STS-122 (1E) Updates

bobblebob · Dec 10, 2007

Plane ride and a skydiver - all in a days work for nasa <img src="/images/icons/laugh.gif" />

rainergerhards · Dec 10, 2007

It's my first post over here, yet I still hope to contribute something. I have just finished a write-up on the ECO sensors - and billslugg post could be the executive summary of it <img src="/images/icons/wink.gif" /> If you'd like to have a look, here it is: http://spacelaunch.gerhards.net/2007/12/space-shuttle-eco-sonsors-in-depth-view.html Any comments and corrections are appreciated. Rainer

MeteorWayne · Dec 10, 2007

That was a good summary, with a bit more detail than what I understood. thanx Wayne <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

tanstaafl76 · Dec 10, 2007

Nice entry there rainer. Two small typos: "All of these sensors are the same. The ECOs are in now way special" - should be "no way special" I assume? "However, these calculations may not be 100% perfect and may not detect some malfunction, thus it is risky to relay on them alone." - should be "risky to rely on them alone." Apart from that, I'm still trying to keep up with the more technical aspects on how these sensors function. It seems amazing that this form of sensor is such proven technology with a long history of operation that suddenly seemed to begin having problems. What about a manufacturing defect of some kind? <div class="Discussion_UserSignature"> </div>

bobblebob · Dec 10, 2007

Yeah thanks i will read all that later. I will know everything about these damn sensors by the time they launch again <img src="/images/icons/laugh.gif" />

MeteorWayne · Dec 10, 2007

A manufacturing defect of the actual sensor seems unlikely. Since these problems cropped up, they have been tested, retested, and tested again. They are hand selected to be the best of the best. As for a manufacturing defect of the sensor system, that seems to be the situation. Should be interesting to see what troubleshooting plan they come up with tomorrow. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

tanstaafl76 · Dec 10, 2007

Do these sensors degrade with use? If so, anyone know how often they are replaced? <div class="Discussion_UserSignature"> </div>

bobblebob · Dec 10, 2007

Yeah the chances of 3 seperate sensors all being faulty seems unlikely. The common thing here is the system that controls the sensors which like yuo say is more likely to be the cause

MeteorWayne · Dec 10, 2007

That's my (educated) guess as well, s_g. Connectors are the bane of all electronics <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

bobblebob · Dec 10, 2007

"Mission managers and engineers at NASA's Kennedy Space Center are evaluating an issue with fuel sensors in the liquid hydrogen tank before determining what step to take next. The team is finalizing a plan to present to space shuttle program management on Tuesday" From Nasa website

rainergerhards · Dec 10, 2007

Hi all, wow... what a fast response ... and many thanks for the kind words and corrections. Will update in a moment. It also looks like I need to find how to configure email notifications of replies <img src="/images/icons/wink.gif" /> Rainer

rainergerhards · Dec 10, 2007

"Yes, the checks during the contdown were improved after STS-114. We may have had failures before that which we never knew about. " Ah, very good information. Will add. Thanks a lot, Rainer

rainergerhards · Dec 10, 2007

"The most likly cause is the wires or the electrical connector at the ET itself." Do you know if there is a picture of the connectors available to the public somewhere? I would really love to see how they look. Being in no way qualified (I am an IT software guy...) I can still envision that those cryogenic temperatures could do funny things to connectors. Do you happen to know if there are any connection points that get really cold? I am not sure if I express my self correctly. I mean runs a connectorless cable from the tank to somewhere in the orbiter and then ends in a connector? Or is there a connector (the other extreme) even inside the ET? Would be great if you have an answer to that... And, of course, the interesting thing is what will come up tomorrow afternoon. Thanks again for all that good information. Rainer

3488 · Dec 10, 2007

I assume it is the liquid Hydrogen Sensors, so we are looking at -253 C / 20 K, so would contraction of the connections be a problem? However, liquid Hydrogen has been a fuel for upteen years, so I would have thought by now, that the proerties of materials in contact with said cryonically cold liquid would be well known. Andrew Brown. <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

