The Pentagon said a failure of a booster rocket prevented an intercepting warhead from reaching its target during testing with a long-range ballistic missile over the Pacific Ocean.

The Missile Defense Agency said in a statement that it was not able to complete the test because the kill vehicle interceptor and booster rocket failed to separate, preventing the interceptor -- called the exo-atmospheric kill vehicle -- from engaging the target warhead in space.

The modified Minuteman II intercontinental ballistic missile was launched (at 3:26 a.m. EST) from Vandenberg Air Force Base in California.

About 20 minutes later and 4,800 miles away, a missile carrying an interceptor was launched from the Ronald Reagan Missile Test Facility in the Marshall Islands in the Pacific Ocean.

Booster has failed before

The statement said the interceptor's booster rocket, which also failed during a previous test, was an incidental part of the test and its failure prevented the military from testing the equipment in question.

A Pentagon spokeswoman said the systems under scrutiny did not indicate problems. The official also said an operational booster rocket is under development and will begin testing next spring.

The flight test, the eighth in the series, would have been the first for a development radar and an airborne laser prototype. Five of the tests have successfully "killed" their targets, and three have failed.

Testing of the Ground-based Midcourse Defense system began in October 1999.

The intercept was to have been the first involving a nighttime launch of an interceptor missile. It was intended to destroy the "enemy" missile at a point some 140 miles above the central Pacific.

``We do not have an intercept,'' said Air Force Lt. Col. Rick Lehner of the Pentagon's Missile Defense Agency.

He said it was ``frustrating and disappointing'' that a glitch that had little to do with advanced missile technology had doomed the eighth, $100 million, flight test of a key part of a planned U.S. layered defense against ballistic missiles.

Five of the flight tests have succeeded in shooting down the target vehicle launched from California's Vandenberg Air Force base. Wednesday's flight was the third failure, including a July 8, 2000, test in which Raytheon's so-called Exo-Atmospheric Kill Vehicle also failed to separate from its booster, in that case because of an electronic module failure.

Separating boosters from their payloads is something the United States has been doing successfully for some 50 years, Lehner said.

A spokesman for Raytheon, Dave Shea, said the company had confidence in its design. High technology seemed an unlikely culprit, he said, as it might have been had the device separated on schedule and yet missed its target in space.

The kill vehicle weighs about 120 pounds. Equipped with two infrared sensors and a visible sensor, it packs a small propulsion system meant to zero in on its target, bypassing decoys expected to accompany any incoming warhead.

'HIT TO KILL'

The botched ``hit to kill'' intercept was meant to demonstrate that, as in previous tests, a warhead tipped with a weapon of mass destruction -- nuclear, chemical or biological -- would be totally destroyed and neutralized in a collision with the ``kill vehicle.''

Lehner said the test had begun without a hitch with the launching of a modified Minuteman intercontinental ballistic missile from Vandenberg, on the central California coast.

Also launched without incident was the interceptor. It was fired from 4,800 miles away on Kwajalein Atoll in the Marshall Islands, for the first time under cover of night, a new wrinkle in the testing program.

The preceding four flight tests, all successes, had bolstered the Pentagon's confidence that the so-called ground-based system to shoot down incoming warheads in mid-course was on track.

President Bush wants to put an Alaska-based ``test bed'' with five missile silos -- and rudimentary operational capabilities -- in place by October 2004.

The site, at Fort Greely, near Fairbanks, would constitute one leg of a projected multilayered defense against missiles from countries such as Iran, Iraq and North Korea, members of Bush's ``axis of evil.''

Developing a missile defense is the Pentagon's single most expensive program, likely to cost hundreds of billions of dollars over coming decades, including for sea-, air- and space-based components.

For each of the past two fiscal years alone, Bush requested and Congress approved $7.8 billion in research, development and testing funds.

Boeing Co. is the lead system integrator for the ground-based mid-course program. TRW Inc. builds the system's battle command, control and communications system. Lockheed Martin Corp. is the prime contractor on the current booster system.

It's the second time the Pentagon's missile defense program has been foiled by a basic aspect of rocket science rather than the new technology being tested.

"We could not complete the test, obviously," Lt. Col. Rick Lehner, a Missile Defense Agency spokesman, said more than two hours after the test.

"I think most people understand this is not anything to do with missile defense technology," said Lehner. "The kill vehicle never got a chance to play."

Delayed 25 minutes by unfavorable weather, the Vandenberg weapon launched at 12:26 a.m. carrying the dummy warhead and decoy. About 20 minutes later another modified Minuteman 2 blasted off from the Kwajalein Missile Range, about 4,200 miles from Vandenberg.

Approximately 10 minutes later and 140 miles above the Pacific Ocean, the prototype ground-based interceptor should have slammed into the warhead.

"Everything was nominal with the target and GBI (ground-based interceptor) until it came time for the kill vehicle to separate," said Lehner.

