Endeavour astronauts aboard the International Space Station are preparing to install the device which will recycle urine into drinking water on the space station and will re-fire the shuttle’s thrusters on Friday. The team will then a day off to recover their energy.

The boost from the Endeavour will raise the orbit of the craft itself along with the space station to which it is docked about a mile. The ISS will then be at the proper altitude to receive a progress spaceship which will deliver cargo to the orbiting station three days after the Endeavour heads back to Earth on Thanksgiving. The normal operational altitude of the ISS is somewhere between 200 and 220 miles above sea level.

The seven astronauts from the Endeavour and the three ISS crew members have been tirelessly since the shuttle’s launch from Florida a week ago. They will get half a day off after holding a news conference in space.

But before that can happen, they’ll have to complete work on the water purifier which, yuck factor aside, will safely convert urine and sweat into drinking water. The contraption came aboard the ISS along with the Endeavour’s astronauts and now it’s being installed, but it seems there’s a bit of a snag.

Astronauts were hoping to run a test batch through the purifier on Thursday, but a combustion-related caution alarm hindered that. Flight controllers wrote it off as a false alarm on account of the fact that there was no actual fire or smoke.

"These are the growing pains we expect to see," said flight director Ginger Kerrick. "These are very complicated pieces of equipment with very complicated software to control them."

The ceremonious urine test was going to be delayed until flight controllers could figure out what’s wrong, but they instead switched to testing another part of the larger purifying system. Samples from the recycling system will be analyzed on Terra before crew members can use the machine next year. Once up and running, the system will be an essential part of plans to expand the station to support six residents instead of the current three.

Meanwhile the two astronauts outside working on the station’s damaged joint completed an almost seven hour spacewalk. Thankfully this time Heidemarie Stefanyshyn-Piper and Shane Kimbrough managed not to drop anything into space, and stayed away from any other unpleasant incidents.

There were however two small problems at the end of the latest spacewalk. Namely Kimbrough had difficulty communicating with Mission Control and reported elevated levels of carbon dioxide in his spacesuit. Neither hitch was serious enough to put him in danger though. The former problem was likely due to a bump to his headset volume control.

As for the latter, "The (carbon dioxide) level never got to a level that we would have been concerned that it would cause him any problems," said lead spacewalk officer John Ray. "We were just managing it to make sure we got him inside before it got to that level, and we did."