Author Topic: SARJ Solution Updates  (Read 55690 times)

Offline dgates

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SARJ Solution Updates
« on: 01/12/2008 12:04 pm »
What are the long term impacts if it turns out the damaged / FOD'ed SARJ goes inop?  Granted, we're a *long* ways away from that but one has GOT to think that the operational lifetime has been impacted here, sooner or later it is going to quit turning. 

In the interim the mitigation plan is to simply not turn it or minimize it's use.  The electrical loads that come online with the addition of Kibo mean it's *gotta turn* to make the juice needed, eh?

How does this potentially impact long term ISS ops, i.e., 6 person crew ops? 

I have this gut feeling that this SARJ issue is a huge big deal from a long term systems ops point of view.  Is it the ISS life-limiter now even, perhaps?  Is this why the external discussion on the subject of SARJ damage "way forward" has been so muted?
« Last Edit: 11/04/2008 12:10 pm by Chris Bergin »
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Offline rdale

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RE: What if: SARJ inop?
« Reply #1 on: 01/12/2008 12:29 pm »
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dgates - 12/1/2008  8:04 AM

Is this why the external discussion on the subject of SARJ damage "way forward" has been so muted?

It's "muted" the same way the questions as press conferences that begin with "I know you don't know, but what if..." There are too many variables to predict everything that might happen with the power system over the next 10 years. I don't think they are 'hiding' anything. They just don't know.

Offline erioladastra

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RE: What if: SARJ inop?
« Reply #2 on: 01/13/2008 08:22 pm »
Muted?  Been talked in various threads.  Been quiet for a little bit because it is taking a while to figure out what is wrong and how to fix it.

Yes, it is a huge deal.  First off all, to correct one thing, the SARJ is currently NOT rotating.  We are keeping it parked to minimize damage.  We consider it no go for movement but we can/do tweak the fixed position if really needed.  However, we are assuming it is not moving until fixed.  If we can never move it again, e can't get much past Kibo to power the loads.  So yes, 6 person crew would be impacted, full payloads being on woul dbe impacted - it would not be good.  

Current leaning is to grease it up (replace the lubrication which is the leading failure right now), replace a TBA or two or maybe a DLA and then go with it until it fails further and we really have to go to the other race ring.  But that is down the road.

Offline DMeader

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RE: What if: SARJ inop?
« Reply #3 on: 01/13/2008 10:18 pm »
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erioladastra - 13/1/2008  4:22 PM
Current leaning is to grease it up (replace the lubrication which is the leading failure right now).....

First I've heard of this....can you elaborate a bit? For instance, replace lubrication where?

Offline Analyst

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RE: What if: SARJ inop?
« Reply #4 on: 01/14/2008 12:09 pm »
I too would be interested in the details.

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Offline dgates

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RE: What if: SARJ inop?
« Reply #5 on: 01/14/2008 03:40 pm »
Thanks for the update!  Finding the root cause is going to make for some interesting EVA work in the near term, and the re-lube and TBA and / or DLA swaps down the road too.  What's on orbit as far as TBA and DLA spares .... I think I remember a comment that there were some aboard but I'd have to look it up.  I sure hope that this allows for lots of SARJ rev's before a race ring swap is needed.

Next stop: looking at the STS-122 EVA detail plans, any SARJ inspection activity programmed? (I should already know this....)  


Thanks again!
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Offline Lawntonlookirs

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Re: What if: SARJ inop?
« Reply #6 on: 01/14/2008 03:55 pm »
I remember on STS 117 when they were doing some EVA on the solar panels.  If I remember they had some tools that were missing and some wiring on the solar panel.  Is it possible that one of the tools that were missing got caught up in the SARJ, or the wiring problem had something to do with the premature wearing of the SARJ?  I don't recall hearing much more about the tools or the wiring as the attention starting going toward a problem with a flight controller computer, and the torn insulation panel on the shuttle.
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Offline dgates

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Re: What if: SARJ inop?
« Reply #7 on: 01/14/2008 04:56 pm »
Quote
Lawntonlookirs - 14/1/2008  11:55 AM

I remember on STS 117 when they were doing some EVA on the solar panels.  If I remember they had some tools that were missing and some wiring on the solar panel.  Is it possible that one of the tools that were missing got caught up in the SARJ, or the wiring problem had something to do with the premature wearing of the SARJ?  I don't recall hearing much more about the tools or the wiring as the attention starting going toward a problem with a flight controller computer, and the torn insulation panel on the shuttle.

