NASA's
looming deadline to retire its space shuttle fleet by 2010 may complicate plans
to complete the International Space Station, according to the agency's top
official.
NASA
Administrator Michael Griffin said that while completing the ISS is a major goal
of both, the agency's return to flight effort and its exploration vision,
meeting the challenge by the 2010 deadline may prove difficult.
"We may not
be able to make the exact completion date that we desire," Griffin told
reporters during a recent shuttle update. "But we will complete it."
Retiring
the three remaining space shuttles in favor of a new crew-carrying vehicle is a
hallmark of NASA's exploration vision - announced by President Bush in January
2004 - which calls for a return of human explorers to the moon, then sending
them to Mars and beyond. The first steps in that vision are resuming shuttle
flights and fulfilling NASA's ISS commitments with its international partners.
"The
President, the space policy that we have, is very firm in that the shuttle will
retire in 2010," Griffin said. "What we'll do if we don't complete the
International Space Station by then is look at other means to complete it."
Griffin and
other NASA spaceflight officials said the agency will accelerate plans for
the shuttle's successor, dubbed the Crew Exploration Vehicle (CEV), in hopes of
minimizing - if not completely closing - any gap in NASA's human spaceflight
capability. NASA had previously expected the first human-carrying CEV flight no
earlier than 2014.
Returning
to flight
NASA's
space shuttle fleet has not flown since the Columbia disaster, which led to the
deaths of seven astronauts and the loss of one orbiter during reentry on Feb. 1,
2003. Damage sustained at launch, when debris from Columbia's external tank
struck the shuttle's left wing, was cited as the cause of the accident.
Shuttle
engineers and managers have spent more than two years revamping the shuttle
launch system to increase flight and astronaut safety, work that will culminate
with the launch of STS-114 - NASA's first return to flight mission - aboard the
space shuttle Discovery no earlier than July 13 of this year.
Without
shuttle flights, space station crews have been limited to two members since Expedition 7
due to limited supplies. The current ISS caretakers - Expedition 11
commander Sergei Krikalev and flight engineer John Phillips - hope to receive a
third crewmate, German astronaut Thomas Reiter, who is expected to ride aboard
NASA's second return to flight shuttle mission.
Russian
Soyuz spacecraft have ferried
crews to and from the ISS, with automated Russian Progress vehicles delivering
vital water, air and food to the station every few months. But the supply and
crew ships do not have the large cargo
capacity of the shuttle, nor can they deliver the large, primary components
that will enlarge the station to core completion.
In the
past, NASA was targeting about 28 shuttle flights to reach core completion of
the space station, but there have been some suggestions that 15 launches, or
even 10, could do the trick, ISS officials have said.
"The
reality is that we don't know how many flights are needed, if we're successful
returning [the shuttle] to flight," said Michael Kostelnik, NASA's deputy
associate administrator for the shuttle and space station programs, during a
space operations summit earlier this year. "The space shuttle is critically
dependent on what we intend to do with the International Space Station and
those requirements are still being worked out."
Grounded
hardware
The absence
of ISS-bound shuttle flights since the Columbia accident has interrupted the
launch flow of eight station components, which currently sit in a Kennedy Space
Center (KSC) facility awaiting their orbiter rides into space, some of which
have required maintenance due to the extended stay.
In April of
this year, engineers had to swap out one of six batteries for the station's P4
truss segment to prevent it from exceeding its lifetime expectancy before
launching into space aboard NASA's STS-115 spaceflight.
Slated for
a May 2003 launch before the Columbia accident, STS-115 is now expected to be
NASA's third shuttle mission after its two return-to-flight demonstrations -
STS-114 aboard Discovery and STS-121 aboard Atlantis.
Other
station hardware being prepared for launch at KSC include additional trusses the
Node 2 module, the Japanese Experiment Module Kibo and the European-built Cupola
which will eventually serve as the space station's viewport.
Discovery's
spaceflight, commanded by NASA astronaut Eileen Collins, has a launch window
that stretches to July 31, and NASA officials hope to launch Atlantis on its
STS-121 mission between Sept. 9 and Sept. 24 of this year.
"Getting
the shuttle back up there is just going to bring the space station back to its
full potential," Collins said.
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