SCRUB: STS-122 Launch Scrub and ECO Evaluations - Dec 6-7

• #120 by John2375 on 06 Dec, 2007 17:05
• oh ok - that makes sense.  I remember them doing mini-tanking tests for STS-38 and STS-35 because of the hydrogen leaks, but yeah, these days w/the thermal issues on the tank I can see why.
• #121 by on 06 Dec, 2007 17:20
• What happens to the LOX and LH2 during the detanking?  It is returned to the storage tanks and reused?
• #122 by Jim on 06 Dec, 2007 17:22
• Quote

  Ray Todd - 6/12/2007  1:20 PM
  
  What happens to the LOX and LH2 during the detanking?  It is returned to the storage tanks and reused?

  
  yes
• #123 by punkboi on 06 Dec, 2007 17:28

• *Sigh* The Launch Prevention Devices strike again...

  And so much for having 4 straight launches this year that took off on the first attempt.

• #124 by dember on 06 Dec, 2007 17:29
• Where are we in the count? Have they recycled to T-11?
• #125 by Joffan on 06 Dec, 2007 17:33
• Are these sensors actually used to determine when MECO should occur, under normal circumstances? (My recollection is that they are not a normal control point for launches, but are only a contingency for engine protection). If they are "contingency" sensors, how quickly does a true "dry" signal need to be acted on to protect the orbiter? Human speed, or quicker? Or if the consequences are less, like SSME damage but no orbiter effects, can they actually be ignored without threatening this mission (although possibly incurring costs for future)?
• #126 by nathan.moeller on 06 Dec, 2007 17:33
• Quote

  punkboi - 6/12/2007  12:28 PM
  
  

  *Sigh* The Launch Prevention Devices strike again...

  And so much for having 4 straight launches this year that took off on the first attempt.

  
  I'll take launch safety assurance over an first-try-four-times-in-a-row record any day.
• #127 by nathan.moeller on 06 Dec, 2007 17:37
• Quote

  Joffan - 6/12/2007  12:33 PM
  
  Are these sensors actually used to determine when MECO should occur, under normal circumstances? (My recollection is that they are not a normal control point for launches, but are only a contingency for engine protection). If they are "contingency" sensors, how quickly does a true "dry" signal need to be acted on to protect the orbiter? Human speed, or quicker? Or if the consequences are less, like SSME damage but no orbiter effects, can they actually be ignored without threatening this mission (although possibly incurring costs for future)?

  
  I don't believe they're used in normal scenarios, but I could be wrong.  I say that because there has been a case of 'low-level cutoff' (STS-93) in which the ECO sensors went dry a little early in the ascent, resulting in a slight underspeed for Columbia.  It would take a small fraction of a section to send and execute the shutdown command.  And there aren't 'contingency' sensors.  They only need two, but they have four for complete redundancy incase one or two fail on the way uphill.  And we're not talking slight damage to SSMEs in the case of ECO sensor failure.  We're talking catastrophic engine failure that would quickly and easily lead to orbiter damage or even destruction, I believe.
• #128 by Jim on 06 Dec, 2007 17:38
• The placement of the sensors take into account the timing needed to shutdown the engines.  Engine fuel depletion can cause many things, two of which are: an Ox shutdown where the metal of the engine burns and or an unloaded H2 turbopump, that goes from spinning at 36,000 rpm to infinity
• #129 by leetdan on 06 Dec, 2007 17:43
• Also, in the case of sensor ECO, the first signal is ignored to guard against a premature shutdown due to sensor faults.  This means that with two potentially failed sensors, there would be no redundancy left in this scenario.
• #130 by mkirk on 06 Dec, 2007 17:46
• Quote

  Joffan - 6/12/2007  12:33 PM
  
  Are these sensors actually used to determine when MECO should occur, under normal circumstances? (My recollection is that they are not a normal control point for launches, but are only a contingency for engine protection). If they are "contingency" sensors, how quickly does a true "dry" signal need to be acted on to protect the orbiter? Human speed, or quicker? Or if the consequences are less, like SSME damage but no orbiter effects, can they actually be ignored without threatening this mission (although possibly incurring costs for future)?

