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#520 by Chris-K-83 on 06 Jan, 2020 11:59
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Sorry, what is the current NET launch date for CFT?
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#521 by gongora on 06 Jan, 2020 14:18
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We don't know yet.
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#522 by edzieba on 06 Jan, 2020 14:37
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So to boil down several pages of discussion:
1) If you launch into a stable orbit, you need RCS to re-enter or are stranded, but you have some time to potentially fix it (ECLSS endurance without guarantee of base-Sun pointing) if the problem is fixable.
2) If you launch into a suborbital trajectory, you have a guaranteed re-entry but no active attitude control for insertion*.
The argument against 2) effectively boils down to "sphere-section entry bodies are not stable without active control", which can be split into to separate issues: a) whether RCS is needed for a nominal insertion to remain stable and b) whether an unstable insertion will self-stabilise.
a) Can be pretty safely answered as "no". A sphere-section entry body with the correct insertion attitude is passively stable throughout the hypersonic and supersonic regimes until the chutes deploy. It may not be stable in the low subsonic regime (as with that Orion boilerplate video) but if you're entering that regime without 'chute control you're merely pondering between 'unsurvivable lithobraking' or 'unsurvivable lithobraking with a pirouette'.
b) Is therefore the major point of contention: what degree of off-axis attitude (and what tumble rate) can be tolerated at insertion to allow a sphere-section body to self-stabilise before exceeding the backshell tolerance?. The answer to that is capsule specific and could be anywhere from "no margin, bullseye or die" to "upsidedown and spinning as long as it's below x RPM".
While a different capsule geometry with additional backshell shielding, Soyuz has shown that "upside-down and uncontrolled" is indeed a potentially survivable insertion state so this state-space may be larger than some assume. How large that survivable state-space is for Starliner specifically is unlikely something anyone outside the Starliner team could definitively answer as it requires simulation of both the geometry and structure of Starliner as well as thermal effects on internal critical components (mainly the 'chute comaprtments.
* Though unless you have a significant spin, pointing can be achieved via reaction wheel or, in dire emergency, finding the heaviest loose object within the cabin and rotating it a sufficient number of times to reorient the capsule, though that starts to get down into the "but what if the Service Module gets stuck?" navel-gazing weeds. -
#523 by jarmumd on 06 Jan, 2020 15:22
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I wanted to make a quick point, since this keeps coming up.
2) 72x181 is the only way to let Starliner burn off enough abort prop to dock safely with the ISS.
There probably is a GN&C desire for a specific mass range at docking for optimal control, but the NDS-B1 is a generic docking system that can handle both CST-100 and Orion (much heavier). So there is no safety issue in terms of handling the mass and associated forces at docking. -
#524 by TheRadicalModerate on 06 Jan, 2020 17:46
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I wanted to make a quick point, since this keeps coming up.
2) 72x181 is the only way to let Starliner burn off enough abort prop to dock safely with the ISS.
There probably is a GN&C desire for a specific mass range at docking for optimal control, but the NDS-B1 is a generic docking system that can handle both CST-100 and Orion (much heavier). So there is no safety issue in terms of handling the mass and associated forces at docking.
There are also torque and moment requirements on both the IDA and NDS, which are a little more complicated than raw mass. Also, I guess that the amount of prop with which you arrive at the ISS probably impacts your down-mass to some extent. However, I'm pretty sure that the "we need to burn off prop" argument for why they insert into 72x181 doesn't hold much water. -
#525 by clongton on 06 Jan, 2020 19:57
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2) 72x181 is the only way to let Starliner burn off enough abort prop to dock safely with the ISS.
Emphasis mine. This is a bogus requirement. Dragon docked to ISS last March with a full load of abort propellant.I email with Hans Koenigsmann from time to time. I hope to take him for a dive in the Giant Ocean Tank at the New England Aquarium. He's a genuine guy. Anyway - on Facebook today I gave him a congratulations and while I was at it I asked him a question I've been wanting the answer to for some time:
Do they dump the D2's unused hypergolic propellants prior/during EDL or does it land with them.
