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A redesigned fuel tank for NASA's (search) first post-Columbia launch emerged from a darkened barge into the morning sunlight Thursday, inspiring dozens of space shuttle workers who gathered to watch.

"We're no longer recovering from the accident. We're really heading toward a launch. Big change in momentum and morale," launch director Mike Leinbach (search) said.

The arrival of the external fuel tank from a manufacturing plant in Louisiana moved the space program closer to its goal of a late spring liftoff for Discovery. It was a suitcase-size piece of insulating foam from Columbia's fuel tank that triggered that shuttle's breakup as it re-entered the atmosphere over Texas nearly two years ago.

On the new tank, no foam piece bigger than a couple of marshmallows should come off, said project manager Sandy Coleman (search). Anything that small would be harmless to the shuttle, she said.

Some workers photographed the 154-foot orange-yellow tank as it was hauled atop a wheeled flatbed into the Vehicle Assembly Building, and others walked alongside, pointing out new features.

Clearly missing were the pair of foam ramps that caused the deadly shedding during Columbia's final flight. In their place were eight new heaters, designed to prevent ice buildup when super-cold fuel is loaded right before launch.

Shuttle program manager Bill Parsons called the tank the safest ever built, "no doubt about it."

Parsons, who was celebrating his 48th birthday, called the tank's arrival the perfect gift.

"It's back to business," said Parsons. "It's getting where we are really feeling like we're going to pull this off, and I think that this is just an indication, one of those big symbols that comes in and says, 'You're there. You're getting there.' "

Within half an hour, the tank was inside the assembly building, where it will undergo a month of final prepping.

The tank will be attached to the two solid rocket boosters in February, and all that will be mounted to Discovery in March. At that month's end, at the launch pad, the tank will be filled for a rare systems test and run-through. NASA is shooting for a liftoff as early as May.

There was good news in orbit, too, on Thursday: The two men aboard the international space station got their primary oxygen generator working after a five-day breakdown.

Discovery will carry much-needed spare parts and supplies to the space station. It will be essentially a test flight, not only for the redesigned shuttle tank but also for the inspection and repair methods for astronauts in orbit.

Michael Kostelnik, deputy associate administrator for the shuttle and station programs, said there is a sense of urgency in resuming shuttle launches, given the station's eroding margins for food, oxygen and other resources. But that's not causing any rush to launch, he stressed.

"We don't have a specific point when the world is going to come apart for [the space station] if we don't get there. We just don't know. It's another one of those uncertainties in the game," Kostelnik said.

Complicating matters for NASA is the need to have two shuttles ready to fly at almost the same time, in case the first one runs into trouble and the second one, Atlantis, has to go get the crew that's stuck at the space station. The fuel tank for Atlantis, featuring even more improvements than the one for Discovery, is expected at Kennedy Space Center in March.

NASA's three remaining space shuttles have been grounded ever since Columbia ruptured on Feb. 1, 2003, killing all seven astronauts aboard.