By Irene Klotz
Cape Canaveral, Florida
Mmm... tasty. But will astronauts enjoy the taste of their own urine recycled?
Astronauts flying aboard space shuttle Endeavour on Saturday plan to deliver a device to the International Space Station that may leave you wondering if Nasa is taking recycling too far.
Among the ship's cargo, which will help prepare the station for an expanded six-person crew, is a water regeneration system that, as one astronaut puts it, "will make yesterday's coffee into today's coffee".
"It's one of these great circle-of-life things," explained Don Pettit, a former space station science officer serving as a mission specialist aboard Endeavour.
The new system distils, filters, ionizes and oxidizes wastewater - including urine -- into fresh water for drinking.
I've got some in my fridge. It tastes fine to me
The US space agency wasn't really thinking about saving the environment when it decided to invest $250m in the water recycling gear.
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.
"In addition we're going to have six people on-station, so our requirements for water will go up."
Ms Magnus replaces Nasa astronaut Greg Chamitoff, who has been aboard the station since June.
Every drop of water on board the ISS is precious
Nasa doesn't plan to start using the new system immediately - engineers want samples to analyse to make sure it functions properly in zero-gravity.
The water has been thoroughly tested on Earth, including blind taste tests that pitted recycled urine with similarly treated tap water.
People may think it's disgusting, but if it's done correctly the water is purer than you drink on Earth
"Some people may think it's downright disgusting, but if it's done correctly, you process water that's purer than what you drink here on Earth," said Endeavour astronaut Heidemarie Stefanyshyn-Piper.
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."
The International Space Station is also being fitted with an extra bathroom unit
Nasa plans to double the station's crew size from three to six as early as May.
Endeavour also will be delivering two new sleeping compartments, more exercise gear, a galley and perhaps most important, a second toilet.
"With six people, you really do need to have a two-bathroom house. It's a lot more convenient and a lot more efficient," Ms Magnus said.
Astronauts also plan to work on the space station's solar power system. Four spacewalks are scheduled to begin repairs on a contaminated rotary joint needed to aim solar panels at the Sun.
The flight is the fourth and final mission of the year.
Nasa had hoped to fly a servicing call to the Hubble Space Telescope last month but delayed the mission to May 2009 to prepare for some additional repair work on the observatory.
In all, Nasa plans 10 more shuttle flights before the fleet is retired in 2010.