CAPE CANAVERAL - It's relatively small. It's boxy. It's the least impressive of the girders that make up the metallic backbone of the International Space Station, which ultimately will stretch the length of a football field in orbit.
But the prime payload for NASA's next station construction mission is considered vital to the agency's plans to complete assembly of the outpost before a September 2010 deadline set by President Bush.
"It's critical because without it, we can't continue the building of the space station," Chuck Hardison, site manager for The Boeing Co. at Kennedy Space Center, said Friday. "So important things come in small packages."
Set for launch aboard shuttle Discovery around Dec. 7, the so-called P-5 Short Spacer [image] will serve as a bridge between segments on the left side of the station's 11-piece central truss.
Relatively small at 4,110 pounds, the segment is 15 tons lighter than the most recently added girder.
But without it, there would be no way to route electrical power, computer commands and coolant between portside segments of truss, which provides an orbital foundation for outpost science labs, solar wings, radiators and spare parts platforms, among other things.
The February 2003 Columbia accident brought station construction to a halt about midway through the job. Assembly resumed last month with the delivery and installation of the new portside truss segment.
NASA plans to launch an additional 14 shuttle missions to complete construction. The upcoming flight -- and three after it -- primarily aimed at finishing enough of the truss to add long-awaited European and Japanese science labs to the outpost.
"This mission is a bridge to our future assembly operations," said NASA payload manager Deborah Hahn. "Hopefully, this will be continued success with the assembly."
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