Shuttle soars into space for 100th time
CAPE CANAVERAL, Florida (CNN) -- The space shuttle Discovery blazed into the sky over central Florida Wednesday evening, embarking on the 100th mission of NASA's venerable program.
It was NASA's fourth attempt in less than a week to launch Discovery on its ambitious space station construction mission.
A launch attempt on Monday was called off when gusts of more than 50 mph prevented technicians from moving a vent hood into position over the external fuel tank, part of the preparation for filling the tank.
On Tuesday, the launch was scrubbed again -- this time because of a stray metal pin that was inadvertently left on the shuttle's exterior. Workers spotted the pin with binoculars during a routine inspection, a few hours before liftoff. It was wedged next to the liquid-oxygen line between Discovery and its external fuel tank.
Rather than risk damage to Discovery, NASA called off the launch.
Discovery was originally scheduled to lift off last Thursday. But NASA postponed the departure because of two mechanical problems -- a sluggish valve and suspect bolts -- which shuttle engineers resolved over the weekend.
The milestone mission finally under way will be as complex as any the space agency has ever attempted.
"We think it is raising the bar. (It's) the most complex station mission so far, with four spacewalks," shuttle program manager Ron Dittemore told CNN.
During those spacewalks, crew members will link the two large components they are carrying to the International Space Station: a docking port for future shuttle rendezvous and a large lattice-like exterior structure called the Z-1 truss.
The Z-1 truss will support the huge U.S. solar arrays, due to arrive on the next shuttle visit.
"You could look at it as a keystone because without it, the growth can't continue," Dittemore said. "We really do need to lay this piece so that the solar arrays can be added and provide power to the lab and we can continue to grow."
Astronauts have not hooked up major pieces to the space station since the initial components were launched in 1998. The last three shuttle visits were essentially supply runs.
Astronauts on the current mission will also practice rescue routines that could be needed during future spacewalks.
One astronaut will try to return to the shuttle after simulating an accident that could leave a spacewalker untethered and floating away from both the orbiter and the space station.
Also, two astronauts will try to determine if it is possible to return a dead or gravely stricken spacewalker to the shuttle's airlock without using special tools.
"The shuttle missions that have gone to the station so far have been extremely successful. This mission takes the level of complexity up a notch," Dittemore said.
Second shuttle mission
Meanwhile, Koichi Wakata, making his second trip into space, will become the first Japanese astronaut to visit the space station. Wakata flew on the space shuttle Endeavour in 1996.
The other crewmembers are Bill McArthur, Brian Duffy, veteran shuttle commander; Pamela Melroy, rookie pilot; and mission specialists Leroy Chiao, Jeff Wisoff and Michael Lopez-Alegria.
Wakata, a graduate of Japan's Kyushu University, worked for Japan Airlines as a structural and systems engineer before joining NASDA, Japan's space agency, in 1992. Although he was not the first Japanese to fly in space, Wakata was the first Japanese to travel in space as a trained astronaut. Mamoru Mohri was the first Japanese to fly on a shuttle, in 1992.
Wakata will operate the shuttle's 50-foot robotic arm, lifting two segments from the orbiter's payload bay and positioning them on the space station. He will also assist his crewmembers during the spacewalks, using the arm to place other crewmembers in their workspaces.
"We feel very confident we will be able to accomplish all the tasks on this flight, and I'm very much looking forward to it," Wakata said.
Once Discovery's 11-day mission is completed, the space station's first permanent crew will be able to move in.
NASA astronaut Bill Shepherd and two Russian cosmonauts are scheduled to lift off from Kazakhstan on October 30. They will spend four months aboard the space station before returning to Earth via the space shuttle. A new three-person crew will take their place.
Shepherd and his crewmates are in Russia preparing for their flight.
CNN Space Correspondent Miles O'Brien, The Associated Press, and Reuters contributed to this report.