Shuttle Questions Q & A (Part 4)

• #840 by Endeavour118 on 28 Mar, 2008 00:13
• i don't know if this has been asked right when the srb's ignite and in the cockpit video i hear someone makes a callout 102 to 102 auto who does that and what does it mean and after the cdr makes the roll program call what is that called and what does it mean?
• #841 by Jim on 28 Mar, 2008 01:08
• Quote

  Susan27 - 27/3/2008  7:59 PM
  
  Hi,
  
  when viewing STS-123 rolling out yesterday night at SLF I noticed the APU-venting as a yellow coloured flash/steam (like a lava-lamp). The narrator said that this would be absolutely normal and the same as on daylight landings...
  
  Question: When watching daytime landings vids I see those "steam" coming out from the APU but the colour is something "grey" but really NOT so extreme bright yellow/orange. Could you explain why on night landings the colour of the steam is like that or does that orange colour have to do with the special lenses NASA uses when TV-recording night landings...?
  
  Thanks in advance!
  
  

  
  It isn't steam but ammonia and hydrogen which sometime burns when it hits the air
• #842 by Jim on 28 Mar, 2008 01:10
• Quote

  cabbage - 27/3/2008  8:58 PM
  
   Is the deadweight of the SRBs a structural concern or a control issue?

  
  yes, and yes
• #843 by DaveS on 28 Mar, 2008 08:50
• Quote

  Endeavour118 - 28/3/2008  2:13 AM
  
  i don't know if this has been asked right when the srb's ignite and in the cockpit video i hear someone makes a callout 102 to 102 auto who does that and what does it mean and after the cdr makes the roll program call what is that called and what does it mean?

  It is to confirm that both PASS and BFS has "moded" over from OPS101 to OPS102 automatically.
  
  Same call gtes done after SRB sep when PASS and BFS "modes" over from OPS102 to OPS103.
• #844 by Susan27 on 28 Mar, 2008 15:35
• Quote

  Jim - 27/3/2008  9:08 PM
  It isn't steam but ammonia and hydrogen which sometime burns when it hits the air

  
  Well, but the same happens on daylight landings, right? If so why dont we see those bright yellow coloured ammonia/hydrogen blowouts on daytime in this colour then...?
  
  Thanks again!
• #845 by Susan27 on 28 Mar, 2008 15:46
• Hello,
  
  at the moment I am watching this intermediate reentry video of STS-123 return:
  
  
  
  At 02:25 min of the vid the first roll-(reversal) right-to-left is been flown by the orbiter. On the corresponding MCC screen the groundtrack is a single line without any curves short until the coast of Florida.
  
  If the shuttle is flying rolls, roll-reversals etc. the ground track has to be also curved, isnt that correct this way? If so why the ground track at the displays on MCC is a straight line then...?
  
  Thanks very much in advance!
• #846 by Jim on 28 Mar, 2008 15:53
• Quote

  Susan27 - 28/3/2008  12:35 PM
  
  

  Quote

  Jim - 27/3/2008  9:08 PM
  It isn't steam but ammonia and hydrogen which sometime burns when it hits the air

  
  Well, but the same happens on daylight landings, right? If so why dont we see those bright yellow coloured ammonia/hydrogen blowouts on daytime in this colour then...?
  
  Thanks again!

  
  It is "washed out" by the bright sunlight
• #847 by Jim on 28 Mar, 2008 15:59
• Quote

  Susan27 - 28/3/2008  12:46 PM
  
  Hello,
  
  at the moment I am watching this intermediate reentry video of STS-123 return:
  
  
  
  At 02:25 min of the vid the first roll-(reversal) right-to-left is been flown by the orbiter. On the corresponding MCC screen the groundtrack is a single line without any curves short until the coast of Florida.
  
  If the shuttle is flying rolls, roll-reversals etc. the ground track has to be also curved, isnt that correct this way? If so why the ground track at the displays on MCC is a straight line then...?
  
  Thanks very much in advance!

  
  It is curved.  It slightly curves up the Yucatan.
• #848 by Lee Jay on 28 Mar, 2008 16:16
• Quote

  Jim - 28/3/2008  10:59 AM
  
  

  Quote

  Susan27 - 28/3/2008  12:46 PM
  
  Hello,
  
  at the moment I am watching this intermediate reentry video of STS-123 return:
  
  
  
  At 02:25 min of the vid the first roll-(reversal) right-to-left is been flown by the orbiter. On the corresponding MCC screen the groundtrack is a single line without any curves short until the coast of Florida.
  