It's not an "obvious" problem since so much of SARJ is instrumented for failure detection.  DLA's and trundle bearings sort of tell ya of they have a problem.   So, the "let's take a look" on EVA's to come are really important to finding out what is causing the motor current spikes and the debris found.  It's too early to speculate about what they might find, but the ISS is pretty much a workshop for now with all the station assembly ops going on.  Nobody on this planet is better trained and could be more carefull than the guys and gals that are doing this work but ...  stuff happens.  It'll be interesting to see if the add-on EVA for the SARJ inspection comes to pass.... any news on that?
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Offline helton831

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Re: What if: SARJ inop?
« Reply #8 on: 01/14/2008 04:59 pm »
Quote
Lawntonlookirs - 14/1/2008  8:55 AM

I remember on STS 117 when they were doing some EVA on the solar panels.  If I remember they had some tools that were missing and some wiring on the solar panel.  Is it possible that one of the tools that were missing got caught up in the SARJ, or the wiring problem had something to do with the premature wearing of the SARJ?  I don't recall hearing much more about the tools or the wiring as the attention starting going toward a problem with a flight controller computer, and the torn insulation panel on the shuttle.
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I mentioned this a while ago, I recalled not only tools went missing but several bolts and bolt retainer clips on the SARJ covers as well were liberated. I remember they were watching one item going through the SARJ. When I saw the damage I thought that that scraping around the race ring was exactly what you would see from something hard like a retainer clip jammed in the works.  Likely it is to obvious to be the root cause.
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Offline Lawntonlookirs

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Re: What if: SARJ inop?
« Reply #9 on: 01/14/2008 05:13 pm »
I agree that it sounds to obvious, but by the reports that were observed with the metal filings, it sure sounds like something you would see if a foreign body found its way into the mechanism.  The people that are performing the EVA are well trained on what they are doing and how the ISS is put togeter so I would think if it was a foreign body they would know. :cool:
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Offline Lee Jay

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Re: What if: SARJ inop?
« Reply #10 on: 01/14/2008 05:24 pm »
If this were caused by dragging a hard object against the race ring, the observed damage would be scoring, not the observed spalling or macropitting.  Incidentally, I don't understand how a lack of lubrication would have caused either failure mode.  I would think that would lead to micropitting or scuffing.  Perhaps it did and the micropitting turned into macropitting over time, but my poorly-informed guess is that it just doesn't have enough cycles on it for that.

Offline stockman

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Re: What if: SARJ inop?
« Reply #11 on: 01/14/2008 05:26 pm »
Quote
Lee Jay - 14/1/2008  1:24 PM

If this were caused by dragging a hard object against the race ring, the observed damage would be scoring, not the observed spalling or macropitting.  Incidentally, I don't understand how a lack of lubrication would have caused either failure mode.  I would think that would lead to micropitting or scuffing.  Perhaps it did and the micropitting turned into macropitting over time, but my poorly-informed guess is that it just doesn't have enough cycles on it for that.

I agree on that one as well. Especially since the other SARJ is older and yet is in pristine working condition.
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Offline dgates

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Re: What if: SARJ inop?
« Reply #12 on: 01/14/2008 05:28 pm »
How many rev's do you suppose the starboard SARJ might have on it, anyway?  Nominal ops would be one rev / orbit, so a rough estimate ought to be feasable to figger.....  let's see, how may rev's per day ... starboard SARJ Ops start / end date .... Bueler?  Bueler?
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Offline litton4

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Re: What if: SARJ inop?
« Reply #13 on: 01/14/2008 05:42 pm »
Quote
stockman - 14/1/2008  6:26 PM

Quote
Lee Jay - 14/1/2008  1:24 PM

If this were caused by dragging a hard object against the race ring, the observed damage would be scoring, not the observed spalling or macropitting.  Incidentally, I don't understand how a lack of lubrication would have caused either failure mode.  I would think that would lead to micropitting or scuffing.  Perhaps it did and the micropitting turned into macropitting over time, but my poorly-informed guess is that it just doesn't have enough cycles on it for that.

I agree on that one as well. Especially since the other SARJ is older and yet is in pristine working condition.

I thought that the current thinking was that the preload on the TBA or DLA had been set too high, resulting in voids under the Nitride layer on the ring being "crushed", resulting in spalling of fragments from the affected face.

Sort of like running a roller over a rusty steel surface. The pictures look very much like rusty steel with the rust layer removed.

