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#200
by
psloss
on 01 Aug, 2010 15:57
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Attitude control still on 2 CMGs, still working to bring CMG 1 back online.
A quick question - the crew have installed a jumper to bring a third CMG online. Does your post mean that CMG-1 is that third CMG, or is CMG-1 the only remaining offline CMG? Thanks.
The former. The capability provided by the jumper is there, but at the time of the call, CMG-1 was not yet being used for attitude control.
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#201
by
psloss
on 01 Aug, 2010 16:02
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"Early edition" of today's status report is online:
http://www.nasa.gov/directorates/somd/reports/iss_reports/2010/08012010.htmlExcerpt (reformatting is mine):
Thermal Loop A ETCS Pump Shutdown: After losing one cooling system pump (of two), ISS is currently stable, although thermally on single string (no redundancy). Last night (at 7:48pm EDT) RPC1 (Remote Power Controller 1) in RPCM (RPC Module) S11A_D tripped open, powering off the Loop A ammonia pump of the S1 ETCS (External Thermal Control System), resulting in the loss of one half of the cooling to ISS.
This required a number of powerdowns (i.e., turning off selected systems for thermal protection), including redundant power to four CQs (Crew Quarters), three in Node-2, one in Kibo JPM, with both fans in each CQ remaining functional but zero fault-tolerant (crew is still Go for CQ use). Due to loss of heater power, MBS (Mobile Base System), SSRMS (Space Station Remote Manipulator System), and SPDM (Special Purpose Dexterous Manipulator) are currently zero fault-tolerant. T2/COLBERT treadmill alignment guides are installed and should remain installed during crew sleep periods to protect against LOAC (Loss of Attitude Control) while attitude control is degraded; the latter also renders use of unisolated exercise (Russian Velo) NoGo to reduce momentum perturbations; all other exercise is currently permitted. S-band is operating nominally (on String 2, with String 1 in hot backup); Ku-band is operating nominally; audio subsystem is operating nominally (Node-2, COL & JPM are zero fault tolerant for C&W/Caution & Warning annunciation and voice comm); no video from Node-2, Node-3, COL & JPM modules; HCOR (high-rate communications outage recorder) is operating nominally; Russian UHF: no issues, both radios are deactivated.
Possible causes of the RPC trip include an electrical fault in the cabling between the RPCM and ammonia pump, electrical fault in the EMI (electromagnetic interference) filter, electrical fault in the pump control board, or an electrical fault in the pump. The RPC tripped because of an overcurrent; this points toward hardware components that do not have internal current limiting, such as the EMI filter, pump control board, and the pump itself (they get their current limiting function from the RPCM). A mechanical failure of the pump is considered unlikely.
After a pump restart attempt this morning, RPC1 tripped again There will be more attempts. There are two spare pumps on orbit. It will take two EVAs to remove and replace the pump. ISS is stable, but single string, and it is desired to get Loop A back as soon as possible. The teams are looking at replacing the Thursday (8/5) spacewalk with the first of two EVAs, followed by the second EVA on 8/7 (Saturday). The spacewalks need special planning since the system is in a reduced power configuration.
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#202
by
psloss
on 01 Aug, 2010 16:31
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Crew is still doing the PFCs that Rob noted before, but ground says the plan is to do a conference with the Team 4 folks at 17:30 GMT. (That would be a little less than an hour from now; 12:30 Central, 13:30 Eastern.)
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#203
by
psloss
on 01 Aug, 2010 16:44
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Additional details (update) and briefing schedule on NASA's main ISS page:
http://www.nasa.gov/mission_pages/station/main/Repeating here:
Mission Operations personnel and ISS Program management met Sunday morning to discuss the status of the loss of cooling loop A Saturday night on the International Space Station when a circuit breaker tripped just before 7 p.m. Central time Saturday night that resulted in the failure of the Pump Module for loop A that feeds ammonia to maintain the proper cooling for systems and avionics.
An attempt overnight Sunday to close the circuit breaker and restart the Pump Module was not successful.
The station is in a stable configuration with most systems receiving cooling and many systems operating with redundancy following the installation of jumper cables from the Destiny Lab’s power system overnight. The crew is not in any danger and is monitoring systems and relaxing on an otherwise off duty day.
One of two Control Moment Gyroscopes (CMG 1) that was taken off line Saturday night was spun up once again this morning, enabling the station to operate with three of four CMGs to electrically control the orientation of the outpost. Temperatures on the Main Bus Switching Units, which route power to various systems, are a little higher than normal, but well within normal parameters and are stable.
The flight control and management teams today approved a preliminary plan to replace a planned spacewalk Thursday by Expedition 24 crewmembers Doug Wheelock and Tracy Caldwell Dyson with at least two spacewalks to swap out the failed Pump Module that resides on the station’s S1 truss. There are two spare Pump Modules on stowage platforms on the station’s truss. The replacement module under consideration for replacement resides on External Stowage Platform 2, which is adjacent to the Quest airlock. The crew is being informed that replanning for alternate spacewalk activity is underway.
Although a final decision on a new spacewalk plan is still pending engineering and timeline analysis, the most likely scenario would call for an initial spacewalk no earlier than Thursday by Wheelock and Caldwell Dyson to replace the Pump Module and structurally bolt it into place on the S1 truss, with an additional spacewalk by the duo two or three days later to mate fluid and electrical connections.
To protect for spacewalk activity later this week, the flight control team plans to vent residual ammonia in the lines between the Ammonia Tank Assembly on the S1 truss and the failed Pump Module Tuesday to prepare for the module’s eventual replacement.