His answer: "We bring it back, un-tank and use it"
Question answered - thanks Hans! -
#526 by Rocket Science on 06 Jan, 2020 20:36
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I’m pretty sure the vapor seen in the video is condensation forming from the low pressure areas formed on the leeward side of the capsule as it tumbled. Similar phenomena to the vapor cones formed by transonic aircraft.
Vortex shedding... -
#527 by Opie on 06 Jan, 2020 21:36
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Yeah I couldn’t think of the words and I didn’t want to compare it to the strake vorticies on aircraft.
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#528 by CJ on 08 Jan, 2020 03:09
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I'm delighted by the NASA announcement of the investigation into the OFT timer issue. They seem to be taking the sensible course at the moment; waiting until they know what actually happened (root causes, etc) before deciding whether or not the mission needs to be reflown.
https://forum.nasaspaceflight.com/index.php?topic=47917.msg2033114#msg2033114
In other words, they want to find out what happened before reacting to it and making a decision on what to do about it. IMHO, this is the only sensible approach.
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#529 by Comga on 08 Jan, 2020 03:22
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A NASA email just alerted me to the ASAP Annual report for 2019.
The short summary of the CST-100 OFT anomaly , written just after the late December mission, isQuoteHowever, due to an anomaly with the Mission Elapsed Timer, the spacecraft burned more fuel than anticipated prior to the orbital insertion burn, and rendezvous with the ISS was not possible.
It is not clear that there is anything wrong with “the” Mission Elapsed Timer. It was probably counting accurately.
It seems pretty obvious that there are multiple problems with how Starliner acquired that datum and how it handles it.
“burned more fuel than anticipated” is putting it more than mildly.
No mention of the confused startup of the capsule ADCS system.
No mention of the need for ground override to improvise the orbit insertion burn on the fly.
Similarly the issue with Starliner’s Ground Abort Test only deploying two chutes sounds fully resolved by adding a step to check the attachment.QuoteAdditional tests and inspections have been added to the procedures to prevent a reoccurrence of the problem.
It’s as if checking had never occurred to anyone on the dozens of previous parachute landings.
Is the problem the missing step or the process that doesn’t catch missing steps?
ASAP is still harping on Amos-6 and “load-and-go” despite 110 successful fuelings with sub-cooled props since then, almost all of which occurred prior to any NASA mandates modifications to the COPVs
However the Starliner engine leaks don’t even get mentioned.
We could go on contrasting ASAP’s advocacy of continued caution on NASA’s 9-year-running “most urgent” CCP to LEO, with their praising the integrated mission risk management for the Artemis five-year-sprint to the lunar surface.
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#530 by Comga on 08 Jan, 2020 03:35
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I'm delighted by the NASA announcement of the investigation into the OFT timer issue. They seem to be taking the sensible course at the moment; waiting until they know what actually happened (root causes, etc) before deciding whether or not the mission needs to be reflown.
https://forum.nasaspaceflight.com/index.php?topic=47917.msg2033114#msg2033114
In other words, they want to find out what happened before reacting to it and making a decision on what to do about it. IMHO, this is the only sensible approach.
The investigation is good, if unavoidable.
However, they are already presuming the results.
The very announcement of an investigation says it could be that astronauts critical to manning the ISS could be allows to ride aboard a “test” mission.
This seems to be reacting to what happened before they start to figure out what went wrong. -
#531 by b0objunior on 08 Jan, 2020 04:08
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I'm delighted by the NASA announcement of the investigation into the OFT timer issue. They seem to be taking the sensible course at the moment; waiting until they know what actually happened (root causes, etc) before deciding whether or not the mission needs to be reflown.
https://forum.nasaspaceflight.com/index.php?topic=47917.msg2033114#msg2033114
In other words, they want to find out what happened before reacting to it and making a decision on what to do about it. IMHO, this is the only sensible approach.
The investigation is good, if unavoidable.
However, they are already presuming the results.
The very announcement of an investigation says it could be that astronauts critical to manning the ISS could be allows to ride aboard a “test” mission.
This seems to be reacting to what happened before they start to figure out what went wrong.
Again with this? Let the investigation do it's thing before saying it's already bad.
