Eight minutes after liftoff, the missile released a beach ball-sized object that collided with a large ballistic missile launched from Hawaii. The 9,000-mile-per-hour space wreck destroyed both vehicles.

With the attention of a jittery world turned elsewhere, the event went almost unnoticed. Raytheon, the manufacturer of the missile, issued a brief press release and a few newspapers, this one included, gave it a couple of paragraphs the next day.

And that was that.

But high above the Pacific that night, defense experts say, a small but potentially significant step was taken toward more security in an increasingly dangerous world.

The test showed that a highly mobile, sea-based antimissile system -- one that could encircle and neutralize the missile threat of "rogue nations" such as North Korea or Iraq -- might work.

The system is still being tested, and defense officials were careful with their praise. But it has "a great future," said Duncan Lennox, editor of London-based Jane's Strategic Weapon Systems.

In theory, the ship-based system could also protect the continental United States, not only from medium-range missiles, but maybe even from the high-flying and super-fast intercontinental variety.

And, in stark contrast to the grandiose and costly Star Wars schemes calling for a powerful laser in space, it is a system that is largely already paid for, and therefore could be operational many years sooner.

There is a need to move quickly these days, experts say, because there are missiles in more hostile hands than ever before.

"The proliferation of ICBM and cruise missile designs and technology has raised the threat to the U.S. . . . to a critical threshold," CIA director George J. Tenet told the Senate Intelligence Committee earlier this month. "Most intelligence community agencies project that by 2015 the U.S. most likely will face ICBM threats from North Korea and Iran, and possibly from Iraq.

"This is in addition to the longstanding missile forces of Russia and China," Tenet said. "Short and medium-range ballistic missiles pose a significant threat now."

The system tested off Hawaii makes use of the Navy's Aegis aircraft defense system, already at sea around the world on about 50 Navy vessels. It also makes use of the Navy's antiaircraft Standard Missile, a reliable mainstay of the Aegis system.

In the test, the Aegis radar system aboard the guided-missile cruiser USS Lake Erie detected the launch of a medium-range Aries test missile from Kauai, Hawaii, about 300 miles away. Even so-called medium-range missiles can travel thousands of miles, and become spacecraft for part of the trip.

After detecting the launch, the Aegis system automatically plotted an intercept course and then launched a new version of the Navy's Standard Missile called the SM-3.

The test was designed as a "fly by," according to Raytheon officials, only a test of the system's electronics. But things went better than planned. The SM-3's warhead, or "kill vehicle," apparently performed flawlessly. It separated from the SM-3 in outer space, located its approaching target, then flew directly into the missile's path. A very high speed collision destroyed both.

The launch was the fourth in a planned series of nine. But Ed Miyashiro, Raytheon's vice president for Navy air defense systems, said last week that testing might speed up.

"Once we do it a couple of times, we'll consider accelerating the program," he said. "This puts us ahead of the game."

The idea that an existing, ship-based, antiaircraft missile might be adapted for the tougher job of missile defense was born in the early 1990s.

The Aegis antiaircraft system was "already part of a large and growing fleet (of ships)," Miyashiro said. "It provided a lot of what was needed. We could leverage off all that infrastructure and capability. It provided an immense amount of flexibility."

In addition, he said, the Navy's Standard Missile is very fast, satisfying the first requirement of an antimissile weapon.

"Faster is better," he said. "If you are trying to engage a ballistic missile, you need speed to get there in time."

But intercepting missiles, especially in space, is a tricky business for the fastest of missiles, and U.S. officials were careful to limit their praise of the test.

"The system has so much potential," said Lt. Col Rick Lehner of the Missile Defense Agency, a new Defense Department office created Jan. 2 to coordinate the nation's numerous missile programs. "But it was strictly a developmental test flight. We have another planned this spring."

For now, he said, the Aegis system is seen as a weapon against medium-range missiles, not the higher and faster ICBMs. But that could change, he said, as the potential of the system is studied.

"There is a great future for the system," said Lennox, editor of Jane's Strategic Weapon Systems. "The Aegis system is basically radar with software, designed to engage aircraft up to about 70,000 feet.

"To succeed as an antiballistic missile system it must look up to targets in space -- hundreds of miles up.

"It's a great system, and it will work," he said. "But there is still a long way to go."

More missiles in more hands around the world

"The Persian Gulf War was a wakeup call," said Raytheon's Miyashiro. "Iraq's SCUD missiles were a sign of a new and changed threat."

There is no doubt the missile threat has changed since the collapse of the Soviet Union. While the superpowers have reduced their stocks of ICBMs, a host of nations are making medium-range missiles a weapon-of-choice. Just a few examples:

In 1998 North Korea flew a Taepo Dong missile over the islands of Japan, a crude warning of its power to strike its neighbors.

China has an active missile program and has used it to threaten Taiwan over reunification. It has built one missile base within range of Taiwan, according to the Defense Department, and is reportedly at work on another.

