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the hit to kill tests

An overview and update on the seven hit-to-kill tests conducted by the Defense Department between October 1999 and October 2002.

For decades, Kwajalein, a fly speck of an island in the middle of the Pacific, has been a U.S. missile test site. In tests of the midcourse missile defense system, this is where the military launches its "kill vehicle" -- a miniaturized package of sensors, computers, and thrusters -- which is designed to zoom up 140 miles, home in on an enemy warhead during the midcourse of its flight, and smash it to bits through the sheer force of the collision. The Pentagon calls this "hit to kill." It has been likened to hitting a bullet with a bullet, though at speeds of 15,000 m.p.h., the kill vehicle and the enemy warhead are traveling much faster than the speed of a bullet.

In the run-up to each test, the teams on Kwajalein ready Raytheon's $24 million kill vehicle, along with Boeing's $12 million booster rocket. At Vandenberg A.F.B. in southern California, 4,300 miles away, other crews prepare the $19 million Minuteman target rocket. Equipped with its mock warhead, the Minuteman rocket will simulate the flight of an enemy missile. At $100 million apiece, the hit-to-kill tests rank as the most expensive half-hour in military testing.

At least 20 developmental tests were originally planned, and each of these must succeed before operational testing can begin -- testing conducted by military service personnel instead of industry contractors and performed in realistic operational environments, at night, in bad weather, in conditions that would approximate battle.

Since 1997, the "kill vehicle" component of the Ground-Based Midcourse Defense (GMD) system has been tested eight times. In the first two tests, conducted in June 1997 and January 1998, the kill vehicle would simply "fly by" the dummy warhead without trying to hit it so that the kill vehicle's ability to locate the warhead and distinguish it from decoys could be evaluated. In the first, a Boeing kill vehicle was used; in the second, one manufactured by Raytheon. In both, the Pentagon declared the tests successful.

However, in March 2002, the General Accounting Office released a report that concluded that in the June 1997 test, the sensor used to discriminate between the warhead and decoys did not work as claimed -- allegations that had first been lodged by a whistle-blower (at TRW) and supported by the research of MIT physicist Theodore Postol.

The GAO concluded that the sensor systems on the kill vehicle malfunctioned and the sensor often detected targets where there were none. The report added that the contractors chose to analyze only about 12 seconds of data (out of more than 60 seconds taken) due to sensor malfunction and other problems. Toward the end of the test, the software began to incorrectly identify a decoy as the warhead. This data was eliminated in the contractor's analysis.

The first "hit to kill" or "flight-intercept test" -- that is, the program's first shot at actually hitting a mock warhead in space -- was conducted on Oct. 2, 1999. There have been six more hit-to-kill tests since then. Of the seven tests, five have been deemed successful by the Defense Department -- meaning that the kill vehicle was able to home in on and destroy the mock warhead -- but a fuller analysis reveals less encouraging details. In two of the successful tests, for instance, critical elements of the system failed. (See table.)

In addition, the earlier fly-by tests had included numerous decoys, but that had proved too difficult. So in the first five hit-to-kill tests, only one decoy accompanied the dummy warhead. It was a balloon much larger and brighter than the warhead, which made it easy for the kill vehicle to recognize. And it was easier still because a computer told the kill vehicle to look for the smaller of the two objects. In each test, in other words, the kill vehicle had been helped with the most critical technology of midcourse defense: being able to distinguish, in about 100 seconds, between a warhead and the swarm of decoys almost certain to be launched to disguise it.

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"We are testing to learn; we are not testing as pass-fail for some operational reason," Lt. Gen. Ronald Kadish, head of the Pentagon's Missile Defense Agency, has said. In fact, all of the tests thus far have been "developmental" tests, designed to identify the strengths and weaknesses of the system's components, not "operational tests," which are conducted under realistic "combat" conditions. Philip Coyle, director of operational test and evaluation at the Pentagon from 1994 to 2001, and a consultant to FRONTLINE on "Missile Wars," says that "for all practical purposes, the first five flight intercept tests have been essentially the same." All seven tests, for example, were conducted with the mock warhead following the same flight course.

