Discovery's final countdown: Space shuttle launch signals NASA transition
As Discovery prepares for her last space shuttle launch, NASA's human spaceflight program shifts from space station ferry-service to missions to the moon, Mars, and beyond.
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Between launch and landing, however, a packed schedule remains. In addition to Robonaut 2, the orbiter is packing what missions payload manager Scott Higgenbotham calls "one big honkin' radiator," to remain at the space station as a spare, should one of the existing radiators – which shed excess heat from the station's interior – fail.Skip to next paragraph
In Pictures Space photos of the day: Space Shuttle Discovery
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The radiator is bolted to a platform, which astronauts will attach to the outside of the station to serve as storage space for the additional spare parts slated to arrive during the final two missions.
Discovery's false starts
This launch originally was scheduled for early November. But as controllers filled the shuttle's bullet-shaped external fuel tank with liquid oxygen and liquid hydrogen, they detected a hydrogen leak that forced them to scrub the launch.
When technicians returned to the pad after the fuel had been removed to inspect the tank, they found cracks in key structural supports, or stringers, on the tank's outer shell.
Mission managers opted to roll the orbiter back to the cavernous Vehicle Assembly Building, where they discovered more cracked stringers.
Repairs went smoothly, but mission managers continued to postpone the launch until they were convinced both that they understood the reasons for the stringer cracks and that the repairs had addressed that problem.
Investigators traced the problem to stringers that were strong enough to handle the stress that fueling imparts to the empty tank, but not strong enough to handle that stress when coupled with stress unexpectedly added during construction.
Now, "the hardware is ready to fly," says Michael Moses, who heads the shuttle's mission managements team.
As for weather, "We've had some really great weather coming all the way up to launch," says Kathy Winters, shuttle weather officer. Some isolated showers may pop up during the afternoon close enough to the launch site to warrant yet another postponement. But she gives that a 20-percent chance of happening.
Her bumper-sticker forecast? "Good payload, good launch," she says.