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#60 by on 12 Dec, 2007 20:54
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Chris Bergin - 12/12/2007 3:20 PM
QuoteMike_1179 - 12/12/2007 9:08 PM But the issue is likely not with the sensors, it's with the wiring and circuitry in the tank and the Point Sensor Box.
Correct, and given the absolute bulk of L2 documentation on the issue focuses on the LH2 feedthrough connector, that's the top candidate so far.If that is the case then would that be a quick and easy fix at the pad?
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#61 by Chris Bergin on 12 Dec, 2007 21:23
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Justin Wheat - 12/12/2007 9:54 PM
QuoteChris Bergin - 12/12/2007 3:20 PM
QuoteMike_1179 - 12/12/2007 9:08 PM But the issue is likely not with the sensors, it's with the wiring and circuitry in the tank and the Point Sensor Box.
Correct, and given the absolute bulk of L2 documentation on the issue focuses on the LH2 feedthrough connector, that's the top candidate so far.If that is the case then would that be a quick and easy fix at the pad?
They've got to prove it, and no, it wouldn't be simple to R&R.
The main issue is a lot of documentation "proves" it tested out fine....but the kicker is it's only tested in cryos when during tanking. That's why they are resimulating via a tanking test. -
#62 by ChrisC on 12 Dec, 2007 23:25
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Regarding the LH2 feedthrough area, I liked the theory proposed by someone here that perhaps in addition to the cryo environment, it had something to do with the mass loading of the tank. That is, as the tank gets loaded with tons of fuel, the structure deforms in a way (unnoticed until ... next Tuesday!) that is causing those connectors to lose contact. On one hand it doesn't make sense because the tank isn't hanging off the shuttle, it's the opposite, so the mass loading of the tank should have no effect on that interface, but perhaps it does strain the tank structure between the shuttle attachment points in a way that causes a strain / disconnect at that feedthrough. Anyway, that was the most interesting theory I've heard so far.
Note that I am NOT on L2. And will remain that way, otherwise I'd never leave this site
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#63 by Joffan on 13 Dec, 2007 00:04
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ChrisC - 12/12/2007 5:25 PM
Regarding the LH2 feedthrough area, I liked the theory proposed by someone here that perhaps in addition to the cryo environment, it had something to do with the mass loading of the tank. That is, as the tank gets loaded with tons of fuel, the structure deforms in a way (unnoticed until ... next Tuesday!) that is causing those connectors to lose contact. On one hand it doesn't make sense because the tank isn't hanging off the shuttle, it's the opposite, so the mass loading of the tank should have no effect on that interface, but perhaps it does strain the tank structure between the shuttle attachment points in a way that causes a strain / disconnect at that feedthrough. Anyway, that was the most interesting theory I've heard so far.
Note that I am NOT on L2. And will remain that way, otherwise I'd never leave this site
Mass loading should certainly deform the tank, as it now has more mass at the bottom than the top; and temperature effects may cause some deformation also, although I fully expect that the NASA designers will know by how much in both cases. Any deformation could feasibly strain a linkage along the siganl path. So yes, a very interesting and plausible theory; which does not of course make it true.
And sadly I feel exactly as you do about L2... I'd love to join, but I don't know if I trust myself to limit my time on there
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#64 by Ford Mustang on 13 Dec, 2007 02:31
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Just confirming what I think I'm seeing..
There's a webcam in the SSPF, saying 'Columbus Module in SSPF Highbay'. Has the module been transported BACK to the SSPF, or have they not updated it yet?
[small]Reference image located below.[/small]
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#65 by nathan.moeller on 13 Dec, 2007 04:28
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Ford Mustang - 12/12/2007 9:31 PM
Just confirming what I think I'm seeing..
There's a webcam in the SSPF, saying 'Columbus Module in SSPF Highbay'. Has the module been transported BACK to the SSPF, or have they not updated it yet?
[small]Reference image located below.[/small]
Hasn't been updated. There's no reason to take Columbus back to the SSPF. If they remove it from the payload bay, it'll just sit in the PCR in the RSS until they're ready to fly. Even then, I can't think of a great reason to remove it (yet). -
#66 by Chris Bergin on 13 Dec, 2007 10:29
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Launch pad configuration is continuing, taking Atlantis out of the launch config (complete) with access being re-installed.