The tasks originally planned for Thursday’s previously scheduled spacewalk by Wheelock and Caldwell Dyson to install a power extension cable to the Unity module prior to the delivery of the Permanent Multipurpose Module on the STS-133 mission in November and to install a Power and Data Grapple Fixture to the Zarya module to support future robotics work will be deferred to a later date.
A briefing to discuss the station’s status and spacewalk replanning efforts is scheduled Monday on NASA Television at 3 p.m. Central time originating from the Johnson Space Center with Mike Suffredini, ISS Program Manager and Courtenay McMillan, Expedition 24 Spacewalk Flight Director. This briefing replaces a previously scheduled briefing on Tuesday.
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#204
by
GoForTLI
on 01 Aug, 2010 17:35
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Almost ready for the EVA conference. MCC-H is configuring comm, and Tracy is rounding up the personnel on orbit.
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#205
by
rdale
on 01 Aug, 2010 17:36
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Sounds like they are going to privatize that conference.
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#206
by
FinalFrontier
on 01 Aug, 2010 17:42
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Edited:
Not as bad as I thought, there are two spares on orbit they said.
Still, how quickly can they get a new pump in?
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#207
by
Space Pete
on 01 Aug, 2010 17:50
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What are the chances that the P1 RPCM R&R, originally attempted using the SPDM, could be included in any EVA activities? I know it's not a priority, but if it turns out that EVA-2 only takes 4 to 5 hours, then would they use the extra time to "get it done while they're at it"?
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#208
by
FinalFrontier
on 01 Aug, 2010 17:57
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I think right now is the immedeate problem. Losing this system is pretty serious. They should get that fixed first
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#209
by
psloss
on 01 Aug, 2010 18:01
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Still, how quickly can they get a new pump in?
Addressed, at least preliminarily, in the last status report. Posted the link a few posts above.
"The flight control and management teams today approved a preliminary plan to replace a planned spacewalk Thursday by Expedition 24 crewmembers Doug Wheelock and Tracy Caldwell Dyson with at least two spacewalks to swap out the failed Pump Module that resides on the station’s S1 truss."
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#210
by
GoForTLI
on 01 Aug, 2010 18:03
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Sounds like they are going to privatize that conference.
S/G-2 normalized. Sounds like the conference is over.
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#211
by
dsmillman
on 01 Aug, 2010 18:07
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Has a pump module been replaced before? Does anyone know if there is a published EVA checklist for replacement of the the pump module?
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#212
by
PahTo
on 01 Aug, 2010 18:14
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I wonder if this has anything to do with the previous issues with opening the valve on the NTA? Or is that on the other loop? I can't imagine the ammonia pump would be impacted by N2 pressure issues, but I'm not in that line of work.
Good thing this happened just before an already planned EVA. While procs will be totally different, the event fits the overall timeline in some fashion...
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#213
by
rdale
on 01 Aug, 2010 18:18
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I wonder if this has anything to do with the previous issues with opening the valve on the NTA?
Since the exact point of failure is not known, it's hard to guess at the cause until we know what is broken.
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#214
by
PahTo
on 01 Aug, 2010 18:20
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Thanks Bill Harwood--his latest article states this this failure is the same loop (A) as the NTA valve issue (and sorry if I missed it earlier in this thread).
Should be an exciting and busy week--good luck to all the teams!
I wonder if this has anything to do with the previous issues with opening the valve on the NTA? Or is that on the other loop? I can't imagine the ammonia pump would be impacted by N2 pressure issues, but I'm not in that line of work.
Good thing this happened just before an already planned EVA. While procs will be totally different, the event fits the overall timeline in some fashion...
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#215
by
axmor61
on 01 Aug, 2010 18:23
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"The flight control and management teams today approved a preliminary plan to replace a planned spacewalk Thursday by Expedition 24 crewmembers Doug Wheelock and Tracy Caldwell Dyson with at least two spacewalks to swap out the failed Pump Module that resides on the station’s S1 truss. There are two spare Pump Modules on stowage platforms on the station’s truss. The replacement module under consideration for replacement resides on External Stowage Platform 2, which is adjacent to the Quest airlock. The crew is being informed that replanning for alternate spacewalk activity is underway."
To be more exactly, there are 4 spare Pump Modules on stowage platforms: one on ESP-2 (the one to be considered for the swap), one on ESP-3, and one on each ELC-1 and ELC-2.
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#216
by
AnalogMan
on 01 Aug, 2010 18:39
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Has a pump module been replaced before? Does anyone know if there is a published EVA checklist for replacement of the the pump module?
There is a time-line for Pump Module R&R for STS-116 (where the spare is stored on ESP2).
http://www.nasa.gov/centers/johnson/pdf/163526main_EVA_116_F.pdfWarning its 42Mb in size, 505 pages. Time-lines are given on page 254 (P1 truss) and page 314 (S1 truss).
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#217
by
Space Pete
on 01 Aug, 2010 18:39
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Will this EVA officially be classified as an Unplanned EVA or a Contingency EVA?
If it is classed as a Contingency EVA, then this will be the first ever US Contingency EVA in history (excluding the whole STS-27 business).
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#218
by
rdale
on 01 Aug, 2010 18:56
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#219
by
rdale
on 01 Aug, 2010 18:56
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Evening DPC taking place. Removing SPHERES ops tomorrow, adding EVA review and Metox recharge if you can find a volunteer.
