STS-122 (1E) Updates

[rainergerhards]

Great notes, one small correction: the tanking test will be done with liquid hydrogen. The liquid helium will be used in the bench (lab) test - and maybe hydrogen there, too, if the failure does not show up under the slightly higher helium temperatures.<br /><br />I liked this statement most: "The primary goal is to troubleshoot the system as it is and restore its functionality. We would only consider other measures if we fail with this." That sounds pretty focussed <img src="/images/icons/smile.gif" /><br /><br />On the reflectometer: its pretty low-tech but highly efficient. I used a cheap one 20 or so years ago when I troubleshooted ethernet cabling at that time. Even the pretty low priced things worked amazingly well at pointing you where the wire was cut or shortened <img src="/images/icons/wink.gif" /><br /><br />We just need to hope that the problem reoccurs...<br /><br />Rainer

 

[MeteorWayne]

Thanx for the correction.<br />I guess that was the point of requiring replentish, vs tanking time to run the tests. If it is LH2, then it is WAY more important it be in the safest condition possible before humans nuzzle up to operate the TDRs.<br />Apparently they don;t have a remotely operable one available.<br />I find that hard to believe, but not impossible, considering the safety beaurocracy (not that that's a bad thing in most cases) <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[rainergerhards]

I have just posted the notes (with all horrible typos and such) I have taken during the conference:<br /><br />http://spacelaunch.gerhards.net/2007/12/shuttle-manager-hales-teleconference.html<br /><br />I plan to edit them tomorrow. I think with the context you already have, it can contribute a bit to the overall picture.<br /><br />Rainer

 

[billslugg]

TANSTAAFL76<br />I suspect that bubble formation could be a problem. Did you ever put a straw all the way down to the bottom of a carbonated soda only to see it develop bubbles and float? And then you go to take a sip and the straw ends up inside your nose? I hate it when that happens. LH2 is also a funky stuff. Weird things happen in it. <br /><br />Ever see the Liedenfrost effect? If not, you must do this right now. And I mean everybody. I'm serious. Go get a cast iron skillet and put it on the stove. Get a carpenter's level and shim it with your significant other's best cutlery until it is dead level. Put the flame at highest heat for about 10 minutes, until all the old gunk has burned off and the skillet will get no hotter. Now turn off the heat, use an oven mitt, and spoon a blob of water right in the center of the skillet. It will sit there hovering over the skillet perfectly still and not boil. The skillet is so hot that water is being made into steam so fast that the blob will levitate and not get hot enough to boil. At some point, the blob will cool the skillet underneath it just enough that the insulating layer cannot be maintained any more, the blob will touch the skillet, and POP!, the blob will explode! <br /><br />EDIT: As my wife is sleeping, I was able to sneak into the kitchen and replicate the above. It helps if you have an electric stove. The one we got rid of generated about 5KW while the gas burner we have now only does about 3.5. I could not get it hot enough to really hold a big blob. My blob would break up into numerous tiny ones. The smallest would penetrate the vapor layer and pop, but I did make a few 1/2" or so blobs that sat there for 45 seconds or so just as calm as could be. And then - POP - gone! <br /><br />Tomorrow I will move the experiment to the shop. I have authority there, and can do whatever I want. Yes dear. I will fire up my old shop skillet over a hot plate and then go at it with the oxy torch until red hot. In a minute dear. Th <div class="Discussion_UserSignature"> <p> </p><p> </p> </div>

 

[tanstaafl76]

<br />Cool stuff Bill, I will have to try the skillet trick when I get home today.<br /><br />If on the off chance bubble formation DOES have something to do with it, is it possible it could be an issue with how the fuel is being delivered to the tank (i.e. something about the pumping system causing more bubbles than usual) instead of the actual sensors. In other words, the sensors could be working fine, but because of their bubbly fuel delivery method, it is causing more bubbles to land/form on the sensors than what they are designed to handle.<br /><br />Does anyone happen to know if the type of pump used to deliver the LH2 has changed in recent years? Perhaps they've upgraded it to a "faster" fueling system that causes more bubbles in the LH2? <br /><br />Just speculating here of course, humor the layman!<br /> <div class="Discussion_UserSignature"> </div>

 

[rocketwatcher2001]

<font color="yellow">GSE?? <br />Unknown acronym </font><br /><br />Ground Support Equipment. Sometimes also called "yellow gear" because it often installed in the same places where actual flight equipment would normally go, so it's painted yellow to easily tell it apart from flight equipment. <div class="Discussion_UserSignature"> </div>

 

[billslugg]

