Space shuttle Discovery made its long-delayed trip to the launch pad Monday, cheered on by flag-waving workers who have waited 21/2 years for a rebirth of the American space program.

"America, the dream is still alive," astronaut Dave Hilmers told a Fourth of July crowd of several hundred engineers, technicians and others who watched as the 85-ton spaceship edged out of an assembly building into the glare of floodlights at 12:50 a.m."What more fitting present can we make to our country than this on the day of its birthday," said Hilmers, one of five crew members scheduled to fly Discovery on the first post-Challenger mission, set for early September.

Discovery, attached to its external fuel tank and two solid-fuel booster rockets, was perched on the broad back of a giant tracked transporter that lumbered along at less than 1 mph in covering the 4.2-mile route to the pad in 61/2 hours.

The shuttle arrived at Pad 39B at 7:30 a.m., and technicians began connecting its various systems to the launch tower, including air-conditioning and electricity, and extending platforms from the pad so workers can have access to the shuttle.

NASA scheduled the move in the early morning to avoid thunderstorms and lightning that are common during the daytime in the summer months.

For three hours, starting at 8 a.m., space center workers and their families were permitted to drive personal cars past the launch pad for a good look at Discovery before a service structure enclosed it.

A recording of "The Star Spangled Banner" was played as the shuttle began the move to Launch Pad 39B, the same pad from which Challenger was launched on the flight that killed seven astronauts on Jan. 28, 1986.

"It's been a long 21/2 years since Challenger, and I'm very pleased with the progress we've made during that time," Forrest S. McCartney, director of the Kennedy Space Center, said at the rollout ceremony. "It's been a team effort. This is a proud day."

McCartney presented Hilmers with a book containing the names of more than 15,000 Kennedy Space Center workers who have labored to return the shuttle fleet to space.

Hilmers said the astronauts would carry the book, bearing the inscription "The KSC team is with you," into orbit aboard Discovery, "knowing that our journey will be safer because of you."

"It kind of brings tears to your eyes after so long a time of struggling and looking at ourselves inwardly and outwardly, and here it is; it's finally a reality," Hilmers said.

"This is what I call a happy Fourth of July," said astronaut Bob Crippen, a veteran of four shuttle flights who is now deputy director of shuttle operations.

Workers were to spend several hours securing Discovery on the pad and then begin preparing it for a critical test-firing of its three main liquid fuel engines. The test, with the spaceship bolted firmly on its launch mounts, is set for July 24.

The following day, a final pre-flight test-firing of the redesigned solid-fuel booster rocket is planned at the Morton Thiokol plant in Utah. Both tests must be passed before Discovery is certified for flight.

The failure of a seal in a booster rocket joint doomed Challenger 73 seconds after liftoff. Since then, the booster has been significantly redesigned and tested, and hundreds of other modifications have been made to the shuttle main engines and other systems.

Hilmers and four other veteran shuttle crew members will be at the controls when Discovery blasts off on a four-day mission. The others are commander Rick Hauck, Dick Covey, Mike Lounge and George Nelson.

They will deploy a communications satellite, conduct scientific and technical experiments and check out changes made to the orbiter systems.