Supporters of the ambitious and controversial US plans for a new national missile defence system (NMD) breathed a sigh of relief yesterday following the successful interception on Saturday night of a ballistic missile warhead. The warhead was fired from California and intercepted by a missile launched from the Marshall Islands in the western Pacific.
The missiles, which collided 144 miles above the Pacific in a dramatic flash of light, met at a combined speed of 16,000 miles per hour, four times the speed of a tank shell - the equivalent of shooting down a bullet with a bullet.
The test, the first this year, cost $100 million, and was the fourth in its series. The last two, in January and July last year, were unsuccessful, fuelling deep scepticism in Congress that even a limited version of President Bush's four-year target for missile defence is attainable.
Mr Bush has asked Congress for $8.3 billion to finance defence missile research and testing in 2002, a $3 billion increase over this year.
"We believe we had a successful test, in all aspects right now," Lieut-Gen Ronald T. Kadish, director of the Ballistic Missile Defence Organisation, told journalists.
He termed it "one step on a journey" towards building a multi-layered shield against missiles that could be tipped with nuclear, chemical or biological warheads.
But Saturday's test, in which the "kill vehicle" distinguished the warhead from one decoy balloon, is still light years away from demonstrating an ability to protect the US from a multiple attack using many decoys. To make the test more likely to succeed the defensive missile's computer was programmed with the infra-red profiles of the warhead and balloon making identification far easier than it would be in a real event.
"This test was as easy as it gets," said Dr Tom Collina of the Union of Concerned Scientists.
The test was delayed for two minutes by Greenpeace protesters who managed to get on to the island on Vandenberg Air Force Base in California where the missile was fired from. Four demonstrators were arrested.
In a statement Greenpeace warned that "as countries race to counter the Bush proposed shield with weapons of mass destruction, the US will be responsible for single-handedly destroying treaties of peace and arms control and creating a proliferation dynamic that will put us all at great risk".
The test kicked off at 10:40 p.m. (EDT) with a Minuteman II intercontinental ballistic missile streaking into the night sky on a fiery plume from Vandenberg. Twenty-one minutes and 34 seconds later, an interceptor lifted off from Kwajalein Atoll in the Republic of the Marshall Islands, 4,800 miles away.
The "kill vehicle" was a 120lb device with its own propulsion, communications, infra-red seeker and guidance and control systems. It separated from the rocket booster as planned and reached the impact point in space about eight minutes after the launch from Kwajalein.
Reporters monitoring the test from a video-teleconference room in the Pentagon could see the white flash. The video then switched to the Kwajalein mission control room where military and civilian officials broke into loud cheers.
The test is likely to be followed by four other similar ones, part of a programme of up to 17 flight tests. These will involve ground- and sea-launched missiles in the coming 18 months.
Administration officials admit the multi-layered approach to missile defence will soon mean breaches of the Anti-Ballistic Missile (ABM) Treaty, although Saturday's test does not constitute a violation. The ABM, which Mr Bush regards as obsolete, allows for some testing of land-based anti-missile missiles and the establishment of a land-based site to protect a specific target or city.
It does not allow for a nationwide system of anti-missile defences which, the theory has been, would undermine the central tenet of nuclear defence, "mutually assured destruction".
US officials, who announced last week that work on an Alaskan launch site will begin immediately, insist that agreement can be reached with Russia to amend the ABM.
But Moscow remains deeply hostile and senior Russian defence officials have said Russia may consider putting multiple warheads on existing inter-continental ballistic missiles if the Bush administration proceeds.
In Congress there are concerns that the technical difficulties involved in stopping a multiple attack will not be overcome. There are also fears that the Bush plan will lead to a re-escalation of the arms race.
Sceptics also point to the fact that missile defence does nothing to stop a possible attack on the US by means of a container bomb delivered by sea to one of the many US ports.