Missile Impossible?

By MARK THOMPSON

Ten...nine...eight...seven..."

On a heavily guarded launchpad at Vandenberg Air Force Base, 125 miles up the Pacific Coast from Los Angeles, a 63-ft.-tall gleaming white rocket sits and waits. Secreted in the nose of the 37-year-old Minuteman II is a 5-ft.-long cone--a mock warhead--and a deflated Mylar balloon. Let's say they are part of an incoming missile from North Korea or Iran. Meanwhile...

Six...five...four...

About 4,800 miles away on Kwajalein Atoll, perched atop a Pacific coral reef, another rocket sits and waits. Nestled inside its nose cone is a $20 million bullet known as the exoatmospheric kill vehicle. It looks more like a mobile moonshine still than a snub-nosed round, but in the vacuum of space, there are no points for style. Its job is to find and then destroy the incoming "warhead" from Pyongyang or Tehran.

"Three...two...one...Ignition."

This Friday, sometime between 7 and 11 p.m. Pacific time, the Pentagon plans to fire the rocket from California, then fire the interceptor from the Pacific. It hopes the resulting collision will persuade President Clinton to give the order to start building a $30 billion system to protect the U.S. from missile attack. Success could signal the most profound change in U.S. national security since Washington decided to contain Soviet expansionism in 1947. That is why so much is riding on this week's test for the military, its contractors and the space shield's many proponents in Washington.

This decisive test is the third in a planned series of 19 for the Pentagon's projected National Missile Defense system. While Pentagon officers insist there will be future chances to halt its construction, a success this week could make that politically all but impossible. Congress is chafing to fund the system (see following story) and was heartened by the first test, in which an interceptor pulverized a fake warhead last October. In a second test in January, however, the interceptor missed its target by 241 ft. when a cooling line clogged and shut down its heat-seeking sensors. As a TIME investigation shows, little is being left to chance this time. So little, in fact, that this may be a test in name only--an expensive piece of Potemkin performance art to win enormous military appropriations. Exactly what is going to be tested on Friday?

There are virtually no unknowns in the procedure. The Pentagon knows the type of rocket launching the target as well as the nature of the target; it knows how powerful the rocket's engine is, where it is coming from and when it is being launched. The crew launching the interceptor will even get to listen in on the countdown of the warhead's rocket as it takes place. All that is valuable intelligence--and much, if not all of it, would be denied to the U.S. if a rogue state decided to strike. Such advantages "place significant limitations" on the value of the test, says Philip Coyle, the Pentagon's chief weapons tester.

The test favors a positive outcome in other ways. Much of the gear now being tested won't end up in the operational system. The rocket that will ultimately be deployed to lift the interceptor into space--still in development--will shake 10 times as violently as the more gentle boosters scheduled for the first seven tests. While the Pentagon says the shield will defend against "tens" of incoming warheads, all 19 of the Pentagon's tests are against a lone incoming warhead. Jacques Gansler, the Pentagon's top weapons buyer, told Congress last week that the testing program will grow more complex as the system develops. "The system design is solid," he declared. But some skepticism remains on Capitol Hill. Thus every phase of Friday's test will be carefully scrutinized.

Here is what the missile shield's proponents hope will happen--with a lot of apparent help from Pentagon planners:

Five minutes into its launch, the California rocket will release its mock warhead. The accompanying balloon will quickly inflate to its 6-ft.-plus diameter. Traveling less than a mile away from the mock warhead, the balloon is supposed to lure the interceptor away from its intended target. The warhead and the balloon, along with the container in which they rode into space, will reach a top speed of 14,700 m.p.h. and a peak altitude nearly 1,000 miles above the earth.

Within moments of liftoff, the infrared sensors on a Pentagon satellite perched 22,000 miles above the earth should pick up the rocket's flaming plume. The satellite will alert ground-based radars in Hawaii and Kwajalein, which will begin searching the northeastern skies for the intruder. In a fully deployed system, early-warning radars in Alaska, California, Britain, Greenland and Massachusetts would get the alarm. Updates on the target's path will pour into the U.S. Space Command's outpost at Cheyenne Mountain, Colo. Computers there will assemble a "weapons task plan" based on the incoming weapon's trajectory and any decoys trying to fool the U.S. interceptor. Within minutes, the first draft of this electronic map will be zapped nearly 6,000 miles to Kwajalein and into the interceptor's electronic brain.

The trouble is that in this week's test the interceptor won't rely solely on satellites and early-warning radars to trace its target. It will be looking for a target traveling a familiar path--the same California-to-Kwajalein arc used in the previous two tests. And this relatively short distance--as well as safety concerns--means the mock warhead won't be traveling as fast as a genuinely hostile one. This "single end-game geometry," said an independent review panel headed by retired General Larry Welch last fall, "raises questions about the ability of the flight-test program to verify system performance." The Pentagon says it will use computer simulations to replicate other attack angles and ensure that the system can defend against incoming warheads following different paths.

The Pentagon concedes its tests don't mirror reality. Pentagon test watchdog Coyle tells TIME that all attempted intercepts until 2004 will occur with the defenders fully briefed in advance on the "timing, direction and countermeasures" employed. And, Coyle adds, because of safety concerns, even in later tests "the soldiers may have a pretty good idea about the timing, direction and nature of the threat."

