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#160 by meekGee on 22 May, 2022 15:39
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Interesting, thanks....
Also the cooling loop. That would have been serious if people were on board, right?
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36:32 in the post-docking media briefing:Quote from: Boeing's Mark NappiWe monitored the temperature inside the crew module and had some good readings on that. It's interesting because the lack of the crew may have contributed to the gulden* problem that Steve talked about, because with nobody there to generate a little bit more heat the system just got a little bit colder.
* The Freon-like coolant used in the Starliner's cooling loops. Sounds like "gulden" (but it is not a spicy brown mustard!). How should it really be spelled?
Earlier in the briefing they said that one possible cause was some moisture which may have been in the coolant which, due to the lower than normal temperature, may have come out of solution and frozen, causing the high pump pressures which alerted them to the problem. They alleviated it by periodically bypassing a radiator in order to raise the coolant loop temperature. -
#161 by DaveS on 22 May, 2022 16:47
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Sound like Hi-load Flash Evaporator System (FES) duct ice-ups that tended to happen on several shuttle launches. It also happened sometimes on-orbit due to left-over water from its use on ascent. It was never considered a hazardous condition as they had reliable procedures to bake it out in the sun if it came to that and the fact there was a second duct that they could use....
Also the cooling loop. That would have been serious if people were on board, right?
...
36:32 in the post-docking media briefing:Quote from: Boeing's Mark NappiWe monitored the temperature inside the crew module and had some good readings on that. It's interesting because the lack of the crew may have contributed to the gulden* problem that Steve talked about, because with nobody there to generate a little bit more heat the system just got a little bit colder.
* The Freon-like coolant used in the Starliner's cooling loops. Sounds like "gulden" (but it is not a spicy brown mustard!). How should it really be spelled?
Earlier in the briefing they said that one possible cause was some moisture which may have been in the coolant which, due to the lower than normal temperature, may have come out of solution and frozen, causing the high pump pressures which alerted them to the problem. They alleviated it by periodically bypassing a radiator in order to raise the coolant loop temperature. -
#162 by nhcowboy on 22 May, 2022 17:17
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I just have one question re. the thruster failure/loss/shutdown/anomaly (or whatever the non-inflammatory, politically correct term is) - aren't all of the thrusters used in a launch abort? And if so, does the loss of a thruster on one side necessitate shutting down one on the opposite side to avoid an asymmetric thrust situation? If that's the case, the loss of 2 thrusters in the same doghouse would really mean the loss of a total of 4. That sounds to me like a crew safety issue.
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#163 by Widford on 22 May, 2022 17:23
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I just have one question re. the thruster failure/loss/shutdown/anomaly (or whatever the non-inflammatory, politically correct term is) - aren't all of the thrusters used in a launch abort? And if so, does the loss of a thruster on one side necessitate shutting down one on the opposite side to avoid an asymmetric thrust situation? If that's the case, the loss of 2 thrusters in the same doghouse would really mean the loss of a total of 4. That sounds to me like a crew safety issue.
I believe they use different engines in an abort. -
#164 by Kaputnik on 22 May, 2022 17:23
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I just have one question re. the thruster failure/loss/shutdown/anomaly (or whatever the non-inflammatory, politically correct term is) - aren't all of the thrusters used in a launch abort? And if so, does the loss of a thruster on one side necessitate shutting down one on the opposite side to avoid an asymmetric thrust situation? If that's the case, the loss of 2 thrusters in the same doghouse would really mean the loss of a total of 4. That sounds to me like a crew safety issue.
The launch abort thrusters are a separate system, it was the orbital manoeuvring ones that had an anomaly. -
#165 by mn on 22 May, 2022 18:17
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Something in the thrusters did fail in some way or the backups wouldn't of been needed. Why? No clue. What does it mean? No clue. Is it a big deal? Probably not as NASA allowed docking.
.....
NASA allowed docking means they determined that the issue is not a threat to ISS, that doesn't tell us anything on what NASA thinks of the issue as it relates to crew safety. -
#166 by arachnitect on 22 May, 2022 18:18
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I just have one question re. the thruster failure/loss/shutdown/anomaly (or whatever the non-inflammatory, politically correct term is) - aren't all of the thrusters used in a launch abort? And if so, does the loss of a thruster on one side necessitate shutting down one on the opposite side to avoid an asymmetric thrust situation? If that's the case, the loss of 2 thrusters in the same doghouse would really mean the loss of a total of 4. That sounds to me like a crew safety issue.
