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#2520
by
sivodave
on 12 Feb, 2012 08:56
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Hi all.
Question about the ET. Apart the changes to the ligth version and then superlight version, have there been other changes in the ET structure or systems before the Columbia accident?
Thanks very much
Davide
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#2521
by
alk3997
on 12 Feb, 2012 18:27
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Quote from: sivodave on 02/05/2012 07:53 PMHi all.
Question about the star trackers. I know that two different types were used, namely the solid state start tracker and the image dissector tube star tracker.
I'd like to know the advantage of the one type respect the other. Which
one was better? could an orbiter have both types at the same time?
Thanks very much
Regards
Davide
Yes, the two types could be used interchangeably and mixed on the same flight. I suspect the older ones were simply becoming unsupportable due to their age.
Thanks DMeader. Just another question: in what sense the only ones became unsupportable? Unsupportable from a software point of view or maintenance? If they were unsupportable, why they flew with both type together?
Thanks very much
Regards
Davide
The software didn't "know" which type of star tracker was being flown. There were a lot of pieces of equipment we had to know which type was being used, but not the star trackers. For the other equipment, the selection was usually done with an I-Load (or TMBU update), so it wasn't that difficult as long as there wasn't a late change.
Usually aging equipment that needs to be replaced was due to the inability to find spare parts. I suspect that the image dissector tube was not a very common part and is probably no longer made.
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#2522
by
Zoe
on 14 Feb, 2012 23:41
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I've been looking at the launch attempts for all shuttle missions and have noticed a few examples of recycles back to T-20 minutes for another launch attempt on the same day. The question is, was there ever one of these that actually launched? As all of these missions were in the early days there isn't much information available and the examples I have read about ended up getting scrubbed in the end, for example STS-1 (I beleive) and STS-61-C.
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#2523
by
psloss
on 14 Feb, 2012 23:59
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I've been looking at the launch attempts for all shuttle missions and have noticed a few examples of recycles back to T-20 minutes for another launch attempt on the same day. The question is, was there ever one of these that actually launched? As all of these missions were in the early days there isn't much information available and the examples I have read about ended up getting scrubbed in the end, for example STS-1 (I beleive) and STS-61-C.
Off the top of my head, 51-F is one.
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#2524
by
alk3997
on 15 Feb, 2012 13:50
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I've been looking at the launch attempts for all shuttle missions and have noticed a few examples of recycles back to T-20 minutes for another launch attempt on the same day. The question is, was there ever one of these that actually launched? As all of these missions were in the early days there isn't much information available and the examples I have read about ended up getting scrubbed in the end, for example STS-1 (I beleive) and STS-61-C.
The reason that was possible at that time was there were 4-hour launch windows. So, there was enough time to go back to 20 minutes, work a problem and restart at the transition to OPS 1. Once the orange pumpkin suits were added, the window was reduced to 2.5 hours. If a rendezvous was required, then the window was (much) shorter (from a little over an hour down to 5 minutes). So there was no time to recycle to 20 minutes.
Andy
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#2525
by
Zoe
on 16 Feb, 2012 01:37
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Some interesting reading on this subject in the S0007 volume 2 recycle control sequence. One strange procedure I noticed is that it says that if a cutoff has occurred after T-16 seconds and the launch is not going to be scrubbed then the sound surpression water tank is to be refilled. From reading previous threads I thought the rule was that if you went below T-31 seconds then you had to scrub so why does S0007 contain procedures for same day launch attempt when the countdown is as low as T-16 seconds?
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#2526
by
alk3997
on 16 Feb, 2012 03:24
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Some interesting reading on this subject in the S0007 volume 2 recycle control sequence. One strange procedure I noticed is that it says that if a cutoff has occurred after T-16 seconds and the launch is not going to be scrubbed then the sound surpression water tank is to be refilled. From reading previous threads I thought the rule was that if you went below T-31 seconds then you had to scrub so why does S0007 contain procedures for same day launch attempt when the countdown is as low as T-16 seconds?
I don't remember any rule that said you had to scrub after a T-31 hold. The time limit for scrubbing was T-6.6 seconds when the SSMEs started. I forget if the H2 igniters (the sparklers) had a second cartridge or not, which would have allowed for a second attempt if the hold was between T-11 seconds and T-6 seconds.
Kind of irrelevent later in the program because of the limited duration windows.
