This story was updated at 5:10 p.m. EDT.
CAPECANAVERAL - Discovery is moving in the wrong direction but for the rightreasons, workers said as the shuttle began rolling back to the launch pad atKennedy Space Center this morning.
The gigantic crawler-transporter first nudged forwardat 6:44 a.m. under cloudy skies, delayed from a 2 a.m. start while paperworkwas completed. Then it moved steadily along the river-rock-lined crawlerway at nearly 1 mph.
The shuttle paused near the Vehicle Assembly Building early this afternoon with an overheated bearing in the crawler-transporter. Workers repacked the bearing in grease and let it cool, NASA spokesman Bruce Buckingham said. It was under way again before 3 p.m. and entered the Vehicle Assembly Building about 4:30 p.m.
"It's another slow step in the right direction, and it's another indicationthat we're not going to fly until it's safe to do so," said crawler supervisorRay Trapp of Port St. John as he watched the ship move slowly off the pad.
Brian Jones and a couple of co-workers were there to take pictures of the ship,for "the excitement of going back to flying again," he said.
The rollback, which will allow NASA to substitute the shuttle's external fueltank, was essential for safety reasons, he said.
"I think it's a good thing," said Jones, an elevator worker for contractorUnited Space Alliance who lives in Mims. "It has to be right before it goes."
The new fuel tank will have a heaterdesigned to prevent ice from building up as supercold propellants are loaded.Ice and insulating foam can fly off the tank during launch and strike theorbiter.
Such a strike fatally damaged Columbia during its January 2003 launch, leadingto a breach that allowed hot gases to penetrate the orbiter when it tried tore-enter the atmosphere.
Discovery, moving at nearly 1 mph, should reach the Vehicle Assembly Buildingin mid-afternoon.
It is expected to roll back to the pad with the new tank and solid rocketboosters my mid-June, aiming for a July 13 launch.
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