Shuttle Questions Q and A (2)

• Shuttle Questions Q and A (2) by Chris Bergin on 01 Apr, 2006 02:20
• A continuation of the 586 post, 18,000 views thread http://forum.nasaspaceflight.com/index.php?topic=625
  
  

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  Shuttle Q&A Part 1
  Shuttle Q&A Part 2
  Shuttle Q&A Part 3
  Shuttle Q&A Part 4
  Shuttle Q&A Part 5
• #1 by psloss on 01 Apr, 2006 02:55
• OK, the ET diffuser "what ifs" have me wondering about elaborating on some countdown terms I've heard over the years, but never seen much discussion.
  
  First question: what's the difference between a Redundant Set Launch Sequencer (RSLS) hold and an RSLS abort?  Is it the difference between a hold by the RSLS before or after main engine start?  Or is there more to it than that?
  
  And second question has to do with the terms used in some of these cases over the years...for holds inside of T-31 seconds but prior to main engine start, I've heard the word "breakout" used in at least one case and "cutoff" used more often...is there any distinction between the two given the context?  Or do they mean different things?
  
  Thanks,
  
  Philip Sloss
  
• #2 by mkirk on 01 Apr, 2006 15:33
• Quote

  psloss - 31/3/2006  8:55 PM
  
  OK, the ET diffuser "what ifs" have me wondering about elaborating on some countdown terms I've heard over the years, but never seen much discussion.
  
  First question: what's the difference between a Redundant Set Launch Sequencer (RSLS) hold and an RSLS abort?  Is it the difference between a hold by the RSLS before or after main engine start?  Or is there more to it than that?
  
  And second question has to do with the terms used in some of these cases over the years...for holds inside of T-31 seconds but prior to main engine start, I've heard the word "breakout" used in at least one case and "cutoff" used more often...is there any distinction between the two given the context?  Or do they mean different things?
  
  Thanks,
  
  Philip Sloss
  

  
  Okay. here is Countdown 101
  
  HOLD is defined by the LCCs (launch commit criteria) as "an interuption of the countdown for any reason.  Holds may be preplanned or occur for unfavorable weather, problem investigation, repair of hardware, or correction of conditions unsatisfactory for launch or flight".
  
  CUTOFF is defined as "Automatic or manual command to stop the launch sequencer after initiation of the "Automatic Launch Sequence Start".
  
  In Practice:
  
  A HOLD can be called at anytime between the start of the countdown at T-43 Hours until T-31 seconds.  The NTD (Nasa Test Director) will then stop the count at the approprate point.  Begining at T-9 Minutes there are a handfull of GLS (ground launch sequencer) milestones or Hold points where the countdown can be stopped at.  These predetermined points are based on vehicle conditions that can be maintained for a period of time during the countdown without adverse effects on hardware.
  
  These Milestones are:
  T-9 minutes 00 seconds     GLS Sequence Start
  T-7 minutes 30 seconds     OAA (Orbiter Access Arm) Retract
  T-5 minutes 00 seconds     APU Start
  T-4 minutes 00 seconds     Purge Sequence 4
  T-2 minutes 55 seconds     LOX Tank Pressurization
  T-1 minute  57 seconds     LH2 Terminate Replenish
  T-31 seconds                   RSLS (Redundant Set Launch Sequencer) Start
  
  After T-5 minutes if a hold is called the clock will continue to T-31 seconds and hold there unless a request is made to stop at one of the other milestones such as T- 2 minutes 55 seconds to avoid pressurizing the liquid oxygen tank.
  
  After T-31 seconds the only option is a "Cutoff" which would result in a recycle to a more stable vehicle configuration at T-20 minutes at which point the scrub procedures would be implemented.
  
  An "RSLS Abort" is called when the countdown is "Cutoff" after the first main engine start command is issued.  This occurs when engine number 3 is given the command to start at T-6.6 seconds (engines start in reverse order 3-2-1 in 120 millisecond intervals).
  
  I would have to know the context of your second question about "Brakeouts".  I think you are referring to the GLS breakout points after T-31 seconds and these are just points where a specified GLS sequence would occur if the countdown is stopped.  These are based on the vehicle's configuration at the "Cutoff" point.
  
  Mark Kirkman
• #3 by Jim on 01 Apr, 2006 16:32
• I have been on console and have heard the NTD request "GLS give cutoff".  I don't remember all the details.  What would happen after T-31sec that it would have to be a manual cutoff. It wasn't the range.
• #4 by Mark Max Q on 01 Apr, 2006 19:23
• How does the hand off to the orbiter for Auto Sequence Start happen?
  
