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Modeling is irrelevant when you don't know the cause of the failures or even have an idea. 5 thrusters failed and 4 came back and apparently they don't know why

Modeling is irrelevant when you don't know the cause of the failures or even have an idea. 5 thrusters failed and 4 came back and apparently they don't know why in either case.

krisoft 2y ago
> or even have an idea. They have an idea. "Tests of a similar control jet on the ground suggested a Teflon seal in an internal valve could swell at higher temperatures, restricting the flow of propellant to the thruster." That is the idea they have and they are checking if it matches with the measured signals / explains the observations.
mauvehaus 2y ago
If they know what is/was wrong, they can model what happens if the problem reoccurs even if they don't know why it occurred, disappeared, or might reoccur. But yeah, about the only thing more irritating than having a problem occur for reasons you don't understand is having it disappear for reasons you also don't understand.
numpad0 2y ago
I think they're just being great manager-engineers just as they should be. The root-ish cause so far determined is Teflon seal soaking in rocket fuel and bulging, constricting flow. Downstream it is creating improper oxidizer/fuel ratio and excess heat at thrusters which is triggering alarm and automatic shutdown. These were all explained in plain and accessible English in NASA press conferences and I've watched it online. I'd been a space fan for long enough that I know "improper O/F ratio" usually goes under a picture of a fireball or an artist's impression file image. There were multiple spacecrafts that at least blew off engines that way. The JAXA SLIM mission just this January had it that way. The fact that NASA/Boeing Starliner team keep triggering it and getting away with it is probably technically magnificent. With that prior knowledge, one way I can interpret those corpospeak is "we aren't sure if we can continue to do that and not finally kill the engines, or worse yet, turn everything into a bomb with people inside or around". Many are instead receiving "we technically know such and such [unintelligible] but we aren't sure of anything and we have no idea". That's a great demonstration of public relations skills.
- dotnet00 2y ago
  They're running with the theory of it being the teflon seals, but IIRC the problem is that it doesn't explain why the thrusters appeared to be operating relatively normally in a test at the station. The seal deformation should be permanent, in which case the thrusters shouldn't have recovered on their own, meaning that they might not have caught the real issue. That's what's making the risk difficult to quantify.

Modeling is irrelevant when you don't know the cause of the failures or even have an idea. 5 thrusters failed and 4 came back and apparently they don't know why in either case.

krisoft 2y ago

> or even have an idea. They have an idea. "Tests of a similar control jet on the ground suggested a Teflon seal in an internal valve could swell at higher temperatures, restricting the flow of propellant to the thruster." That is the idea they have and they are checking if it matches with the measured signals / explains the observations.

mauvehaus 2y ago

If they know what is/was wrong, they can model what happens if the problem reoccurs even if they don't know why it occurred, disappeared, or might reoccur. But yeah, about the only thing more irritating than having a problem occur for reasons you don't understand is having it disappear for reasons you also don't understand.

numpad0 2y ago

I think they're just being great manager-engineers just as they should be. The root-ish cause so far determined is Teflon seal soaking in rocket fuel and bulging, constricting flow. Downstream it is creating improper oxidizer/fuel ratio and excess heat at thrusters which is triggering alarm and automatic shutdown. These were all explained in plain and accessible English in NASA press conferences and I've watched it online. I'd been a space fan for long enough that I know "improper O/F ratio" usually goes under a picture of a fireball or an artist's impression file image. There were multiple spacecrafts that at least blew off engines that way. The JAXA SLIM mission just this January had it that way. The fact that NASA/Boeing Starliner team keep triggering it and getting away with it is probably technically magnificent. With that prior knowledge, one way I can interpret those corpospeak is "we aren't sure if we can continue to do that and not finally kill the engines, or worse yet, turn everything into a bomb with people inside or around". Many are instead receiving "we technically know such and such [unintelligible] but we aren't sure of anything and we have no idea". That's a great demonstration of public relations skills.

dotnet00 2y ago
They're running with the theory of it being the teflon seals, but IIRC the problem is that it doesn't explain why the thrusters appeared to be operating relatively normally in a test at the station. The seal deformation should be permanent, in which case the thrusters shouldn't have recovered on their own, meaning that they might not have caught the real issue. That's what's making the risk difficult to quantify.