Vapour trails light up the California sky this morning
Ten volunteers, including one Briton, breached security at the Vandenberg Air Force Base in California to protest against the test launch, which eventually went ahead at 0409 BST.
Four swimmers dodged coastguards, a helicopter and a navy vessel to land on the base, then took four inflatables into the exclusion zone.
The four - Briton John Wills, from Guernsey, and Americans Brent Hanssen, Kelly Osborne and John Aguilar - were arrested, a Greenpeace spokesman said.
Another 14 people were later arrested when FBI agents boarded a Greenpeace boat moored close to the base.
It is a failure for world peace because it brings us one step closer to a new nuclear arms race.
Among those were arrested were the boat's captain, Bill Nandris, 32, from London, and an unnamed British photographer.
The $100m (£76m) launch went ahead 40 minutes late despite two Greenpeace divers and boats being within the safety zone area, the spokesman
The US declared the test a success after the missile interceptor destroyed a mock nuclear warhead over the Pacific Ocean.
It was the first test of the "hit-to-kill" technology that the administration of US President George W Bush hopes will become a key element of
a missile defence network.
Two out of the three previous tests had failed.
Greenpeace has reacted to the successful test by accusing the US of risking the start of a new arms race.
Protesters outside the Vandenberg airbase on Saturday
Greenpeace International nuclear disarmament campaigner, William Peden, said: "The Bush administration is claiming the Star Wars missile test was a success - it is a total failure.
"It is a failure for world peace because it brings us one step closer to a new nuclear arms race.
"It is now clear George Bush is hell bent on full implementation of the Star Wars programme regardless of global opposition."
Greenpeace has been stepping up its protest action in recent months in a bid to stop the Star Wars plans.
Earlier this month protesters staged a two-day occupation of the Menwith Hill satellite station, in the Yorkshire Dales, which would be used in the Son Of Star Wars programme.
Next week Greenpeace says it will send a raiding party to another key US base in Greenland to stage another protest.
President Bush will be visiting heads of government in Western Europe and Russia next week and defence issues will be at the top of the agenda.
Copyright 2001 BBC