WASHINGTON — A recent U.S. National Research Council (NRC) report that concluded, among other things, that boost-phase missile defense systems are impractical is fundamentally flawed and cannot serve as a basis for policy formulation, according to a pair of scientists.

In an article published Sept. 20 in the Bulletin of the Atomic Scientists, George N. Lewis and Theodore A. Postol were unsparing in their assessment of the report prepared by an expert NRC panel: “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.”

The NRC report — titled “Making Sense of Ballistic Missile Defense: An Assessment of Concepts and Systems for U.S. Boost-Phase Missile Defense in Comparison to Other Alternatives” and released Sept. 11 — said the only viable interceptors today are those that engage missiles in the midcourse phase of flight, as they coast through space. So-called boost-phase interceptors, designed to hit missiles during the powered phase of flight, cannot be deployed close enough to enemy launch sites to have much chance of success.

Lewis and Postol, who in the past have criticized what they see as exaggerated claims about the capabilities of ballistic missile defense systems, took a different tack in slamming the NRC report’s conclusion about boost-phase interceptors. It is based, they said, on erroneous assumptions about the speed of potential interceptors and the time during which missiles being developed by North Korea and Iran are in the powered, or boost, phase of flight.

“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,” the authors said. “This totally erroneous set of assumptions is the source of the … report’s incorrect conclusion that a boost-phase ballistic missile defense of the United States is not technically achievable.”

The article cited a previous study by the American Physical Society that “mentioned” interceptors capable of reaching speeds of 10 kilometers per second and criticized the NRC report for considering only those with much slower speeds.

The 2004 American Physical Society study did in fact mention interceptors capable of 10 kilometers per second but expressed doubts that these are technically feasible. The U.S. Missile Defense Agency had a program do develop a high-speed interceptor dubbed the Kinetic Energy Interceptor, whose target velocity was 6-8 kilometers per second. That program was canceled in 2009.

The 2004 American Physical Society study also concluded, like the NRC report, that boost-phase interceptors are infeasible from a practicality standpoint.

Lewis and Postol did not directly address what was among the report’s more notable  findings, which is that the deployment of high-speed missile interceptors and X-band radars somewhere in the northeastern United States would make U.S. territorial defenses far more effective. The current U.S. territorial shield relies on interceptors deployed at Vandenberg Air Force Base, Calif., and Fort Greely, Alaska.

But the authors did take issue with the report’s conclusions about the ability of ground-based radars to discriminate between missile warheads and decoys and other debris, which has long been viewed as a major obstacle to effective missile defenses. Ground-based radars are the primary cuing tool for the U.S. territorial shield, or Ground-based Midcourse Defense system, and figure heavily into future plans for the Phased Adaptive Approach for the defense of Europe.

While the NRC panel questioned the ability of current radar systems to discriminate between warheads and decoys, it suggested that better fusion of data from those sensors with data from optical seekers on the interceptors’ kinetic kill vehicles could help solve the problem.

Lewis and Postol challenged that assessment, saying it is based on false assumptions about X-band radar capabilities.

“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 authors said. “The new radars proposed … however, are far too small to be able to discriminate between missiles and decoys at the ranges needed.”

The authors credited the NRC report with suggesting ways to improve target discrimination but said it failed to offer specifics of how these measures might be applied during actual hostilities.

Lewis and Postol concluded that in light of its problems, the report “cannot serve as a basis for formulating national policy on ballistic missile defense.” The authors said they had expressed their concerns to the NRC prior to the report’s release but were told that there were “no bureaucratic mechanisms” for taking those concerns into account in the document.

The NRC’s press office in Washington did not respond by press time to a request for comment.

Warren Ferster is the Editor-in-Chief of SpaceNews and is responsible for all the news and editorial coverage in the weekly newspaper, the spacenews.com Web site and variety of specialty publications such as show dailies. He manages a staff of seven reporters...