Fuel delivery bubbles would have been long gone. I'm sure LH2 is very thin like water. They pump a tank full of LH2, wait around a while and any gas bubbles would float on up. Any bubbles I would consider here would be from boiling of the LH2. <div class="Discussion_UserSignature"> <p> </p><p> </p> </div>

 

[tanstaafl76]

The real question is if you dropped a spoonful of LH2 into a hot skillet would it float!<br /><br /> <div class="Discussion_UserSignature"> </div>

 

[billslugg]

I will say that the answer is yes. My Dad took me to a rocket motor testing facility in California way back in the late 60's up in the hills beyond LA. Down in some canyon somewhere. They made everybody leave their matches and lighters at the gate on the way in. Some guy had a 50 gallon pail of liquid nitrogen. He did a chip shot into it with his bare hand and put about a cup of it on the floor. It skittled all over, but some of the drops just sat there. I am certain that LH2 on a hot skillet would not last very long, but I bet you would see the effect. <div class="Discussion_UserSignature"> <p> </p><p> </p> </div>

 

[rainergerhards]

I have an question on the testing that is carried out during the countdown. It is said that the sensors are commanded into inverting their state. Does anybody has any details on how this is done in the actual hardware? I assume it is not just the point sensor box that inverts its output signal (that would not be a valid test, wouldn't it?).<br /><br />Rainer

 

[rainergerhards]

---quote---<br />"Does anybody has any details on how this is done in the actual hardware?"<br /><br />This is performed by the point sensor box.<br /><br /><br />" I assume it is not just the point sensor box that inverts its output signal (that would not be a valid test, wouldn't it?). "<br /><br />It is a vailid test because it allows a fail wet sensor to be seen if it happens with the sensor under LH2. <br />---unquote---<br /><br />Thanks for the answers, but I think I expressed my self not clear enough. What I am thinking about is this:<br /><br />Lets start with an extremely simplified model of the ECO System:<br /><br />sensing element <-- /> cabling <--> PSB <--> GPC<br /><br />My question is which parts of this system are actually checked by the SIM commands. What I intended to say was that I do not think it is on the PSB output side (PSB <-- /> GPC), because that effectively would not test any of the ET/orbiter components except PSB output (and they are troubleshooting primarily the cabling, right?).<br /><br />It was also noted that PSB as well as the sensing element performed well (as far as this could be told). Now I recall that the actual sensor is just a platin wire. And the measurements are done in the PSB. The cabling/connectors in between are just ... cabling and connectors (no electronics components). So what actually switch the SIM commands? Obviously, it seems to happen in the PSB, but why then can they detect an open circuit in some other part of the signal path? This is what gives me a hard time...<br /><br />Any insight would be highly appreciated.<br /><br />Rainer

 

[rainergerhards]

"Yes, the sim dry is set by the sensor box (PSB). An open in the sensor or wire down stream from the PSB will over ride the sim command in the PSB and the indication will change to wet when the sim dry command is set on and the sensors are covered in LH2. <br /><br />Does that help you?"<br /><br />Thanks again, shuttle_guy, for your patience and good information. Much appreciated!!!<br /><br />I took a few minutes to digest these sentences. They are even more fact-filled than it looks on first view.<br /><br />I am still not 100% sure, so I thought I keep asking. Let me explain the potential scenarios I see after thinking about this new information. In my experience, that's the best tool to see where I misunderstood. And please bear with me if I am emitting totally nonsense now - remember, I am a software guy... <br /><br />First, let me re-iterate an important assumption: I assume that there is no active component between the sensor element and the PSB - just cables and connectors. With the sensor element also being a passive wire-type detector, there actually is nothing passive between the outbound wire from the PSB to the sensor ("PSB outbound") and the inbound wire from the sensor to the PSB ("PSB inbound"). If that assumption is wrong, everything below is wrong, too.<br /><br />I have looked at this schema while I thought about your note:<br />http://www.gerhards.net/Gallery-spaceshuttle-pic-ECO_charts4.phtml<br /><br />I now see two ways how the SIM could actually work:<br /><br />In scenario #1, the wiring (including the sensor element) is used as a kind of data transfer relay. For example, a special voltage might be applied to the PSB outbound connector. Then, it is checked if that very same voltage is seen on the PSB inbound side, too. If not, there is obviously a failure in the circuit.<br /><br />In scenario #2, the PSB's voltage interpretation is inverted, probably in the "test

 

[rainergerhards]

oops... Yes, "nothing active" meant. I am glad you took the time looking into this. You have definitely enhanced my understanding considerably, even though there is not the ultimate answer available right now. Can't praise you enough for this! <img src="/images/icons/smile.gif" /><br /><br />Rainer

 

[scottb50]

The liquid helium will be used in the bench (lab) test - and maybe hydrogen there, too, if the failure does not show up under the slightly higher helium temperatures...<br /><br />LH -253C, LHE -268C, Helium is colder. Thats why they pressurize the tank with Helium. <div class="Discussion_UserSignature"> </div>

 

[rainergerhards]

LH2/helium temperatures: noted, will be corrected during edit later today. Thanks!