The launch abort thrusters are a separate system, it was the orbital manoeuvring ones that had an anomaly.
OMAC thrusters are used in aborts. -
#167 by Kaputnik on 22 May, 2022 18:57
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I just have one question re. the thruster failure/loss/shutdown/anomaly (or whatever the non-inflammatory, politically correct term is) - aren't all of the thrusters used in a launch abort? And if so, does the loss of a thruster on one side necessitate shutting down one on the opposite side to avoid an asymmetric thrust situation? If that's the case, the loss of 2 thrusters in the same doghouse would really mean the loss of a total of 4. That sounds to me like a crew safety issue.
The launch abort thrusters are a separate system, it was the orbital manoeuvring ones that had an anomaly.
OMAC thrusters are used in aborts.
I stand corrected. Whilst not being the actual LAS propulsion, OMAC provides attitude control during an abort burn. -
#168 by Chris Bergin on 22 May, 2022 19:12
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Note to all: If you can't be civil, you get your post deleted. Up to you if you think it's worth spending 10 minutes on a post that's going to get deleted just to wave your manhood around for the time it takes for someone to report to it mod. Think on, it's really embarrassing.
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#169 by AnnK on 22 May, 2022 21:44
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How is this going to affect the Starliner test program? I was hoping for better performance was the Starliner.
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#170 by StormtrooperJoe on 22 May, 2022 22:02
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How is this going to affect the Starliner test program? I was hoping for better performance was the Starliner.
I imagine not a lot and that they will still move forward to the crewed test. While 2 thruster failures is not exactly a great look for Boeing, ultimately there is a lot of redundancy here for a reason, NASA just needs to needs to stay on Boeing's butt and insure these issues are being worked on. Of course, this assumes the rest of the flight goes well. -
#171 by omelet1978 on 23 May, 2022 03:15
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So how much redundancy is built into Starliner with these thrusters.
So they have 4 groups of 3 thrusters on the top, bottom, let and right. If the third thruster had failed could Starliner have shut off the thrusters on the opposite side and still continued the mission. Basically if the thrusters on the left and right were not in use would the thrusters on the top and bottom be enough to do the job? -
#172 by AstroWare on 23 May, 2022 05:47
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So how much redundancy is built into Starliner with these thrusters.
So they have 4 groups of 3 thrusters on the top, bottom, let and right. If the third thruster had failed could Starliner have shut off the thrusters on the opposite side and still continued the mission. Basically if the thrusters on the left and right were not in use would the thrusters on the top and bottom be enough to do the job?
if you consider each axial OMAC a thrust balanced pair (so 6 pairs), and you need (2) pairs to do a nominal burn, the logical answer is you can have 4 thrusters fail and still have 2 pair remaining to do the burn.
...
I have no inside knowledge of the control logic, but I was researching this the other day when it happened.
1. During the orbital insertion burn, the webcast reported during the maneuver "Four good orbital maneuvering thrusters" which indicates that a nominal insertion uses (4) OMAC thrusters.
2. There are 20 OMAC thrusters. (12) aft facing, (4) forward facing, and (4) arranged for Roll*.
For lack of a published thruster mapping, I've named the axial (+) thrusters:
(Aft looking forward, cw)
Pod 0
#1 Axial +
#2 Axial +
#3 Axial +
Pod 90
#4 Axial +
#5 Axial +
#6 Axial +
Pod 180
#7 Axial +
#8 Axial +
#9 Axial +
Pod 270
#10 Axial +
#11 Axial +
#12 Axial +
From the webcast, it doesn't switch to the ACS telemetry view until one thruster has already turned off. Then it cuts away until the end of the burn, and the system has a new config. So some of this is observed and some has to be an educated guess.
Config 1: 3,6,9,12 (12 shutdown early?)
