The United States and its International Space Station partners have agreed on a new schedule to complete the outpost by 2010. The updated assembly sequence has been made necessary by the long hiatus in flights of the U.S. space shuttle, the only vehicle capable of carrying big pieces of station hardware.
With shuttle flights to resume later this year, the U.S., European, Russian, Canadian, and Japanese space agency chiefs met in Florida to endorse a compressed plan finishing the station in 16 shuttle missions over the next four years.
Two factors have mandated the new schedule. First, the loss of the shuttle Columbia in 2003 has caused a more than three-year pause in assembly visits. Second, President Bush has ordered an end to shuttle service in 2010, earlier than NASA had previously planned.
NASA chief Michael Griffin says there is not enough time to pursue an earlier plan for 28 shuttle flights to the station during the assembly phase.
"The main thing that you're seeing here today is the decision to put together an assembly sequence that allows us to have very high confidence that we will finish the space station assembly by the time the shuttle must be retired," said Michael Griffin.
Griffin says the new schedule emphasizes building and delays use of the station until construction is complete.
"We are deferring the utilization of that station largely while we concentrate on building it," he said. "Our earlier plans, which were better plans, frankly, allowed us to utilize it as we built it to a much greater extent than we can now accommodate. That's the difference that you're seeing. But the end product is very much as we have envisioned it."
As a result, the current plan delays increasing the size of the crew to six until 2009. Only two crewmen inhabit the station now, a minimum number to keep the outpost running in the absence of shuttle flights. A third crewman will be added with the next shuttle mission, planned for late May.
That would not be a station assembly flight, but rather one to test improvements minimizing launch debris falling from the shuttle's external fuel tank, something that doomed Columbia by puncturing its wing. But two more shuttle flights planned this year are devoted to expanding the space station.
NASA's Griffin says even if the shuttle launch schedule should slip, there would be no affect on the deadline to finish the station by 2010.
"We have substantial schedule slack at this point, almost a full year," explained Michael Griffin. "So we would have to have substantial difficulties that we do not now envision in maintaining our flight rate in order to start any consideration of contingency plans."
The new station construction plan calls for earlier launches of European and Japanese science laboratories. Other segments to be added are a Russian laboratory; a U.S. tunnel connecting four labs; a two-armed Canadian crane; and an unpiloted European cargo vehicle that can dock with the station automatically.