  
  Here is a very high level overview of how these ECO sensors work that I wrote for Interspacenews during the STS-114 timeframe.
  
  http://www.interspacenews.com/interspace%20News%20Web%202/sections/In%20focus/ECO%20Sensors.htm
  
  Bill Harwood wrote one for CBS/Spaceflight Now that is probably better to undersand than mine (since he writes much better than me) so if anyone knows where that link is feel free to post that here as well.
  
  Mark Kirkman
• #131 by JimO on 06 Dec, 2007 17:51
• Quote

  mkirk - 6/12/2007  12:46 PM
  
  Bill Harwood wrote one for CBS/Spaceflight Now that is probably better to undersand than mine (since he writes much better than me) so if anyone knows where that link is feel free to post that here as well.
  
  Mark Kirkman

  
  I thought I had, a few pages back...
  
  Yup, here at 8:59 AM:
  
  Harwood has put up a good historical background here:
  http://spaceflightnow.com/shuttle/sts122/071206ecos/
  
  
• #132 by mkirk on 06 Dec, 2007 17:56
• Quote

  JimO - 6/12/2007  12:51 PM
  
  

  Quote

  mkirk - 6/12/2007  12:46 PM
  
  Bill Harwood wrote one for CBS/Spaceflight Now that is probably better to undersand than mine (since he writes much better than me) so if anyone knows where that link is feel free to post that here as well.
  
  Mark Kirkman

  
  I thought I had, a few pages back...
  
  Yup, here at 8:59 AM:
  
  Harwood has put up a good historical background here:
  http://spaceflightnow.com/shuttle/sts122/071206ecos/
  
  

  
  Sorry JimO, as usuall I am late to the party.
  
  
  
  Mark Kirkman
• #133 by Joffan on 06 Dec, 2007 18:11
• Thanks for the answers guys. I guess the summary is: the ECO sensors wouldn't be used to determine actions in a perfectly nominal ascent, but if a tank runs dry early without engine cutoff, the rapid consequences could include loss of orbiter and crew.
  
  (and Mark, your link leads back here...)  (no longer... thanks again)
• #134 by Yegor on 06 Dec, 2007 18:13
• When should we expect the next attempt to launch?
• #135 by mkirk on 06 Dec, 2007 18:15
• Quote

  Joffan - 6/12/2007  1:11 PM
  
  Thanks for the answers guys. I guess the summary is: the ECO sensors wouldn't be used to determine actions in a perfectly nominal ascent, but if a tank runs dry early without engine cutoff, the rapid consequences could include loss of orbiter and crew.
  
  (and Mark, your link leads back here...)

  
  Sorry.  I fixed it.
  
  http://www.interspacenews.com/interspace%20News%20Web%202/sections/In%20focus/ECO%20Sensors.htm
  
  Mark Kirkman
• #136 by mkirk on 06 Dec, 2007 18:16
• Quote

  Yegor - 6/12/2007  1:13 PM
  
  When should we expect the next attempt to launch?

  
  Just too soon to call, not enough data yet.
  
  Tomorrow is very unlikely!!!
  
  Mark Kirkman
• #137 by nathan.moeller on 06 Dec, 2007 18:19
• Quote

  Yegor - 6/12/2007  1:13 PM
  
  When should we expect the next attempt to launch?

  
  Last time something like this happened (STS-114) it took about two weeks before the next attempt.  But it all depends on how fast they can find a source for the problem and resolve it.  We'll just have to sit back and let them work their magic.
• #138 by dember on 06 Dec, 2007 18:21
• What about STS-115?
• #139 by Yegor on 06 Dec, 2007 18:22
• Thank you very much for quick answers!