Config 2: 3,5,9,11 (11 shutdown early)
Config 3: 1,3,7,9
Config 2 shows 0 and 180 pods using outboard OMAC thrusters. And 90 and 270 pods using center OMAC. I'm guessing that config 1 used 6 and 12 since that would be the same outboard engine pair that would match the 0 and 180 pods. Config 3 shows two OMACs burning from each of the 0 and 180 pods respectively. The software logic may be smart enough to disable the whole pod if two failures occur (as happened) and to use a balanced arrangement using only other pods.
If that logic was in place, the software my not have used the third thruster in that pod even if it would have operated normally. Or would only use it as a last resort.
The software also shouldn't have to use purely balanced arrangements, but seems to do so.
So IF valves 12 and 11 failed, and if pod 270 had been removed from the available thrusters (thruster 10 collateral damage). Then config 3 (observed on the webcast) makes sense to me.
So what happens if one of those failed?
Well, if any of the 4 failed off (say #1), then the 2/8 pair would have replaced the failed thruster and it's opposed pair. (2,3,8,9)
After that, you either have to go back and trust thruster 10, or burn fewer longer, or burn asymmetrical.
So you can lose (4) OMACs and still perform a balanced burn. (But one of those may have been disabled by SW)
( Or flip the ship 180 and use the four axial- thrusters!!! )
I was worried about this issue at first, but the reduculous amount of redundancy is comforting. Consider this:
Dragon has 16 non-abort thrusters
Starliner has 60
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Disclaimer: this is just my observations!! Also didn't mean for the post to get this long... Lol
*They could be used for pitch/yaw as well but easiest to think of them as roll.
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#173 by satcomopsuk on 23 May, 2022 07:50
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Hi
Been hampered by cloudy skies here so unable to see the Starliner approach , however last night the cloud thinned enough to get a quick look at OFT-2 docked to Harmony.
Hopefully others will get a clearer shot over the next few nights.
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#174 by laszlo on 23 May, 2022 11:52
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So how much redundancy is built into Starliner with these thrusters.
So they have 4 groups of 3 thrusters on the top, bottom, let and right. If the third thruster had failed could Starliner have shut off the thrusters on the opposite side and still continued the mission. Basically if the thrusters on the left and right were not in use would the thrusters on the top and bottom be enough to do the job?
if you consider each axial OMAC a thrust balanced pair (so 6 pairs), and you need (2) pairs to do a nominal burn, the logical answer is you can have 4 thrusters fail and still have 2 pair remaining to do the burn.
... [long explanation deleted, look at it in the original post]
Thruster burns do not have to be done in balanced pairs. That's the theoretically ideal situation because it results in no unwanted coupled torques but even when all thrusters are functioning perfectly it will never happen. The reason for that is that it requires all thrust axes to be perfectly lined up with the vehicle's center of gravity. Even if you could make that happen, the instant you fired the thrusters and consumed fuel that condition would no longer hold. Because of this, all spacecraft must be able to detect unwanted torques and cancel them out by firing other thrusters, even if the original firing was done with a perfectly functioning balanced pair.
Since a spacecraft has that capability anyway, it can now handle unbalanced thrusters. Unbalanced thrusters are actually a normal part of spacecraft operations, not just something that happens during a failure. The selected thrusters are varied to level wear, balance fuel consumption between multiple fuel systems, to prevent jet impingement in some situations, to prevent burning up someone performing an EVA, etc.
So there's plenty of options beyond just physical redundancy, especially if it's a soft error that can be reset. One neat trick that AstroWare alluded to is to simply redefine the spacecraft axes so that pitch becomes roll or yaw. There's a really thorough discussion of all these issues and techniques in Frank O'Brien's excellent book The Apollo Guidance Computer: Architecture and Operation from Springer Praxis Books. The section on the workings of the DAP (Digital Auto Pilot) gives some really good context to the issues that were seen on the Starliner.
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#175 by laszlo on 23 May, 2022 11:56
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Hi
Been hampered by cloudy skies here so unable to see the Starliner approach , however last night the cloud thinned enough to get a quick look at OFT-2 docked to Harmony.
Hopefully others will get a clearer shot over the next few nights.
It's cruel not to give us information on how you took this image. -
#176 by greybeardengineer on 23 May, 2022 12:16
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Also the cooling loop. That would have been serious if people were on board, right?
...
