. The U.S. now has 1,000 Minuteman and 54 Titan II ICBMs, each with a single warhead; 656 submarine-launched Polaris missiles, some of them already fitted with multiple warheads; and hundreds of additional H-bombs in B-52 and B58 bombers.

With all this overkill, the critics ask, would the U.S. not have enough of its deterrent left for an overwhelming retaliatory strike even if the Soviets did wipe out most of the U.S. ICBMs? No one knows for sure. Some of the remaining ICBMs might misfire. The B-52s and B-58s are vulnerable to Soviet fighters and antiaircraft missiles; many of them probably would not reach their targets. Laird hints at Soviet antisubmarine warfare developments that may seriously threaten the Polaris submarine fleet in a few years. Further, he says that Moscow is developing an advanced ABM that could be more effective than its present Galosh system.

Laird’s opponents are not convinced. Among the most outspoken is an M.I.T. triumvirate—Jerome Wiesner, who was scientific adviser to President Kennedy; George Rathjens, recently of the U.S. Arms Control and Disarmament Agency; and Steven Weinberg, a physicist. In a critique released last week, the trio argued “In order to launch a first strike of the sort envisioned by Secretary Laird, the Soviets would need SS-9s with extraordinary accuracy and high reliability; they would need to solve the problem of coordinating an attack on our bombers and Minutemen; they would need to deal with our nuclear-armed tactical aircraft; they would need an effective antisubmarine-warfare system; and they would need a widespread ABM system. We find it unlikely that they will achieve any one of these capabilities, much less all of them.”

Albert Wohlstetter of the University of Chicago, an articulate defender of Safeguard, disagrees. All these things are within U.S. capabilities, he argues, and to be safe, the U.S. must assume that anything it can do the Soviet Union can eventually do too. Wohlstetter questions Rathjens’ conclusion that, at worst, “a quarter of our Minuteman force could be expected to survive a Soviet pre-emptive S59 attack.” Wohlstetter complains that Rathjens overestimates by two-thirds the blast resistance of U.S. silos and unjustifiably assumes that the Soviet multiple warheads would carry only one-megaton payloads. “Where scientists differ,” he concedes, “laymen may be tempted to throw up their hands and choose to rely on the authority of those scientists they favor.”

Wohlstetter’s own calculations agree with those of John Foster, the Pentagon’s Director of Research and Engineering. Foster says that the Russians would need only 420 SS-9s to attack 1,000 U.S. silos—assuming that the SS-9s would each carry three separate five-megaton warheads. Foster concludes: “About 95% of the silos could be destroyed. This would mean 50 of the 1,000 Minuteman missiles would survive.

Will it work?

One question about how well the U.S. ABM would work—or if it would work at all—turns on the vulnerability of its radar guidance. Without it, Spartan and Sprint would journey blind. A nuclear blast outside the atmosphere can create radar blackouts lasting critical tens of seconds, as both U.S. and Soviet tests demonstrated in the early 1960s. A “precursor warhead,” launched just ahead of a missile attack and detonated as a kind of nuclear smoke screen for the following ICBMs, could black out U.S. perimeter acquisition radar and disrupt the ABM defense.

Cornell Physicist Hans Bethe, a Nobel laureate who believes Safeguard to be sound in principle but not yet necessary to U.S. defense, replies that it is possible to intercept the enemy warheads with Sprints at altitudes below 30 miles, where radar blackout is not a serious problem. Further, the PAR installations are designed to overlap enough for one to take over the functions of another —at least in theory—if the second is blacked out or even physically destroyed by a missile that penetrates the ABM defenses.

Another point is that the system requires the most complicated assemblage of sophisticated computers and other electronic gear ever put together, which raises doubts about its reliability—especially since by its nature it can never be tested under conditions accurately simulating a nuclear attack. Wiesner also contends that any ABM is limited by the defender’s guessing about the technology of the weapons it is designed to intercept. The attacker can add chaff and decoys as “penetration aids” to confuse the defender’s radar and exhaust the supply of ABMs. Says Wiesner: “I do not think the defender is ever going to know really what to expect; the variety of techniques available to a nation planning an offensive system is great enough to keep an anti-ballistic-missile system totally off balance.”

What will it cost?

