CAPE CANAVERAL, Fla. An Air Force Delta 2 rocket darted off a seaside launch pad in an after-dark spectacular here Wednesday, lofting a $42 million military navigation satellite that will act as a round-the-clock guide for U.S. armed forces and "smart" weapons, as well as civilian planes, trains and automobiles.

The 12-story rocket and its 1-ton cargo -- a Navstar Global Positioning System (GPS) satellite -- blasted off from Cape Canaveral Air Force Station at 9:48 p.m. Eastern Daylight Time (Thursday, 01:48 GMT), and then arced over the glimmering Atlantic Ocean as it made a supersonic dash into a starlit night sky.

A close-up of the boosters at ignition.

Built by the Boeing Co., the $50 million rocket dropped the satellite off in orbit 25 minutes after liftoff, marking the first successful GPS deployment since the Clinton administration made highly precise military signals available to the general public earlier this month.

"In plain English, we are unscrambling the GPS signal," said White House Science Advisor Neal Lane.

"Its rare that someone can press a button and make something you own more valuable, but thats whats happening. All the people whove bought a GPS receiver for a boat or a car, or whether they use one in business or for recreation, will find that they are 10 times more accurate."

Twice delayed in April due to technical problems, the $90 million mission is being staged to replace the very first advanced GPS satellite, which was launched in 1989 and served well beyond its seven-year design life before breaking down in orbit March 26. The old bird was officially decommissioned April 14.

If all goes well, the new satellite over the next two weeks will use on-board thrusters to nudge itself toward its orbital destination. Power-producing solar arrays will be deployed and the satellite's batteries will be charged as the spacecraft undergoes about three weeks of testing before it is ready to be pressed into service.

Made by Lockheed Martin, the satellite is the latest in a series originally designed to guide U.S. troops, fighter jets, bombers, ships and submarines on missions around the world.

Radio navigation signals emitted by the spacecraft -- and 27 others now working in orbit -- are so accurate that military forces can determine their exact location within feet (meters), their speed within a fraction of a mile (kilometer) per hour and the exact time within a millionth of a second.

In wartime, GPS satellite signals are used to guide high-tech "smart weapons," zeroing in on enemy military targets with uncanny precision. The $2.5 billion GPS network also played a key role in the 1991 Persian Gulf War, showing U.S.-led coalition forces the way around featureless Middle Eastern deserts.

The Delta launches, carrying the new GPS satellite.

Once classified top-secret by the Pentagon, the GPS-satellite constellation now plays an increasingly ubiquitous role in civilian life and commercial business.

Air freight, trucking and shipping companies -- as well as car-rental agencies and railroad firms -- all use signals from the satellites to track far-flung fleets, and GPS has become the navigation system of choice among police and fire departments, ambulance services, recreational boaters and backpackers.

The popularity of the GPS system, meanwhile, is expected to grow quickly and exponentially.

The reason: President Clinton signed an executive order May 1 lifting a longstanding ban on civilian use of the more precise military signals broadcast from the GPS satellites, which are designed to ring the planet in six groups of four, with spares parked in nearby orbital positions.

Up until then, private pilots, boaters and rental-car drivers -- as well as law-enforcement agents, firefighters, skiers, hikers and other civilian users -- received less accurate GPS signals than the military out of fear that potential enemies could use the system to target missiles and other weapons with pinpoint precision.

Now, however, civilian users can gauge exact positions within 33 feet (10 meters), rather than 300 feet (91 meters), which was the longtime restriction.

Clinton administration officials are quick to note that the military still can selectively block the more accurate signals over any global trouble spot at any time.

But at the same time, the move is expected to spur more widespread civil, commercial and scientific use of the GPS worldwide, giving a boost to what already is an $8 billion market for satellite navigation equipment and services.

Clinton, in fact, expects the availability of the most accurate signals to spawn new applications and new businesses that in turn will fuel U.S. and global economies.

"GPS has become a global utility. It benefits users around the world in many different applications, including air, road, marine and rail navigation, telecommunications, emergency response, oil exploration, mining and many more," Clinton said earlier this month. "This increase in accuracy will allow new GPS applications to emerge and continue to enhance the lives of people around the world."