  If the shuttle is flying rolls, roll-reversals etc. the ground track has to be also curved, isnt that correct this way? If so why the ground track at the displays on MCC is a straight line then...?
  
  Thanks very much in advance!

  
  It is curved.  It slightly curves up the Yucatan.

  
  Don't forget, Susan, that the vehicle is still high in very thin atmosphere at that point, and can therefore generate only small amounts of lift, plus it's still traveling on the order of Mach 20 which means those small lateral loads will produce extremely large radius turns.
• #849 by Endeavour118 on 30 Mar, 2008 05:09
• Quote

  DaveS - 28/3/2008  5:50 AM
  
  

  Quote

  Endeavour118 - 28/3/2008  2:13 AM
  
  i don't know if this has been asked right when the srb's ignite and in the cockpit video i hear someone makes a callout 102 to 102 auto who does that and what does it mean and after the cdr makes the roll program call what is that called and what does it mean?

  It is to confirm that both PASS and BFS has "moded" over from OPS101 to OPS102 automatically.
  
  Same call gtes done after SRB sep when PASS and BFS "modes" over from OPS102 to OPS103.

  what is the call that i think the plt makes after the cdr makes the roll program call
• #850 by mkirk on 30 Mar, 2008 15:29
• Quote

  Endeavour118 - 29/3/2008  12:09 AM
  
  

  Quote

  DaveS - 28/3/2008  5:50 AM
  
  

  Quote

  Endeavour118 - 28/3/2008  2:13 AM
  
  i don't know if this has been asked right when the srb's ignite and in the cockpit video i hear someone makes a callout 102 to 102 auto who does that and what does it mean and after the cdr makes the roll program call what is that called and what does it mean?

  It is to confirm that both PASS and BFS has "moded" over from OPS101 to OPS102 automatically.
  
  Same call gtes done after SRB sep when PASS and BFS "modes" over from OPS102 to OPS103.

  what is the call that i think the plt makes after the cdr makes the roll program call

  
  The call I believe you are referring to is “LVLH”.  
  
  This is an internal intercom call for the Commander and Pilot to reset the reference frame for the ADI (attitude direction indicator).  Both the CDR and PLT will flip a switch on their forward instrument panels from the REF (reference) to LVLH (local vertical, local horizontal) position.  
  
  The "ball" is in the REF position prior to launch to prevent math singularities in the guidance system's computation of attitude that are caused by the nose up orientation of the orbiter on the launch pad.  After the roll manever the LVLH position allows the ball to act more like a traditional ADI on a high performance airplane.
  
  Mark Kirkman
• #851 by mkirk on 30 Mar, 2008 15:43
• Quote

  jeff122670 - 27/3/2008  3:41 PM
  
  GLS go for Auto Sequence Start...................does it occur at T-31 or T-27?  i have heard both..... i am assuming it is commanded at -31 and actually completes at -27.......
  
  can anyone answer?
  

  
  I can see where some of the confusion comes from here.
  
  First off it is true – as PSLOSS pointed out – that for STS-1 the timing of the countdown was different which is why you hear 27 seconds in the launch commentary.
  
  As for how things are today.  The GLS (ground launch sequencer) will send the “Go for Auto Sequence Start” command at T-31 seconds.  The on board RSLS (redundant set launch sequencer) will verify that command at T-28 seconds.  The RSLS is in control of the count from T-31 seconds, however, both the GLS and RSLS will send commands and perform verifications as the count progresses.
  
  Mark Kirkman
  
  
• #852 by jcopella on 30 Mar, 2008 20:30
• Quote

  mkirk - 30/3/2008  11:43 AM
  The RSLS is in control of the count from T-31 seconds

  
  I realize this may be considered nit-picking, but that's not really true.  The onboard & ground sequencers are synchronized but really neither can be said to be fully "in control" of the other.  The ground & flight systems are functionally interdependent all the way to T-0.
  
  I had a long post about this, but thought I'd save it unless someone really wants to dive into the weeds.
  
  The bottom line is that the ground & onboard clocks are independent but synchronized, and either the flight sequencer or the ground sequencer can call a hold at any point all the way to T-0.  The magic about 31 sec is that after that point a request for a hold will initiate breakout safing (scrub), and the magic of T-10 sec (LPS go for SSME start) is that a hold after that point will result in an RSLS abort (possibly a lengthy scrub and more pucker for everyone).
  
