"Not to spoil anything, but I think up here the appropriate words are 'Yippee!'" space station commander Mike Fincke told Mission Control early Tuesday morning, shortly before bedtime.
"There will be dancing later," Mission Control replied.
Astronauts had spent a frustrating five days trying to get the urine processor working. But until early Tuesday, the machine couldn't last the four hours needed for a successful test run.
The urine processor ran for five hours Monday night, and flight controllers restarted it in the middle of the night. Another urine processor test was planned later Tuesday, shortly after the seven astronauts on the docked space shuttle Endeavour and the three space station crew members woke up.
Flight director Brian Smith said everything had to go well Tuesday and Wednesday in order for enough recycled water samples to be collected to return to Earth aboard Endeavour.
NASA added a 16th day to Endeavour's mission so astronauts could tinker with the urine processor. Endeavour is now set to undock Friday and land in Florida on Sunday.
The urine processor makes up a section of the $154 million water recycling system that was delivered to the space station by Endeavour. The machine is crucial to providing drinking water for the space station's crew, which is supposed to double to six members next year.
Samples of the processed urine, sweat and condensation will be tested on Earth before astronauts can start drinking the purified water next year.
In an effort to fix the problem, Fincke and Endeavour astronaut Donald Pettit had removed vibration grommets, which were used to mount a centrifuge in the urine processor, and bolted the piece down.
In other good news, the Endeavour astronauts learned Tuesday that the four spacewalks they performed during the mission paid dividends. The focus of the spacewalks was cleaning and lubricating a jammed solar-wing joint on the station's right side.
Mission Control said the early morning test went well. "I guess 'victory' clearly is the word," said shuttle commander Christopher Ferguson.
That joint had not worked properly for more than a year, preventing the solar wings on that side from pointing automatically toward the sun to generate electricity. Grinding parts left the joint full of metal shavings that kept it from rotating.
Smith cautioned that months of testing still were ahead to make certain the rotary joint was functioning 100 percent.