Just a few weeks ago, on September 11, the National Academy of Sciences issued a report titled "Making Sense of Ballistic Missile Defense: an Assessment of Concepts and Systems for US Boost Phase Missile Defense in Comparison to Other Alternatives." It is an astonishing document, given that it purports to be the product of a respectable scientific institution. It contains numerous flawed assumptions, analytical oversights, and internal inconsistencies. It also contradicts basic, scientific results from other published studies that have already been independently reviewed and verified. These serious problems lead to fundamental errors in many of the report's most important findings and recommendations, ultimately undermining its credibility as science-based analysis.
The National Academy concluded that the United States could not field a workable boost-phase missile defense against intercontinental ballistic missiles (ICBMs) launched from North Korea or Iran. This conclusion is totally incompatible with the findings of earlier science-based reports on this defense system and the ballistic missile threat.
In particular, the National Academy report heavily depends on results from an American Physical Society study on boost-phase missile defenses published in 2003. That study discussed boost-phase interceptors that have speeds up to 10 kilometers per second, while the National Academy report only considers the interceptors that have speeds of 4.5 and 6 kilometers per second. Even though the National Academy report frequently cites the American Physical Society study, it provides no justification for neglecting the higher-speed interceptors considered in that study.
Moreover, the National Academy of Sciences report ignores the vast amount of new information that has become publicly available about missiles under development by both Iran and North Korea in recent years. A boost-phase defense attempts to destroy intercontinental ballistic missiles after they are launched and before they complete powered flight; these missiles cannot release warheads and countermeasures until this powered phase ends. Nations with limited technical and industrial capacities are incapable of implementing effective countermeasures against such a boost-phase defense, giving it an inherent advantage over midcourse defenses that seek to intercept missiles at high altitudes, where a wide range of potentially highly effective countermeasures is available.
It is now known, thanks to recent comprehensive studies by the EastWest Institute and the International Institute for Strategic Studies, that the only vehicle Iran or North Korea might eventually be able to convert into an ICBM in the next decade or two has a powered flight time of a little more than eight minutes. Yet the National Academy of Sciences assumes, as if there were no data to the contrary, that North Korea and Iran could build a much more advanced ICBM that finishes powered flight in half the time the North Korean launch vehicle requires.
The two assumptions we have just described -- an arbitrarily slow interceptor and an unreasonably fast-burning ICBM target -- reduce the ranges at which boost-phase defenses could operate by a factor of three to four. This totally erroneous set of assumptions is the source of the National Academy of Science report's incorrect conclusion that a boost-phase ballistic missile defense of the United States is not technically achievable.
Similarly, the National Academy report reaches erroneous conclusions about both the nation's Ground-Based Midcourse Defense system and the European Phased Adaptive Approach by basing the conclusions on greatly overestimated radar ranges. The report proposes deploying new X-band radars alongside existing early warning radars in order to address the midcourse defense system's inability to discriminate actual warheads from debris or decoys. The new radars proposed by the National Academy, however, are far too small to be able to discriminate between missiles and decoys at the ranges needed. In fact, the National Academy approach exactly mirrors one proposed by the Clinton administration, which would also have deployed new X-band radars alongside existing early warning radars -- except that those suggested radars were nearly 400 times more powerful in terms of the signal-to-noise ratio obtained against a given target.
The excessive radar ranges assumed by the National Academy also directly contradict technical findings in an important Defense Science Board report released by the Defense Department last year. The report found that the ranges of the radars in the European Phased Adaptive Approach were too short to provide even basic tracking data for missile defense purposes. Our own calculations also demonstrate this to be the case. Yet the National Academy of Sciences report simply states that the radars currently in the European Phased Adaptive Approach are sufficient to make it work, without showing any evidence of how this contradictory conclusion was reached.
The Defense Science Board also reported that neither the European Phased Adaptive Approach nor the Ground-Based Midcourse Defense system can reliably tell the difference between warheads and decoys or rocket debris. The board's report showed how such an inability to discriminate meant that the systems would not work in combat. The National Academy of Sciences report mentioned ways to improve discrimination, but offered no specific technical insight about how such capabilities could be made workable during hostilities.
In 1999, the CIA published an unclassified National Intelligence Estimate that enumerated very simple countermeasures against missile defense systems that, the agency concluded, could be implemented by any adversary able to build an ICBM. Yet the National Academy's report has nothing specific to say about how their proposed systems could be used by the Ground-Based Midcourse Defense and European Phased Adaptive Approach systems to defeat such countermeasures. Instead, the National Academy, without any evidence to support its claims, states that its approach to discrimination "offers the greatest probability" of success against countermeasures. This claim is remarkable -- particularly because the radars that the National Academy points to as essential for such discrimination have ranges that are far too short to collect the basic data that would be needed to discriminate between decoys and warheads.
The National Academy of Sciences report contains serious inconsistencies that become obvious when it is compared with last year's Defense Science Board report and the earlier American Physical Society Boost-Phase Study. The National Academy also has no answer to how the defense systems it recommends could cope with countermeasures that could be deployed by adversaries that build ICBMs. In addition, the National Academy's report has serious internal contradictions that are inconsistent with the underlying physics of its own recommendations.
Given these problems, this report cannot serve as a basis for formulating national policy on ballistic missile defense. Prior to the publication of the report, we communicated our concerns to the National Academy of Sciences, only to be told that it had no bureaucratic mechanisms for taking them into account. (For additional information, see the two letters we wrote to the chair and ranking member of the House Armed Services Committee on August 20 and Sept. 4.) It is clear that there is a need for a comprehensive, scientifically based, and open review of the technical foundations of the National Academy of Sciences report. Such a review is essential if the National Academy is to fulfill its role as the government's chief science advisor in this important matter of national security.