  And as a famous rabbi once said, the rest is details  :bleh:
• #853 by elmarko on 30 Mar, 2008 21:47
• Bump for my OPS question from the last page, if I may?
• #854 by mkirk on 30 Mar, 2008 22:57
• Quote

  jcopella - 30/3/2008  3:30 PM
  
  

  Quote

  mkirk - 30/3/2008  11:43 AM
  The RSLS is in control of the count from T-31 seconds

  
  I realize this may be considered nit-picking, but that's not really true.  The onboard & ground sequencers are synchronized but really neither can be said to be fully "in control" of the other.  The ground & flight systems are functionally interdependent all the way to T-0.
  
  

  
  Thanks jcopella I was hoping you would chime in here. Please go into more detail if you have more to add, I would really like to make sure I understand this subject as well.  From a crew training perspective we never get into this kind of detail since you can't do anything about it from the cockpit anyway.  
  
  I agree with the bit about not really being in control.  My knowledge of the interaction of the GLS/RSLS is a bit limited and come from high level documents like S0007, GLSDD, FSSRs.  I actually had second thoughts about using that wording in my previous post, but I have heard that phrase for so long (particluarly from PAO) I just gave in to the party line.
  
  I have a nice little chart from the front of S0007 that shows some of the interaction during those last 31 seconds.  I will post it as soon as I get Chris' help since it is above the allowable attachment size.
  
  I also have an old electronic copy of the GLSDD (ground launch sequencer description document)from the STS-96 timeframe that I will forward to Chris for posting.  It is not a user friendly document to read but it does list the GLS checks/commands during the final count.
  
  Mark Kirkman
  
• #855 by mkirk on 30 Mar, 2008 23:09
• Okay with some help from Chris here is the chart I mentioned.  You will have to click on it to make it large enough to read.
  
  Mark Kirkman

  ---

  
• #856 by jcopella on 31 Mar, 2008 04:48
• Quote

  mkirk - 30/3/2008  6:57 PM
  
  

  Quote

  jcopella - 30/3/2008  3:30 PM
  
  

  Quote

  mkirk - 30/3/2008  11:43 AM
  The RSLS is in control of the count from T-31 seconds

  
  I realize this may be considered nit-picking, but that's not really true.  The onboard & ground sequencers are synchronized but really neither can be said to be fully "in control" of the other.  The ground & flight systems are functionally interdependent all the way to T-0.
  
  

  
  Thanks jcopella I was hoping you would chime in here. Please go into more detail if you have more to add, I would really like to make sure I understand this subject as well.  From a crew training perspective we never get into this kind of detail since you can't do anything about it from the cockpit anyway.  
  
  I agree with the bit about not really being in control.  My knowledge of the interaction of the GLS/RSLS is a bit limited and come from high level documents like S0007, GLSDD, FSSRs.  I actually had second thoughts about using that wording in my previous post, but I have heard that phrase for so long (particluarly from PAO) I just gave in to the party line.

  
  Yes, it's a misunderstanding perpetuated by PAO, and I'm a little surprised no one's ever bothered to correct them.  I think it maybe makes for a more dramatic terminal count if they leave the script as written.
  
  Conceptually, the whole system is pretty simple to understand.  PASS & GLS are each receiving timing data from a separate source.  The PASS gets its timing information from the onboard MTUs.  GLS gets its time from Time Code Generators in LPS, and uses this information to drive the countdown clock on the ground.  However, it is GLS' job to establish the GMT of Liftoff, and to communicate this to the RSLS after the OPS 1 Transition.  There are three basic commands involved:
  
  1.  Set GMTLO
  2.  Command Launch Sequence Resume
  3.  Command Launch Sequence Hold
  
  After OPS 1 transition, GLS sends a GMTLO & a resume to RSLS.  The RSLS computes the delta between the GMTLO and the current GMT, and this yields the onboard countdown time, which is called TB0 (time base zero).  This is what the crew sees (as I understand it) on one of the MM101 SPECs.  Although this should agree with the GLS/LPS countdown clock, this value is maintained independently by PASS based on input given to it from the ground!  There is no hardwired timing signal running up the T-0 umbilical via the LDB driving that value -- it is all based on logic in the PASS.  IIRC, there is an OMRSD that governs the allowable error between the RSLS TB0 time and the LPS countdown clock.
  
  At this point GLS & RSLS run in parallel, interacting directly only when there's a countdown clock hold/resume (e.g., the T-9m built-in hold), and at T-31 sec and T-10 sec when the two LPS "go" flags (auto sequence start & SSME start, respectively) are sent.  Since both are interlocked with each other (GLS will hold if the RSLS holds, and vice versa), it's not accurate to say that either one, really, is "in control".  This is true prior to T-31 sec, and it is true after T-31 sec.
  