This was the eighth intercept attempt, and third failure for the Ground-based Midcourse Defense segment.

On July 8, 2000, the prototype interceptor also failed to separate from its booster. Investigations later pinpointed the problem on a simple component.

Lehner said that both military and industry investigations would look into the cause of today's flop. Technicians were already reviewing data from the test to pinpoint what went wrong.

"It's disappointing it didn't separate," said Lehner, adding that this was supposed to be the last test using a modified Minutemen 2 missile to carry the kill vehicle.

Two different boosters are in development to replace the retired Minuteman 2 missiles that carry the kill vehicle. Those boosters are to be tested next spring. The next intercept attempt, using one of those vehicles, is scheduled for fall 2003. It's not known if today's flop will alter that schedule.

Buoyed by a string of successful intercepts, missile defense officials had upped the ante for today's test. It was the first time the interceptor missile launched at night.

"The preceding four flight tests were successes, which has allowed MDA to assume greater risk by accelerating flight test objectives by as much as two years while flying against a more difficult target complex," the Pentagon said in a written statement before the test.

While the intercept never occurred, other aspects of the test did, Lehner said. Positioned off the coast of California, the airborne laser prototype, a modified Boeing 747 aircraft equipped to carry chemical lasers to shoot down a missile, had an observation role in today's test.

"Although no lasers are yet installed on the aircraft, the ABL will use its on-board sensors to locate and track the boosting target missile during the first minutes of its flight in order to test the capabilities of the sensors," a Defense Department statement said.

Lehner said the successful target launch from Vandenberg allowed other aspects of the tests to occur.

"They got exactly what they wanted to get," he said. "All the objectives were met, except for the intercept."

The missile test marks the first of three launches in the next nine days from Vandenberg.

A Titan 2 rocket will ferry a military research satellite to space early Sunday morning. That mission is planned during a 15-minute launch window opening at 6:18 a.m.

A Delta 2 rocket will carry two NASA satellites to space during a Dec. 19 mission from Space Launch Complex-2. That launch will aim between 4:45 and 5:30 p.m.

Staff writer Janene Scully can be reached by e-mail at janscully@pulitzer.net

A modified Minuteman II intercontinental ballistic missile (ICBM) carrying the target warhead was successfully launched from Vandenberg Air Force Base, Calif., at 12:26 a.m. PST, and the booster rocket carrying the EKV was launched approximately 20 minutes later and about 4,800 miles away from Kwajalein Atoll in the Republic of the Marshall Islands. This test was conducted in support of research and development efforts for the Ground-based Midcourse Defense (GMD) program.

This was the final planned test involving the use of the interceptor's booster rocket that has been serving as a surrogate booster system and used for all GMD intercept tests since 1999. In a test on July 8, 2000, an apparently similar anomaly resulted in not completing the test due to the booster and EKV not separating. The surrogate booster is used for the developmental flight test program only, and is not intended for further use in the GMD test program or for a future operational GMD system. Two new booster designs are currently in development and will undergo flight testing beginning next spring. One or both of the new boosters will be used by the GMD program in all future intercept tests beginning late next year.

Initial post-test analysis indicate that all other GMD program elements successfully completed their test objectives, including radars and other sensors, as well as the battle management, command, control and communication elements that are vital in the GMD development effort. In a missile defense research and development program involving a number of different elements such as GMD, the successful integration of system elements is as important as the intercept. USS Lake Erie, an Aegis cruiser, successfully tracked the target missile after launch, and the Airborne Laser, a modified Boeing 747 aircraft, successfully used an installed infrared sensor to detect and track the boosting target missile after launch. The developmental Theater High Altitude Area Defense (THAAD) radar located at Vandenberg Air Force Base also performed well, successfully tracking the target missile after launch.

This was the eighth intercept test of the GMD research and development program. The first test on Oct. 3, 1999, resulted in the successful intercept of a ballistic missile target. The second test took place on Jan. 19, 2000, and did not achieve an intercept due to a clogged cooling pipe on the EKV, but did successfully test the integrated system of elements. The third test, on July 8, 2000, did not result in an intercept due an unsuccessful separation of the EKV and the booster rocket. The fourth test, on July 14, 2001, achieved a successful intercept of a ballistic missile target, as did tests on Dec. 3, 2001, and March 15, 2002. The successful test on Oct. 14, 2002 included the use of a ship-based SPY-1 radar for the first time to track a long-range target missile. The last four tests used all GMD system elements as part of an integrated flight test.

Government and industry program officials will conduct an extensive review of the test results to determine the reason(s) why EKV/booster separation did not occur, as well as a thorough analysis of all test-related data. Due to the vast amount of telemetry and other data collected during the test, it is likely to be at least several days until even a preliminary evaluation is completed.

News media points of contact are Lt. Col Rick Lehner, MDA Communications, at (703) 697-8997 or Ms. Cheryl Irwin, OSD Public Affairs, at (703) 697-5331.