More articles to come over the coming days, so to the ones above speaking about L2 wishes, fear not, I'll be writing up as much as possible into articles. -
#67 by Chris Bergin on 13 Dec, 2007 13:30
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Troubleshooting starts in earnest today, with the splicing of the wires and TDR set up, ahead of the functional test tomorrow.
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#68 by on 13 Dec, 2007 15:09
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What time is the test going to be performed?
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#69 by ETEE on 13 Dec, 2007 15:37
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Joffan - 13/12/2007 1:04 AM
QuoteChrisC - 12/12/2007 5:25 PM
Regarding the LH2 feedthrough area, I liked the theory proposed by someone here that perhaps in addition to the cryo environment, it had something to do with the mass loading of the tank. That is, as the tank gets loaded with tons of fuel, the structure deforms in a way (unnoticed until ... next Tuesday!) that is causing those connectors to lose contact. On one hand it doesn't make sense because the tank isn't hanging off the shuttle, it's the opposite, so the mass loading of the tank should have no effect on that interface, but perhaps it does strain the tank structure between the shuttle attachment points in a way that causes a strain / disconnect at that feedthrough. Anyway, that was the most interesting theory I've heard so far.
Note that I am NOT on L2. And will remain that way, otherwise I'd never leave this site
Mass loading should certainly deform the tank, as it now has more mass at the bottom than the top; and temperature effects may cause some deformation also, although I fully expect that the NASA designers will know by how much in both cases. Any deformation could feasibly strain a linkage along the siganl path. So yes, a very interesting and plausible theory; which does not of course make it true.
And sadly I feel exactly as you do about L2... I'd love to join, but I don't know if I trust myself to limit my time on there !
Unfortunately only the hydrogen tank will be filled for the tanking test. To simulate the mass and coldness of the whole flight ready ET they should really fill the oxygen tank as well, although I realise that the hydrogen sensor circuits are most under suspicion.
Another cause that hasn't been mentioned here is the expansion/contraction of the sensor cable runs especially that which runs inside the tanks. That could be a factor with cryogenic temperatures turning a loose wire taut and possibly breaking it.
So sorry I don't get L2 either or should that be LH2? -
#70 by Andy USA on 13 Dec, 2007 15:47
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You three guys should get on as it's amazing and you'd see they've already found their suspect.
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#71 by DaveS on 13 Dec, 2007 17:06
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Justin Wheat - 13/12/2007 5:09 PM
Tanking is planned to start at 7 am EST Tuesday and only LH2 will be loaded.
What time is the test going to be performed? -
#72 by dember on 13 Dec, 2007 17:31
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Will this be covered on NASA TV? My guess is it wont.
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#73 by anik on 13 Dec, 2007 17:56
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Info from MCC-M: preliminary launch date gotten from NASA is January 7th...
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#74 by Chris Bergin on 13 Dec, 2007 19:10
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From L2 information, including a key presentation, dated today:
STS-122: Troubleshooting begins at pad - NASA identify fault candidate
http://www.nasaspaceflight.com/content/?cid=5309 -
#75 by David AF on 13 Dec, 2007 19:32
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Great article Chris. Talk about solidifying this site as the best space flight news site around....
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#76 by catdlr on 13 Dec, 2007 19:40
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Excellent summary article Chris.
Quote from your article "'Postulated Failure Mechanism Summary: Circuit break caused by contamination of contacts between external plug and feed through pins and internal movement of plug sockets. Contamination is the result of condensing and freezing of air and water vapor within connector on feed through pin surfaces. Solid air and ice are effectively electrical insulators. Cryopumping of ambient air is expected through harness. "
Looks like the engineers have ICE-olated the problem
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#77 by DaveS on 13 Dec, 2007 19:45
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catdlr - 13/12/2007 9:40 PM
No. It's a hypothesis not yet confirmed made from bench tests. It could be A cause, but it's not yet THE cause for Atlantis' LLCO system problems. This is what the tanking test next week is going to show.
Looks like the engineers have ICE-olated the problem
Atlantis' problems could be as simple as a faulty connector pin or damaged wiring etc. But until the tanking test have been concluded and the results analyzed, it's to early to say they have isolated the problem. -
#78 by Peter NASA on 13 Dec, 2007 19:51
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I'd go further and say this is certainly very good data for what is likely to be causing it. Tanking Test now key to recreat and confirm, but it's hopeful!
By the way, very very good article Chris. That was a complex presentation to summarize. -
#79 by trlstyle on 13 Dec, 2007 20:06
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I hope it is not the 7th. I liked the idea of the 2nd a lot more.
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