  What is most significant operationally about the go for auto sequence start at T-31s is that after that point, it is not possible to hold the count.  If something goes wrong that would require a hold after T-31s (detected by either RSLS or GLS), GLS will "breakout" -- i.e., stop the count, initiate safing, and get the vehicle in configuration to transition back to G9.  If something goes wrong after SSME start, then, there's the added complexity of an SSME abort scenario.
  
  

  Quote

  I have a nice little chart from the front of S0007 that shows some of the interaction during those last 31 seconds.  I will post it as soon as I get Chris' help since it is above the allowable attachment size.

  
  Excellent chart.  I can't tell from that who's "controlling the count", can you?
  
  

  Quote

  I also have an old electronic copy of the GLSDD (ground launch sequencer description document)from the STS-96 timeframe that I will forward to Chris for posting.  It is not a user friendly document to read but it does list the GLS checks/commands during the final count.
  
  Mark Kirkman
  

  
  Good stuff... I hope we can post that here on L2 somewhere!
• #857 by briguy700 on 01 Apr, 2008 22:24
• I am NO rocket scientist, just an amateur enthusiast who has no knowledge of engineering, etc, so I am depending on you knowledgeable persons to help me out here.
  
  I have always looked at the three attachment points that connect the Shuttle Orbiter to the External Tank and, for some reason, it surprises me with all the force and power during launch, combined with wind, weight of vehicle, etc, that these attachment points are sufficient to hold the shuttle and tank together against these forces, gravity, etc. I think they use explosive bolts during separation, but what makes these points so strong before hand to hold the weight of these two large objects (tank and orbiter) together ?? Obviously it works, I am just curious. Thanks for your inputs !!
• #858 by Lee Jay on 01 Apr, 2008 23:35
• Quote

  briguy700 - 1/4/2008  4:24 PM
  I have always looked at the three attachment points that connect the Shuttle Orbiter to the External Tank and, for some reason, it surprises me with all the force and power during launch, combined with wind, weight of vehicle, etc, that these attachment points are sufficient to hold the shuttle and tank together against these forces, gravity, etc. I think they use explosive bolts during separation, but what makes these points so strong before hand to hold the weight of these two large objects (tank and orbiter) together ?? Obviously it works, I am just curious. Thanks for your inputs !!

  
  The aft struts are pretty huge:
  
  http://mediaarchive.ksc.nasa.gov/detail.cfm?mediaid=35604
  http://mediaarchive.ksc.nasa.gov/detail.cfm?mediaid=35504
  
  They take all the thrust of launch, and the weight of the orbiter on the pad.  The bipod at the front only keeps the orbiter's nose from moving toward or away from the tank, and side-to-side.  It's bigger than you think, and don't forget how strong bolts are - a "little" one inch bolt of good quality can take more than 100,000 pounds of force.  The entire stack is held down, in hurricane-force winds, by only eight 3 1/2 inch bolts on the SRB aft skirts.
• #859 by rocketguy101 on 02 Apr, 2008 00:21

• Quote

  Lee Jay - 1/4/2008 6:35 PM

  Quote

  briguy700 - 1/4/2008 4:24 PM I have always looked at the three attachment points that connect the Shuttle Orbiter to the External Tank and, for some reason, it surprises me with all the force and power during launch, combined with wind, weight of vehicle, etc, that these attachment points are sufficient to hold the shuttle and tank together against these forces, gravity, etc. I think they use explosive bolts during separation, but what makes these points so strong before hand to hold the weight of these two large objects (tank and orbiter) together ?? Obviously it works, I am just curious. Thanks for your inputs !!

  The aft struts are pretty huge: http://mediaarchive.ksc.nasa.gov/detail.cfm?mediaid=35604 http://mediaarchive.ksc.nasa.gov/detail.cfm?mediaid=35504 They take all the thrust of launch, and the weight of the orbiter on the pad. The bipod at the front only keeps the orbiter's nose from moving toward or away from the tank, and side-to-side. It's bigger than you think, and don't forget how strong bolts are - a "little" one inch bolt of good quality can take more than 100,000 pounds of force. The entire stack is held down, in hurricane-force winds, by only eight 3 1/2 inch bolts on the SRB aft skirts.

  Looking at the pics you posted, I am amazed at the SRB attachment points.  How large are the struts, 9-10 inches in diameter?