  Does the orbiter pick up the count after the T-9:00 hold and thus be in alignment, ready for the T-31?
• #5 by psloss on 01 Apr, 2006 22:31
• Quote

  mkirk - 1/4/2006  10:33 AM
  
  I would have to know the context of your second question about "Brakeouts".  I think you are referring to the GLS breakout points after T-31 seconds and these are just points where a specified GLS sequence would occur if the countdown is stopped.  These are based on the vehicle's configuration at the "Cutoff" point.
  
  Mark Kirkman

  Thanks, as usual, Mark.  I'm familiar with the GLS milestones, but your answer is a good primer.
  
  I think I've heard it a couple of times, but the specific count I'm thinking of is one of the several STS-51 scrubs; general reference:
  http://www.nasa.gov/mission_pages/shuttle/shuttlemissions/archives/sts-51.html
  
  In this case, it was the attempt on 24 July 1993; actually, looking at the description there, I think you've already hit on it:
  

  Quote

  Launch was delayed on Saturday, July 24, due to a problem with the right hand solid rocket booster (SRB). The ground launch sequencer detected an unacceptably slow speed rate of a hydraulic power unit located inside the shuttle's right hand solid rocket booster. The hydraulic power unit (HPU) was replaced and retested.

  
  I believe the SRB HPUs are started at T-25 seconds; shortly thereafter, I believe the call (not sure if this was the GLS console operator, but that would be my guess) was "we have a breakout."  I believe the clock stopped at T-19 seconds, but I'm not sure that's necessarily a high priority action (so maybe the cutoff was given before T-19).
  
  (Someday, I'll digitize this, but don't have the tapes handy these days.)
  
  So if I'm reading your description, the call was indicating a GLS breakout that had followed a RSLS hold...is that close?
  
  Thanks,
  
  Philip Sloss
  
• #6 by psloss on 01 Apr, 2006 22:46
• Quote

  Jim - 1/4/2006  11:32 AM
  
  I have been on console and have heard the NTD request "GLS give cutoff".  I don't remember all the details.  What would happen after T-31sec that it would have to be a manual cutoff. It wasn't the range.

  That occurred memorably on STS-93 -- the 20 July 1999 attempt was stopped by manual call just before main engine start; in the background one can hear a call to "give cutoff," almost overlapped by the same request from the NTD.  It was amazing, even considering all the practice, how quickly that happened, since it sounds like the initial call came in right around T-10 seconds.
  
  (Not sure what console, but it had to be MPS-related, since that was a spike in the hydrogen concentration in the aft compartment -- subsequently attributed to a sensor misreading.)
  
• #7 by psloss on 01 Apr, 2006 22:51
• A quick add for the "armchair" folks like me; there's an old outline of the terminal count that's been available for a while, but somewhat obscure.  It's a good general, high-level reference, though it's a bit old:
  http://science.ksc.nasa.gov/shuttle/countdown/count.html
  
  FWIW.
  
• #8 by Chris Bergin on 01 Apr, 2006 23:01
• Quote

  psloss - 1/4/2006  10:46 PM
  
  
  That occurred memorably on STS-93 -- the 20 July 1999 attempt was stopped by manual call just before main engine start; in the background one can hear a call to "give cutoff," almost overlapped by the same request from the NTD.  It was amazing, even considering all the practice, how quickly that happened, since it sounds like the initial call came in right around T-10 seconds.
  
  (Not sure what console, but it had to be MPS-related, since that was a spike in the hydrogen concentration in the aft compartment -- subsequently attributed to a sensor misreading.)
  

  
  And here's the video for that (first link)
  
  http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=442&start=1
  
  From the audio, you can hear something being said at T-9.5 seconds, with the "Cutoff, give cutoff....cutoff is given" through to T-7 seconds.
• #9 by Jim on 02 Apr, 2006 13:25
• Quote

  Mark Max Q - 1/4/2006  1:23 PMHow does the hand off to the orbiter for Auto Sequence Start happen?Does the orbiter pick up the count after the T-9:00 hold and thus be in alignment, ready for the T-31?

