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Editor's Note: This story was written for APS News by Jordan Raddick.
"How do you assess something as successful when it didn't work at all?" asked George Lewis of MIT, one of the recipients of this year's Joseph A. Burton Forum Award, given annually by APS to recognize physicists who work towards resolving issues of physics in society. Lewis said that the Army assessed the Patriot missile, used in the Persian Gulf War to shoot down enemy missiles, to be 61% successful. However, analysis of news media footage showed that almost every Patriot missed its target. With President Bush likely to pursue plans for a National Missile Defense system, Lewis said, determining the effectiveness of antimissile missiles is important. "We only have one experience with ballistic missile defense," Lewis said of the Patriot.
Lewis was one of three arms control physicists to receive this award, which was given at this year's April meeting in Washington, DC. All three-Lewis, David Wright, and Lisbeth Gronlund-spoke about arms control issues during the prize session.
Lewis said that the Army classified all data it used in its analysis of the Patriot's performance during the war; however, its methodology was unclassified. Its definition of success required only that the Patriot arrived at its programmed intercept point, and that the missile it was defending against caused no significant ground damage. This methodology allowed the Army to declare the Patriot successful even if the Patriot missed the other missile completely. Lewis said that since the Patriot data were unavailable, it was fortunate that such good video was available for independent analysis. "Physics cannot be classified," he said, in response to a question about how analysis could be done without access to classified data.
David Wright, of MIT and the Union of Concerned Scientists (UCS), spoke about how he used knowledge of North Korea's previous missile tests to estimate the state of that country's current missile program. In 1998, North Korea launched a three-stage missile over Japan in an attempted satellite launch. Japanese Navy vessels knew where each stage of the missile splashed down; Wright used these data to calculate the missile's speed when each stage separated, from which he calculated each stage's thrust. He compared these data to data from previous North Korean missile tests to estimate the current technological level of the North Korean missile program. Since North Korea is considered a primary potential missile threat to the United States, a technical understanding of their missile program is valuable input to the debate over national missile defense. "By doing a relatively simple technological analysis," Wright said, "you can learn interesting things."
The third award recipient, Lisbeth Gronlund from UCS and MIT, spoke about the testing that would be required to gauge the effectiveness of a National Missile Defense system. She said that there is a law that requires new military hardware to be tested thoroughly before it is bought. "This is a rational attempt to make sure the US buys systems that work," she said. However, under President Clinton, the Pentagon decided that rather than consider the procurement decision to be about buying a certain number of interceptors, they would consider it to be a decision to buy a National Missile Defense system, therefore exempting it from the legal requirement. Clinton's plan, which Bush will likely renew, calls for the President to decide whether to purchase the interceptors in 2003, before operational tests begin.
Gronlund said that, according to a leak from a classified document, the Pentagon wanted to have 95% statistical confidence that the National Missile Defense system would be 95% effective against ballistic missiles. To achieve this level of confidence and effectiveness, the system would have to succeed forty-seven times out of fifty tests, and would have to repeat this performance across a wide range of missile approach trajectories, day and nighttime conditions, and enemy countermeasures. Gronlund stated that the military would not be able to conduct all the tests required to obtain the confidence and effectiveness it seeks.
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