STS-114 Mission Update Thread (Part 2)

[tap_sa]

<font color="yellow">"ET's are always new equipment"</font><br /><br />True, but are the electronics in them alwayd brand new, I'm not sure.<br /><br />From the press conferences and other stuff running on NASATV I've got the impression that if they for example have to build a new point sensor box they don't just go to Radioshack shopping the latest and coolest transistors etc. that are compatible (at least by common sense) to the original specs. Instead they stored batches of the original components from the 80s or so, pick them up from a warehouse and build from those. So even if the product is new, the parts can be old. I guess certifying the use of latest Radioshack part is quite a heavy process. The problem in this methodology is that time alone can and will have adverse effects even on the parts laying safely at the storage.

 

[shuttle_rtf]

>Why did they do the tanking test if they were not looking for ice formation? These blokes are now trying to say that they do not do tanking tests as a matter of course.<<br /><br />Ah right. Well I believe they do Tanking Tests to check out pad operations (like pipes, hardware, processes etc.etc.) which makes sense if they've not used the pad for over two years.<br /><br />I don't believe they do a Tanking Test before every launch (thus it's not a matter of course).<br /><br />

 

[alokmohan]

When STS may take off finally?Or it is doomed?

 

[shuttle_rtf]

No, Alokmohan, it's certainly not doomed. All you are seeing is due diligence on the issue noted from launch day.<br /><br />Currently, STS-114's launch is noted as "no sooner than" the end of next week.

 

[haywood]

I you go here...<br /><br />http://mediaarchive.ksc.nasa.gov/search.cfm?cat=4<br /><br />You'll see several pictures of the replacement Point Sensor Box being worked on.<br /><br />Interesting to note...if you open the Large version of the first picture you be able to read the "Date of Manufacture"...8902.<br /><br />Also interesting...if you look at the 6th picture, you see a green pen stuck in the top of the testing console to keep the wire from falling down.<br /><br />We've all done that.<br /><br />

 

[SpaceKiwi]

Crap. <img src="/images/icons/frown.gif" /><br /><br />As you said, it looks like it's going to be another UA.<br /><br />I wonder how concerned they will be even if they can get a functioning set of ECO sensors? Given how 'touchy' these circuits seem to have become, I wonder if test-cycling them during the launch countdown without incident is going to give you comfort that they would correctly read DRY once in flight? <div class="Discussion_UserSignature"> <p><em><font size="2" color="#ff0000">Who is this superhero?  Henry, the mild-mannered janitor ... could be!</font></em></p><p><em><font size="2">-------------------------------------------------------------------------------------------</font></em></p><p><font size="5">Bring Back The Black!</font></p> </div>

 

[earth_bound_misfit]

S_G, whats the chances of this UA being caused by something easy to overlook, eg excessive voltage drop on the Bus when the newly installed ET heaters kick in? <div class="Discussion_UserSignature"> <p> </p><p> </p><p>----------------------------------------------------------------- </p><p>Wanna see this site looking like the old SDC uplink?</p><p>Go here to see how: <strong>SDC Eye saver </strong>  </p> </div>

 

[najab]

><i> Proving that is another matter since the failures apparently only occur when the ECOs are near crogenic temperatures.</i><p>I know this is the obvious first question, but I assume that somewhere around KSC there's an engineer with a bunch of ECO resistors sitting in a dewar flask of LH2 carefully monitoring how their resistance changes over the course of a few hours? Also, I assume that someone has checked to make sure that the transistors in the test circuit aren't sensitive to the temperature changes that occur in the aft fuselage over the course of several hours of having cryogenic prop flowing through there?</p>

 

[najab]

><i>Thank you very much for your input but we are smarter that we appear to be.</i><p>That's why I said it was an obvious question (where obvious reads "stupid")!!! <img src="/images/icons/laugh.gif" /></p>

 

[tap_sa]

What happens during the ECO sensor test? Are the resistors in the tank heated up to simulate the dry situation?<br /><br />Been pondering if something like this could happen:<br /><br />- the ECO sensor heats up, either by normal design or accidental power surge from faulty test circuitry.<br />- LH2 in the immediate contact of the sensor starts to boil<br />- pressure in the tank keeps the resulting gaseous hydrogen localized so that it effectively insulates the resistor from LH2.<br />- the boil-phenomenon doesn't revert once the show-dry test command ends because for reason X too much current is still forced though the warmer (higher resistance) resistor, which creates enough heat to maintain the insulating GH2 area.<br />- resistor stays warmer than it should, thus reading dry<br /><br />Still working on the X...

 

[najab]

If I'm asking you to stick your neck out too far, say so - there must have been some 'watercooler' talk in the CE's office about launching with 3 ECO sensors. Is it a solid no-go, or something that <i>might</i> be considered?

