Seven NASA astronauts and the space shuttle Endeavour are poised to launch Friday evening on what they've called an extreme home-improvement job at the International Space Station.

Endeavour is set to blast off at 7:55 p.m. EST (0055 Nov. 15 GMT) from a seaside launch pad at NASA's Kennedy Space Center hauling a cargo pod packed with new life-support gear, including a $250 million recycling system that turns astronaut urine into drinkable water.

"This mission is all about home improvement," said Endeavour commander Chris Ferguson. "Home improvement both inside and outside the space station."

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Ferguson and his STS-126 crew are launching on a 15-day mission to install a new kitchen, bathroom, two spare bedrooms, an all-in-one exercise machine and the water-recycling system to help boost station crew sizes up to six people next year.

Four spacewalks are also planned during the mission to clean and grease an ailing solar array joint so the outpost can generate more power.

"There comes a time to start doing maintenance," said Endeavour lead spacewalker Heide Stefanyshyn-Piper. "This is it, and we're ready to go."

Set to launch spaceward with Ferguson and Stefanyshyn-Piper are Endeavour pilot Eric Boe and mission specialists Don Pettit, Steve Bowen, Shane Kimbrough and Sandra Magnus. Boe, Bowen and Kimbrough are making their first spaceflight.

Magnus is set for a longer mission than her crewmates and expects to spend almost four months in space as part of the station's three-person Expedition 18 crew.

She'll replace fellow NASA astronaut Greg Chamitoff, who has lived aboard the station since June.

Endeavour has a 70 percent chance of good launch weather for Friday's planned liftoff, with the potential for thick clouds and nearby rain showers posing the only threat.

Those chances dwindle to just 30 percent on Saturday due to an approaching cold front, but should clear up on Sunday, said NASA shuttle weather officer Kathy Winters.

A launching shuttle can trigger lighting if it flies through thick storm clouds, and NASA flight rules require clear weather around a nearby runway so the shuttle can land in an emergency.

Space-station makeover

Ferguson and his crew have a tall order ahead to deliver their cargo pod Leonardo and its load of new station equipment.

The centerpiece of the new gear is the water-recovery system, which will collect astronaut urine, wastewater and sweat condensed from the station's interior, then filter it through a seven-step process to produce clean water suitable for drinking, food preparation, bathing or other uses.

The water can also feed into a U.S. oxygen generator, which uses electrolysis to separate water into breathable oxygen and hydrogen.

"I don't think there's ever been a closed-loop system like the one that's on the [International Space Station]," said Mike Suffredini, NASA's station program manager.

Since the launch of its first module in 1998, the space station has grown in size and capability, Suffredini said. It requires more than the current three-person crews to keep its systems in order while continuing space science research, he added.

If it works as designed, the system should be able to recycle 93 percent of the water put into it — 85 percent of urine alone, said Bob Bagdigian, NASA's project manager for the station's environment-control and life-support system at the Marshall Space Flight Center in Huntsville, Ala.

If all goes well, the new system should complete its testing regime sometime around May, Bagdigian said.

It's then that NASA and its international partners hope to launch the first six-person crew.

Endeavour's STS-126 mission is NASA's fourth shuttle flight of 2008 and the second this year slated for a nighttime launch.

Of the 123 shuttle flights since 1981, about one-fourth have launched at night, NASA officials said.

"We're really excited to share our version of a sunrise with you tomorrow night," said NASA test director Charlie Blackwell-Thompson. "Night launches are always special."

NASA will provide live webcast coverage of Endeavour's launch tonight on NASA TV beginning at 2:30 p.m. EST (1930 GMT). Click here for SPACE.com's live mission coverage and NASA TV feed.

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