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Leading Scientists See Fatal Flaw in Missile Defenses

By Elizabeth Sullivan

The United States last week took its first step on the path to building missile defenses. A Pentagon contractor began felling trees in Alaska for five missile interceptor silos for which ground is to be broken next spring. President Bush says these silos will be part of a system of missiles and lasers that can shoot down enemy missiles, to protect Americans from nuclear blackmail or catastrophic attack by rogue states.

The Pentagon plans to use the Alaska missiles for expanded tests, to simulate a real attack. But the decision to build the silos is turning the soft rumble of scientific dissent into a roar. Many of the nation's leading physicists now say that the missile-seeking technology at the core of the proposed system won't work in a real attack.

They contend that the government has underestimated the likelihood that rogue states will use warhead-masking decoys, such as Mylar balloons or wire chaff, multiple decoys or decoys that mimic the appearance or heat signature of the real warhead. If that happens, the critics say, there is no evidence that our defensive missiles will be able to pick out the actual weapon.

"I think we owe it to ourselves to examine all technology that can be used for defense against missile attack," said Lawrence Krauss, head of the Case Western Reserve University physics department and author of "The Physics of Star Trek." "But there's a 'can't-do' principle" that drives good science, he said. "And in this regard, the 'law of physics' that I think is important is that any defensive system can inevitably be defeated by countermeasures that are simpler and cheaper."

Pentagon officials and missile-defense proponents acknowledge that tests carried out so far haven't replicated a real missile attack. That's not the objective, they say. "We're not testing a missile-defense system. We're testing missile-defense technology," said Lt. Col. Rick Lehner, spokesman for the Pentagon's Ballistic Missile Defense Organization.

However, the Pentagon has tacitly recognized the intractability of the decoy problem with its latest proposal to "layer" attempts to shoot down an incoming missile all along its trajectory, including just after launch and right before impact. Defense Secretary Donald Rumsfeld says this "layered defense" at the core of a proposed 57 percent increase in the missile-defense budget will make it much tougher for an enemy to use effective decoys.

The core concept of ground-based missile defenses is this: to fire into space a garbage-can-sized bullet atop an intercept missile as soon as warning comes of an enemy missile launch. Ideally, five bullets, or "kill vehicles," would be fired for each incoming warhead. The kill vehicles then have about six minutes to find the incoming warhead and use only the force of impact to smash it to smithereens. To do that, the kill vehicle must select the warhead and not a decoy.

Philip Coyle, who ran the Pentagon's technology testing office for the last six years and is now with the Center for Defense Information, a Washington think tank, likened this to "trying to hit a hole-in-one when the hole is going 15,000 miles an hour and the green is covered with other holes that look just alike."

At least $54 billion has already been spent on creating missile defenses. The final price tag could be more than triple that amount. The effort involves developing scores of new technologies at once, ranging from new infrared "eyes" radars and computer programs that can track and target the incoming warhead to a new generation of low-orbit satellites.

That complexity means doing simple things first, government scientists say. "You have to crawl before you walk," said Bill Davis, an Alabama-based Pentagon consultant who has worked on ballistic missiles since the 1950s. The Pentagon says that's why its recent missile tests have used only a single balloon decoy that stands out because it is so much larger, brighter and of a different temperature than the prototype warhead.

But many scientists say that's tantamount to rigging the last four intercept tests, two of which scored hits. The failures both came because of unrelated technical problems. Ted Postol, a Massachusetts Institute of Technology physicist and former Pentagon missile scientist who has analyzed Pentagon data from a 1997 flyby test, said none of the 10 decoys used in that test could be distinguished from the warhead. After that test, Postol said, the Pentagon simply pared the complexity and number of decoys, from 10 to one.

Lehner said more decoys will be added in future tests. In the meantime, he said, the Pentagon is refining its decoy-detecting abilities using computer simulations. But he questioned how likely it was that rogue states such as North Korea, Iran or Iraq could add complex or heavy decoys to a big, bulky warhead and manage to heft all that weight the thousands of miles required to reach a U.S. city. "A rogue nation is fairly limited just by what they're technologically capable of doing," Lehner said.

The American Physical Society, which with 42,000 members is the nation's largest professional physicists' organization, has called for a delay in building missile defenses until the decoy problem can be solved. But decoys aren't the only potential glitch, according to the critics, who include 50 Nobel laureates. Instead of using a warhead hidden by decoys, an enemy could fire a shotgun blast of bomblets at the United States, said retired Case Western Reserve University physics professor Benjamin Segall. A limited missile defense shield would not be able to shoot down 100 bomblets filled with deadly anthrax before they reached a U.S. city.

Moreover, all four intercept tests used a radio beacon on the warhead to track it from the moment of launch and then steer the interceptor bullet to within 500 miles of the warhead. Lehner said the beacon was needed because the radar and satellites intended to do the same thing haven't been built yet. The beacon is not a homing device and doesn't rig the test, he said. But critics say such "simulations" could prove better than the real thing, since the real thing remains on the drawing boards.

"Whether the actual data from the satellite would be as good as the simulated data is now, we're obviously several years and several billion dollars away from answering that question," said John Pike, who runs GlobalSecurity.org, a Virginia-based watchdog group.

Then there is the question of what's driving the decision to start building missile silos next spring. Lehner said the silos would answer scientific concern by improving test realism, including increasing the number, range and complexity of tests.

But the five silos to be built at Fort Greely, Alaska, cannot be used for testing, since the rocket boosters might drop onto populated areas. About 3,000 people live near the old Army base and nearby town of Delta Junction. Wild buffalo herds still roam in the heavily forested area, about 100 miles southeast of Fairbanks. The interceptors will be fired from Fort Greely only in case of an actual attack, Lehner said. For tests, they'll be trucked 500 miles southwest to Kodiak Island, where two other silos are to be built, he said.

Lehner said this awkward arrangement is so the Fort Greely silos can be used in case of any future attack. The Pentagon believes North Korea could be within a decade of acquiring a missile that could hit U.S. cities.

But that also means construction could be construed as deployment of a national missile defense system, potentially violating the 1972 Anti-Ballistic Missile treaty. And for that reason, critics say scientific concerns about the workability of the system should be addressed before the first silos are built.