Trouble setting up a urine processor on the International Space Station won't prevent Endeavour's crew from returning home with water samples that NASA wants to analyze on the ground, mission managers said this evening. Since the processor has run for up to two hours before shutting down, enough urine has been processed to provide the necessary water samples by Tuesday.
The samples will include only 10 percent processed urine, rather then the 30 percent targeted.
As a result, there is no need to extend Endeavour's 15-day mission for a day to collect samples, though it's still an option if anything else goes wrong. Endeavour is now scheduled to undock from the station on Thanksgiving and land at Kennedy Space Center next Saturday.
Engineers believe the processor problem lies with a centrifuge mounted on isolators in a component that distills water from urine. They say a sensor is aggravated by the jostling centrifuge, and have proposed removing the isolators and hard mounting the centrifuge.
Mike Fincke, commander of the station's three-person Expedition 18 crew, is scheduled to work on that fix for about two hours Sunday morning.
"We'll see if that solves the source of the problem," said Ginger Kerrick, a lead space station flight director.
Samples have been run through a processor that purifies sweat and other condensation captured from the air inside the station, and an on board apparatus that tests water quality is also functioning well.
Though the water samples needed for this mission appear to be satisfactory, a broader question remains about whether the urine processor will function well enough to support six-person crews, which is the system's primary purpose.
"Those numbers have not been crunched yet," Kerrick said. "We do need to be able to answer that question."
Officials were enthusiastic about today's spacewalk, even though it did not complete repairs to a solar wing rotary joint as hoped before the mission.
They say there is ample time to do that Monday, without sacrificing any critical activities in the mission's fourth and final spacewalk.
"The crew executed as perfect an (spacewalk) as I've ever seen," said John Ray, the mission's lead spacewalk officer. "They were right on top of their game right out the door, and they just stayed at a very steady, even pace."
Final work left on the rotary joint consists of cleaning and greasing a section measuring about 30 degrees of the circular joint, and replacing one bearing assembly. Ray estimated it will take about two hours Monday, including preparation and clean-up.
Today's spacewalkers could have been pushed another 30 minutes, but the remaining tasks were expected to take a bit longer, so they were called in.
"We knew it was going to be very challenging to get it all done in three (spacewalks)," said Ray. "It's just a lot of work, it's a tough job, time consuming and it requires a lot of tools to be handled in each section."
The Endeavour crew has about five hours of downtime to look forward to Sunday, after a packed first nine days of the mission.
"It's been a long mission," said Kerrick. "Tomorrow will be Flight Day 10, and they really need to take that time off."
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