The space
shuttle Discovery is once again atop its Florida launch pad, after receiving a
fresh external tank in preparations for NASA's first orbiter flight
since the Columbia disaster.
It took
Discovery and its Mobile Launch Platform more than 10 hours to reach Launch Pad
39B Wednesday at NASA's Kennedy Space Center in Cape Canaveral.
"It's a good
one to have under our belts again," NASA spokesperson Bruce Buckingham said of
the successful rollout.
Wednesday's
rollout began at 1:58 a.m. EDT (0558 GMT) as Discovery's massive crawler carrier
inched its way out of the 52-story Vehicle Assembly Building (VAB) and onto the
4.2-mile (6.7-kilometer) track to the launch pad.
The space shuttle
was initially slated to begin rollout operations at about 12:01 a.m. EDT (0401
GMT), but difficulties switching power systems from the VAB to the transporter
carrier, as well as minor clearance issues and the need to remove some access
platforms, led to the delay, NASA officials said.
USA crawler
drivers halted the massive shuttle transporter periodically to allow
overheating bearings a chance to cool down before continuing toward the launch
pad.
"We had a
few stops on the way, but it's there," said Tracy Yates, a spokesperson for
shuttle contractor United Space Alliance (USA).
At 12:17
p.m. EDT (1617 GMT), Discovery's Mobile Launch Platform settled onto the launch
pad, Buckingham added.
Set to
launch no earlier than July 13, Discovery first reached
its launch pad on April 7, but returned
to NASA's massive Vehicle Assembly Building to switch to a new external tank -
originally slated to fuel the Atlantis orbiter during STS-121 - equipped with a
heater
to cut down ice buildup.
Shuttle
managers believed that ice
debris from Discovery's original external tank could endanger the orbiter
if it shook loose during launch and struck a vulnerable area. That tank will
also be equipped with an additional heater to prevent ice buildup.
Minimizing
the amount of ice and foam debris from shuttle external tanks at launch has been
a prime concern for NASA since the Columbia orbiter was struck by a
suitcase-sized chunk of tank insulation foam during launch in 2003. That debris
gouged a hole in Columbia's protective thermal skin, and later allowed hot
gases to enter the orbiter's wing during reentry on Feb. 1, 2003. The orbiter
broke apart while flying over Texas, killing its seven-astronaut crew.
Discovery's
STS-114 mission will test a series of orbiter and external tank modifications
to increase shuttle flight safety, as well as resupply the International Space
Station.
It will be followed
by a second test flight, Atlantis' STS-121 mission, later this year, NASA
officials said.
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