Countdown to 100th space shuttle flight underway

NASA clocks have begun counting down for the 100th space shuttle flight, a space station construction mission.

NASA clocks have begun counting down for the 100th space shuttle flight, a space station construction mission.

Space shuttle Discovery is scheduled to lift off in the early hours of Friday morning. Forecasters put the odds of acceptable weather at 60 per cent.

Discovery's seven-member crew will use the shuttle robot arm to attach a docking port and girderlike truss to the international space station. They will also perform four back-to-back spacewalks to wire up the new pieces.

Astronaut Leroy Chiao, the lead spacewalker, considers it NASA's most ambitious construction flight. Chiao and his crewmates have been prepping for the job for three years. They should have flown two years ago but got held up by space station problems in Russia.

"We've been following the hardware that we're going to put on board since its infancy," astronaut Jeff Wisoff said as he arrived at the Kennedy Space Center. "Now we're just about at game day and we're ready to do it. On Thursday, we hope to be leaving town."

The 11-day mission comes close on the heels of a space station visit by Atlantis. During that flight, which ended Sept. 20, astronauts and cosmonauts got the station's new living quarters ready for occupancy.

Discovery must fly before the space station's first permanent crew can launch aboard a Russian rocket from Kazakstan. NASA astronaut Bill Shepherd and his two-cosmonaut team are scheduled to depart Oct. 30 on the four-month mission.

Altogether, NASA plans eight shuttle flights to the space station over the next year to haul up more modules and supplies. "We're on the doorstep of something truly special," astronaut Michael Lopez-Alegria said. "Over the next not only couple of weeks but couple of years, you're going to see some pretty amazing things unfold."