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."
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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