Presumably they haven't found a "smoking gun" in any of the closeout docs from comparing the 2 SARJ assemblies.

Any reports of what testing has been done?

I presume that flying another S3/S4/S5 assembly is out of the question (even assuming you could extent the Shuttle life to allow time for that before further major construction.

Could they install an additional (shortened) array back on Z0 to augment the stalled arrays?
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Offline Lee Jay

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Re: What if: SARJ inop?
« Reply #14 on: 01/14/2008 05:48 pm »
Quote
litton4 - 14/1/2008  11:42 AM

Quote
stockman - 14/1/2008  6:26 PM

Quote
Lee Jay - 14/1/2008  1:24 PM

If this were caused by dragging a hard object against the race ring, the observed damage would be scoring, not the observed spalling or macropitting.  Incidentally, I don't understand how a lack of lubrication would have caused either failure mode.  I would think that would lead to micropitting or scuffing.  Perhaps it did and the micropitting turned into macropitting over time, but my poorly-informed guess is that it just doesn't have enough cycles on it for that.

I agree on that one as well. Especially since the other SARJ is older and yet is in pristine working condition.

I thought that the current thinking was that the preload on the TBA or DLA had been set too high, resulting in voids under the Nitride layer on the ring being "crushed", resulting in spalling of fragments from the affected face.

Me too...and lubrication wouldn't have a dramatic effect on an overloaded condition, especially at these extremely low velocities.

Offline dgates

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Re: What if: SARJ inop?
« Reply #15 on: 01/14/2008 05:50 pm »
I believe that they will regain full operational capability of the starboard SARJ.  It may end up with a shortened operational life but it will still work for a long long time.  Lots of rudundency built into the system for starters, plus the ability to swap out ORU's --- the DLA's, the TBA's, the motor controllers... etc.
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Offline Jorge

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Re: What if: SARJ inop?
« Reply #16 on: 01/14/2008 06:33 pm »
Quote
litton4 - 14/1/2008  12:42 PM

Quote
stockman - 14/1/2008  6:26 PM

Quote
Lee Jay - 14/1/2008  1:24 PM

If this were caused by dragging a hard object against the race ring, the observed damage would be scoring, not the observed spalling or macropitting.  Incidentally, I don't understand how a lack of lubrication would have caused either failure mode.  I would think that would lead to micropitting or scuffing.  Perhaps it did and the micropitting turned into macropitting over time, but my poorly-informed guess is that it just doesn't have enough cycles on it for that.

I agree on that one as well. Especially since the other SARJ is older and yet is in pristine working condition.

I thought that the current thinking was that the preload on the TBA or DLA had been set too high, resulting in voids under the Nitride layer on the ring being "crushed", resulting in spalling of fragments from the affected face.

That is indeed the current thinking by those who should know.

Quote
I presume that flying another S3/S4/S5 assembly is out of the question (even assuming you could extent the Shuttle life to allow time for that before further major construction.

You presume correctly.

Quote
Could they install an additional (shortened) array back on Z0 to augment the stalled arrays?

You mean Z1. No spare array, so lots of $$$ that don't exist. Won't happen.
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Offline stockman

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Re: What if: SARJ inop?
« Reply #17 on: 01/15/2008 05:11 pm »
Sorry if this is in the wrong place and covered already - What ever happened to the plan to run the SARJ through a partial or full rotation with the Canadarm camera recording the open cover that they left on the last spacewalk? I thought that was going to be done in December - With the delay in shuttle I would have thought they would have had plenty of time to do this. Any update is appreciated. Thank you

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Offline erioladastra

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Re: What if: SARJ inop?
« Reply #18 on: 01/16/2008 01:54 am »

TBAs were removed from 1 J/A since not likely the cause.

To answer a previous question - no SARJ stuff for 1E.  Some tasks, if they fit and make sense, may be added to the 1/30 EVA but nothing planned for now on 1E.  Depending on how the next EVA goes that could change of course.

Offline daveglo

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Re: What if: SARJ inop?
« Reply #19 on: 01/16/2008 09:52 pm »
IF (big if) the problem lies in pre-loading of the DLAs (and they certainly weren't wired right from the get-go), and it's obvious that the existing race ring is trashed, it sounds like the flip to the inboard ring is the permanent solution.  The grease idea might buy some time, but I'm kind of surprised that would be considered a workable fix.  That stuff is going to get everywhere (ever packed a wheel bearing?), and I would imagine it will end up carrying the FOD with it, endangering the ultimate ring swap.

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