For the 14-site system the Administration has proposed, Laird estimates the price at $10.8 billion. Officials point out that annual review of the need for the program could cut the project off long before that much is spent. ABM critics argue, however, that the final cost will turn out to be much higher. They fear that Safeguard may be only the first segment of a greatly expanded “thick” deployment. Senator Stuart Symington of Missouri, a former Secretary of the Air Force, has put the cost of such a system as high as $400 billion, although even many of Safeguard’s detractors find that figure outlandish. One criticism of Safeguard’s cost goes to a fundamental question of national policy: Should even $10.8 billion be spent on a doubtful weapons system when there are so many desperate domestic needs for the money?

What are the alternatives?

Some of the opposition believe that Safeguard could be shelved by substantially hardening ICBM sites at a smaller cost ($6 billion to $7 billion). The Pentagon wants to do that in addition to Safeguard; the Air Force is already seeking out “hard rock” silo locations that would make ICBMs more resistant even to multimegaton near misses. Wiesner, Rathjens and Weinberg suggest that the number of ICBMs could be doubled for the price of Safeguard, which would mean that more than 1,000 missiles would survive an attack by the 420 SS-9s that the Pentagon’s Foster hypothesized. Wohlstetter answers: “There are safer and cheaper ways of getting [an assured] force of a given size than to buy a much larger one, most of which is susceptible to annihilation.”

Others argue that the ABM is simply not needed because the President of the U.S. can order an all-out counterstrike as soon as he knows that the enemy has launched his offensive missiles; the Minuteman missiles would not be vulnerable to attack because they would be already en route to their targets when the enemy missiles landed. But the President would have only minutes to make this decision. Says Foster: “No President should be required to launch his missiles and ensure the deaths of 100 million human beings on each side just because it is reported that destruction seems imminent.”

What about the Chinese threat?

The Johnson Administration’s original rationale for an ABM system was that it would protect U.S. cities against attack by relatively few Chinese missiles. Since the ABM is now primarily to defend missile sites rather than cities, Wiesner’s group contends that it would not be completely effective against a Chinese attack on population centers. Actually, Safeguard is designed to give some protection to the cities—not nearly enough to ward off a massive attack of sophisticated Russian missiles, but sufficient, in the planners’ view, against the Chinese. The critics say that even the Chinese birds may be too good for Safeguard. Replies Wohlstetter: “There is a striking inconsistency in the way ABM opponents treat the Chinese and the Russians. They assume that the Russians cannot, by 1976 or 1977—20 years after Sputnik—do what we know how to do now. When considering the ability of the Chinese to penetrate an ABM defense, they attribute to them penetration systems that cost us many billions of dollars, a dozen years of trials and many failures to develop. These are rather backward Russians and very advanced Chinese.”

Wiesner makes one telling point, however, suggesting that the Chinese rationale is a red herring. Presidents Johnson and Nixon both indicated that the U.S. would be willing to stop work on ABM if the Russians would do the same as part of an arms-limitation agreement. If that happens, Dr. Wiesner asks, does the Chinese threat suddenly vanish?

Will ABM escalate the arms race?

The Administration contends that Safeguard as such is purely defensive. Indeed, said President Nixon, switching emphasis from defense of the cities to protecting ICBM sites is an earnest of U.S. good faith. If the U.S. sought to guard all its major population centers, it could then—theoretically—attack the Soviet Union first and be relatively safe from a counterstrike.

There is another view, however. By protecting the ICBM sites, while the Soviets thus far have set up only a primitive ABM defense in the Moscow region, the U.S. may encourage the U.S.S.R. to develop vastly more effective offensive weapons—such as MIRVs, Multiple Independently Targetable Re-entry Vehicles—to overcome the U.S. ABM defense. The Soviets may also feel compelled to deploy a more sophisticated ABM system themselves. The U.S. has already tested MIRVs of its own, although they will not be operational for several years. If the cycle of ABM-MIRV goes on unabated, both nations will be tempted to spend great sums of money that will not really increase their security; the new weapons may, in fact, diminish safety. The prospect of a new lap in the arms race could also decrease the chances for serious agreement during the strategic arms-limitation talks that the U.S. hopes to begin with the U.S.S.R. next month. ABM development has not yet done that. The Soviets have not interpreted Safeguard as sufficiently hostile to keep them from taking part in the discussions.