36:32 in the post-docking media briefing:Quote from: Boeing's Mark NappiWe monitored the temperature inside the crew module and had some good readings on that. It's interesting because the lack of the crew may have contributed to the gulden* problem that Steve talked about, because with nobody there to generate a little bit more heat the system just got a little bit colder.
* The Freon-like coolant used in the Starliner's cooling loops. Sounds like "gulden" (but it is not a spicy brown mustard!). How should it really be spelled?
Earlier in the briefing they said that one possible cause was some moisture which may have been in the coolant which, due to the lower than normal temperature, may have come out of solution and frozen, causing the high pump pressures which alerted them to the problem. They alleviated it by periodically bypassing a radiator in order to raise the coolant loop temperature.
The "gulden" could be a pronounced acronym. Seems to be common practice (like "lee-ho" - LiOH, lithium hydroxide). The G or GL in that acronym could be glycol. It is definitely *not* GLDN as in glycol dinitrate.
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#177 by AstroWare on 23 May, 2022 12:38
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So how much redundancy is built into Starliner with these thrusters.
So they have 4 groups of 3 thrusters on the top, bottom, let and right. If the third thruster had failed could Starliner have shut off the thrusters on the opposite side and still continued the mission. Basically if the thrusters on the left and right were not in use would the thrusters on the top and bottom be enough to do the job?
if you consider each axial OMAC a thrust balanced pair (so 6 pairs), and you need (2) pairs to do a nominal burn, the logical answer is you can have 4 thrusters fail and still have 2 pair remaining to do the burn.
... [long explanation deleted, look at it in the original post]
Thruster burns do not have to be done in balanced pairs. That's the theoretically ideal situation because it results in no unwanted coupled torques but even when all thrusters are functioning perfectly it will never happen. The reason for that is that it requires all thrust axes to be perfectly lined up with the vehicle's center of gravity. Even if you could make that happen, the instant you fired the thrusters and consumed fuel that condition would no longer hold. Because of this, all spacecraft must be able to detect unwanted torques and cancel them out by firing other thrusters, even if the original firing was done with a perfectly functioning balanced pair.
Since a spacecraft has that capability anyway, it can now handle unbalanced thrusters. Unbalanced thrusters are actually a normal part of spacecraft operations, not just something that happens during a failure. The selected thrusters are varied to level wear, balance fuel consumption between multiple fuel systems, to prevent jet impingement in some situations, to prevent burning up someone performing an EVA, etc.
So there's plenty of options beyond just physical redundancy, especially if it's a soft error that can be reset. One neat trick that AstroWare alluded to is to simply redefine the spacecraft axes so that pitch becomes roll or yaw. There's a really thorough discussion of all these issues and techniques in Frank O'Brien's excellent book The Apollo Guidance Computer: Architecture and Operation from Springer Praxis Books. The section on the workings of the DAP (Digital Auto Pilot) gives some really good context to the issues that were seen on the Starliner.
Agree 100%. It was a first order simplification for sure. Even with balanced pairs, look at how many of the smaller thrusters we're firing to keep the spacecraft pointed.
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#178 by Jim on 23 May, 2022 22:46
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So how much redundancy is built into Starliner with these thrusters.
So they have 4 groups of 3 thrusters on the top, bottom, let and right. If the third thruster had failed could Starliner have shut off the thrusters on the opposite side and still continued the mission. Basically if the thrusters on the left and right were not in use would the thrusters on the top and bottom be enough to do the job?
Two thrusters firing for 62 seconds is the same as three firing for 41sec and 4 thrusters firing for 31 sec.
It is more than triple redundancy (3 thrusters in each doghouse.) -
#179 by yg1968 on 24 May, 2022 00:14
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So how much redundancy is built into Starliner with these thrusters.
So they have 4 groups of 3 thrusters on the top, bottom, let and right. If the third thruster had failed could Starliner have shut off the thrusters on the opposite side and still continued the mission. Basically if the thrusters on the left and right were not in use would the thrusters on the top and bottom be enough to do the job?
Two thrusters firing for 62 seconds is the same as three firing for 41sec and 4 thrusters firing for 31 sec.
It is more than triple redundancy (3 thrusters in each doghouse.)
Yes, Steve Stich mentioned in the press conference that even if the three thrusters in the same doghouse had failed, they still would have been OK.