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#2527
by
Zoe
on 16 Feb, 2012 04:12
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http://forum.nasaspaceflight.com/index.php?topic=10600.950It was discussed back in 2008 and the suggestion there was that it would take more than a day before another attempt could be made due to the SRB HPUs. STS-93 for example had a 48 hour turnaround I do see reference in the S0007 to a "manifold refill" if second launch attempt is to be made so it does seem that there is a procedure for this.
Out of interest, how long would it have taken to get from a GLS cutoff to resuming the count at T-20 minutes in an STS-93 situation where the issue could have been quickly resolved? It says 1 hour 30 minutes in the S0007 where it says to refill the sound surpression water tank although I'm not sure if this is referring to the time it would take to refill the tank before the count could be resumed. Obsviously this would never be an option for an ISS mission like STS-93 but would be intersted to know if it could have been done within the later 2.5 hour launch windows.
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#2528
by
psloss
on 16 Feb, 2012 11:54
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It was discussed back in 2008 and the suggestion there was that it would take more than a day before another attempt could be made due to the SRB HPUs.
That was specific to that 61-C cutoff, which was due to an indication of a HPU overspeed. This would be one of the topics in the case of any cutoff after T-31 -- whatever was "wrong" might be worth analyzing/discussing overnight. And if something appeared to be broken (as with the HPU), then scrub might be the only option.
Out of interest, how long would it have taken to get from a GLS cutoff to resuming the count at T-20 minutes in an STS-93 situation where the issue could have been quickly resolved? It says 1 hour 30 minutes in the S0007 where it says to refill the sound surpression water tank although I'm not sure if this is referring to the time it would take to refill the tank before the count could be resumed.
Kind of an interesting topic; there are multiple references to IMU alignment unplanned hold time in the 90 minute range back in the 80s contributing to the length of recycles (51-F on 29 July 1985, 61-C on 6 January 1986, etc.)
Subsequently, there were a few launch attempts later in the program that were delayed for long periods at T-9 minutes...would be interesting to see whether the unplanned hold time was extended for the original KT-70 units and/or the HAINS units. Or maybe that coupled with other software and procedural changes. After the crew-on-back limits were more strictly enforced, there were a couple of cases in the late 80s and early/mid 90s with long-ish holds that ran close to 90 minutes or a bit longer. The last long one I can think of was with STS-64 in September, 1994.
Obsviously this would never be an option for an ISS mission like STS-93 but would be intersted to know if it could have been done within the later 2.5 hour launch windows.
Nit: STS-93 was the last Shuttle IUS deploy mission; it had a longer window than Mir or ISS rendezvous/docking missions. Probably in the 60 minute range (which was exhausted on the second attempt, due to weather).
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#2529
by
Zoe
on 16 Feb, 2012 12:25
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That was specific to that 61-C cutoff, which was due to an indication of a HPU overspeed. This would be one of the topics in the case of any cutoff after T-31 -- whatever was "wrong" might be worth analyzing/discussing overnight. And if something appeared to be broken (as with the HPU), then scrub might be the only option.
I was referring to mkirk's comments that said you were done for the day once you go past T-31 seconds and that there was a rule about this before STS-61-C was mentioned in that converstation. Having been reading these threads since then I always thought that would be the case until I discovered the S0007 recycle control sequence that contained procedures for a second launch attempt even if there was a cutoff after T-31 seconds. For the December launch attempt though of STS-61-C I note
http://www.space-shuttle.com/challenger2.htm says that the countdown was recycled to T-20 minutes but it was hopeless so it would seem that they didn't immediately scrub after the cutoff at T-14 seconds although this could of course just be referring to the fact that the countdown has to be recycled to T-20 minutes after a cutoff regardless of it there is going to be a scrub or not.
Kind of an interesting topic; there are multiple references to IMU alignment unplanned hold time in the 90 minute range back in the 80s contributing to the length of recycles (51-F on 29 July 1985, 61-C on 6 January 1986, etc.)
According to the "Some Trust in Chariots" book about Challenger, there was also a recycle on January 7 although exactly why they had to recycle to T-20 minutes and count back down to T-9 minutes when they could have just waited at T-9 minutes until the end of the window is not clear.
After the crew-on-back limits were more strictly enforced, there were a couple of cases in the late 80s and early/mid 90s with long-ish holds that ran close to 90 minutes or a bit longer. The last long one I can think of was with STS-64 in September, 1994.
