ECO Senors Suck

[elguapoguano]

We got through a possible Hurricane, then a Fuel Cell Problem, and what kills us..... That damn ECO sensor. WTF is the deal with those things. The last three missions have been affected by those damn things. Since I don't remember hearing about problems with them before, the only reason I can see for their problems is the redesign of the External Tank. <div class="Discussion_UserSignature"> <font color="#ff0000"><u><em>Don't let your sig line incite a gay thread ;>)</em></u></font> </div>

 

[spacester]

It sounds like it's not the sensors themselves but the wiring and 'black boxes' in between the sensors and the computers to me. It occurs to me that a certain long-time sdc poster has posted stories about questionable practices in crimp fittings on some orbiter wiring. IIRC. <div class="Discussion_UserSignature"> </div>

 

[nyarlathotep]

Word.

 

[earth_bound_misfit]

Yep, their a right royal pain in the butt. <img src="/images/icons/frown.gif" /> <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>

 

[spacester]

Thanks much! Wow, it's so cool knowing what's going on, I love it!<br /><br />But I also now officially hate ECO sensors. These things have been under such scrutiny and yet they're so squirrely out on the pad. That just sucks. :-(<br /><br />I don't suppose there are other applications for these particular sensors, they must be totally specialized for STS ET and nothing else? <div class="Discussion_UserSignature"> </div>

 

[baktothemoon]

****, again? Great, we've found the Achilles heal of the countdown, an ECO sensor failure. Just launch, we have three left. This better not happen on STS-116. Is this the same part of the sensor failing every time?

 

[georgeniebling]

is something happening during rollout (crawler) that is "breaking" the ECO sensor?

 

[trailrider]

Did I read it right? The article on Space.com says these sensors are from the same lot that caused trouble before! Seems to me they should have s***canned the whole lot!<br /><br />Am I correct in that the sensors don't become "active" until later in the flight, towards MECO, or could they cause an inadvertant shutdown of the whole SSME package if a second sensor wet "dry" early in the flight?<br /><br />Jay Barbree was on MSNBC this morning, just before the decision to scrub, and it sounded like there was a Class A p###ing contest going on between the members of the MMT!<br /><br />Hope it was the right decision. But then hindsight is always 20/20!<br /><br />Ad Luna! Ad Ares! Ad Astra!<br />

 

[geminivi]

I know lightening has been considered as a catalyst for these recent electrical problems. But it does seem too unconfortably a coincidence.

 

[georgeniebling]

Trailrider asked: Am I correct in that the sensors don't become "active" until later in the flight, towards MECO, or could they cause an inadvertant shutdown of the whole SSME package if a second sensor wet "dry" early in the flight? <br /><br />----<br /><br />*Could* that happen? The whole SSME system shut down mid-ascent? <br /><br />Results pre/post SRB sep would be what?

 

[colchadisatlend]

I am now accepting memberships into the new club I am starting...the <b>I HATE ECO SENSORS Club</b> <img src="/images/icons/mad.gif" /> Anyone here interested in joining?

 

[tronchaser]

I understand that the ECO sensors are difficult to benchtest prior to installation. Are they not a capacitive type prox switches? Could they not use acoustic transducers for the indication levels?

 

[tronchaser]

In past there have electrical problems in the shuttle system resulted from lightening strikes. But the systems with the gremilins can not be affected from the lightening strike without damaging the ground support equipment first. The damage to the support equipment would very obvious.

 

[bobw]

They are not prox sensors, they are RTDs. When the question came up on the STS 114 mission thread, Shuttle_Guy wrote "The ECOs operate by measuring electrical resistancehich varies with temperature."<br /><br /> Here's a link to the post <div class="Discussion_UserSignature"> </div>

 

[earth_bound_misfit]

So in others words their thermistors. <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>

 

[bobw]

Not sure. Thermistors are solid state while RTDs are just a metal element. I saw pictures last time and it looked like metal plated onto a ceramic substrate as opposed to a semiconductor thing which is why i am calling them RTDs. I could be wrong , it wouldn't be the first time. <div class="Discussion_UserSignature"> </div>

 

[tronchaser]

Thanks, that explains alot. If they using RTDs for the ECO sensors. I do not know when they are not termpermental. I know they can handle a wide temperature range. I use to use them in oven applications. But found out they become faulty in a short while. We then started using thermalcouplers. I do not believe thermalcouplers can be used effectively on the ET, because of the low temps. <br /><br />

 

[bobw]

