The US missile defence system managed by Boeing has enjoyed a major breakthrough, hitting a simulated enemy missile over the Pacific in the first successful intercept test of the programme since 2008, the US Defence Department said.
The intercept will help validate the troubled Boeing-run Ground-Based Midcourse Defence (GMD) system, which provides the sole US defence against long-range ballistic missiles, and the Raytheon kill vehicle that separates from rocket to hit an incoming warhead.
"This is a very important step in our continuing efforts to improve and increase the reliability of our homeland ballistic-missile defence system," said Missile Defence Agency director Vice Admiral James Syring.
Syring said that the agency would continue its ongoing drive to ensure that the ground-based interceptors and overall defence system were effective and dependable.
It was reported on Friday that the Pentagon was restructuring its US$3.48 billion contract with Boeing for management of the missile defence system, to put more emphasis on maintenance and reliability.
Sunday's test came after the system had failed to hit a dummy missile in five of eight previous tests since the administration of former president George W.Bush rushed to deploy the system in 2004.
Earlier this month, Syring said that another test failure would have forced the Pentagon to reassess its plans to add 14 more interceptors to the 30 already in silos in the ground in Alaska and California.
During the test, a ground-based interceptor launched from Vandenberg Air Force Base, California, hit a target built by Lockheed Martin. The target was launched from the US army's Reagan Test Site on Kwajalein Atoll in the Marshall Islands, according to the Pentagon and Lockheed.
Lockheed said the unarmed, 14-metre-long target was configured to closely mirror the capabilities of ground-launched missiles that can travel 3,000 to 5,000 kilometres.
All components involved in the test appeared to have performed as designed, the Pentagon said. Programme officials will spend the next several months assessing the performance of the system using telemetry and other data obtained during the test.
The test marked the first successful intercept by Raytheon's Exoatmospheric Kill Vehicle Capability Enhancement II, which failed in both previous tests conducted in 2010.
Jim Chilton, vice-president of Boeing Strategic Missile & Defence Systems, said the test demonstrated the system's performance under "an expanded set of conditions that reflect real-world operational requirements". Boeing said the operational complexity of the GMD system was "a major engineering challenge".
Raytheon underscored the importance of testing and said Sunday's successful intercept kept the United States on target to increase its interceptor inventory to 44 from 30 by 2017.
Northrop Grumman integrated data from US missile-warning satellites and sea-based radars to help identify, track and destroy the target.
Ten of the interceptors now in place carry the kill vehicle used in Sunday's test. The other 20 carry an earlier kill vehicle that failed in a July 2013 test. Syring has said a fix would be implemented for that issue by year's end.
Riki Ellison, founder of the Missile Defence Advocacy Alliance, hailed the successful test as a big step forward for the troubled programme, and said it would allow US military commanders to reduce the number of interceptors that would be fired at an incoming ballistic missile.
"This success is a significant milestone that demonstrates the system's reliability and increases the confidence of the North American combatant commander responsible for the defence of the country," he said.
Critics said the Raytheon kill vehicle had still only succeeded in one of three tries, and urged Congress to rethink plans to buy 14 more of the flawed interceptors at a cost of US$75 million each, or just over US$1 billion.
"Would you spend a billion dollars on an insurance policy that only worked one-third of the time?" said Tom Collina, research director at the Arms Control Association. "We need to put the money into making the system better, not bigger."
Phil Coyle, former Pentagon chief tester and a long-time critic, called for accelerated work on a new design. "We need to make sure we have a system that works, not expand a system we know to be deeply flawed," he said in a statement.