WASHINGTON, D.C.--Proponents of the controversial $7 billion National Missile Defense System (NMD) being developed by the Pentagon believe that interceptor missiles will be able to crash into enemy warheads as they sail high above the atmosphere (Science, 16 April 1999, p. 416 ). Don't count on it, says the Union of Concerned Scientists (UCS). According to a technical report released today by the union, any country that can build an intercontinental ballistic missile can also take simple countermeasures to sidestep the NMD's interceptors.
The "Star Wars" program and other previously proposed missile defense systems sought to thwart an attack of thousands of missiles; the NMD aims to protect the United States from a few dozen nuclear missiles launched by a weak but unpredictable foe such as Iraq or North Korea. To see if the system can meet this less ambitious goal, an 11-member UCS review panel led by Andrew Sessler, a physicist at Lawrence Berkeley National Laboratory and former head of the American Physical Society, used unclassified data to study how the NMD would match up against three countermeasures.
The panel found that the heat of a nuclear warhead can be concealed by a metal shroud filled with chilly liquid nitrogen, making the warhead virtually invisible to the interceptors' infrared eyes. Similarly, interceptors won't know which target to hit if the warhead hides in one of a flotilla of radar-reflecting balloons, which will whiz along together in the emptiness above the atmosphere. The missile defense also can be overwhelmed if each incoming missile carries dozens of small warheads containing chemical or biological weapons.
Pentagon planners say they will "study" the report. In the meantime, the findings provide ammunition for skeptics in Congress, who fear deploying the system will shatter the 1972 Anti-Ballistic Missile Treaty. "We may build, at great expense, a system that will be obsolete by the time it is deployed," says Representative Thomas Allen (D-ME), a member of the House Armed Services R&D subcommittee. The next missile test is slated for June, and the Clinton Administration may decide by October to deploy the first phase of the system, which could be in place by 2005.