Sunday, November 23, 2008

725p 11/22 Update: Final bearing work deferred to 4th EVA


Posted: 7:25 PM, 11/22/08

By William Harwood
CBS News Space Analyst

Changes and additions:

   SR-50 (11/22/08): Spacewalk begins; urine processor troubleshooting continues
   SR-51 (11/22/08): Cleaning goes smoothly in initial stages of EVA
   SR-52 (11/22/08): Two trundle bearings installed; astronauts ahead of schedule at halfway point
   SR-53 (11/22/08): Astronauts told to wrap up spacewalk; one trundle bearing left for EVA-4


7:25 PM, 11/22/08, Update: Astronauts told to wrap up spacewalk; one trundle bearing left for EVA-4

Spacewalkers Heidemarie Stefanyshyn-Piper and Stephen Bowen are in the final stages of a grueling spacewalk to clean and lubricate the space station's right-side solar array rotary joint. They had hoped to install six trundle bearings today to complete a three-spacewalk overhaul. But with the spacewalk closing in on the seven-hour mark, flight controllers told the astronauts to defer installation of the final bearing assembly and re-attachment of a final few thermal covers to a fourth spacewalk Monday.

"We don't think we're going to be able to complete this starboard SARJ activity and get in before seven (hours and) 30 (minutes)," mission control radioed around 7 p.m. "It's not worth going past seven-thirty to try to press that. We've got time available on EVA-4, we've got a good (grease) gun sharing plan to complete the SARJ work on EVA-4 and if we get Heide to start packing her bag now, we estimate that she'll have (an elapsed time) of seven hours. So that's what we would like to do. Next step for her would be to start packing bags."

"OK, no problem, Houston," spacewalk coordinator Robert "Shane" Kimbrough replied from the shuttle Endeavour.

"And we really appreciate how hard you all are working. I know it's painful to call it quits like that, but we think it's the right thing to do."

Stefanyshyn-Piper had removed the final trundle bearing assembly when mission control told the crew to start cleaning up. The final bearing assembly will be installed Monday. A two-orbit "auto-track" test to rotate the right-side solar alpha rotary joint and measure vibration levels and drive motor currents will be rescheduled. The test had been planned for early Sunday, but it now likely will move to early Tuesday. Engineers do not want to rotate the massive joint until the lubrication and bearing replacement work is complete.

Inside the space station, meanwhile, flight engineer Sandra Magnus reported collecting initial water samples from the lab's new recycling equipment, presumably from processed condensate. Engineers are continuing to assess problems with a centrifuge motor in the system's urine processing system.

Specialists now suspect a sensor in a distillation unit is physically interfering with the centrifuge motor when extended operation causes thermal expansion. It is not yet clear what can be done to fix the problem or whether it might be possible to obtain water samples by operating the unit for shorter periods and then allowing cool down.


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