Missile Shield Put in the Cross Hairs

They compare it to hitting a bullet with a bullet.

But knocking a nuclear warhead out of the sky is much harder than that. It’s more like picking a real bullet out of a cloud of fakes, then chasing it down at 20 times the speed of sound and nailing it just right.

President Bush set off world reaction when he proposed developing a missile shield that would have to accomplish such a feat. His administration has offered few details on how the system would work, but enough is known about the available options that scientific critics already have a long list of reasons why it won’t.

Putting a man on the moon was straightforward compared to this, says Nobel Prize-winning physicist Charles Townes. As chairman of the Apollo Project’s science advisory panel, Townes helped deliver Neil Armstrong to the Sea of Tranquillity. He also advised President Reagan’s “Star Wars” project and the MX missile program of the 1970s.

The Apollo program had a fixed goal with known parameters, Townes said. It was extremely challenging technically, but nobody could change the rules once the effort got underway.

With missiles, potential enemies can change the rules at a moment’s notice, making a highly expensive weapon system useless.

“You’ve got to solve all conceivable problems, in a sense,” said Townes, who won a 1964 Nobel for inventing the laser. “I don’t think building anything at this point is justified.”

Other critics are harsher. One called the missile shield the Pentagon has been working on for a decade “technically hopeless.”

Defenders of the system-- which would cost about as much as building and running the international space station for 20 years--say the project has merit.

“I would say we’re very close to a demonstration of the technical feasibility of the system,” said William Davis, former deputy ballistic missile defense program manager with 40 years of experience in missile design.

Of course, whether it works is only a small part of the missile defense debate. Overshadowing the science is a political debate over whether the whole idea of a missile shield is a good one. The technical feasibility of the plan often gets buried under the rhetoric.

The current plans for a missile shield are far less ambitious than the Star Wars visions of the 1980s.

Back then, Ronald Reagan’s Strategic Defense Initiative called for a space-based system that could defeat thousands of incoming Soviet missiles.

Now the goal is to fend off a few dozen missiles. In 1999, Congress directed President Clinton to deploy such a system as soon as it became technologically possible. He considered it, but declined to give the go-ahead near his term’s end.

The current blueprint calls for up to 250 defensive missiles, based in Alaska and maybe North Dakota. If an enemy attacked, these missiles would be launched to intercept the incoming warheads.

A series of radar stations would guide the interceptors into the right neighborhood. Then each interceptor would release what the Pentagon calls a “kill vehicle”--a 120-pound warhead outfitted with cameras and heat sensors to help it find its target.

This approach--the mid-course intercept system--would cost $60 billion and take a little more than a decade to build.

“I think it’s easy to show that mid-course is a technically hopeless situation,” claims physicist Theodore Postol, a Massachusetts Institute of Technology professor and well-known critic of missile defense.

He argues that any nation with a weapons program advanced enough to build an ICBM could easily develop countermeasures to outwit the U.S. system.

For example, an attacker could scatter decoys around each missile. In the near-vacuum of space, there is no gravity or air resistance. Light decoys and heavy missiles would behave in the same way. Even giant Mylar balloons could fool the most sophisticated sensors in such an environment.

Lt. Col. Rick Lehner, a spokesman for the Ballistic Missile Defense Organization, insists that the Pentagon has developed classified means to defeat decoys that Postol and foreign weapons designers don’t know about.

“It’s just a matter of keeping up with what we believe a potential adversary like North Korea or Iran might be able to develop,” Lehner said. “We’re very confident that we have the ability to deal with the missile threat.”

The missile defense did distinguish between a real warhead and a fake during one flight test, in October 1999. But critics have disputed whether that test really demonstrated the system’s ability to outwit decoys. In two subsequent tests, mechanical failures occurred before the decoy ever came into play. The Pentagon plans a fourth intercept test this summer.

The early test flights have been too compromised to demonstrate the system’s feasibility, said Col. Daniel Smith of the Center for Defense Information, a Washington-based defense think tank. The center’s researchers are often critical of missile defense.

But while the tests haven’t shown the system will work, they also haven’t shown it won’t work, defenders say. They emphasize that the failures so far have been caused by mechanical problems, not fatal design flaws.

“We’re improving as we go along, and I think we will demonstrate in the next few tests that we’re getting there,” Davis said.

Defense analyst Baker Spring of the conservative Heritage Foundation points out that the submarine-launched Polaris missile system, a backbone of America’s nuclear deterrent during the Cold War, failed all of its first 11 tests.

Even so, Pentagon officials are considering an alternative to their current approach. Instead of waiting to attack until a missile is at its apogee high above the atmosphere, a “boost-phase intercept” system would hit it as soon as it took off.

The boost-phase system could use either rocket-powered warheads aboard ships or high-powered lasers carried by aircraft. The idea would be to zap enemy missiles out of the sky within a few minutes of launch.

A boost-phase missile shield would be very expensive, and potentially dangerous for the aircraft or warships involved. In fact, a joint study in the mid-1990s by the Navy and Air Force concluded that the expense and risk were just too high, at least for defending against shorter-range missiles.

Perhaps most daunting, the technology needed to create such an interceptor does not yet exist.

A sea-based system would require modifying the Navy’s current AEGIS technology. That could take 20 years and cost up to $40 billion.

As for using an airborne laser, it would have to shoot through the atmosphere hundreds of miles without being diverted by turbulence, extreme temperatures, dust or anything else. The equipment would have to be powerful enough to shoot down a missile, yet light enough to fly aboard a 747 or similar aircraft.

Those obstacles are not insurmountable. But even the best missile defense couldn’t stop terrorists from delivering weapons of mass destruction by truck, low-flying airplane or suitcase, defense analyst Smith points out. And any country with a modest nuclear arsenal, such as China, could easily beef up its stockpile to counter the missile shield.

“There’s nothing really to stop them,” Smith said. “The question then comes down to: Is it all worth the money and the effort?”