Nasa fuels shuttle for liftoff

The only possible obstacle appeared to be thunderstorms in the forecast.

A temporary window cover fell off the shuttle and damaged thermal tiles near the tail Tuesday afternoon. The problem was announced just two hours after Nasa declared Discovery ready to return the nation to space for the first time since the Columbia disaster.

The mishap was an eerie reminder of the very thing that doomed Columbia damage to the spaceship's fragile thermal shield.

Discovery and its crew of seven were set to blast off at 3:51 p.m. EDT on a flight to the international space station.

Fueling of the external tank, originally set to begin before sunrise, began more than an hour late after workers changed a part on a launch-pad heater. Nasa officials said the swapping out of the part wasn't expected to affect the launch time.

The husband of Discovery commander Eileen Collins said Wednesday that his wife expressed having "some butterflies" when they talked the night before.

"Anytime you're an astronaut, you run a risk," Pat Youngs told The Associated Press. "But from all I've seen, from management, engineers ... support personnel and the astronauts themselves, there is a lot of hard work to right things and get back to spaceflight." It will be Collins' fourth shuttle flight.

The plastic cover on one of Discovery's cockpit windows came loose Tuesday while the spaceship was on the launch pad, falling more than 60 feet and striking a bulge in the fuselage, said Stephanie Stilson, the NASA manager in charge of Discovery's launch preparations.

No one knows why the cover held in place with tape and weighing less than 2 pounds fell off, she said. The covers are used to protect the windows while the shuttle is on the launch pad, then removed before liftoff.

Two tiles on an aluminum panel were damaged, and the entire panel was replaced with a spare. Stilson called it a minor repair job.

Space agency managers held one last meeting Tuesday to address lingering technical concerns and later pronounced Discovery ready to fly.

"We have done everything that we know to do," Nasa Administrator Michael Griffin said afterward.

The families of the seven astronauts killed during Columbia's catastrophic re-entry praised the accident investigators, a Nasa oversight group and the space agency itself for defining and reducing the dangers.

Like those who lost loved ones in the Apollo 1 spacecraft fire and the Challenger launch explosion, the Columbia families said they grieve deeply "but know 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," they said in a statement. "Godspeed, Discovery."

Discovery will be setting off on the 114th space shuttle flight in 24 years with a redesigned external fuel tank and nearly 50 other improvements made in the wake of the Columbia tragedy.

A chunk of foam insulation the size of a carry-on suitcase fell off Columbia's fuel tank at liftoff and slammed into a reinforced carbon panel on the shuttle's wing, creating a hole that brought the spacecraft crashing down in pieces during its return to Earth on Feb. 1, 2003.

During their 12-day flight, Discovery's astronauts will test various techniques for patching cracks and holes in the thermal shielding.

The crew members also will try out a new 50-foot boom designed to give them a three-dimensional laser view of the wings and nose cap and help them find any damage caused by liftoff debris. That is on top of all the pictures of the spacecraft that will be taken by more than 100 cameras positioned around the launching site and aboard two planes and the shuttle itself.