Future Anti-Missile Research Directed to Countermeasures.

• Author: Erwin, Sandra I.

Despite the Bush administration's bullish outlook on the deployment of a missile-defense shield during the next decade, there is a lot of work yet to be done in the laboratory, said U.S. government scientists.

The United States could end up spending between $20 billion and $100 billion to deploy ground-, air-, sea- and space-based anti-missile weapons during the next two decades. The goal is to be able to intercept and destroy in flight, both tactical and intercontinental ballistic missiles that would be launched by potential enemies, such as Iraq, Libya or North Korea.

But it would be foolish to deploy such anti-missile systems unless they were intended to defeat not just the rogue-nation ICBM blitzes that U.S. intelligence agencies predicted will occur in the decades ahead, but also more advanced threats and sophisticated countermeasures that may not have been conceived yet, these scientists said.

Among the most challenging technological problems confronting the U.S. missile-defense program, they explained, is the development of more capable sensors and interceptor weapons that can counter multiple targets simultaneously, accurately discriminate between warheads and decoys and put enough kinetic energy on the target to destroy it.

The so-called "hit-to-kill" technology--based on the notion that a warhead (nuclear, chemical or biological) can be destroyed by smashing a high-speed projectile against it--has been tested quite extensively in the past 30 years, said Darrell Collier, chief scientist at the Army Space and Missile Defense Command.

During a question-and-answer session with reporters in Huntsville, Ala., Collier acknowledged that mounting criticism about the lack of emphasis on countermeasures has prompted U.S. program officials and scientists to focus more attention on this issue. Countermeasures are techniques--such as decoys, chaff and jamming--designed to fool an interceptor. But Collier cautioned that those who accuse the U.S. government of not doing enough work to address countermeasures may nor be informed enough, given that "countermeasures is a very difficult subject to discuss in the open." Much of the technology related to countermeasures is classified, Collier said.

Nevertheless, he said, "It's beneficial to be reminded that you've got to work this problem in a very uncertain environment--and that the guys on the other side might well be thinking of these. ... With countermeasures, we have to make investments and keep working. It's not a dosed universe."

The idea that a kill vehicle is largely ineffective unless it can discriminate between warheads and decoys has led to new requirements in the missile-defense arena that had not been addressed in the earlier years of the program, Collier said. In the 1960s and 1970s, he said, scientists worried primarily about chaff and jamming. "Decoys were not considered back then."

In an attempt to address critics' concerns, the Army and the Ballistic Missile Defense Organization have created a program called Hercules. Its purpose is to capture the...