Would these have just been long holds though rather than recycles? Even for STS-51-F I have seen it just referred to as a long hold even though in this case there was a recycle.
Also even though it wasn never going to launch, I believe there was a recycle during a tanking test for STS-114.
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#2530
by
psloss
on 16 Feb, 2012 20:05
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That was specific to that 61-C cutoff, which was due to an indication of a HPU overspeed. This would be one of the topics in the case of any cutoff after T-31 -- whatever was "wrong" might be worth analyzing/discussing overnight. And if something appeared to be broken (as with the HPU), then scrub might be the only option.
I was referring to mkirk's comments that said you were done for the day once you go past T-31 seconds and that there was a rule about this before STS-61-C was mentioned in that converstation. Having been reading these threads since then I always thought that would be the case until I discovered the S0007 recycle control sequence that contained procedures for a second launch attempt even if there was a cutoff after T-31 seconds.
My point was that whatever caused the cutoff inside the "go for auto sequence start" GLS milestone might preclude use of any hypothetical capability to recycle. So in the case of the December, 1985, attempt -- or the STS-51 attempt in July, 1993 -- even if there had been an unlimited launch window, the failure that caused the cutoff was also going to require a lengthy R&R (multiple days).
For the December launch attempt though of STS-61-C I note http://www.space-shuttle.com/challenger2.htm says that the countdown was recycled to T-20 minutes but it was hopeless so it would seem that they didn't immediately scrub after the cutoff at T-14 seconds although this could of course just be referring to the fact that the countdown has to be recycled to T-20 minutes after a cutoff regardless of it there is going to be a scrub or not.
It might not have been immediately announced, but it might also have taken longer to review the data back then to see what caused the cutoff. It wasn't long after it was reported the problem was a HPU overspeed that it was reported they were done for the year.
According to the "Some Trust in Chariots" book about Challenger, there was also a recycle on January 7 although exactly why they had to recycle to T-20 minutes and count back down to T-9 minutes when they could have just waited at T-9 minutes until the end of the window is not clear.
Possibly the same thing as one of the drivers from the previous day's recycle -- the IMUs needed to be realigned. Forgot to add to earlier post; this has been linked before, but you can see some references to this in the Space Shuttle Missions Summary book:
http://www.jsc.nasa.gov/history/reference/TM-2011-216142.pdfThe realign is noted in the Jan. 6 attempt after the recycle, but given a long weather hold on the 7th, they also might have held past the unplanned hold limit for the IMUs at that time (or knew they were going to hold that long) and based on the procedures at the time had to recycle to T-20.
After the crew-on-back limits were more strictly enforced, there were a couple of cases in the late 80s and early/mid 90s with long-ish holds that ran close to 90 minutes or a bit longer. The last long one I can think of was with STS-64 in September, 1994.
Would these have just been long holds though rather than recycles?
Refer to the SSMS book link. There were a few other situations like that back then (post RTF after 51L) and that was during a period of time (late 80s/early 90s) when the Shuttle program was upgrading hardware, so it's conceivable that the countdown clock held at T-9 but different procedures were executed. (But that's why I was wondering about upgrades related to either the original IMUs or the HAINS units and whether that changed/extended the unplanned hold capability.)
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#2531
by
psloss
on 17 Feb, 2012 01:07
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After the crew-on-back limits were more strictly enforced, there were a couple of cases in the late 80s and early/mid 90s with long-ish holds that ran close to 90 minutes or a bit longer. The last long one I can think of was with STS-64 in September, 1994.
The Space Shuttle Missions Summary Book notes another long weather hold I'd forgotten about -- the STS-73 launch attempt on 15 October 1995. It did get a little better than these two shots, but not good enough when the crew-on-back time ran out.
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#2532
by
Zoe
on 17 Feb, 2012 01:26
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My point was that whatever caused the cutoff inside the "go for auto sequence start" GLS milestone might preclude use of any hypothetical capability to recycle. So in the case of the December, 1985, attempt -- or the STS-51 attempt in July, 1993 -- even if there had been an unlimited launch window, the failure that caused the cutoff was also going to require a lengthy R&R (multiple days).
So effectively even though second launch attempt after cutoff below T-31 seconds was allowed in S0007, it's very unlikely it would ever have been used due to the reasons you said above. I can't find any reference to the rule mkirk talked about but if there was a rule then this would not have been in S0007?
