Shuttle launch called off due to ‘anomaly’

Safety first
Discovery's mission management team has been extraordinarily careful about the launch preparations, following the lessons learned in the wake of Columbia's loss.

NASA said it would launch no shuttles until the issues raised by the Columbia tragedy were identified and corrected. Investigators determined that Columbia's wing was damaged by foam insulation that flew off the external fuel tank just after launch — a mishap that was caught on tape but dismissed as a cause for concern at the time. Sixteen days later, during the shuttle's atmospheric re-entry, hot gases entered through the breach in the wing and destroyed the shuttle from the inside.

The Columbia Accident Investigation Board cited technical flaws as well as lapses in NASA's "safety culture." Since then, NASA says it has changed the agency's culture to be more attentive to problems, and it has reworked dozens of shuttle components and processes to minimize the risk of damage during launch.

More than 100 cameras have been set up to monitor Discovery's liftoff for any sign of flying debris. After the ascent to orbit, astronauts will use a brand-new 50-foot (15-meter) extension boom, equipped with laser rangefinders and a high-resolution camera, to take an up-close look at the shuttle's protective skin.

Is the shuttle safe?
NASA Administrator Griffin told reporters on the eve of the launch that the shuttle was as safe as engineers could make it. "There is nothing that we know of that we have not addressed," he said.

At the same time, he acknowledged that risks still remained. "Can there be something that we don't know about that can bite us? Yeah. This is a very tough business," he said.

Ironically, a launch-pad accident came to light just hours later: Engineers found that a 2-pound (1-kilogram) plastic-and-foam cover had fallen off one of Discovery's cockpit windows and damaged two tiles on an engine pod. Fortunately, the tiles were attached to a panel that could be easily switched out, and the pre-launch schedule was not seriously disrupted.

NASA sources told NBC News that the cover might have been dislodged when an airbag was being retracted from that area of the shuttle.

The mission agenda
Collins and her crew have been training for this flight for more than two years.

The shuttle is to bring 28,000 pounds (12,700 kilograms) of payload to the space station, including food and supplies, a replacement guidance gyroscope and a space storage platform. Three spacewalks have been scheduled:

• Spacewalkers will test tools that have been developed since the Columbia tragedy to fix cracks in the shuttle's protective skin, using sample materials. Those tools include a daub-on applicator, a special type of caulking gun and a series of patches equipped with expansion bolts. Griffin acknowledged that the tools on this mission didn't have "any substantial repair capability" but said the lessons learned would lead to improvements.
• A second spacewalk is aimed at removing a balky gyroscope from the space station and putting in the replacement. Backup gyroscopes have still been keeping the station in the proper position, but NASA wants to have the full complement working.
• The storage platform, which can hold supplies for future spacewalks, will be installed on the station's exterior during the final scheduled outing.

Columbia remembered
During the preparations for launch, Columbia was never far from the minds of the astronauts and launch workers. Collins has said her crew would present a tribute to Columbia's astronauts during Discovery's mission, but she kept mum about the details.

The families of the Columbia astronauts praised NASA's efforts over the past two years in a statement released Tuesday, and said that "the exploration of space must go on."

"We hope we have learned, and will continue to learn, from each of these accidents, so that we will be as safe as we can be in this high-risk endeavor," the families said. "Godspeed, Discovery."

Griffin said Discovery's mission would honor not only Columbia's astronauts, but other space explorers as well: "Every space launch we do is a tribute to all those who have gone before — the crews who have died as well as the crews who lived."

He specifically cited the loss of three astronauts in the 1967 Apollo 1 fire and seven astronauts in the 1986 Challenger explosion. "Going back even further to 100 years of aviation, the safety systems that we who fly have learned and know are written in other people's blood," Griffin said.

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