Urine processor appears to run normally in extended test
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: November 24, 2008
After three false starts and around-the-clock troubleshooting, the newly installed urine processor aboard the international space station was fired back up late Monday and appeared to run relatively smoothly after additional work earlier in the day to stabilize a centrifuge in the system's distillation sub-system. Despite occasionally sounding like a washing machine in the spin cycle, the processor continued running well past the times of earlier shutdowns.
"It looks like we are still spinning and it's been three hours and 18 minutes or something like that," station commander Mike Fincke reported just before 11:30 p.m.
"Yes, the UPA has been going very well," Robert Hanley replied from Houston. "Our regen (regenerative life support system) guys are actually smiling, which is really nice, here in the control center."
A few minutes later, Fincke said he could hear a change in the sound of the centrifuge.
"Stand by... I'm just hearing some washing machine noises that are coming from the UPA that wasn't there before and I can see on our motor currents that it's spiking a little bit. You guys probably see the same."
"Yeah, Mike, we see the same thing," Hanley replied.
"It definitely sounds like a washer in a spin cycle," Fincke said.
"OK, we copy that, Mike. And we think you may be hearing the sound go back to normal," Hanley said, apparently referring to telemetry.
"And we hear it going back to normal now and we can see the motor current dropping, so that sounds good," Fincke said.
A few minutes past midnight, Fincke said "I'd like to congratulate the entire team because we've been operating for four hours and two minutes now."
"Yes, everybody's very happy down here," Hanley said "it's looking good so far."
"Well, not to spoil anything, but I think up here we're feeling the appropriate words are 'yippee!'"
"There will be dancing later," Hanley said.
The urine processor assembly is a key component in a new system designed to convert condensate and urine into potable water for drinking, meal preparation, personal hygiene and oxygen generation. The closed-loop life support system is required before NASA can boost the station's crew size from three to six next May.
But the astronauts and flight controllers have had problems getting the urine processor assembly up and running. The first two test runs ended with computer-commanded shutdowns after about two hours of operation. Telemetry indicated a speed sensor was physically interfering with the operation of the centrifuge, possibly due to thermal expansion or harmonic effects as the spinning hardware warmed up.
Fincke and Endeavour astronaut Don Pettit removed rubber vibration dampers from the centrifuge housing to firmly lock the unit down in a bid to change the vibration modes thought to be contributing to the problem. In a third test run, the processor operated past the two-hour mark but eventually shut down with the same signature: slower motor speeds and higher currents.
On Monday, Fincke added two more bolts to add additional support to the distillation unit housing. The processor was restart shortly after 8 p.m. and was still running at midnight. Engineers planned to run the unit for five hours before shutting it down, allowing it to cool off and starting a new test run.
Earlier Monday, mission managers agreed to extend Endeavour's mission one day to give engineers more time to troubleshoot the UPA problem. During a briefing following the crew's fourth and final spacewalk Monday, station flight director Ginger Kerrick said flight planners are hoping for the best but, playing it safe, planning for the worst: bringing the distillation unit back to Earth for repairs if it fails to operate in an acceptable manner.
"The ground teams are looking at options for returning the urine processor assembly, potentially either in the shuttle middeck or in the MPLM (cargo module)," Kerrick said. "We hope to have a bingo time of sorts where we can continue out troubleshooting up to a certain time and, based on where the processor will be returning on the shuttle, MPLM or middeck, that bingo time will be slightly different. The addition of the plus one day does give us some additional time for further troubleshooting."
Even if the processor fails to operate normally, Kerrick said mission managers could still opt to leave the unit in place if tests show it can be operated in an on-again off-again way.
"If it passes and keeps running, I think our engineers will get comfortable that they have found a solution," Kerrick said. "If it fails, the alternative method is to operate it in one-hour and 45-minute increments with cool downs in between. We have not tested that yet, but we still have time with the additional docked day to test that theory. ... So I think there's two ways for folks to get comfortable with the urine processor remaining on board."
Earlier Monday, astronauts Stephen Bowen and Robert "Shane" Kimbrough staged a successful spacewalk to finish lubricating the station's two solar alpha rotary joint mechanisms. They also retracted a balky berthing latch on the Japanese Kibo module, mounted one of two GPS antennas and installed a new television camera on the station's solar power truss.
A major goal of Endeavour mission was to clean and lubricate the main drive in the station's right-side SARJ mechanism and replace 11 of 12 bearing assemblies. That work spilled over into Monday's spacewalk, but Bowen had no problems installing a final bearing assembly and completing the lubrication of a 30-degree segment of it's 10-foot-wide drive gear.
The starboard SARJ suffered extensive damage to one of its three bearing race rings because of a lubrication breakdown in space. Engineers hope the Endeavour crew's cleaning, lubrication and bearing replacement will reduce rolling friction and vibration and allow periodic "auto-track" sun tracking to improve power generation.
Engineers plan to test the starboard SARJ starting at 5:30 a.m. Tuesday, commanding the massive joint to operate in auto-track mode for two full orbits. Sensors will measure vibration levels and drive motor currents while television cameras looks for any signs of unwanted shaking.
The astronauts said they wanted to watch the test, but flight controllers late Monday told them to stay in bed. Any vibrations caused by crew members moving around inside the station could affect data being collected to assess SARJ performance.
"They did want to see it and I can appreciate that, but we need to minimize disturbances on the space station so that we get the best data that we can," Kerrick said. "We're looking at some accelerometer data, vibration data, and we want to make sure that what we're seeing is truly caused by the SARJ and not by eager crew members looking out the window."
While Bowen serviced the starboard SARJ Monday, Kimbrough worked to lubricate the port-side drive gear's bearing races. The port mechanism has operated normally to this point, but Bowen reported today that he could see signs of wear on the outer bearing race similar to, but not as serious as, the damage on the right-side gear.
"I'm sure that got a lot of discussion back with our SARJ engineering team, Kerrick said. "That was a surprise to me, something different than we had heard reported from the port SARJ. But at the same time, we know the port SARJ could be susceptible to the same failure the starboard SARJ saw, so it seems to me we caught it in time."