President Obama’s plans for reducing America’s nuclear arsenal and defeating Iran’s missiles rely heavily on a new generation of antimissile defenses, which last year he called “proven and effective.”
His confidence in the heart of the system, a rocket-powered interceptor known as the SM-3, was particularly notable because as a senator and presidential candidate he had previously criticized antimissile arms. But now, a new analysis being published by two antimissile critics, at M.I.T. and Cornell, casts doubt on the reliability of the new weapon.
Mr. Obama’s announcement of his new antimissile plan in September was based on the Pentagon’s assessment that the SM-3, or Standard Missile 3, had intercepted 84 percent of incoming targets in tests. But a re-examination of results from 10 of those apparently successful tests by Theodore A. Postol and George N. Lewis, being published this month, finds only one or two successful intercepts — for a success rate of 10 to 20 percent.
Most of the approaching warheads, they say, would have been knocked off course but not destroyed. While that might work against a conventionally armed missile, it suggests that a nuclear warhead might still detonate. At issue is whether the SM-3 needs to strike and destroy the warhead of a missile — as the Pentagon says on its Web site.
“The system is highly fragile and brittle and will intercept warheads only by accident, if ever,” said Dr. Postol, a former Pentagon science adviser who forcefully criticized the performance of the Patriot antimissile system in the 1991 Persian Gulf war.
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