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

• #400 by psloss on 08 Dec, 2007 11:31
• Quote

  ntschke - 8/12/2007  7:18 AM
  
  Maybe this is available here on another site but I haven't found it yet...does anyone know if there is an ET reference guide, schematic, cut-away view etc that might be of use in visualizing the different components invovled in this debate?

  NASA.gov reposted schematics:
  http://www.nasa.gov/mission_pages/shuttle/main/
  
  Or do you mean something else?
  
  (And actually, the overall schematic is in Mark's Interspacenews story that has been linked in this thread already.)
  
• #401 by Bejowawo on 08 Dec, 2007 11:41
• Quote

  psloss - 8/12/2007  1:15 PM
  
  

  Quote

  Trekkie07 - 8/12/2007  1:17 AM
  
  I'm aware of the Columbia low-level cutoff on STS-93... what was the other occurrence of the use of the ECO sensors?

  51-F.  In both cases the LOX low-level sensors went dry first, as designed.
  

  
  If I read it correctly, this time the LH2 sensors failed, right? Are those same sensors used in the LOX tank or do they have a different design. (I am wondering why only those sensors in the LH2 tank show this erroneous readings.)
  
  Couldn't it be that the material of the sensors has changed over time to an extent, that it is susceptible to a "chemical" LH2 attack in some way. As I work steel industry, I experienced quite a few cases where H2 is altering material to a point where it's beyond it's designed behaviour and has to be replaced.
• #402 by ntschke on 08 Dec, 2007 11:41

• Quote

  psloss - 8/12/2007 7:31 AM

  Quote

  ntschke - 8/12/2007 7:18 AM Maybe this is available here on another site but I haven't found it yet...does anyone know if there is an ET reference guide, schematic, cut-away view etc that might be of use in visualizing the different components invovled in this debate?

  NASA.gov reposted schematics: http://www.nasa.gov/mission_pages/shuttle/main/ Or do you mean something else? (And actually, the overall schematic is in Mark's Interspacenews story that has been linked in this thread already.)

  Thanks,I saw those from an erlier post and they help but I thought in the past, somehwere, I saw a nice detailed cut away view of the ET and exploded views of the seperate tanks, pipes, etc.  Just tying to get an idea of access and internal workings of the bottom of the tank. 

  And just to get my "Mulligan" dumb question of the day out of the way early...I'm assuming that the shear velocity of the vehicle throughout ascent (and at the point that ECOs would even be needed) keeps the fuel forced to the bottom of the tank?  I assume at those speeds the tank almost always "feels" like its in a vertical position?

• #403 by joncz on 08 Dec, 2007 11:47
• Quote

  ntschke - 8/12/2007  7:41 AM
  
  And just to get my "Mulligan" dumb question of the day out of the way early...I'm assuming that the shear velocity of the vehicle throughout ascent (and at the point that ECOs would even be needed) keeps the fuel forced to the bottom of the tank?  I assume at those speeds the tank almost always "feels" like its in a vertical position?

  
  It's not the velocity, it's the acceleration, but yes, that's what keeps the fuel filling the bottom dome.
  
• #404 by ShuttleFan75 on 08 Dec, 2007 11:47
• Quote

  ntschke - 8/12/2007  12:41 PM
  
  Thanks,I saw those from an erlier post and they help but I thought in the past, somehwere, I saw a nice detailed cut away view of the ET and exploded views of the seperate tanks, pipes, etc.  Just tying to get an idea of access and internal workings of the bottom of the tank.

  
  L2, STS-122: ECO SYSTEM INFO/BACKGROUND on the STS-122 Special Section has the Booster Console handbook area for ECO and lots of very cool schematics and images of the sensors that are obviously not on NASA.gov
  
  I've bumped it for you, as I know you're on L2.
• #405 by psloss on 08 Dec, 2007 11:53
• Quote

  ntschke - 8/12/2007  7:41 AM
  
  And just to get my "Mulligan" dumb question of the day out of the way early...I'm assuming that the shear velocity of the vehicle throughout ascent (and at the point that ECOs would even be needed) keeps the fuel forced to the bottom of the tank?  I assume at those speeds the tank almost always "feels" like its in a vertical position?

  Shortly before liftoff both tanks are pressurized and then the MPS maintains a "top" pressure (ullage pressure) within them; this isn't the best link, but it was quick:
  http://spaceflight.nasa.gov/shuttle/reference/shutref/orbiter/prop/et.html
  
  The program folks here can explain better.
  
• #406 by ntschke on 08 Dec, 2007 11:54

• Quote

  ShuttleFan75 - 8/12/2007 7:47 AM

  Quote

  ntschke - 8/12/2007 12:41 PM Thanks,I saw those from an erlier post and they help but I thought in the past, somehwere, I saw a nice detailed cut away view of the ET and exploded views of the seperate tanks, pipes, etc. Just tying to get an idea of access and internal workings of the bottom of the tank.