 

[earth_bound_misfit]

Plan to land shuttle here<br />By Ainsley Pavey<br />July 17, 2005<br />From: The Sunday Mail (Qld)<br /> <br /><br />QUEENSLAND'S Amberley RAAF base has been placed on stand-by in case of an emergency landing by US space shuttle Discovery.<br />Top-secret plans for Queensland's involvement in the event of a mishap have been revealed to The Sunday Mail as NASA waits to launch its first shuttle mission since the Columbia tragedy in 2003.<br /><br />An Australian Defence Force spokeswoman has confirmed "suitable arrangements" are in place to allow the 100-tonne spacecraft to land at Amberley, outside Ipswich, home of Australia's F111 fighter bombers. <br /><br />The secret plans caught Queensland Premier Peter Beattie off-guard.<br /><br />An Australian Defence Force source said: "This is the first time Amberley has been included in an emergency landing scenario.<br /><br />"They are very secretive, they would prefer to keep it as quiet as they can. Only a few people high up the chain know details. As part of the ANZUS Treaty, when they call out, we act."<br /><br />A NASA spokesman said an emergency landing in Australia would be "very last-minute".<br />"It would only be in an extreme emergency, some drastic situation in which it was de-orbiting and couldn't make it back to the US," he said. <br /><br />Complete story here <div class="Discussion_UserSignature"> <p> </p><p> </p><p>----------------------------------------------------------------- </p><p>Wanna see this site looking like the old SDC uplink?</p><p>Go here to see how: <strong>SDC Eye saver </strong>  </p> </div>

 

[tap_sa]

<font color="yellow">" the hugh thermal mass of the Liquid Hydrogen would not allow what you describe"</font><br /><br />If the boiling would somehow get started the resulting vapors would have lower heat capacity and poor thermal conductance, ie good insulator. Same effect that allows people to walk on burning coal, moisture on their feet evaporates creating a thin film that protects from burns. Or if you spill water on a hot stove and the conditions are right then sometimes a drop of water just floats there several minutes, similar thin film under it. I bet this phenomenon has a name but can't remember it right now.

 

[redgryphon]

<font color="yellow">The first ECO problems were declared a unexplained anomaly and I expect the latest problems will be a UA as well. </font><br /><br />s_g, if this is going to be declared a UA, can the program complete all the analysis, close out the entire fault tree and get comfortable with the UA before the end of the July window?

 

[farmerman]

One of the pictures shows Monica Hagley looking at a point sensor chassis box. With women looking like that running around KSC no wonder why it takes so long to launch the shuttles. She's easy on the eyes. Two words "space babe"

 

[dougbaker]

If I understand it a dry condition is the same as an open circuit. So is it possible, that switching to the test condition created the open circuit? I know when the test was switched off, the sensor showed dry until the tank was drained. (I think actually some time after the tank was drained), at this point the sensors would have returned to ambient temperature, things expand and the short was closed. So it appears to work correctly now. I would bet, that if they filled the tank enough to put the sensor into the cold state, it would again show dry i.e. the short would open up again as materials contracted.<br /><br />The only think my theory is missing, is the event that caused the sensor and wiring inside the tank to develop the short after being in the cold state for several hours. Somehow turning on the test caused this. I know the test changes the electrical properties, but just changing the voltage and / or current would be unlikely to cause a short. What else was going on at the time of the test? <br /><br />Because the tank was switched it would appear to not be a tank problem, however, it is possible, that the sensors and wiring have a problem that was on both tanks. <br />There was some history of bad welds early in the lifetime of these sensor parts.<br />See earlier post for link to document with history<br />

 

[skie]

I was watching a movie from 1969 called Marooned. In it a NASA director of some sort is talking to members of the press and here are his words:<br />"Because of men like these we've taken the first step off this little planet. The trip to the moon was just a walk around the block, we're going to the stars. Another worlds, another civilizations! Men will be killed in this effort just as they're killed in cars and aeroplanes, in bars and in bed."<br /><br />Too bad the excitement died down then.

 

[henryhallam]

Thanks for keeping us informed. I really hope the cause of the problem is found soon. That would be much more satisfactory than just waiving the launch criterion and flying with 3/4.

 

[shuttle_rtf]

Hale's got to be careful with some of the more sensationalist media tomorrow if this is still a UA....I hope they find something so any doubts are dismissed.<br /><br />Ever been through anything similiar to this current UA troubleshoot, SG?

 

[ltm_se]

SG, what is your gut feeling about issues with the space shuttle? Do you feel like it has more problems now then when the hardware was young? <br /><br />Also, replacing parts like the sensor box with brand new equipment would probobly be a very long process with man rating and testing it etc. But how long was this process back in the 70ths when the shuttle was designed? This is a general hypothetic question and not a question regarding the current problem.

 

[shuttle_rtf]

>Oh yes, a few times. We chased one last year for 7 months and it closed as a UA. <<br /><br />That's helpful to know, thanks.

 

[rvastro]

S_G<br />Were there problems with ECOs early in the program (1981-1986)?

 

[shuttle_rtf]

Another Tanking Test coming, SG? <br /><br />Checking around still, but one Engineer believes this is the case.

 

[rvastro]

Ahhh, thanks a bunch!

 

[erauskydiver]

Might as well make that tanking test an actual launch attempt.