Possibly the same thing as one of the drivers from the previous day's recycle -- the IMUs needed to be realigned. Forgot to add to earlier post; this has been linked before, but you can see some references to this in the Space Shuttle Missions Summary book:
http://www.jsc.nasa.gov/history/reference/TM-2011-216142.pdf
Interestingly one source I have said that the countdown on January 6 was recycled first to T-9 minutes and then back to T-20 minutes. If the LOX drainback issue resulted in the recycle to T-9 then maybe it was IMU alignement issues that required a recycle back to T-20 minutes. However I am not convinced about this as I believe GLS cutoff was called at T-31 seconds which would have required a recycle all the way to T-20 minutes.
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#2533
by
mkirk
on 17 Feb, 2012 03:33
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My point was that whatever caused the cutoff inside the "go for auto sequence start" GLS milestone might preclude use of any hypothetical capability to recycle. So in the case of the December, 1985, attempt -- or the STS-51 attempt in July, 1993 -- even if there had been an unlimited launch window, the failure that caused the cutoff was also going to require a lengthy R&R (multiple days).
So effectively even though second launch attempt after cutoff below T-31 seconds was allowed in S0007, it's very unlikely it would ever have been used due to the reasons you said above. I can't find any reference to the rule mkirk talked about but if there was a rule then this would not have been in S0007?
Possibly the same thing as one of the drivers from the previous day's recycle -- the IMUs needed to be realigned. Forgot to add to earlier post; this has been linked before, but you can see some references to this in the Space Shuttle Missions Summary book:
http://www.jsc.nasa.gov/history/reference/TM-2011-216142.pdf
Interestingly one source I have said that the countdown on January 6 was recycled first to T-9 minutes and then back to T-20 minutes. If the LOX drainback issue resulted in the recycle to T-9 then maybe it was IMU alignement issues that required a recycle back to T-20 minutes. However I am not convinced about this as I believe GLS cutoff was called at T-31 seconds which would have required a recycle all the way to T-20 minutes.
Sorry if my answer back then confused you! Time to back step from that a little bit….Honestly I don’t think a “cut-off” after T-31 in itself meant that a second attempt was out of the question. I do know that was the assumption on my part – and most of the people I worked with – during the Space Station era where the short launch windows ruled the day. I do remember beating the subject to death in the MCC back rooms with my co-workers during the STS-93 launch attempts (which wasn't a station flight) and that likely accounts for my “know it all attitude” in my previous answer.
Anyway, the other stuff I mentioned would certainly come into play after T-31 seconds and apart from the issue that stopped the countdown in the first place, a second launch attempt would be dependent on where the “cut-off” occurred. Were the HPUs started? I think another HPU start was technically permissible, but if I recall correctly there was only enough fuel for 165 seconds of total run time, so you would have to ensure that the fuel quantity redline was satisfied on the second run thru. Did the sound suppression and firex systems flow? Did the ROFIs fire? I’m almost positive that you had only one shot with the ROFIs, but if there is a GSE expert out there hopefully they will confirm or rebut that.
The LCC (Launch Commit Criteria) had 3 or 4 sections that discussed General rules, crew constraints, RSLS constraints, sequencing, safing, etc that may provide you with more info. In earlier versions there was even a section titled Hold & Cut-off Guidelines, but it was ultimately deleted and absorbed by other sections. I don’t remember what it said and since I am traveling I don’t have access to my shuttle documents right now. Even if I was back at my office I’m not sure I could stand to look at my shuttle stuff now – too depressing given the recent retirement.
As stated by others in response to your question, all of those factors were pretty much irrelevant for Space Station launches since you simply could not recycle and get back into the launch posture in time – thus if a “cut-off” occurred you were done for the day and the only reasonable course of action was to safe the vehicle and then head out the south gate to “Shuttle’s” for some hot wings and a select cold beverage.
Mark Kirkman
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#2534
by
psloss
on 18 Feb, 2012 15:13
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So effectively even though second launch attempt after cutoff below T-31 seconds was allowed in S0007, it's very unlikely it would ever have been used due to the reasons you said above. I can't find any reference to the rule mkirk talked about but if there was a rule then this would not have been in S0007?