  
   The GLS instructs the GPC's at T-31  initiate autosequenct
  
• #10 by mkirk on 02 Apr, 2006 17:05
• Quote

  Chris Bergin - 1/4/2006  5:01 PM
  
  

  Quote

  psloss - 1/4/2006  10:46 PM
  
  
  That occurred memorably on STS-93 -- the 20 July 1999 attempt was stopped by manual call just before main engine start; in the background one can hear a call to "give cutoff," almost overlapped by the same request from the NTD.  It was amazing, even considering all the practice, how quickly that happened, since it sounds like the initial call came in right around T-10 seconds.
  
  (Not sure what console, but it had to be MPS-related, since that was a spike in the hydrogen concentration in the aft compartment -- subsequently attributed to a sensor misreading.)
  

  
  And here's the video for that (first link)
  
  http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=442&start=1
  
  From the audio, you can hear something being said at T-9.5 seconds, with the "Cutoff, give cutoff....cutoff is given" through to T-7 seconds.

  
  
  For STS-93 I was in a part of the MCC (Mission Control Center) called the SCA (Sim Control Area) where many of the training instructors gather to watch over the data on consoles identical to those in the FCR (flight control room).  While I remember the actual STS-93 launch quite well for obvious reasons, I don't really recall many of the details for the two scrubs.  After a while  many of the missions seem to just run together.
  
  The proper call for a Cutoff is "CGLS, Give Cutoff". Both the GLS console operator and the NTD are spring loaded to respond to those words immediately.  For that particular scrub the CHGD (hazardous gas detection system console) operator made a call "CGLS, Give Cutoff" and I believe what you here after that is the NTD echoing the command.  CHGD had noticed a spike of 640 ppm in the Hydorgen concentration in the orbiter's aft compartment.  This could be indicative of a fuel leack...as it turned out I believe they decided that it was bad data from the sensors and we could have launched with no problem...I will get into the problems on the actual launch when I have more time to review my notes and tapes.
  
  To answer Jim's Question:
  "What would happen after T-31sec that it would have to be a manual cutoff. It wasn't the range."
  
  Basically any parameter not directly monitored by the GLS or RSLS would require a manual cutoff.  One of the ovious ones as you said would be a range issue.  
  
  One of the more recent times that I can recall would have been the STS-88 launch attempt.  MCC and LCC were both looking at APU hydraulics data and while MCC cosidered it to be within limits the LCC needed more time to reach that conclusion.  Holding at T-31, a go was finally given to pick up the count but by that time the short launch window had elapsed...by a couple of seconds as I recall.  This meant we had used up our performance margin of availabel fuel in the external tank. MCC tracks this and immediately John Shannon the Flight Director called "NTD, Houston Flight, WE ARE NO GO FOR LAUNCH"...NTD responded with a Cutoff request.  This was not an automatic cutoff because the hold time constraint of "LOX performace margin" is not a parameter that the GLS or RSLS would track.
  
  As I said in another thread...that launch scrub frightened us a little bit...you just don't want to run around with your hair on fire that late in a countdown.  There were a lot of lesssons learned from the STS-88 launch attempt.
  
  I can also speculate that maybe a known condition that was masked, biased, or bypassed by the GLS software prior to T-31 and then later shows behavior that is suddenly erratic or beyond the waivered value, would require a manual cutoff.
  
  I should add if I understand Firing Room Protocol correctly; even if a systems operator sees something that the GLS/RSLS should be calling an automatic cutoff for, he/she should back that up with the verbal request for a cutoff to the CGLS console.  You should never ASSUME that the GLS will automatically take care of it.
  
  Mark Kirkman
• #11 by mkirk on 02 Apr, 2006 17:18
• Quote

  Mark Max Q - 1/4/2006  1:23 PM
  
  How does the hand off to the orbiter for Auto Sequence Start happen?
  
  Does the orbiter pick up the count after the T-9:00 hold and thus be in alignment, ready for the T-31?

  
  The way the GLS (ground launch sequencer) and RSLS (redundant set launch sequencer...the onboard computers) interact is actually a little more complex than you might think.  At T-31 second the GLS will give the onboard computers the GO for Auto Sequence and at T-28 seconds the onboard computers check to make sure the go was given.
  
  While the RSLS is "driving the count" both the GLS and RSLS will issue there own commands and both will cross check each other.
  
  For instance at T-27.92 seconds the RSLS will command the Vent Door Sequence (all vent doors open) this is an onboard command.
  
  At T-28 seconds the GLS will issue commands to start the SRB HPUs (Hydraulic power units) and then perform a gimbal test of the SRB nozzles...these are gorund based commands.
  
