CAPE
CANAVERAL, Fla. - The space shuttle Atlantis is moving ever closer to its Monday
launch toward the Hubble Space Telescope, but there's a second
spaceship standing by for a rescue mission NASA hopes it never needs.
That ship
is the space shuttle Endeavour, which sits atop a launch pad here at NASA's
Kennedy Space Center poised
for a mission of mercy to rescue the seven astronauts aboard Atlantis if
their spacecraft is damaged beyond repair during the Hubble flight.
Atlantis is
slated to launch Monday at 2:01 p.m. EDT (1801 GMT) so its astronauts can
perform the fifth and final overhaul of the
19-year-old Hubble Space Telescope. With Endeavour also primed for flight,
it is the last time ever that both of NASA's shuttle launch pads will be
occupied at the same time. But it is also an unprecedented first: It's the only
time NASA is launching one shuttle with another on rescue duty.
"Every
mission up to this point has been preparing us for this type of rescue
scenario," Mike Moses, head of Atlantis' mission management team for the Hubble
flight, told reporters Saturday. "We basically kind have been building to this
point."
NASA
believes the chances of needing the rescue flight are extremely unlikely, but
the agency drew up plans for one just in case.
Mission:
Space rescue
The reason
for the rescue mission is simple. If Atlantis is irreparably damaged during
flight, its crew won't be able to reach the safe haven
of the International Space Stationto seek refuge for the months required
to ready an unprepared shuttle for a rescue. Hubble flies higher than the space
station (about 350 miles up, while the station sits at 220 miles) and in a different
orbital inclination - or tilt with respect to Earth's equator.
Without
access to the space station, Atlantis would only have enough food and air to
keep its crew alive for 25 days, even less time if serious damage is discovered
late in the mission.
It's that
risk that prompted NASA to cancel the flight outright five years ago after the
Columbia accident that killed seven astronauts in 2003. A piece of fuel tank
foam punched a hole in the heat shield on Columbia's left wing during its
liftoff, leaving the shuttle vulnerable to the searing hot temperatures of
re-entry.
NASA
resurrected the Hubble mission in 2006 with the caveat that a rescue ship be at
the ready. By then, the space agency had resumed shuttle flights after the
Columbia tragedy and successfully tested heat shield inspection and repair
techniques in space. Those techniques have since become standard features of
shuttle flights, and a rescue mission would only launch if they prove
inadequate, NASA officials said.
"I think
we're going into this with open eyes," Altman told SPACE.com. "I have a
lot of confidence that we're going to be able to pull this off."
NASA has
also taken steps to reduce the chances of space junk and micrometeorites
mortally wounding Atlantis. Because Hubble flies in an orbit littered
with more space trash, there's a slightly higher risk of damage from the
orbital debris – about a 1-in-229 chance of a critical strike. To offset that,
NASA plans to fly Atlantis down to a safer orbit just after releasing Hubble
back into space near the end of the flight.
How the
rescue mission works
According
to NASA's plan, when Atlantis blasts off toward Hubble on Monday, Endeavour
will be just seven days away from launching the rescue mission, which NASA has
christened STS-400. While Atlantis is in space, NASA will continue preparing
Endeavour until it is just three days from launch-ready status.
Meanwhile,
the rescue mission's small four-man crew commanded by veteran astronaut Chris
Ferguson would also be on standby alert. Endeavour and its rescue crew will
remain at the ready until Atlantis lands or is cleared for re-entry, mission
managers said. Ferguson's crew is a fresher team assigned after a broken part
on Hubble delayed this mission by seven months last fall.
If the
rescue flight is required, NASA would begin the three-day countdown toward
Endeavour's launch. Ferguson and his rescue crew already plan to be here at the
launch site ready to fly, Moses said.
Meanwhile,
Altman and his crew would power down Atlantis to conserve their supplies. If the
rescue mission launches within the first two or three days of the Hubble
flight, Atlantis could keep its crew alive for nearly a month. But if the
damage is discovered later, during a standard late heat shield inspection, the
shuttle will likely only have 16 days of air left, Altman said in an interview.
Double
shuttle rendezvous
According
to NASA's plan, Endeavour would arrive at Atlantis about 23 hours after
launching into space. Endeavour would slowly rise up from below to meet its
sister ship, then reach out its robotic arm and grab onto Atlantis' own robotic
appendage. The two shuttles would be just 24 feet (7 meters) apart, connected
only by the bent 50-foot (15-meter) shuttle arm.
A series of
three tricky spacewalks would follow to move Atlantis astronauts from their
stricken ship and into Endeavour. Once the seven Hubble astronauts are safely transferred - Altman would be among the last to leave - Atlantis would be
abandoned and all 11 spaceflyers would return home on Endeavour.
Atlantis,
meanwhile, would be left in space to be remotely ditched in a fiery demise over
the Pacific Ocean.
Moses said the
decision to launch the rescue flight won't be easy, especially since it
involves launching more astronauts into space to save their stranded comrades.
"You're
putting another set of crew at risk to go up and rescue," Moses "We're more
than willing to do it, we're postured to do it, but again there's a lot of risk
trades we're going to have to do when that scenario comes."
SPACE.com
is providing continuous coverage of NASA's last mission to the Hubble Space
Telescope with senior editor Tariq Malik at Cape Canaveral and reporter Clara
Moskowitz in New York. Click
here for mission updates and SPACE.com's live NASA TV video feed.
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