If I understand your question correctly, then yes, I am just talking about the sensor. Not about the circuits which monitor its resistance.<br /><br />I have been designing, programming and maintaining industrial controls for most of my adult life and I really have more fun reading tech manuals than Sci-Fi. I would really like to see the instructions for a lot of the stuff on the STS; the re-press valves, the fuel cells and, of course, the ECO sensor system. I can't find that stuff. Everywhere I look just calls them "sensors" which leaves me pretty cold. Shuttle_guy said they work by temperature changes to resistance which means they definately are not proximity sensors. The best I have found about them is this picture. I can't be sure but my guess is that it is an RTD. I would much rather be wrong and know for sure than to keep guessing <img src="/images/icons/smile.gif" /> Below is a link to the original picture which I cropped and zoomed.<br /><br />http://en.wikipedia.org/wiki/Image:Sts_et_ecographic.jpg <div class="Discussion_UserSignature"> </div>

 

[bobw]

By limiting my google search to the .gov domain I found the original picture. Still can't read the fine print. I also found this report. Maybe those diagonal lines are the half a thousandth inch diameter wire sensing element strung between posts on the sensor. <br /><br />It is hard to imagine how something like that could work sometimes and not work other times.<br /><br /><br />MSFC PRACA : 2003-02-12 07:54 <br />MSFC Problem Reporting and Corrective Action (PRACA) System<br />WHOLE RECORD REPORT( + ADDENDUM)<br /><font color="yellow">snip</font><br />Fail Date03/15/1980 <br /><font color="yellow">snip</font><br />Problem Description<br />1) DURING MPTA FIRING 8, LO2 FEEDLINE ECO SENSOR 4, HAD A DRY<br />INDICATION TWO SECS AFTER ECO SENSORS 1, 2 , AND 3. 2) REF - MARS<br />T32651<br /><br />Contractor Investigation/Resolution<br /><br />1) CAUSE - A) DYNAMIC TESTING AT WYLE LABS FAILED TO REVEAL CAUSE OF<br />DELAY BETWEEN SENSING ELEMENTS. B) TWENTY-EIGHT FLOW CYCLES IN LO2 QUAL<br />TEST FIXTURE FAILED TO REVEAL CAUSE OF DELAY. C) REF ROCKWELL<br />INTERNATIONAL DR HB6600-000. D) POST-TEST INSPECTION REVEALED NO<br />ANOMALIES. UNIT SENT BACK TO SUPPLIER FOR RECLEANING & ACCEPTANCE<br />TESTING. E) UNIT REDESIGNED AS A RESULT OF PREVIOUS RELATED FAILURE.<br /><br />2)RESOLUTION - THE .0002 DIAMETER MOLYBDENUM/RHENIUM ELEMENT SENSING WIRE<br />IS SUSPECTIBLE TO SEVERE OXIDATION IN THE AREAS WHERE THE WIRE IS<br />SUBJECTED TO LOCALIZED STRESS. THE LOX ECO SENSOR, PER MCR 7116, WILL<br />BE REDESIGNED USING 0.0005 DIAMETER PLATINUM WIRE. THE NEW LOX SENSORS<br />WILL BE IDENTIFIED AS MC432-0205-0022. THE PLATINUM SENSING WIRE IS<br />PRESENTLY QUALIFIED & USED IN ALL OF THE POINT LEVEL SENSORS LOCATED<br />INSIDE OF THE EXTERNAL TANK. THE NEW CONFIGURATION WITH PLATINUM WIRE<br />HAS SUCCESSFULLY COMPLETED THE DELTA QUAL FLOW TESTS AT WYLE<br />LABS/HUNTSVILLE, AL. THE NEW LOX ECO SENSORS ARE EFFECTIVE ON STS-1 &<br />SUBS, & WILL BE REPLACED ON MPTA AS S <div class="Discussion_UserSignature"> </div>

 

[MeteorWayne]

Got a pretty good chuckle, there and here as well <img src="/images/icons/smile.gif" /> <br /><br />They do serve a vital purpose, should they ever be needed. <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>

 

[elguapoguano]

I'm just so glad we've made it to LEO in this launch window, even if extended by a day. Looks like Flynn might just have to buy you that beer shuttle_guy. Hate to see the air fare... <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> <font color="#ff0000"><u><em>Don't let your sig line incite a gay thread ;>)</em></u></font> </div>

 

[earth_bound_misfit]

"I have met about 7 people from all over the world that post here"<br /><br />Cool! Wish I could afford a trip over. <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>

 

[earth_bound_misfit]

Well if you ever in Canberra, I would love to catch up. I'm sure Jon Clarke would too! <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>

 

[tronchaser]

Yes, that looks like a RTD. <br /><br />A change in resistance is a good way to check for fluid levels. I normally check fluid level limits or part positioning on conveyors/ robots with prox switches (inductive or capacitive switches). I have used RTDs in industrial oven applications. But found that they fail due to heat fatigue. Their wide range of operating.