  In other words, after T-31 seconds the GLS still has work to do and it does its tasks and then reports to the RSLS that from its perspective it is "Go For Launch".  At the same time the on board computers via the RSLS will have a set of tasks to perform such as the vent sequence, setting the throttle commands, opening engine valves, or commanding the onboard master events controller to arm the SRB ignition and T-0 release pyros.
  
  Mark Kirkman
• #12 by psloss on 02 Apr, 2006 17:26
• Quote

  mkirk - 2/4/2006  1:05 PM
  
  The proper call for a Cutoff is "CGLS, Give Cutoff". Both the GLS console operator and the NTD are spring loaded to respond to those words immediately.  For that particular scrub the CHGD (hazardous gas detection system console) operator made a call "CGLS, Give Cutoff" and I believe what you here after that is the NTD echoing the command.  CHGD had noticed a spike of 640 ppm in the Hydorgen concentration in the orbiter's aft compartment.  This could be indicative of a fuel leack...as it turned out I believe they decided that it was bad data from the sensors and we could have launched with no problem...I will get into the problems on the actual launch when I have more time to review my notes and tapes.
  

  At the time, it was said that the primary haz gas detector "burped" some hydrogen that it re-detected...I don't have the primary sources, but I stumbled onto a few STS-93 press briefing excerpts, including the countdown status briefing between the first and second attempts which discuss this scrub.  Assuming these will convert over, I can post them...Chris?
  
  Philip Sloss
  
• #13 by Chris Bergin on 02 Apr, 2006 19:36
• Go for it, that'd be great!
• #14 by psloss on 05 Apr, 2006 12:50
• Quote

  mkirk - 2/4/2006  1:05 PM
  
  One of the more recent times that I can recall would have been the STS-88 launch attempt.  MCC and LCC were both looking at APU hydraulics data and while MCC cosidered it to be within limits the LCC needed more time to reach that conclusion.  Holding at T-31, a go was finally given to pick up the count but by that time the short launch window had elapsed...by a couple of seconds as I recall.  This meant we had used up our performance margin of availabel fuel in the external tank. MCC tracks this and immediately John Shannon the Flight Director called "NTD, Houston Flight, WE ARE NO GO FOR LAUNCH"...NTD responded with a Cutoff request.  This was not an automatic cutoff because the hold time constraint of "LOX performace margin" is not a parameter that the GLS or RSLS would track.
  
  As I said in another thread...that launch scrub frightened us a little bit...you just don't want to run around with your hair on fire that late in a countdown.  There were a lot of lesssons learned from the STS-88 launch attempt.

  FWIW,
  
  We've posted a clip of the NASA TV coverage of this launch attempt now; the excerpt runs from T-5 minutes and counting through the cutoff and beginning of the recycle.  The "no go" call by the flight director to NTD is obscured by the PAO, though I think it can be barely heard.
  
  http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=2078
  
• #15 by psloss on 10 Apr, 2006 21:34
• We don't see these very often, but right now the KSC website has up operational TV (OTV) camera 095 on channel 3...looks like a slewing test of the Ku-band antenna.  (Frame also attached.)
  http://science.ksc.nasa.gov/shuttle/countdown/video/
  
  The quick, specific question is which OPF bay is this?  (I imagine that this could be deduced based on which orbiter is where in its processing flow, but I'll throw it out, anyway.)  The general question is whether there's an online reference for which OTV cameras are in what location?  Some of them I've picked up from spectating over the years, but some of the ones in the OPF (090s) and VAB (080s) bays I'm a little shakier on.  (Although some of the VAB cameras are on the roof, which are a bit more obvious.)
  
  Thanks,
  
  Philip Sloss
  

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• #16 by Jim on 10 Apr, 2006 22:22
• I have a book somewhere with all the locations.  The pad cams also lists what they are suppose to look at certain times in the countdown
  
  Just found out it is an ITAR doc.
  
• #17 by Davie OPF on 10 Apr, 2006 22:26
• I think that's Discovery, with her KU Band Antenna in OPF3.
• #18 by SRBseparama on 11 Apr, 2006 02:43
• Quote

  Davie OPF - 10/4/2006  5:26 PM
  
  I think that's Discovery, with her KU Band Antenna in OPF3.

  
  
  Why's it sticking out like that? It's just asking for a lamp to be knocked on to it!  
• #19 by Rocket Guy on 11 Apr, 2006 02:55
• I believe that's Endeavour. Ku band antenna testing on ov-105 in work today and Tuesday.
  
  Edit: I will add though, that of course could be any of them, but as testing is underway on that one specifically they may have their cameras trained on it.