KENNEDY SPACE CENTER, Fla.--After a last-minute Air Force computer glitch threatened to derail launch, the shuttle Discovery, carrying an all-veteran crew of six, critical supplies, and a final U.S. module for the International Space Station, blasted off with seconds to spare and vaulted into orbit Thursday to begin its 39th and final flight.

Several relatively large pieces of foam insulation fell away from the shuttle's repaired external tank during the climb to space, including some that hit the ship's heat shield. But the observed impacts occurred well after Discovery was out of the dense lower atmosphere where debris impacts pose the greatest threat. No obvious heat shield damage could be seen, but engineers will carry out a detailed analysis over the next several days to make sure.

The shuttle Discovery climbs away from pad 39A at the Kennedy Space Center to kick off its 39th and final mission.

Discovery's crew, running three-and-a-half months behind schedule because of cracks in the external tank, strapped in just after 1:03 p.m. EST to await liftoff at 4:50:27 p.m., roughly the moment Earth's rotation carried the launch pad into the plane of the space station's orbit.

But trouble with an Air Force range safety system computer put the launch in doubt as the countdown ticked into its final minutes. With the end of Discovery's short 3-minute launch window approaching, Launch Director Mike Leinbach ordered engineers to pick up the countdown at the T-minus-9-minute mark and to press ahead in hopes the Air Force would be ready in time.

The problem was not immediately resolved and the countdown entered an unplanned "hold" at the T-minus-5-minute mark. Finally, with time running out, the glitch was resolved, the countdown resumed, and Discovery blasted off at 4:53:24 p.m., just 3 seconds before the end of the available launch window.

"Well, it was kind of an exciting last few minutes of this countdown," Leinbach told reporters later. "Several of us have been around for many, many countdowns, and this was one for the record books.

"This was Discovery's last (launch), a great way to go out," he said. "She gave us a little bit of a fit today, but it's a great way to get (Commander) Steve Lindsey and his crew on orbit. I'm very, very proud of my launch team and all the rest of the people who worked so hard on Discovery."

Because of the tank repairs and extensive re-application of protective foam insulation, flight controllers were on the lookout for any signs of foam debris falling away from the tank during the first few minutes of flight, when the dense lower atmosphere can cause debris to hit the shuttle with a high relative velocity.

Live television views from a camera mounted on the side of the tank showed several relatively large pieces of debris separating and falling away roughly four minutes after launch.

The most aerodynamically dangerous period from a debris impact standpoint is the first 2 minutes and 15 seconds of flight. While several pieces appeared to hit Discovery's heat shield, no obvious signs of impact damage could be seen.

Pieces of foam insulation can be seen falling from the shuttle Discovery&39's external tank about four minutes into flight. A relatively large piece is framed by the bipod struts holding the shuttle&39's nose to the tank.

"We did see some foam losses," astronaut Charles Hobaugh radioed the crew later from mission control in Houston. Given the timing of the releases, he added, "we have no concerns for the vehicle or success. We'll find out more, of course, as we go through the ascent video with a finer-tooth comb and also after we do the surveys. So we're looking forward to all that."

Joining Lindsey on the shuttle's flight deck for the climb to space were pilot Eric Boe, Ascent Flight Engineer Al Drew, and astronaut Nicole Stott, a space station veteran. Physician-astronaut Michael Barratt, another station veteran, and Stephen Bowen, a former Navy submariner, were strapped in on the shuttle's lower deck.

A veteran of two previous shuttle flights, Bowen joined Discovery's crew in January after Timothy Kopra, the mission's original flight engineer and lead spacewalker, was injured in a bicycle mishap near his home in Houston.

The primary goals of the 133rd shuttle mission are to deliver critical spare parts, supplies, and a U.S. storage module to the International Space Station as NASA completes the lab's assembly more than 12 years after construction began in 1998.

Only two more shuttle flights are planned, one by Endeavour in April and a final mission by Atlantis in late June, before all three of NASA's orbiters are decommissioned and turned into museum displays. A decision on where the shuttles will end up is expected later this year.

Large crowds gathered along area roads and beaches to witness Discovery's final launching and the shuttle did not disappoint, putting on a dramatic show as it climbed away through a mostly clear sky atop a torrent of fiery exhaust.

For Leinbach, the end of the line for Discovery will come on the Kennedy Space Center runway when the craft rolls to a stop after its 13th and final mission to the space station.

"Landing day's going to be tough," he said. "Landing day of Discovery, and then Endeavour and especially Atlantis, the last mission, you'll see a lot of people on the runway who will probably choke up some. Because it's the end of a 30-year program that not only have we worked in and made our livelihoods in but we've grown to love and appreciate and feel like we're doing something special for the country and, really, the world."

He said Discovery is "a great ship. This is her 39th mission, we'd have quite a few left in her had the program been extended. But it wasn't, and so it's kind of bittersweet to get the last flight out of her. But she's going to perform perfectly fine on orbit and bring the crew home safely."

Lindsey and Boe plan to oversee a two-day rendezvous with the space station. The crew will carry out a now-routine heat-shield inspection Friday before guiding the shuttle to a docking at the station's forward port around 2:20 p.m. Saturday.

Waiting to welcome the shuttle astronauts aboard will be Expedition 26 commander Scott Kelly, Alexander Kaleri, Oleg Skripochka, Catherine Coleman, Dmitry Kondratyev, and Italian astronaut Paolo Nespoli.

Discovery is scheduled to spend seven days docked to the space station, departing on March 5 and landing back at the Kennedy Space Center two days later.

But U.S. and Russian space managers are considering a one-day mission extension for an out-of-this-world photo opportunity.

The idea is to insert a new flight day 10 in the crew's timeline--March 5--so Kelly, Kaleri, and Skripochka can undock in the Soyuz TMA-01M spacecraft and photograph the space station with the shuttle and a full complement of European, Japanese, and Russian cargo ships and crew capsules attached.

Discovery's mission is the last time all of the international spacecraft will be docked at the station at the same time before the shuttle fleet is retired later this summer.

Assuming the fly-around is approved--and no decisions are expected until after Discovery reaches the space station--Discovery would undock on March 6 and land in Florida around midday on March 8.