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#640
by
kdhilliard
on 22 Jun, 2024 15:30
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Do we know why CFT-1 is limited to 45 days? ...
No.
The 45-day figure came, without rationale, during the Post-Docking news conference in response to a question at
1:08:06.
[1:08:06]
Joy Roulette, Reuters:
Hi. Thank you for taking my followup question. I know Boeing and NASA are in the midst of a battery redesign study connected to Starliner's batteries. I was wondering if the teams are going to take a look at that while Starliner is on the space station at all or run any tests related to the batteries.
And also, how long can Starliner on this Mission stay docked to the International Space Station. Thank you.
[1:08:35]
Steve Stich, manager, NASA’s Commercial Crew Program: I can start and see if Mark has anything to add. Yes, we do have a battery upgrade that we're studying right now. Obviously, we're collecting data from this flight relative to that battery upgrade. So far the batteries have been performing well.
And if I remember right, the dock duration can go up to 45 days.
[Murmurs of assent from other panel members.]
No indication there if the 45 days is at all related to the battery study.
It's quite possible that the 45 day certification is a conservative one which could easily be extended with some sharpened pencils, that it was considered sufficient for this mission's planning, and that the full 210-day certification will come only after data from this test flight is analyzed.
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#641
by
DanClemmensen
on 22 Jun, 2024 15:47
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Do we know why CFT-1 is limited to 45 days? ...
No.
The 45-day figure came, without rationale, during the Post-Docking news conference in response to a question at 1:08:06.
[1:08:06]
Joy Roulette, Reuters:
Hi. Thank you for taking my followup question. I know Boeing and NASA are in the midst of a battery redesign study connected to Starliner's batteries. I was wondering if the teams are going to take a look at that while Starliner is on the space station at all or run any tests related to the batteries.
And also, how long can Starliner on this Mission stay docked to the International Space Station. Thank you.
[1:08:35]
Steve Stich, manager, NASA’s Commercial Crew Program: I can start and see if Mark has anything to add. Yes, we do have a battery upgrade that we're studying right now. Obviously, we're collecting data from this flight relative to that battery upgrade. So far the batteries have been performing well.
And if I remember right, the dock duration can go up to 45 days.
[Murmurs of assent from other panel members.]
No indication there if the 45 days is at all related to the battery study.
It's quite possible that the 45 day certification is a conservative one which could easily be extended with some sharpened pencils, that it was considered sufficient for this mission's planning, and that the full 210-day certification will come only after data from this test flight is analyzed.
That did not sound like the result of an actual engineering analysis. It sounded to me like an arbitrary but conservative number that was comfortably larger than Steve thought was the longest reasonable CFT, and at the time of that news conference, that was a reasonable response.
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#642
by
meekGee
on 22 Jun, 2024 16:12
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Do we know why CFT-1 is limited to 45 days? ...
No.
The 45-day figure came, without rationale, during the Post-Docking news conference in response to a question at 1:08:06.
[1:08:06]
Joy Roulette, Reuters:
Hi. Thank you for taking my followup question. I know Boeing and NASA are in the midst of a battery redesign study connected to Starliner's batteries. I was wondering if the teams are going to take a look at that while Starliner is on the space station at all or run any tests related to the batteries.
And also, how long can Starliner on this Mission stay docked to the International Space Station. Thank you.
[1:08:35]
Steve Stich, manager, NASA’s Commercial Crew Program: I can start and see if Mark has anything to add. Yes, we do have a battery upgrade that we're studying right now. Obviously, we're collecting data from this flight relative to that battery upgrade. So far the batteries have been performing well.
And if I remember right, the dock duration can go up to 45 days.
[Murmurs of assent from other panel members.]
No indication there if the 45 days is at all related to the battery study.
It's quite possible that the 45 day certification is a conservative one which could easily be extended with some sharpened pencils, that it was considered sufficient for this mission's planning, and that the full 210-day certification will come only after data from this test flight is analyzed.
That did not sound like the result of an actual engineering analysis. It sounded to me like an arbitrary but conservative number that was comfortably larger than Steve thought was the longest reasonable CFT, and at the time of that news conference, that was a reasonable response.
He said he "recalled" it. He didn't improvise on the spot, he was referencing a number that was arrived at previously, and other people remembered that too.
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#643
by
SoftwareDude
on 22 Jun, 2024 18:27
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#644
by
SoftwareDude
on 22 Jun, 2024 21:05
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#645
by
Vettedrmr
on 22 Jun, 2024 21:25
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Is it impossible to test the ground thrusters to understand overheating? Why does Starliner have to be in space to test for conditions that cause overheating?
At this point, it's not finding the root cause in the origination of the problem; it's understanding the problem well enough to convince yourself that you can do something to mitigate the demonstrated risk of thruster failure after undocking from ISS. If you can't do that, then tougher solutions are required.
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#646
by
DanClemmensen
on 23 Jun, 2024 00:39
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Is it impossible to test the ground thrusters to understand overheating? Why does Starliner have to be in space to test for conditions that cause overheating?