MeteorWayne · Dec 10, 2007

Maybe not as well known as we thought <img src="/images/icons/smile.gif" /> Judging by Wayne Hale's comments a few days ago, they are very disappointed. They thought they had this problem figured out and resolved. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

billslugg · Dec 10, 2007

TANSTAAFL76 So the idea is that the liquid hydrogen is of a certain temperature, and if the sensor is not covered by the LH2 the sensor is going to be a different (and I assume, higher?) temperature. Ok I'm a layman, but could it be something as stupid as bubbles in the LH2 that could be throwing off the sensor? When the liquid goes away, and is replaced by a gas, there is no temperature change. You have to drive some btu's through the system to see what is there. You have to heat the element and see how fast it is being cooled. If it is submerged in LH2 its temperature will not change with an increase in current. If it is in H2 then the temperature and thus the resistance will shoot up. <div class="Discussion_UserSignature"> </div>

rainergerhards · Dec 10, 2007

"Yes, the checks during the contdown were improved after STS-114. We may have had failures before that which we never knew about." I have now changed that to --- I could not find any indication of sensor malfunction prior to STS-114, the "return to flight" mission. However, I have been told that pre-STS-114 flights did not have the same rigor checks in the flight procedure as they exist have today. So it may very well be that there always were problems with the sensors, but these were "just" never detected. It should also be noted that there was never a space shuttle main engine cutoff due to an ECO sensor. It is believed, however, that on some flights the cutoff happened just a second or so before the ECO sensors would have triggered one (STS-93 was mentioned as an example). The amount of fuel left in the tank can not be analyzed post-flight, as the external tank is the only non-reusable component of the shuttle stack and lost after being separated from the orbiter. --- Does that sound OK? I can't remember where I got STS-93 from, I think it was on Saturdays press conference... Rainer

rainergerhards · Dec 10, 2007

"The connector in question is at the ET and it does get very cold. During the off load of LH2 after the last launch attempt the team drained the tank below the connector but kept liquid H2 on the failed ECO sensors. The goal was to let the connector warm up but keep the sensors cold and see if the indications returned to normal. I was not there at the time and do not know the test results. " Ah, this is very interesting. Obviously they are looking at the this issue. That triggers a next question: is the female part of the connector on the cold side and the male part on the (relatively) warm? Or vice versa? With just common sense here in my side, that could make quite a difference. This popped up my mind because a number of years ago (actually ages...) I worked at a machine tool manufacturing plant. When the engineers over there needed to fit some heavy component together, they put the inner part into a very cool liquid (don't know what it was) and then fit it into the outer part. After it warmed up again, these both had an excellent mate. Wouldn't have worked the other way around. <img src="/images/icons/wink.gif" /> On the other side, I read in the STS-114 report that, and later heard, that temperature-based tests have been made. I am sure that what I call common sense was not overlooked but simply has been tested and been found not to be an issue. Still interesting, though... (thinking about what could be is a premier way for me to increase my understanding, I hope I am not upsetting anyone with that...). And many thanks for trying to find the pictures. That would be really great. Rainer

tanstaafl76 · Dec 10, 2007

Thanks for the reply billslugg: <blockquote>In reply to:<hr />When the liquid goes away, and is replaced by a gas, there is no temperature change. You have to drive some btu's through the system to see what is there. You have to heat the element and see how fast it is being cooled. If it is submerged in LH2 its temperature will not change with an increase in current. If it is in H2 then the temperature and thus the resistance will shoot up.<hr /></blockquote> Ok, so would there be any way that bubbles could form on or around the sensors (honestly I don't know the properties of LH2 so I don't even know if that's possible)? Could small bubbles be made into larger ones once you try to heat the sensor element if it were enough to convert some additional LH2 to H2 bubbles? It also seems like there should be a more foolproof way to measure fuel level, like via some sort of secured float object or something. Of all the complicated systems on the shuttle, I would think the "gas gauge" would be one of the most reliable! <div class="Discussion_UserSignature"> </div>