  L2, STS-122: ECO SYSTEM INFO/BACKGROUND on the STS-122 Special Section has the Booster Console handbook area for ECO and lots of very cool schematics and images of the sensors that are obviously not on NASA.gov I've bumped it for you, as I know you're on L2.

  Thanks to all of you.  Also, I found this on wiki (http://en.wikipedia.org/wiki/Space_Shuttle_external_tank):

  "There are eight propellant-depletion sensors, four each for fuel and oxidizer. The fuel-depletion sensors are located in the bottom of the fuel tank. The oxidizer sensors are mounted in the orbiter liquid oxygen feed line manifold downstream of the feed line disconnect. During SSME thrusting, the orbiter general-purpose computers constantly compute the instantaneous mass of the vehicle due to the usage of the propellants. Normally, main engine cutoff is based on a predetermined velocity; however, if any two of the fuel or oxidizer sensors sense a dry condition, the engines will be shut down.

  The locations of the liquid oxygen sensors allow the maximum amount of oxidizer to be consumed in the engines, while allowing sufficient time to shut down the engines before the oxidizer pumps cavitate (run dry). In addition, 1,100 pounds (500 kg) of liquid hydrogen are loaded over and above that required by the 6-1 oxidizer / fuel engine mixture ratio. This assures that cutoff from the depletion sensors is fuel-rich; oxidizer-rich engine shutdowns can cause burning and severe erosion of engine components.

  Four pressure transducers located at the top of the liquid oxygen and liquid hydrogen tanks monitor the ullage pressures"

  

• #407 by psloss on 08 Dec, 2007 12:00
• (Sorry to the mods -- this discussion should be moved over to Q & A...)
  
  Here's a post that Mark made a while back -- scroll down to the part on NPSP:
  http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=7886&start=1#M139197
  
• #408 by Jim on 08 Dec, 2007 12:14
• Quote

  ntschke - 8/12/2007  7:54 AM
    Also, I found this on wiki

  
  please don't use wiki for space
• #409 by Martin FL on 08 Dec, 2007 14:11
• I know Chris will be writing it up, so I'm not teasing, but the presentations on L2 really show they could do this even with no ECOs. They just won't get into a problem of relying on the ECOs unless there was a big problem with the engines or MPS. I know Hale said that last night, but reading it in black and white says a lot.
• #410 by Life_Support_32 on 08 Dec, 2007 14:17
• Maybe I interpreted this wrong, but didn't they say at the press conference last night that the onboard computer system won't even use the ECO sensors unless they are within 10 seconds of nominal MECO anyways?  At that point, the velocity and altitude would leave only an ATO with the OMS engines, not the RTLS or TAL that other people are talking about.
• #411 by psloss on 08 Dec, 2007 14:33
• Quote

  Life_Support_32 - 8/12/2007  10:17 AM
  
  Maybe I interpreted this wrong, but didn't they say at the press conference last night that the onboard computer system won't even use the ECO sensors unless they are within 10 seconds of nominal MECO anyways?  At that point, the velocity and altitude would leave only an ATO with the OMS engines, not the RTLS or TAL that other people are talking about.

  Remember that the vehicle acceleration is 3g for the last several seconds of a nominal ascent.  Cutting off at "arm" would cause a still substantial underspeed and may be beyond the delta-V capability of the OMS and RCS.
  
• #412 by psloss on 08 Dec, 2007 14:35
• Bump.  Having some pagination issues with forum threads like this now, too...
  
• #413 by Chris Bergin on 08 Dec, 2007 14:39
• We'll start a new one shortly. For some reason, some of the long threads jump to the next page, but don't display that latest post (at the start of the new page).
• #414 by Real Madrid on 08 Dec, 2007 15:53
• Launch window (edited after user seemed to forget about copyright. Though we knew this already! - James).
  
  http://www.cbsnews.com/network/news/space/122/122windows.html
  
• #415 by dember on 08 Dec, 2007 15:56
• Is this news conference scheduled for 1:00?
• #416 by James Lowe1 on 08 Dec, 2007 15:57
• Quote

  dember - 8/12/2007  10:56 AM
  
  Is this news conference scheduled for 1:00?

  
  No, as stated in the article on the front of the site (do read it), the MMT starts at 1pm.
• #417 by dember on 08 Dec, 2007 15:59
• thanks james.
• #418 by trlstyle on 08 Dec, 2007 16:05
• MMT meets at 1 - so any what time should we hear if Sunday is a go or not?
• #419 by James Lowe1 on 08 Dec, 2007 16:14
• Quote

  trlstyle - 8/12/2007  11:05 AM
  
  MMT meets at 1 - so any what time should we hear if Sunday is a go or not?

  
  Probably a few hours later at least.