At this point, it's not finding the root cause in the origination of the problem; it's understanding the problem well enough to convince yourself that you can do something to mitigate the demonstrated risk of thruster failure after undocking from ISS. If you can't do that, then tougher solutions are required.
Two separate sets of goals:
1)Determine the safest way to return Sunni and Butch to Earth. This requires evaluating the problems with this specific Starliner and its current condition.
2)Gather enough data to determine whether or not the CFT can result in certifying Starliner for later operational missions.
These goals mostly overlap, but not completely.
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#647
by
SoftwareDude
on 23 Jun, 2024 00:58
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Is it impossible to test the ground thrusters to understand overheating? Why does Starliner have to be in space to test for conditions that cause overheating?
At this point, it's not finding the root cause in the origination of the problem; it's understanding the problem well enough to convince yourself that you can do something to mitigate the demonstrated risk of thruster failure after undocking from ISS. If you can't do that, then tougher solutions are required.
Two separate sets of goals:
1)Determine the safest way to return Sunni and Butch to Earth. This requires evaluating the problems with this specific Starliner and its current condition.
2)Gather enough data to determine whether or not the CFT can result in certifying Starliner for later operational missions.
These goals mostly overlap, but not completely.
I wondered if testing should have caught a heating problem earlier. Wouldn't thrusters be tested on a test stand with the same rate of sustained firing as the maximum needed?
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#648
by
Vettedrmr
on 23 Jun, 2024 01:02
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I wondered if testing should have caught a heating problem earlier. Wouldn't thrusters be tested on a test stand with the same rate of sustained firing as the maximum needed?
In a vacuum chamber? In clusters of 4? For time periods similar to a docking sequence? With black body radiation factors implemented?
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#649
by
SoftwareDude
on 23 Jun, 2024 01:06
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I wondered if testing should have caught a heating problem earlier. Wouldn't thrusters be tested on a test stand with the same rate of sustained firing as the maximum needed?
In a vacuum chamber? In clusters of 4? For time periods similar to a docking sequence? With black body radiation factors implemented?
I take it that you are saying testing the heating has to be in a vacuum.
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#650
by
Vettedrmr
on 23 Jun, 2024 01:41
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I wondered if testing should have caught a heating problem earlier. Wouldn't thrusters be tested on a test stand with the same rate of sustained firing as the maximum needed?
In a vacuum chamber? In clusters of 4? For time periods similar to a docking sequence? With black body radiation factors implemented?
I take it that you are saying testing the heating has to be in a vacuum.
Don't get me wrong; what Boeing has allowed to happen is inexcusable. BUT, re-creating an environment simulating space is a lot harder than just a test stand.
Here's a current example. SpaceX is going to have to demonstrate the ability to re-start a Raptor on their 2nd stage (Starship) before the FAA will grant a launch license to SpaceX for an orbital flight. Recognize that this vehicle has just been under power for 8 minutes or so. But now it's in microgravity, in a vacuum, etc. Those environmental changes are enough that the FAA doesn't just assume that a system that just ran will be able to run again in that environment. They're requiring that engine to restart before they'll allow 100 tons of stainless steel to be placed into orbit.
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#651
by
SoftwareDude
on 23 Jun, 2024 01:51
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I wondered if testing should have caught a heating problem earlier. Wouldn't thrusters be tested on a test stand with the same rate of sustained firing as the maximum needed?
In a vacuum chamber? In clusters of 4? For time periods similar to a docking sequence? With black body radiation factors implemented?
This brings up the other question: Are these thrusters different from those on the OFT-2? Was there a problem with them then? It seems like OFT-2 would have seen this problem.
I take it that you are saying testing the heating has to be in a vacuum.
Don't get me wrong; what Boeing has allowed to happen is inexcusable. BUT, re-creating an environment simulating space is a lot harder than just a test stand.
Here's a current example. SpaceX is going to have to demonstrate the ability to re-start a Raptor on their 2nd stage (Starship) before the FAA will grant a launch license to SpaceX for an orbital flight. Recognize that this vehicle has just been under power for 8 minutes or so. But now it's in microgravity, in a vacuum, etc. Those environmental changes are enough that the FAA doesn't just assume that a system that just ran will be able to run again in that environment. They're requiring that engine to restart before they'll allow 100 tons of stainless steel to be placed into orbit.
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#652
by
DMeader
on 23 Jun, 2024 19:09
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None of that has anything to do with the current situation.
Gases become warmer when they are compressed. When they expand they cause cooling, like when your canned-air duster gets cold when you use it. Also, the thrusters are bi-propellant, not mono-propellant where the prop is decomposed by a catalyst.
We really should refrain from such uninformed speculation.
(edit) referring to deleted post, but the conclusion is still valid.
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#653
by
Mr. Scott
on 23 Jun, 2024 20:13
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None of that has anything to do with the current situation.
