CAPE CANAVERAL, Florida (Reuters) – As NASA prepares to double the number of astronauts living aboard the International Space Station, nothing may do more for crew bonding than a machine being launched aboard the space shuttle Endeavour on Friday.

It’s a water-recycling device that will process the crew’s urine for communal consumption.

"We did blind taste tests of the water," said NASA’s Bob Bagdigian, the system’s lead engineer. "Nobody had any strong objections. Other than a faint taste of iodine, it is just as refreshing as any other kind of water."

"I’ve got some in my fridge," he added. "It tastes fine to me."

Delivery of the $250 million wastewater recycling gear is among the primary goals of NASA’s 124th shuttle mission, which is due to launch at 7:55 p.m. EST on Friday (0055 GMT on Saturday) from the Kennedy Space Centre in Florida.

If the shuttle lifts off on time, it would arrive at the space station on Sunday so astronauts could begin 11 to 12 days of home improvements.

In addition to the water recycler, Endeavour carries two small bedrooms, the station’s first refrigerator, new exercise gear, and perhaps most important for a growing crew -- 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," said Endeavour astronaut Sandra Magnus, who will take over as a space station flight engineer from Greg Chamitoff.

NASA wants to make sure the water recycling system is working well before adding another three astronauts to the station’s crew.

Reusing water will become essential once NASA retires its space shuttles, which produce water as a byproduct of their electrical systems. Rather than dumping the water overboard, NASA has been transferring it to the space station.

"We can’t be delivering water all the time for six crew," said space station flight director Ron Spencer. "Recycling is a must."

NASA expects to process about six gallons (23 litres) of water per day with the new device. The goal is to recover about 92 percent of the water from the crew’s urine and moisture in the air.

The wastewater is processed using an extensive series of purification techniques, including distillation -- which is somewhat tricky in microgravity -- filtration, oxidation, and ionization. The final step is the addition of iodine to control microbial growth, Bagdigian said.

The device is intended to process a full day’s worth of wastewater in less than 24 hours.

"Today’s drinking water was yesterday’s waste," Bagdigian said.