NASA's redesigned space shuttle fuel tanks should no longer shed dangerous pieces of foam when launches resume next spring, officials said Thursday.

But if a shuttle wing is gouged by insulating foam or some other debris during liftoff, astronauts still will not be able to fix a hole the size of the one that brought down Columbia.

Speaking on the one-year anniversary of the Columbia accident investigation report, shuttle program manager Bill Parsons said he and others warned from day one that finding a way to repair the reinforced carbon edges of the wings in orbit would be a technical challenge.

"I mean, it's just not something that you're going to go out and come up with some kind of material that can deal with the return environment of up to 3,000 degrees and be able to just say, 'OK, we can just do this repair and there you go,'" Parsons said.

Added NASA's spaceflight chief, Bill Readdy: "The first priority is fix the tank, fix the tank, fix the tank and make sure that we don't have a debris environment that would cause something like that."

As for fixing the cultural problems that contributed to the Columbia disaster, NASA (search) is making progress, said Thomas Krause, chairman of Behavioral Science Technology Inc. (search), the California company hired to help transform the space agency.

There is strong evidence that employees are not as afraid to speak up at meetings; bosses encourage dissenting opinions and don't interrupt as much, Krause said.

So far, NASA has complied with five of the 15 return-to-flight recommendations set forth by the Columbia Accident Investigation Board on Aug. 26, 2003.

The remaining 10 must be completed by December for NASA to launch Discovery to the international space station by mid-March to mid-April, the space agency's goal.

"It's been a hard year, but we've made significant progress in getting this vehicle ready for return to flight," Parsons said.

Discovery's external fuel tank should be delivered from Lockheed Martin Corp.'s assembly plant in New Orleans to Kennedy Space Center by early November. That is an essential step in meeting a spring 2005 launch date, Parsons said.

The tank will no longer have thick foam insulation on the spot where it tore off Columbia at liftoff. New heaters will be there instead, to prevent ice buildup when the tank is filled with super-cold fuel.

The application of foam in other critical parts of the tank will be improved, along with testing. The tank also will be equipped with a camera, near the top, to document any lost foam in that area or damage to Discovery's belly.

Numerous cameras will be trained on Discovery at liftoff, from the ground, air and ocean. Radar also will be used to track any launch debris.

The first two post-Columbia shuttle launches — both considered test flights — will take place in daylight to help NASA spot any debris. After that, the radar could make it easier for NASA to resume night launches.

The Discovery astronauts will be able to repair cracks as small as a fraction of an inch, or plug holes in the wings as big as 4 inches. Anything bigger — the gash in Columbia's left wing was between 6 and 10 inches — and the shuttle crew will have to move into the space station until shuttle Atlantis can be launched to rescue them.

NASA figures Discovery's seven-person crew could survive on the space station for as long as long as two months.

Officials hope a long inspection boom with lasers on the end, for sensing any gaps on the underside of the shuttle, will be ready in time for Discovery's flight.

NASA expects its return-to-flight effort to cost more than $1 billion.

Columbia broke apart over Texas during re-entry on Feb. 1, 2003. All seven astronauts were killed.

The space agency is aiming for three shuttle flights in 2005 and then five a year through 2010, by which time station construction should be completed. The three remaining shuttles will be retired at that point, and NASA's focus will shift to flying to the moon and beyond that to Mars.