NASA Prepares for Discovery's Liftoff

The six astronauts who will man the final mission of Discovery, NASA's most traveled space shuttle, this afternoon have been counting down to liftoff.

The forecast improved to 90 percent "go" for a 4:50 p.m. liftoff. At the Johnson Space Center in Houston, flight director Richard Jones looks back on the shuttle's career. It is a poignant time for the space agency the shuttle program is ending after 30 years. Jones said he is proud to be a part of Discovery's last flight.

"What I will look back on is that this mission was just one of many, many accomplishments and it was part of the shuttle era," Jones said.

Discovery's 11-day voyage will take it to the International Space Station, where it will add another module for storage and experiments, an exterior experiment platform and a robot -- the first humanoid robot in space -- to work inside the space station. Two spacewalks are scheduled for maintenance work.

It is the first space flight for the $2 million Robonaut, known as R2, which is tasked with showing how dexterous robots behave in space. The robot is made of aluminum, weighs 330 pounds, and is 3 feet 4 inches tall. When Discovery docks to the space station, the combined weight of the two spacecraft will equal one million points a space first.

One astronaut, though, won't be making the historic trip: Tim Kopra was bumped from the mission a month ago after he broke his hip in a bicycle accident. Kopra, who was the lead spacewalker, will be watching closely from Mission Control. He has a six-month tour of duty on the space station. Originally scheduled for launch Nov. 1, Discovery has been repeatedly delayed because of cracks in structural ribs, or stringers, in the ship's external tank. NASA managers believe their engineering analysis has finally revealed the root cause of the cracks, and a relatively straightforward modification cleared the way for today's launch.

When Discovery lands after this final mission, it will have flown 143 million miles. Astronaut Nicole Stott said she can't help feeling sentimental about this space shuttle.

"It is kind of cool that the vehicle named Discovery has this kind of history to it, the most flights," she said. "I think it really sums up what the space program is all about.

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NASA Shuttle Launch

NASA has given a unanimous "go" for Thursday's planned launch of space shuttle Discovery.

It will be the final flight for Discovery, the world's most traveled rocketship.

Shuttle managers met Wednesday and agreed to proceed with the flight after a four-month delay caused by fuel tank cracks. Liftoff is scheduled for 4:50 p.m. Thursday. There's an 80 percent chance of good weather.

Six astronauts will ride Discovery up to the International Space Station. They will deliver and install a closet full of space station supplies, and drop off a humanoid robot. Robonaut will become the first humanoid in space.

Discovery has already logged nearly 143 million miles, more than any other reusable spacecraft.