 

[scottb50]

I would think if temperature was the culprit LHE would show an exaggerated effect. Wouldn't being that cold affect the resistance in the wiring quite a bit. Another thought is the pressure exerted pumping the LH might be causing Solid Hydrogen crystals to form. <div class="Discussion_UserSignature"> </div>

 

[MeteorWayne]

The pressure is nowhere near high enogh for that. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[strandedonearth]

<font color="yellow">Some guy had a 50 gallon pail of liquid nitrogen. He did a chip shot into it with his bare hand and put about a cup of it on the floor. It skittled all over, but some of the drops just sat there.</font><br /><br />I've had the Liedenfrost effect demonstrated to me by pouring liquid nitrogen over the back of my hand.* <br /><br />*kids do not try this at home!<br />

 

[montmein69]

1) I read that the new testing system that was installed after the issue appeared (RTF), gives directly the sensors' results. And that indicated that the "sensors" were working properly, although the results obtained at the avionic aft bay were wrong or erratic.<br /><br />Is this confirmed ? I mean : are all the parts of the circuit inside of the point_sensor_box (and by the way in the ET) clean ? Or do they have to investigate the part inside the ET ?<br /><br />2) Do we know if this test "at the source" is directly taken on the sensors, or is there an electronic stage ("to put in shape" the signal like a logic digital chip) in the point_sensor_box in the ET ?<br /><br />http://www.nasa.gov/images/content/122590main_ECO_charts5.JPG<br /><br />It would be useful to have the signification of the captions in the exploded view.<br /><br />A lot of photos or diagrams shown in papers are from bench circuits, not the real one. <div class="Discussion_UserSignature"> </div>

 

[montmein69]

OOOOps ... sorry , I misunderstood and confused the round shape "sensor container" (in which the sensors are) located in the ET (only the sensors and wiring : passive components) as I saw it on the middle of this diagram<br />http://www.nasa.gov/images/content/122488main_ECO_sensors.jpg<br /><br />Is this the correct photo of this container ?<br />http://img101.imageshack.us/img101/152/ecosensorec2.jpg<br /><br />and the rectangular shape "point_sensor_box" (with electronic components : active components) in the avionic bay number 5 <br /><br />The correct term I would have used to describe the circuit is "block" ? The output of the first one is the input of the second and each one modify the signal (filter, amplification, convert analogic to digital ...)<br /><br /> /> A typical receiver or measurement system is composed of a<br /> /> signal sensor, analog signal processing block,<br /> /> data converter, interface, and digital processing block<br /><br />Each day is useful to learn as well in technics as in American language.<br />Thanks to be so comprehensive. <br /><br />I really expect the december 18th test will give the answer and the way to fix the issue. <div class="Discussion_UserSignature"> </div>

 

[MeteorWayne]

I wasn't aware there was a problem with the scheduled tanking test.<br />What was the hang up? <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[MeteorWayne]

Thanx for the explanation. Makes perfect sense. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[vulture2]

I am not at all comfortable with the idea of launching with a system that has a failure we do not completely understand. If the problem is intermittent and the fault has not been positively identified, how will a 4/4 launch commit criteria assure safety? Suppose the system fails after the test? If we don't know exactly what caused the fault, how can we be sure it won't recur? How does a bench test help when the fault may not be present in the bench system? With the number of recent failures it's hard to believe that the design is adequate. <br /><br />Conversely, how likely is it that the Shuttle would actually run out of LH2? If the sensors provide a false positive (as occurred once with all three engine temperature sensors) it could put the vehicle in a high-risk abort mode. Does having the sensor really improve safety over simply eliminating it if the sensor has a high failure rate and the contingency it detects is rare?<br /><br />Wouldn't it make more sense to determine if a sensor is really needed, and if so, to redesign it to be more reliable? Even if the Shuttle goes away, we'll still have the improved sensor. If NASA is really an R&D agency, isn't developing enabling technology more important than just flying up and down?

 

[rainergerhards]

I hope the problem will show up again so that the root cause can be found. If I understood correctly, if that happens, the repair most probably means rollback and de-stack. I assume that puts us way out of the early January launch Window?<br /><br />Rainer

 

[jamie_young]

Focus on the LH2 feed through connector.<br />http://www.nasaspaceflight.com/content/?cid=5309