No, sorry if I'm confusing things, too, but if you're referring to the second 61-C launch attempt (6 January 1986), that did not proceed through the "auto sequence start" milestone:
http://forum.nasaspaceflight.com/index.php?topic=10600.msg315235#msg315235The link in that post (to an archived posting of the 61-C mission report) has a detailed explanation of what happened.
Interestingly one source I have said that the countdown on January 6 was recycled first to T-9 minutes and then back to T-20 minutes.
This may have been standard for re-configuring the vehicle at the time for a recycle inside the late GLS milestones.
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#2535
by
Zoe
on 19 Feb, 2012 04:34
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No, sorry if I'm confusing things, too, but if you're referring to the second 61-C launch attempt (6 January 1986), that did not proceed through the "auto sequence start" milestone:
http://forum.nasaspaceflight.com/index.php?topic=10600.msg315235#msg315235
The link in that post (to an archived posting of the 61-C mission report) has a detailed explanation of what happened.
No, the confusion was over why S0007 contained procedures for another attempt on the same day if the countdown was below T-31 seconds when I thought that once you went below T-31 seconds that was it for the day but it has now been clarified that this did not automatically result in a scrub. As you said above though, on the December launch attempt of STS-61-C this was never going to be an option due to the time needed to resolve the issue.
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#2536
by
Jorge
on 19 Feb, 2012 05:43
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If a rendezvous was required, then the window was (much) shorter (from a little over an hour down to 5 minutes). So there was no time to recycle to 20 minutes.
Depended on the inclination of the rendezvous target. For Mir and ISS, you're right, it was 5 minutes and there was no chance for recycle. For lower inclination targets like HST, the window was longer, around fifty minutes IIRC. Still iffy for a recycle, so your basic point stands.
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#2537
by
Jorge
on 19 Feb, 2012 05:58
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Quote from: sivodave on 02/05/2012 07:53 PMHi all.
Question about the star trackers. I know that two different types were used, namely the solid state start tracker and the image dissector tube star tracker.
I'd like to know the advantage of the one type respect the other. Which
one was better? could an orbiter have both types at the same time?
Thanks very much
Regards
Davide
Yes, the two types could be used interchangeably and mixed on the same flight. I suspect the older ones were simply becoming unsupportable due to their age.
Thanks DMeader. Just another question: in what sense the only ones became unsupportable? Unsupportable from a software point of view or maintenance? If they were unsupportable, why they flew with both type together?
Thanks very much
Regards
Davide
The software didn't "know" which type of star tracker was being flown. There were a lot of pieces of equipment we had to know which type was being used, but not the star trackers. For the other equipment, the selection was usually done with an I-Load (or TMBU update), so it wasn't that difficult as long as there wasn't a late change.
Usually aging equipment that needs to be replaced was due to the inability to find spare parts. I suspect that the image dissector tube was not a very common part and is probably no longer made.
Quite true, though the program had a few spares and we were able to support IDT through the end of the program. Which was a good thing since the IDTs tracked bright rendezvous targets like ISS better than the solid state trackers. We actually reverted the -Z tracker on one orbiter (OV-104) back to IDT for this very reason. At the end of the program, all three orbiters had IDTs in the -Z slot (since that star tracker was prime during rendezvous ops) and solid state trackers in the -Y slot (for tracking dim stars while docked to ISS).
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#2538
by
alk3997
on 23 Feb, 2012 15:07
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Quite true, though the program had a few spares and we were able to support IDT through the end of the program. Which was a good thing since the IDTs tracked bright rendezvous targets like ISS better than the solid state trackers. We actually reverted the -Z tracker on one orbiter (OV-104) back to IDT for this very reason. At the end of the program, all three orbiters had IDTs in the -Z slot (since that star tracker was prime during rendezvous ops) and solid state trackers in the -Y slot (for tracking dim stars while docked to ISS).
Jorge, thanks! I did not know that. I'm hoping it was because this was all transparent to us and not because my memory is faulty :-)
Was it the streaking line effect effect that caused the solid state trackers to be worse for bright objects? I've seen enough CCD and CMOS sensors generate a line above and below a really bright object with a dark background.
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#2539
by
sivodave
on 25 Feb, 2012 22:46
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Hi all,
I'm reading on the CAIB Volume 1 at page 51, that after ET-93 the foam types changed from the NCFI 24-124, NCFI 24-57 and BX-250, but then nothing else is added.
Does anybody of you know which are then new types of foam used after ET-93?
Thanks very much
Davide