Iran is modernizing its ballistic missile inventory. It is developing a version of a North Korean missile with the range to hit Saudi Arabia, Israel and Turkey.

Iraq refuses to allow UN inspectors access to suspected weapon locations, but its use of SCUD missiles during the Gulf War prompted the development of Aegis as an antimissile system, according to Raytheon officials.

Supporters of the Aegis system say it would provide the United States with a mobile shield that could counter a threat from those countries, and also provide regional coverage for U.S. allies or troops deployed overseas.

Michael Levy is the director of the Strategic Security Project for the Federation of American Scientists, an organization founded in 1945 by members of the Manhattan Project who produced the first atomic bomb. It is the oldest organization dedicated to ending the worldwide arms race, achieving nuclear disarmament and avoiding the use of nuclear weapons.

Levy praised the technology demonstrated in the Aegis test -- "any time you can hit a warhead in space it is an impressive feat" -- but he cautioned against too much enthusiasm.

Aegis is a proven system for air defense, he said, "not missile defense."

The Aegis system has another problem, too, he said. It's provocative because it changes the balance of power.

"It's no secret that China sees the system as a way to defend Taiwan," he said.

Doug Richardson, who edits Jane's Missiles & Rockets monthly newsletter, agreed.

"Having invested heavily in ballistic missiles able to threaten Taiwan, China is likely to be very concerned that a small number of guided missile cruisers would be able to protect it," he said.

Arms issues are expected to figure prominently in President Bush's talks in Beijing this week during a trip that will also take him to Japan and South Korea.

What Aegis can do, and what it can't

Even the Aegis system's supporters agree that its near-term value will be defending "theaters" of conflict, or regions. Its value against the ultimate threat posed by ICBMs is uncertain.

"It's not a matter of small tweaks to turn this into a system to defeat an ICBM," said Levy. Here's why:

A ballistic missile is one that follows a flight path based on physics and gravity after an initial boost from a rocket. A ballistic flight path might take place partially in outer space, it might not.

An ICBM, a missile with the range to travel from one continent to another, is larger and much faster than a medium-range weapon, said Lennox, of Jane's Strategic Weapon Systems.

An ICBM might travel through space at 28,000 miles per hour, he said, about twice the speed of a medium-range ballistic missile. "That's a very, very tough target," Lennox said, made even more difficult if the missile releases multiple warheads.

There is also a question about the ability of the Aegis system to distinguish between a warhead and a decoy, said Levy. The flight path of objects in space is determined more by shape than by weight, he said, "so a heavy warhead and a lighter decoy appear much the same."

He said the missiles of less advanced nations may not employ decoy warheads, but ICBMs almost certainly will.

Raytheon's Miyashiro acknowledged the problem, but said, "It's still early; the test was just a first step. We are well aware the way targets look is not always simple."

An ICBM is considered most vulnerable during its boost phase, right after launch, or during its terminal phase, just before it lands, and defense officials say the Aegis system might be effective in those roles, too.

"We're looking at a variety of engagement scenarios," said Miyashiro. "There's a lot of capability in this system, and we are looking at all corners of the envelope. I won't get into specifics, but there is interest."

In its usual configuration as an antiaircraft weapon, the Standard Missile has two stages, or rocket motors. The first burns for about seven seconds when the missile emerges from the ship's launcher. Then a second stage, with a guidance system linked to the Aegis radar, flies to the target aircraft somewhere under 100,000 feet of altitude.

A third stage added to an SM-2 makes it an SM-3, an antimissile missile. "The third stage gets the vehicle into space," said Miyashiro.

With small, moveable nozzles the third stage maneuvers to close in on an approaching ballistic missile, still receiving data and guidance from the Aegis system on a surface vessel far below.

When it reaches a certain distance from its target, it is deemed to be "in the delivery basket." At that point, said Miyashiro, the nose cone is ejected and a final burst of data is transferred to a small device inside called the "kill vehicle."

When released, the kill vehicle is able to use small jets to move laterally, "closing out the errors" on its way to the target.

The two objects come together "pretty damn fast," said Miyashiro. The kinetic energy released at impact "is something like a school bus moving at about 600 miles per hour," said Miyashiro. There is no question of the missile surviving the impact.

The U.S. Missile Defense Agency is working on other anti-missile systems, too, among them an Army ground-based weapon designed to intercept ballistic missiles in the middle phase of flight as the Aegis system does.

Even the Space-Based Laser left over from the Ronald Reagan presidency is not altogether consigned to the scrap heap. There is also a U.S. Air Force aircraft-based laser under development.

But the advantage of the Aegis system is that it is mobile and seemingly closer to deployment.

And the dangers are real and growing, said Lennox, the missile expert for London-based Jane's.

"You could ask a North Korean or an Iranian, and they would say, "Don't be silly. We would never launch a nuclear missile,' because the response would be overwhelming.

"But whether a missile is nuclear, non-nuclear, biological, chemical, whatever . . . it can be a strategic threat," Lennox said. "Let's face it: The U.S., the U.K., France . . . we have interests all around the world.