The Limits of U.S. Missile Defense

Expectations may be running too high.

On March 23, 1983, Ronald Reagan announced the Strategic Defense Initiative, popularly known as “Star Wars.” After thirty-two years and tens of billions of dollars, defending the U.S. homeland against attack by strategic ballistic missiles still poses a daunting challenge. Missile defense ambitions have been regularly scaled-back.

The United States should make prudent investments in missile defense as part of its overall force mix. But Washington should bear in mind the limits of technology and the nature of the relationship between offense and defense, in which offense has and, for the foreseeable future will retain, the advantage.

The Strategic Defense Initiative

When he took office, President Reagan was dismayed to learn that he had no way to defend America from a Soviet missile attack. The sole U.S. anti-ballistic missile site had been shut down in 1974, so he had to rely on nuclear deterrence, a concept with which he was fundamentally uncomfortable. Thus, on March 23, 1983, he announced the Strategic Defense Initiative (SDI), posing the question:

What if free people could live secure in the knowledge that their security did not rest upon the threat of instant U.S. retaliation to deter a Soviet attack, that we could intercept and destroy strategic ballistic missiles before they reached our own soil or that of our allies?

SDI spurred research on a variety of technologies to intercept intercontinental ballistic missiles (ICBMs), submarine-launched ballistic missiles (SLBMs) and their warheads. Some effort went into development of ground-launched interceptor missiles with “hit-to-kill” technology, in which a kinetic kill vehicle would be launched and fly into an incoming warhead, destroying both.

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SDI also prompted exploration of more exotic technologies, including ground and space-based directed-energy weapons. The program put significant emphasis on boost-phase intercept, when the heat from rising ballistic missiles could be readily tracked, and destroying a missile would also destroy all the warheads it carried.

One proposed space-based weapon, Excalibur, planned to use the detonation of a nuclear device to power X-ray lasers that would strike ballistic missiles during or just after their boost phase. SDI also investigated chemical lasers and neutral particle beams. Brilliant Pebbles envisaged deployment of a network of autonomous satellites that could release small hit-to-kill projectiles, which would intercept and destroy ballistic missiles and warheads.

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Star Wars sparked controversy because its testing, to say nothing of its deployment, would have necessitated U.S. withdrawal from the 1972 Anti-Ballistic Missile (ABM) Treaty, which tightly constrained U.S. and Soviet strategic missile defenses. The program provoked a minor panic in Moscow. By 1987, however, knowledgeable Soviet scientists such as Roald Sagdeev had begun to assure Mikhail Gorbachev and others that this was indeed rocket science and very hard to do.

The Pentagon and American scientists also became aware of the limits of technology. Despite significant spending, research and development on directed-energy weapons and Brilliant Pebbles did not produce mature technologies that could be used in deployable missile defenses.

Setting More Modest Goals

Meanwhile, the Cold War drew to a close, and President George H.W. Bush presented a more modest vision for missile defense. Global Protection Against Limited Strikes, or GPALS, was comprised of holdovers from SDI, including Brilliant Pebbles.

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The program represented a significant departure from Reagan’s vision of an impenetrable dome protecting the United States. GPALS aimed to stop a small ballistic missile attack on America and to thwart limited strikes against U.S. troops by theater ballistic missiles rather than to defend the U.S. homeland from an all-out Soviet ICBM assault. Though several of the theater missile defense systems initially included in GPALS are part of U.S. missile defenses today, the broader defense never came online.

President Clinton took office in 1993, and his administration cancelled Brilliant Pebbles, instead directing resources toward theater missile defense, influenced in part by the difficulties that the U.S. military had had in defending against relatively primitive Iraqi SCUD missile attacks during the 1991 Gulf War. The U.S. military developed and later fielded the Aegis SM-3 shipboard missile defense system; a hit-to-kill Patriot missile, the PAC-3; and the Theater High Altitude Area Defense (THAAD) missile system.