Some of the strongest criticism of the tests has focused on the controlled atmosphere in which the tests have taken place. Critics have pointed out that the kill vehicle is programmed with information about the size and shape of the mock warhead, information that would not be available under actual conditions. "That prior information," according to Coyle, "is the most important difference between early developmental tests and the later operational tests."

The table below describes the results of all seven tests since October 1999.

"HIT TO KILL" TESTS: October 1999 - October 2002




Oct. 2, 1999


The first of the hit-to-kill tests was the simplest, testing only the kill vehicle's capabilities. Other key components of the system -- the ground-based radar system for tracking enemy missiles, and an improved booster rocket -- were to be added and tested later.

To compensate for the lack of radar, the mock warhead was equipped with a transponder that broadcast its location to a global-positioning satellite, which in turn guided the interceptor toward the warhead. The kill vehicle successfully separated from the booster, but its telescopes were then unable to locate the warhead. When the kill vehicle widened its field of view, it first focused on a large balloon decoy and homed in on it. The balloon and the mock warhead were close enough together that once the kill vehicle sighted the balloon, it was able to locate the warhead, distinguish it from the decoy, and destroy it.

Critics maintain that the balloon, because of its size and proximity to the warhead, acted as a beacon rather than a decoy, and that if the decoy hadn't been used, the warhead may have escaped detection.

Jan. 18, 2000


The second hit-to-kill test was more complex than the first: an early-warning radar was used to help track the mock warhead and satellites were used to detect its launch.

As in the first test, the mock warhead released one balloon decoy. The intercept failed, however, when the kill vehicle missed the mock warhead by about 70 meters. Later, the Pentagon concluded that the flow of krypton -- which is used to cool the kill vehicle's infrared telescopes so that they are operable in space -- had been obstructed in the final minutes, rendering them unable to guide the kill vehicle toward the warhead.

July 8, 2000


The third intercept test failed because the kill vehicle didn't separate from its booster rocket. The Pentagon determined that the likely cause of the mishap was a faulty processor on the booster, which failed to send a command to the kill vehicle to separate. In addition, the decoy, a balloon, failed to inflate properly.

July 14, 2001


The fourth hit-to-kill test was a repeat of the third -- in which the missile again released a mock warhead and a single balloon decoy. The test resulted in another hit. But during the final stages of the test, a software problem prevented the ground-based radar system from assessing whether the kill vehicle had hit the mock warhead. In fact, the radar reported that it had missed.

Despite acknowledging the problems, the Pentagon hailed the fact that other sensors had indicated that the kill vehicle was able to hit the mock warhead in its "sweet spot," its most vulnerable area, which is measured in centimeters.

Dec. 3, 2001


The fifth test, which again resulted in a hit, followed the same course as all the previous tests: a mock warhead was launched from Vandenberg A.F.B.; the intercept rocket was launched from Kwajalein Atoll; and eight minutes after the kill vehicle separated from the booster, it was able to discriminate between a single balloon decoy and the mock warhead and home in on and destroy the target.

The only variable that changed from the previous test was the target launcher.

(Critics note that the interceptor received a wealth of targeting information prior to the test and questioned its operational realism.)

March 15, 2002


In the most recent test of the GMD, three decoys -- one large balloon and two smaller ones -- were used. Despite the additional decoys, the kill vehicle successfully homed in on the warhead and destroyed it.

Afterward, the Department of Defense indicated that the sensors aboard the kill vehicle had been able to distinguish the mock warhead from the three decoys. However, the Union of Concerned Scientists (UCS) has said that the additional decoys "did not increase the difficulty of the discrimination task, since all the balloons had infrared signals that were significantly different from that of the mock warhead."

Oct. 14, 2002


The Department of Defense twice delayed the seventh intercept test, which was originally scheduled to take place in August 2002, because of problems with the booster rocket. When the test finally took place on Oct. 14, 2002, the kill vehicle again successfully intercepted the mock warhead. The test was said to include a somewhat different target array than the previous test, but the specifics are unknown because the MDA recently classified some details of the tests.

Updated: Oct. 15, 2002

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