Defeating ABMs not hard to do

June 15, 2000|By Jonathan A. Bagger

DURING THE next few months, President Clinton will decide whether to deploy a national missile defense system. Earlier this month, he traveled to Moscow to ask Russian President Vladimir Putin to modify the Anti-Ballistic Missile Treaty, a cornerstone of our national security for almost 30 years.

In Washington, politicians and pundits are engaged in heated debate on the costs and benefits of the proposed missile defense system. Few, though, are asking the most basic question of all: Will it work?

The purpose of the system, which is estimated to cost $49 billion, is to defend the United States from a limited missile attack from a "rogue" state or from the accidental launch of a few Russian missiles. The plan is for ground-based interceptors to race into space and smash into the incoming missiles. Is this too good to be true?

It is.

A recent study by the Union of Concerned Scientists and the Security Studies Program at MIT examined the complete missile defense system and found that its collection of radars, satellite-based sensors and ground-based interceptors could be easily defeated by simple countermeasures.

The countermeasures would confuse or overwhelm the defense.

For example, an attacker could hide its nuclear warheads inside aluminum-coated Mylar balloons and then release them along with dozens of empty balloons. The missile defense sensors cannot distinguish the decoys, so all the balloons would need to be destroyed. Even a minor attack could easily exhaust the supply of interceptors.

Alternately, a warhead could be enclosed in a thin shroud cooled with liquid nitrogen. In that way it would be invisible to the heat-seeking interceptors the defense will use.

An attacker using biological weapons would necessarily separate each missile payload into 100 or more small "bomblets." The bomblets would easily overwhelm the defense.

In fact, a determined terrorist does not even need a missile to deliver a limited nuclear or biological attack.

These problems are endemic to a missile defense in which interceptors hit targets directly in outer space. There is no way to alter the design to make it effective against such countermeasures. These objections are serious and perhaps even fatal to the proposed system.

Moreover, decoys are easier and cheaper to develop and deploy than long-range missiles. They are well within the capability of any state that can deploy such a missile. Indeed, the 1999 National Intelligence Estimate, prepared by the U.S. intelligence community, warned that emerging missile states could use "readily available technology" to develop countermeasures.

In April, the American Physical Society, which represents more than 42,000 physicists, stated that the United States should not deploy a missile defense system until it "is shown -- through analysis and through intercept tests -- to be effective against the types of offensive countermeasures that an attacker could reasonably be expected to deploy with its long-range missiles."

Such tests have not been done, nor will they be done before the president makes his decision. A decision on missile defense is too important to be made without a full understanding of whether the system will work.

Political forces are pushing a hasty decision, before realistic intercept tests have shown that the system can defeat realistic countermeasures. No decision should be made until after the system has been successfully and repeatedly tested against a credible threat.

A viable missile defense system must be based on the laws of physics. Otherwise, all the wishing in the world will not make it work.

Jonathan A. Bagger is a professor of physics at Johns Hopkins University.

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