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Boeing's Starliner


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On 1/14/2020 at 3:13 PM, mikegarrison said:

I really do think this report https://www.nytimes.com/2019/09/18/magazine/boeing-737-max-crashes.html is the best explanation of what really went wrong -- in Boeing, in the airlines, in the FAA, and most importantly in the entire system.

This was hands down one of the best articles I’ve read, thanks for sharing.

Boeing is certainly not innocent in either of these matters but considering that the first level of management Boeing Defense, Space, and Security has in common with Boeing Commercial Airplanes is David Calhoun, the CEO, I think it’s unfair to wrap the 737MAX issues into the Starliner issues.

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2 hours ago, MinimumSky5 said:

https://arstechnica.com/science/2020/01/nasa-and-boeing-are-closely-looking-at-starliners-thruster-performance/

Well, this isn't good.

TLDR: due to an unconventional use of the thrusters during the orbit raising manoeuvre on the orbital test flight, there were multiple issues with thrusters later in the mission, which apparently were severe enough that a simulated docking abort manoeuvre was failed. 

Note that this is coming from an anonymous source within NASA, and Boeing is denying everything.

If true, it sounds like they may need to redo the orbital test. I guess we'll see.

The article you quoted seems a lot more nuanced than your post about it. I would disagree with your "TLDR" summary.

My TLDR summary of this article is: The anomaly event overstressed the thruster system, leading to parts of it being shut down. This later impacted the simulated docking/undocking, leading to the undocking simulation not meeting the delta-v targets. NASA and Boeing are studying whether this was entirely due to the anomaly event or whether it indicated a different system problem that might have to be fixed/retested.

Edited by mikegarrison
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19 minutes ago, sh1pman said:

So, Starliner’s next flight is supposed to be with astronauts, right? That’s going to be scary...

That's not yet been determined. Either it will be with three people (two from NASA, one from Boeing) or they may have to repeat the uncrewed orbital test.

I'm not sure how "scary" it would be, since the capsule landed safely even despite the anomaly. But it remains true that docking/undocking has not been successfully demonstrated by an actual flight to the ISS.

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11 hours ago, mikegarrison said:

If true, it sounds like they may need to redo the orbital test. I guess we'll see.

The article you quoted seems a lot more nuanced than your post about it. I would disagree with your "TLDR" summary.

My TLDR summary of this article is: The anomaly event overstressed the thruster system, leading to parts of it being shut down. This later impacted the simulated docking/undocking, leading to the undocking simulation not meeting the delta-v targets. NASA and Boeing are studying whether this was entirely due to the anomaly event or whether it indicated a different system problem that might have to be fixed/retested.

Well, that'll teach me for trying to sum up an article while running on very little sleep. I can't actually see where i went wrong with my summing up, but that's probably the best reason for me to just post the links.

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30 minutes ago, tater said:

I think the one thruster not firing at all is probably the most concerning bit as that's clearly not attributable to overuse.

I think a lot of investigation will be going into whether or not that was indicative of some deeper problem, or just an unfortunate coincidence.

A single random thruster failure can be tolerated, as the system has redundancy. But if it's indicative of a deeper issue, that's a serious problem.

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6 minutes ago, jadebenn said:

I think a lot of investigation will be going into whether or not that was indicative of some deeper problem, or just an unfortunate coincidence.

A single random thruster failure can be tolerated, as the system has redundancy. But if it's indicative of a deeper issue, that's a serious problem.

Yeah, seems like a lot of testing of the whole thing on the stand is in order... that or going over everything with a fine-tooth comb if their methodology is not to just put it on the stand (CSM together) and test.

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15 minutes ago, tater said:

I think the one thruster not firing at all is probably the most concerning bit as that's clearly not attributable to overuse.

More because of over heating if it burned for too long i think. As RCS tend to have short burns only they might not be rated for burning for long periods. 

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6 hours ago, MinimumSky5 said:

Well, that'll teach me for trying to sum up an article while running on very little sleep. I can't actually see where i went wrong with my summing up, but that's probably the best reason for me to just post the links.

Well, not "wrong". I guess I just thought your TLDR was a little bit too abbreviated. I mean yeah, "the simulated docking/undocking failed", but apparently they way that it failed was that they did not get sufficient delta-v right at the end. This detail helps explain why it might actually be reasonable that the crazy thruster use during the anomaly maybe did reasonably explain the failure. (Or maybe it didn't. Still being studied.)

I still wonder exactly why the thrusters fired so much during the clock problem portion of the flight. Was it something like the capsule continuously trying to point in a the direction needed to burn to the ISS, but the orbit was curving away around the Earth, so the thrusters kept firing to re-orient it?

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45 minutes ago, mikegarrison said:

Well, not "wrong". I guess I just thought your TLDR was a little bit too abbreviated. I mean yeah, "the simulated docking/undocking failed", but apparently they way that it failed was that they did not get sufficient delta-v right at the end. This detail helps explain why it might actually be reasonable that the crazy thruster use during the anomaly maybe did reasonably explain the failure. (Or maybe it didn't. Still being studied.)

I still wonder exactly why the thrusters fired so much during the clock problem portion of the flight. Was it something like the capsule continuously trying to point in a the direction needed to burn to the ISS, but the orbit was curving away around the Earth, so the thrusters kept firing to re-orient it?

The crazy trust use was explained with the clock being wrong and trying to burn at the wrong time. 
However unless the capsule had external position data like GPS or other systems the capsule would simply execute its planned circulation burn. 

In KSP term imagine you do plane your circulation burn  at Ap with Ap at 100 and Pe at 50 Km, however burn was triggered too early so you was at 70 km attitude and pointing a bit up as it would be pointing straight forward. 
This will raise your Ap above 100 wile it might not raise your Pe up to 100, don't bother simulating this now. 

Option two, it was pointed parallel to earth surface because of star trackers or other systems, this should probably give an better orbit, still no ISS or abnormal truster use. 

Option three: they uses gps or other position system. In this case the system should notice that the position is wrong. in this case it has some option. It can burn as planned who is 1 or 2 above or wait until radio contact and signal an emergency. 

Instead something else and weird happened, my guess is that they used the gps position but the errored clock so rater than waiting for maximum attitude or AP to circulate they  tried to do an 100 km circulation burn at 70 km  
Yes that would end well, computers are stupid, programmers tend to be careless. 

Now the question is how bad the software is. Yes it was not an life threatening fail and an crew would most likely spotted and corrected this bug. However I would do an review of the software. 

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  • 2 weeks later...
38 minutes ago, Meecrob said:

Didn't see this posted yet. They found another software bug on Starliner.

https://spacenews.com/nasa-safety-panel-calls-for-reviews-after-second-starliner-software-problem/

Quick summary for the lazy:
The bug has been found when the did some tests during the OFT, when Starliner was in orbit. They did a quick OTA (no wait, it's OverTheVacuum - OTV)  software patch.
It is said that it was a critical bug with potential catastrophic outcome for the mission:

Quote

[...] it would have led to erroneous thruster firings and uncontrolled motion during [service module] separation for deorbit [...]
~ Paul Hill, NASA Aerospace Safety Advisory Panel member

 

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