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#532 by woods170 on 08 Jan, 2020 07:08
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Is the problem the missing step or the process that doesn’t catch missing steps?
The problem is that the process doesn't catch missing steps. Clear indicator to this is that the wrongly installed chute connector was clearly visible on close-out photos. However, nobody bothered to review the close-out photos until AFTER the mishap had taken place.
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#533 by JEF_300 on 08 Jan, 2020 08:42
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A NASA email just alerted me to the ASAP Annual report for 2019.
The short summary of the CST-100 OFT anomaly , written just after the late December mission, isQuoteHowever, due to an anomaly with the Mission Elapsed Timer, the spacecraft burned more fuel than anticipated prior to the orbital insertion burn, and rendezvous with the ISS was not possible.
It is not clear that there is anything wrong with “the” Mission Elapsed Timer. It was probably counting accurately.
It seems pretty obvious that there are multiple problems with how Starliner acquired that datum and how it handles it.
The report doesn't say that there's something wrong with the MET, it says that there was an anomoly with the MET, which is absolutely true, the anomoloy being that it was off by 11 hours. The report doesn't discuss the cause of the anomoly because no one knows what that is.“burned more fuel than anticipated” is putting it more than mildly.
The statement is true. If you feel they should have been more detailed about this that's fine, but this isn't inappropriately vague for a summary, and definitely isn't misleading.No mention of the confused startup of the capsule ADCS system.
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No mention of the need for ground override to improvise the orbit insertion burn on the fly
Lets remmeber that the ASAP report was published just 3 weeks after the OFT, and before any detailed analysis of the flight data could be completed. Given the circumstances, expecting the OFT to be covered in any way other than an extremely vague short summary would be outrageous.
I'm not going to contest your claim of overall ASAP bias here. My point is that they haven't had the opportunity to be biased about the OFT yet. -
#534 by edzieba on 08 Jan, 2020 12:17
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One interesting bit from the ASAP report I'd missed from the monthly reports:Quote
In one particular instance, an issue with flight hardware subcomponents was discovered during some integrated vehicle testing. While this was yet another validation of the value of integrated testing, it was determined that these particular subcomponents were not built to spec but, in spite of that, had apparently passed the subcomponent qualification testing. The subcomponents themselves are very common pieces of hardware for spacecraft, and there is a long history both at NASA and in industry with qualification-testing this kind of hardware prior to acceptance and integration. In this case, the actual quality of the subcomponent hardware was compromised in manufacturing, but the commonly used qualification testing of the subcomponent, developed by experience over time, did not catch the problems with the hardware.
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#535 by Vettedrmr on 08 Jan, 2020 12:30
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One interesting bit from the ASAP report I'd missed from the monthly reports:
Yep, that's a lot of words that can be shortened a lot by "complacency". I experienced it in my career; it's the most insidious of problems to arise in a company/program that does safety-critical work for a living. IMO that's a lot of what Boeing is struggling with across the company.
Have a good one,
Mike -
#536 by abaddon on 08 Jan, 2020 13:41
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Quote
Once underway, the investigation is targeted to last about two months before the team delivers its final assessment.
Is it at all unusual that they're setting an up-front timeline for the completion of the investigation? I don't recall seeing that in previous incident investigations like this. -
#537 by ZachS09 on 08 Jan, 2020 14:56
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Why is everyone discussing the possibility of a second OFT when the data reports from Boe-OFT have not even started?
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#538 by Stan-1967 on 08 Jan, 2020 15:15
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Why is everyone discussing the possibility of a second OFT when the data reports from Boe-OFT have not even started?
Because a primary goal of the first flight was not accomplished. This is a fact.
Whether or not a subjective analysis ultimately informs a different decision than prescribing another test flight does not change the fact Starliner failed to dock with ISS.
Pointing this out is not jumping the gun. -
#539 by abaddon on 08 Jan, 2020 16:05
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C'mon, we all know that unless the investigation finds something unexpected there won't be another uncrewed OFT. Right? Bridenstine has already telegraphed that very transparently, and Boeing isn't going to do one unless NASA insists (and pays for it).
Again with this? Let the investigation do it's thing before saying it's already bad.