Future astronauts poised to blast off for an extended stay on the International Space Station (ISS) might first consider dashing to the restroom for a quick splash at the lavatory, or better yet, a luxurious hot shower. Once on board the ISS, spacefarers are in for a steady diet of sponge baths using water distilled from -- among other places -- their crewmates breath.

If you're squeamish, read no farther, because the crew will eventually include lab rodents -- and they'll be breathing, too. All of the denizens of the space station lose water when they exhale or sweat. Such vapors add to the ambient cabin humidity, which is eventually condensed and returned to the general water supply.

Sometimes it's better not to think about where your next glass of water is coming from!

Rationing and recycling will be an essential part of daily life on the ISS. In orbit, where Earth's natural life support system is missing, the Space Station itself has to provide abundant power, clean water, and breathable air at the right temperature and humidity -- 24 hours a day, 7 days a week, indefinitely. Nothing can go to waste.

In this article, the first of a series about the practical challenges of living in space, Science@NASA will examine how the Space Station's Environmental Control and Life Support System (ECLSS), under continuing development at the Marshall Space Flight Center, will help astronauts use and re-use their precious supplies of water. Future installments will explore air management, thermal control and fire suppression -- in short, all of the things that will make the Space Station comfortable and safe.