In Friday's test, the interceptor will have other advantages that the final product will not possess. The mock warhead, in fact, will basically shout, "Here I am!" to those trying to shoot it down. That's because it will carry a global-positioning-system transmitter, the same satellite technology that keeps motorists from getting lost. Although Pentagon documents say GPS data will help guide the interceptor during test flights, program officials say the data will be used only if other methods fail. Any use of GPS data, says Coyle, "does not suitably stress the system in a realistic enough manner to support acquisition decisions."

In the minutes following the target's launch, the interceptor will receive updated maps as the mock warhead soars over the ocean. Then, like a thirsty traveler about to cross a desert, the interceptor will take a final gulp of data on its nemesis' whereabouts and expected route just before blasting off some 20 minutes after the California launch.

Less than three minutes after leaving Kwajalein, the interceptor--having discarded its boosters--will be flying solo. Zipping across the heavens at 4,900 m.p.h., it will be about 1,500 miles from its target. Over the next six to eight minutes, the interceptor will try to hunt down its prey and guide itself into a suicidal collision with the warhead. It will be receiving guidance from far below as early-warning radar systems detect the incoming warhead. These systems hand off data to a so-called X-band radar system based on Kwajalein, which stabs the sky with a narrow beam of electronic pulses. The X-band's shorter wavelengths and advanced signal-processing capabilities give it the power to "draw" a clear image of the incoming warheads and surrounding decoys from up to 1,000 miles away. (Ultimately, the system's $500 million X-band radar will be based on storm-tossed Shemya Island, Alaska.)

The X-band radar will send its data to the interceptor by way of a supersonic cell-phone system known as the in-flight interceptor communications system. Eventually, 14 IFICS stations will be built, arrayed in pairs in yet to be determined geographic regions. The Pentagon's environmental-impact statement says the pairings are needed to meet unspecified "reliability requirements." The Federation of American Scientists posits that placing the stations in pairs, fairly far apart, reduces the chances that in-flight communications will be lost because of storms that may develop over a single IFICS site.

Once free of its boosters, the interceptor's first job is to confirm where it is. It will do that by finding stars that match a map stored in its memory chips. Having fixed its own location, the interceptor will turn its telescope toward the target's expected location. As the interceptor and mock warhead travel to within 500 miles of each other, the interceptor should pick up the warhead, along with the decoy balloon and launch container. From here on out--in the final 100 seconds--the interceptor will be on its own, getting no guidance from the ground. But it will still be getting help. At this point, the balloon, the designated hindrance, will become the sly helper.

In Friday's test, the big, bright balloon will be the major decoy. (The launch container will play a similar but subordinate role.) But even Pentagon officials acknowledge that the balloon will act more like a beacon that alerts the interceptor to the nearby presence of the real target. The Pentagon concedes the October test might not have succeeded if the decoy hadn't appeared so vivid to the interceptor's sensors. "The large balloon aided in acquisition of the target," Coyle says. "It is uncertain whether the interceptor could have achieved an intercept in the absence of the balloon." In short, the decoy is hardly a decoy. Critics maintain that future interceptors will be unable to distinguish more muted decoys from warheads, especially at long distances and supersonic speeds.

And a crafty foe wouldn't limit itself to the Pentagon's single, simple decoy. The enemy could slip its warhead inside a decoy balloon and deploy it along with a dozen identical balloons, forcing the Pentagon into a futile effort to destroy all of them. The warhead might be cloaked in a shroud of liquid nitrogen, chilling it so that the interceptor's heat-seeking sensors couldn't find it. Chemical or biological weapons might be deployed in dozens of bomblets far too numerous to destroy.

Distinguishing between warheads and decoys requires a wealth of information the Pentagon wouldn't have in a real attack and wouldn't be likely to get. But Pentagon officials insist their relatively crude discrimination technologies will keep improving. They say measuring subtle differences in projectiles' mass, motion, reflection and rotation will enable the Pentagon to pluck the real warhead from among the decoys. But the officials decline to detail the technical wizardry behind their assertion, saying that divulging their techniques would only aid potential foes.

Back in the sky over the Pacific on Friday, physics and chemistry will take over. The interceptor's three sensors--two detecting heat and one detecting visible light--all share the telescope that juts out its front end. The visible-light sensor will get the interceptor into the right neighborhood, but only the infrared sensors can guide it into its target, gently steering it with minithrusters powered by 30 lbs. of liquid rocket fuel. For the heat-detecting sensors to "see" anything, they must be chilled to -330[degrees]F using nitrogen and krypton, funneled to the sensors through a 0.0035-in. diameter pipe.

Each sensor's 65,000 pixels will feed signals into the interceptor's brain, where lightning-fast calculations involving heat, light, mass and motion are cranked into databases searching for the ballistic fingerprints of enemy warheads. As the interceptor rushes toward its possible targets (the warhead, the balloon and the launch container), it will keep them all within view for as long as possible before discarding the ones its computers say have the least likelihood of being the warhead.

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."