The latest space shuttle flight is taking some new recycling equipment to the space station.
The new system distills, filters, ionizes and oxidizes wastewater - including urine -- into fresh water for drinking.
With the space shuttles due to retire in two years, Nasa needed another way to make sure the station crew would have a good supply of fresh water. The orbiters make water as a byproduct of their electrical systems. On missions to the space station, the water is bagged and transferred over to the outpost for storage.
"When the shuttles retire, that nice water-delivery system that we have will go away," said Endeavour astronaut Sandra Magnus, who will be staying behind on the station for a four-month flight.
How well does it work?
The water has been thoroughly tested on Earth, including blind taste tests that pitted recycled urine with similarly treated tap water.
The most frequent comment was the faint taste of iodine in the water, added Nasa's Bob Bagdigian, who oversaw development of the water regeneration system. Iodine is added at the final step of the process to control microbial growth. "Other than that, it is just as refreshing as any other kind of water," Mr Bagdigian said. "I've got some in my fridge. It tastes fine to me."