Although most Americans favor missile defense, forging consensus on NMD will not be easy. Ideology continues to divide Congress on this issue. Two main factions have emerged: those who fear the threat is imminent and favor a rapid deployment and those who remain skeptical of the technology and favor a "wait and see" approach.
Yet there is one thing on which both factions are likely to agree: A single-layer, midcourse defense, like the Clinton administration's land-based option--designed to intercept and destroy incoming missiles after they are well on their way to their targets--is not the answer. Like most midcourse defenses, it has questionable effectiveness against certain countermeasures and so may not provide a net enhancement to our national security.
But the Bush administration shouldn't abandon the land-based option entirely. Rather, it should be recast as part of a more robust defense construct that will give future presidents the confidence to keep the United States actively engaged in a world where intercontinental ballistic missiles and weapons of mass destruction are prevalent. Augmenting the land-based system with sea-based midcourse defense would help. But negating future threats also demands an ability to intercept ICBMs early on during powered ascent, while their engines are burning and before most countermeasures can be deployed.
Consider the advantages. Midcourse defenses must detect, track and destroy small, hard-to-find targets hidden in fields of debris and decoys. In contrast, boost-phase interceptors can home in on the readily discernible plume of the boosting missile. This reduces the technical complexity of the interceptor's seeker, the brain that guides the interceptor to its target. Moreover, the technology that is required to field this capability is relatively straightforward. If we began a purposeful development effort today, we could reasonably expect to bring boost-phase defense on line faster than a midcourse defense. And given the lower technical hurdles, we could be more confident that it would work.
Although it has limited geographical range and could not counter all threats, sea-based boost-phase defense would help to protect against North Korea, the most immediate concern. At the same time, it would have virtually no capability against Russian or Chinese missiles located far inland; that sends a strong signal to those countries that NMD is not directed against them.
Of course, boost-phase defense comes with its own technical challenges. It, too, can be countered. And since the boost phase is fleeting, interceptors that accelerate rapidly to very high speed are required. But compared to the challenges midcourse defense has overcome, these appear manageable.
Boost-phase defense does not eliminate all vulnerabilities, especially if it's brought on line ahead of a midcourse layer. Since the kill mechanism destroys the booster, not necessarily the payload, the warhead may continue intact but fall short of the intended target. While there is a good chance it would fall into the ocean, it could fall on friendly territory. But with North Korean missiles initially capable of reaching Alaska, Hawaii and then California, the Pacific mitigates this vulnerability. And once the land- and sea-based midcourse layers are on line, that threat will be even less.
There is no silver bullet to defend against ballistic missile attack. Effective defense requires multiple, largely independent intercept opportunities. As the administration reviews its NMD options, boost-phase defense should figure prominently. Over the long term, it could provide a key layer in a robust defense with capability against most countermeasures. But even in the short term, it would enable the United States to meet the emerging missile threat, build on the $7 billion already invested in the land-based option and provide time to reduce risk in that program.
The administration should strive to develop a plan that bridges factional difference on NMD. Republicans and Democrats should agree that the additional expense for capable boost-phase interceptors--probably less than $10 billion--would be a worthwhile investment.
Jeffrey A. Isaacson is vice president of RAND and director of the National Defense Research Institute.
This commentary originally appeared in Los Angeles Times on May 3, 2001. Commentary gives RAND researchers a platform to convey insights based on their professional expertise and often on their peer-reviewed research and analysis.