The space
shuttle Endeavour rolled out to a Florida launching pad early Friday to serve
as a rescue craft for its sister ship Atlantis in what is expected to be the
last time in history that NASA has two orbiters in launch position at the same
time.
Riding atop
NASA's Apollo-era crawler carrier vehicle, Endeavour completed the slow
4.2-mile (5.6-km) trek to the seaside Launch Pad 39B at the Kennedy Space Center
in Cape Canaveral, Fla., at about 7:00 a.m. EDT (1100 GMT) after a nearly
eight-hour journey from the massive Vehicle Assembly Building. The shuttle
Atlantis, meanwhile, stood perched atop the nearby Pad 39A for its planned Oct. 10 launch
toward the Hubble Space Telescope.
"This is
the last time that this is ever going to happen," NASA spokesperson Allard Beutel
told SPACE.com from the Florida spaceport.
NASA is
preparing to launch seven astronauts aboard Atlantis next month on the
final service call to the Hubble Space Telescope, where the spaceflyers
plan to perform five back-to-back spacewalks to install new cameras, replace
aging batteries, gyroscopes and other components, add a docking ring and make
tricky repairs to equipment never designed for in-flight maintenance.
A container
packed with the spare parts and new instruments for Hubble will be
delivered to Atlantis atop its launch pad late Saturday after a slight delay so engineers could clean up contamination in one of the cargo elements. The orbital
overhaul is expected to extend the 18-year-old Hubble's mission through at least
2013.
But unlike
recent missions to the International Space Station, where shuttle crews had the
option of awaiting rescue aboard the outpost if their spacecraft suffered
critical heat shield damage, Atlantis astronauts have no such safety net because
they must fly higher and in a different orbit than the station to reach Hubble.
Instead,
NASA plans to have Endeavour and a skeleton crew of four astronauts standing by
in the unlikely event Atlantis' heat shield is damaged beyond repair and the
orbiter is unable to return to Earth. Under that plan, Endeavour would
rendezvous with Atlantis and astronauts would stage a series of three
spacewalks to retrieve the Hubble astronauts before discarding the stricken
spacecraft.
"They would
come up and they'd rendezvous with us," explained Atlantis shuttle pilot
Gregory C. Johnson in a NASA interview. "We would grapple each other, robotic
arm to robotic arm, essentially, and then would transfer crew members between
the shuttles."
NASA
mission managers and Atlantis astronauts consider the rescue plan an extremely
unlikely scenario and are confident their mission will go as planned. Once
Atlantis and its crew return safely to Earth, NASA will move Endeavour from Pad
39B to Pad 39A for its planned Nov. 12 launch to haul fresh supplies and
equipment to the International Space Station.
Pad 39B,
meanwhile, is due to be turned over to NASA's
Constellation program to be modified to launch the new Ares I rockets
designed to loft the agency's Orion shuttle successor into orbit by 2014 and on
to the moon by 2020. The first Ares I test flight is set for June 2009.
"So it will
no longer be a space shuttle launch pad. It will become an Ares rocket launch
pad for NASA's next-generation spacecraft," Beutel said.
Meanwhile,
NASA is enjoying a shuttle flight rarity with both Endeavour and Atlantis atop
their respective launch pads. Two shuttles have stood simultaneously atop the
two launch pads just 17 times before in the NASA's 27-year orbiter history, the last time
in 2001 during the STS-105 and STS-104 missions. Atlantis' October launch will mark NASA's 124th space shuttle flight.
"People
around here are proud of the shuttles and the work they've done on them, so
they're looking forward to seeing two of them prominently displayed on the
launch pad for everyone to see," Beutel said. "Knowing this will be the last
time makes it a little extra special."
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