NASA and its international partners plan to increase space station crews up to six astronauts by no later than April 2009, banking on 16 U.S. shuttle flights and extra Russian Soyuz and cargo ships, the agency's station program chief said Friday.
Michael Suffredini, NASA program manager for the International Space Station (ISS), said the U.S. agency is drawing up plans with Russia's Federal Space Agency for two additional Soyuz flights - and possibly an extra unmanned Progress vehicle - per year to support six-astronaut crews in 2009.
"This contract I expect to sign before the end of the year," Suffredini said in a teleconference with reporters. "The whole discussion of the six-person crew, now that we've got the [assembly] sequence in place, became our priority."
On Thursday, NASA chief Michael Griffin and his space agency counterparts from Russia, Europe, Canada and Japan announced plans to complete the ISS by 2010 - when NASA three remaining space shuttles are set to retire. That plan includes 16 ISS-bound shuttle flights and earlier launches for Europe's Columbus module and the Japanese Experiment Module (JEM).
Two additional "contingency missions" padding NASA's shuttle manifest, aimed at delivering spares and other logistics to the space station, will likely not be needed, Suffredini said.
"Today I would tell you that I have a pretty high degree of confidence that we may not need this flights," he said, adding that they could be performed should they become necessary in the future.
ISS crews, once set at three astronauts per mission pending its construction, have been limited to two-person teams following the drop in NASA shuttle visits after the 2003 Columbia accident. The shuttle Discovery returned to the ISS in July 2005 during NASA's STS-114 return to flight mission.
A second test flight, STS-121 also aboard Discovery, is slated to launch no earlier than May 10, NASA officials have said. That flight, commanded by astronaut veteran Steven Lindsey, is expected to return the ISS to a three-person crew when it ferries European astronaut Thomas Reiter to the orbital complex.
The next shuttle flight dedicated to ISS assembly, STS-115 carrying a new truss segment and solar arrays to the station, is slated to launch aboard the Atlantis orbiter no earlier than Aug. 28. However, the next Russian-built Soyuz vehicle to ferry humans to the ISS is scheduled to launch spaceward on March 29 EST with the station's Expedition 13 crew.
Russia's Soyuz and Progress spacecraft have proved a vital lifeline for the ISS, ensuring new crews and supplies reached the station as NASA recovered from the Columbia accident. During that time, about two Soyuz vehicles ferried astronauts to the ISS each year, with four Progress vehicles arriving with supplies.
"Prior to Columbia, we rotated almost all the crews with the shuttle," Suffredini said.
But the larger, six-person expeditions will likely be a mix, with at least one U.S. or NASA partner astronaut riding shuttles into orbit while other station members arrive by Soyuz, he said, adding that flight schedules, the number of Russian vehicles needed and rotation details still remain to be determined.
Last month, NASA struck a $21.8 million-per-passenger deal with Russia's Federal Space Agency which secures Soyuz seats to return U.S. astronaut and ISS Expedition 12 commander Bill McArthur to Earth and launch Expedition 13 flight engineer Jeffery Williams to the station.
Suffredini said that only two future ISS-bound Soyuz flights will not have a U.S. seat available, and that not every shuttle to the station will carry a new crewmember.
"We'll rotate about one person on the average on a shuttle, and we won't rotate on every shuttle," Suffredini said. "We'll rotate as we need to to make the crews line up right."
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