MeteorWayne · Dec 10, 2007

That's an interesting detail I wasn't ware of, that throttling is done by adjust LOX flow. The education never ends here at SDC!! Thanx, as usual Wayne <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

erioladastra · Dec 10, 2007

"I believe he was talking about LOX ECO sensors. " Actually no, the 4 cases I was referring to where we were within a couple of seconds were indeed LH2.

rainergerhards · Dec 11, 2007

"STS-93 did have a cutoff but it was due to the LOX ECOs detecting a LOX low level due to the LH2 leak in a SSME engine." Thanks for that info. Will remove the part on STS-93 from the paper. Rainer

MeteorWayne · Dec 11, 2007

Copying s_g's post from the Stage to STS-122 thread so no one misses it: Dec. 11, 2007 Michael Curie Headquarters, Washington 202-358-4715 michael.curie@nasa.gov Kyle Herring Johnson Space Center, Houston 281-483-5111 kyle.j.herring@nasa.gov MEDIA ADVISORY: M07-180 NASA ANNOUNCES TELECONFERENCE ABOUT SPACE SHUTTLE LAUNCH PLAN HOUSTON - NASA will host a media teleconference with Space Shuttle Program Manager Wayne Hale at approximately 2:30 p.m. CST, Tuesday, Dec. 11, to discuss the status of shuttle Atlantis' launch on the upcoming STS-122 mission. The teleconference will follow a meeting chaired by Hale that will lay out options to better understand recurring problems with the low-level engine cutoff, or ECO, sensor system in the shuttle and its external fuel tank. Shuttle managers postponed Atlantis' planned launches on Dec. 6 and Dec. 9 because of false readings from the sensor system that monitors the liquid hydrogen section of the tank. The system is one of several that protects the shuttle's main engines by triggering their shut down if fuel runs unexpectedly low. NASA has formed a troubleshooting team to develop a forward plan of action to address the problem. The team will present its findings and recommendations to the Space Shuttle Program Tuesday morning. To participate in the teleconference, reporters must R.S.V.P. by 1:30 p.m. Tuesday to NASA's Johnson Space Center newsroom at 281-483-5111. Live audio of the event will be streamed online at: http://www.nasa.gov/newsaudio For STS-122 crew and mission information, visit: http://www.nasa.gov/shut <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

MeteorWayne · Dec 11, 2007

Scibblenotes of teleconference. Really, all was said by Wayne Hale in the first 5 minutes. A few good questions were asked, but added little to the information, with one exception. 2 teams researching. short term: this launch. Long term, in case problem is not fully understood, find it. Plan is to run a full tanking test, next Tuesday (a week from now). This would be most likely with Liquid Helium, rather than hydrogen, since after replentish is established, red team well go in to find anomolies in wiring/connectors using TDR. Too close for LH2 use. There are "roughly" 100 feet of wiring and connectors between the LH2 sensors and the PSB. The technique to be used is something I happen to know about. It's called Time Domain Reflectometry. The idea is that you send a quick pulse down a wire. Any discontinuities (i.e. bad connections) or even crimps in the wire will create a reflection. Knowing the speed of EM down the wire, you measure the time back, and you can find out where the problems are. As Wayne said, cable and phone companies use it all the time. It's rather amazing, that by using the speed of light, you can find out where a fault is in an electrical cable, even a few dozen feet away. This is not something that will help during flight, but at this point, the idea is to find and fix the problem, as it should be. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

MeteorWayne · Dec 11, 2007

They said they would not let test crew into the area until the tank was full and in replentish. Too dangerous before that. The TDR testing is better than you think. It can show faults well before there is a problem noticed. It can show faults just thinking about becoming faults. <img src="/images/icons/smile.gif" /> That's why a safer (for the onsite folks) Helium test makes sense. Expensive, or endangering lives? Let's go expensive. Even if the LH2 temperature is needed to cause the open circuit, the Helium temp will be more than enough to pinpoint the problem. In theory, anyhow. GSE?? Unknown acronym <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

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