Missile Impossible?

The interceptor's thrusters will fire in precisely choreographed microsecond bursts to guide it into a collision with its chosen target. There are no explosives aboard the interceptor. The sheer kinetic force of the crash at a combined speed of nearly 17,000 m.p.h. makes explosives superfluous. The process is often described as "hitting a bullet with a bullet," but that imagery is misleading. There is no head-on collision. In fact, when the collision occurs, interceptor and target are both on the way down, pulled by gravity; the interceptor hits the side, not the nose, of the target. If all goes according to plan, both the interceptor and the warhead will disappear into a fiery cloud of what Pentagon officials like to call "space dust." If things go amiss, the only thing turning into space dust will be the $100 million cost of the test.

Like the term "military intelligence," the phrase "Pentagon testing" is something of an oxymoron. Military officers and contractors have long bent the rules and faked results to keep programs on track and money flowing. Watching the preparations for this week's test, Coyle remains skeptical of the rush to field the missile shield. He says the push to build a system with "immature" hardware and inadequate testing is a hallmark of troubled Pentagon programs.

The U.S. military, in missile tests conducted for several programs, has succeeded in "hitting a bullet with a bullet" in space only four times in 14 tries, or about 30% of the time. "While the four successful intercepts provide support for the hit-to-kill concept," the General Accounting Office noted two weeks ago, "the 10 failed attempts raise questions about reliability." No one wants to build a $30 billion missile shield that would shoot down less than a third of incoming warheads. But that statistical shortcoming has only increased the pressure on this test--and its consequences for the federal budget.

The Pentagon is demanding that each interceptor have about a 90% chance of killing its target. To achieve that, the military plans to have the final operational system fire four interceptors at each suspected warhead, pushing the chances of a kill to above 95%. But that will drive the cost higher too. In fact, those odds are unprecedented for a system of such complexity, especially one that must be on perpetual alert. Even the B-2 bomber, perhaps the Pentagon's most pampered weapon, has proved to be capable of performing its mission only 43% of the time.

"There is a legacy of overoptimism about the state of progress in developing reliable hit-to-kill performance," General Welch's panel concluded late last year. The general was slightly more sanguine last week before the Senate Armed Services Committee, stressing that he had no reservations about the Pentagon's ultimate ability to develop a missile shield. "The program is on track," he declared. That may have been good news for politicians gung-ho to send $30 billion of taxpayer money into space. But Welch didn't play down the challenge. "There's probably only about a thousand things that can go wrong," he said as the hearing ended. "And that's a very conservative estimate."