Gases become warmer when they are compressed. When they expand they cause cooling, like when your canned-air duster gets cold when you use it. Also, the thrusters are bi-propellant, not mono-propellant where the prop is decomposed by a catalyst.
We really should refrain from such uninformed speculation.
SMH
https://en.m.wikipedia.org/wiki/Joule%E2%80%93Thomson_effect#:~:text=Helium%20and%20hydrogen%20are%20two,enthalpy%20at%20typical%20room%20temperatures.
Helium and hydrogen are two gases whose Joule–Thomson inversion temperatures at a pressure of one atmosphere are very low (e.g., about 40 K, −233 °C for helium). Thus, helium and hydrogen warm when expanded at constant enthalpy at typical room temperatures.
[deleted]
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#654
by
Vettedrmr
on 23 Jun, 2024 20:23
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This brings up the other question: Are these thrusters different from those on the OFT-2? Was there a problem with them then? It seems like OFT-2 would have seen this problem.
I think this was your question in your latest update. IDK if they're the same or not; I *assume* they're the same, since I've not read anything about them being different. So you question is a good one: why are these failing so much? And yes, I know they brought 4 of them back on line, but that's just using software to work around a hardware problem.
Whatever it is, IMO Boeing has their work cut out for convincing NASA to bring their astronauts on Starliner.
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#655
by
meekGee
on 23 Jun, 2024 20:49
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This brings up the other question: Are these thrusters different from those on the OFT-2? Was there a problem with them then? It seems like OFT-2 would have seen this problem.
I think this was your question in your latest update. IDK if they're the same or not; I *assume* they're the same, since I've not read anything about them being different. So you question is a good one: why are these failing so much? And yes, I know they brought 4 of them back on line, but that's just using software to work around a hardware problem.
Whatever it is, IMO Boeing has their work cut out for convincing NASA to bring their astronauts on Starliner.
There's three separate issues, right?
The propellant valve that's been acting up, and that's the same valve design as OFT-2 which has a defect in it, but that's been attributed to environmental moisture, and the fix was a work around (weather covers) which means if the cause was misdiagnosed, we're getting a little glitch in the matrix. (Or else there are two independent defects in the valve)
Then there's thruster overheating, which should have shown up on OFT-2 but did not.
And then the Helium leak. Why didn't it show up before? That was kind of the reason it was believed to be a one-off, but now that it happened 5 times, again, what are the odds? If this Starliner is unintentionally different from the OFT-2 Starliner in a systemic way, that's a worse problem (from a QC PoV) than if only one leak developed. What if #6 develops during undocking?
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#656
by
Vettedrmr
on 23 Jun, 2024 21:03
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I forgot about the prop valve. But I thought that had a workaround that they were comfortable with. But yeah, that has to be understood as well.
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#657
by
SoftwareDude
on 23 Jun, 2024 21:51
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This brings up the other question: Are these thrusters different from those on the OFT-2? Was there a problem with them then? It seems like OFT-2 would have seen this problem.
I think this was your question in your latest update. IDK if they're the same or not; I *assume* they're the same, since I've not read anything about them being different. So you question is a good one: why are these failing so much? And yes, I know they brought 4 of them back on line, but that's just using software to work around a hardware problem.
Whatever it is, IMO Boeing has their work cut out for convincing NASA to bring their astronauts on Starliner.
There's three separate issues, right?
The propellant valve that's been acting up, and that's the same valve design as OFT-2 which has a defect in it, but that's been attributed to environmental moisture, and the fix was a work around (weather covers) which means if the cause was misdiagnosed, we're getting a little glitch in the matrix. (Or else there are two independent defects in the valve)
Then there's thruster overheating, which should have shown up on OFT-2 but did not.
And then the Helium leak. Why didn't it show up before? That was kind of the reason it was believed to be a one-off, but now that it happened 5 times, again, what are the odds? If this Starliner is unintentionally different from the OFT-2 Starliner in a systemic way, that's a worse problem (from a QC PoV) than if only one leak developed. What if #6 develops during undocking?
There were other things, a seemingly small thing when something happened to the power in the suits as the spacecraft switched to internal power, and they had to switch something on and off again. Then there was also a power glitch, a loss of power to some system(s) after the spacecraft docked. I remember a question from the ground, "What were you doing when that happened?"
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#658
by
zoey
on 23 Jun, 2024 23:05
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There were other things, a seemingly small thing when something happened to the power in the suits as the spacecraft switched to internal power, and they had to switch something on and off again. Then there was also a power glitch, a loss of power to some system(s) after the spacecraft docked. I remember a question from the ground, "What were you doing when that happened?"
There was also the sublimator using more water than expected and having to be refilled twice (once after launch and once on station)
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#659
by
laszlo
on 23 Jun, 2024 23:09
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...And yes, I know they brought 4 of them back on line, but that's just using software to work around a hardware problem.
Or it was a software problem, i.e., limits too conservative based on the conditions of the previous flight which were different than the one this flight encountered. Things like that happen when you move from a sample of 1 to 2 to 3.