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The orbiting electricians have nearly finished their work on the International Space Station. Now it’s time for the plumbers.

The space shuttle Endeavour and its seven-member crew are set to launch early Friday evening for a 15-day mission to the orbiting outpost. Their assignment resembles an episode from the Home and Garden Channel’s “Designed to Sell”: Add a bathroom, upgrade the kitchen.

Endeavour is slated to deliver a shower-and toilet-stall combo, appliances for the galley, a new recycling system that turns waste water into drinking water, and two of what will be four new private sleeping quarters for crew members. To keep the station crew in shape, the shuttle is also bringing an exercise machine.

Until now, station-assembly missions have focused on building the basic structure and ensuring that it has power. Now, missions are increasingly aimed at getting the interior ready for six crew members, rather than the current three.

Unlike the past, “the station won’t look any different on the outside” when Endeavour’s mission ends, says Michael Suffredini, the space-station program manager at the National Aeronautics and Space Administration. “But it will be dramatically different on the inside.”

It’s hard for earthlings to envision how important the shift in emphasis to creature comforts can be. Take the new refrigerator Endeavour will deliver. The station already has one. But it’s dedicated to storing science samples, not cheese. The station’s current water dispenser, in a Russian module, has only a few temperatures: hot, less hot, and tepid. Cold drinks are hard to come by. The only time station crew members get them is when the shuttle arrives, which explains in part why visiting shuttle crews get such a warm welcome. With a second fridge on board the space station, cold beverages will become a regular feature with snacks and meals.

“It seems kind of trivial, but six months of lukewarm orange juice can kind of bum you out,” says Sandra Magnus, a mission specialist on this flight who will remain on the space station as part of a crew swap.

For the long haul, however, an absolute must-have is an advanced water-recycling system that will all but eliminate the need to bring fresh water from Earth. The water is used not only for drinking and bathing but to produce oxygen to breathe.

Currently, the station’s life-support system can capture and use water vapor the astronauts exhale. But that hardly meets the need. So the station receives a significant infusion of fresh water with each shuttle flight – a byproduct of the orbiter’s fuel cells. Water also arrives during unmanned resupply flights. But with launch costs currently running about $10,000-per-pound, water needs on the station that are projected to top one metric ton a year, and a soon-to-be-retired shuttle, a largely self-sustaining water system is mandatory.

The answer: the “water recovery system.” It takes human urine, gray water from bathing, and water vapor the crew exhales, distills and purifies it, salts it slightly to improve the flavor, then returns it to the tap and shower head.

“I like to call it our coffee machine,” quips Don Petitt, another mission specialist on this flight. “It takes yesterday’s coffee and makes it into today’s coffee.”

Although the idea of recycling waste water for drinking carries a heavy “yuck” factor, the notion is gaining traction on Earth, particularly in arid regions such as the US Southwest, where long droughts and a changing climate are expected to dry out the region further. In space, the future of human space exploration depends on such “closed loop” systems.

Between now and the next shuttle flight, currently scheduled for February, the system will undergo extensive tests. If all goes well, the station crew should be able to draw on it later next year. NASA officials say they expect to see the crew grow to six as early as next May.

As currently designed, the system gives off hydrogen as a byproduct, which will be vented to space. A future upgrade will collect the hydrogen, combine it with carbon dioxide, and produce additional water, as well as methane.

For the space station, the methane also represents waste. Down the road, however, the methane could be used as rocket fuel, notes Edward Francis, vice president and general manager for space, land, and sea at Hamilton Sundstrand, which designed and built the system. “It’s essential that we come up with ways to close the cycle” for water. The prospect of trying to bring water along on extended trips to the moon or on a two-year voyage to Mars “would be overwhelming.”

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