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#380
by
Comga
on 27 Dec, 2019 01:02
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2) The egg-timer is reliable. Your egg will be done right if the clock is programmed right. It is the simplest approach and I do not agree with people that say the system should have been smarter. Trying to derive a better clock through heuristics from multiple inputs is even more risky and very difficult to do right.
Relying on an egg-timer is NOT reliable. What if your system crashes and has to reboot? With cosmic particles impact computer systems in LEO, this can (and will) happen even if your system as ZERO bugs. Which is why you either A) harden your hardware against radiation to the extreme, or B) use multiple redundant computers (usually 3), or C) both.
Relying on a single source is very risky.
No kitchen egg timer has ever undergone a Single Event Upset from radiation.
I had assumed all of us in this thread knew that “egg timer” was not to be taken literally, but you proved me wrong. A software egg timer in space would certainly be susceptible without proper precautions having been taken.
But maybe you can explain your position? You believe a software timer cannot undergo a “single event upset”?
Relax
We are in agreement that multiple simple timers, perhaps even based on the target instantaneous launch window, could be polled to get for or five orders more accuracy that the 11 hr error Starliner pulled for the MET.
Even a spring loaded dial timer couldn’t be that bad.
We know they won’t do that, because it’s ridiculous, but so is pulling the MET, not checking it, and letting it drive the system into a state of confusion. (You saw the ADCS firings on the wall display, didn’t you?)
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#381
by
CyndyC
on 27 Dec, 2019 02:31
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I've had an alternative theory to the +11 hour offset coming from the countdown initialization. The countdown actually started 11 hours and 20 minutes before launch according to SFN, not just 11 hours. There's little reason to be suspicious of the breakwire input, a mechanism that has been used many times before, and guess what, liftoff actually occurred at T+1.1 seconds after ignition at T0. In the post-launch conferences, the wrong data pulled from the EDS was referred to as a coefficient, implying it was a multiplier, not a linear time reading. So somehow maybe the 1.1 seconds got multiplied by 10.
Edit: And then somehow got converted from "seconds" to "hours".
The launch timeline I pulled from Chris Gebhardt's first of two Starliner launch articles at
https://www.nasaspaceflight.com/2019/12/boeing-ula-momentous-starliner-uncrewed-test-flight/. Something else he said that might be enlightening, "Per the planned schedule, after completing the Orbit Insertion Burn, Starliner was to immediately – within 20 seconds – begin its on-orbit testing and demonstration sequence." That might be part of the explanation for the excess thruster activity, Starliner "thinking" the burn was completed, although not all of the explanation going by other reports.
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#382
by
TheRadicalModerate
on 27 Dec, 2019 05:44
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I don't know the format of the interface between the Atlas and the Starliner, but I wouldn't be at all surprised if it was really primitive--like, "send me what's at this address" primitive.
That'll work fine, as long as both the Atlas and Starliner builds are synchronized, so that the proper pointers are exported from the Atlas side to the Starliner side before the Starliner stuff is compiled and linked. But if you get a last-minute Atlas build that isn't accompanied by a corresponding Starliner build, then you're going to have a problem. Since those builds are coming from two different organizations, it's easy to envision a process oopsie occurring that leaves the pointers out of sync.
I assume that the attitude control problems were pretty simple: Tidal forces will spin the vehicle around at different rates at different parts of the orbit, so if the attitude control system thinks that the vehicle is somewhere other than where it actually is, it's going to be constantly fighting the tides to maintain what it thinks is the right attitude, and it'll go through prop at a hefty clip.
I think Boeing finally admitted that the TDRS drop-out was due to the attitude stuff, which explains why it took them so long to get control back.
While all of this is easily explainable, it also sounds really fragile. That's really what needs to be looked at before any decisions about a subsequent launch are made.
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#383
by
Rocket Science
on 27 Dec, 2019 18:38
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Just checking the thread after the Christmas busyness... It's seems all I missed was a "popcorn fight over egg timers"...
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#384
by
Ike17055
on 28 Dec, 2019 13:14
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except there was a clearly identified problem THAT WAS IGNORED.
(Also, a tight timetable) ... There will be a thorough review, of course, and the right people will make the decision.
The right people made the decision to launch Challenger, despite engineering objections.
A tight timetable also drove that decision.
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#385
by
clongton
on 28 Dec, 2019 14:21
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except there was a clearly identified problem THAT WAS IGNORED.
Ignored by the "right people". That was the point.
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#386
by
Comga
on 29 Dec, 2019 14:47
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With the caveat that I only looked through the two Update threads for the SpaceX DM-1 flight, there are only three tweets on DM-1 from Bridenstine. That includes the formal, PR office composed on letterhead, post-launch congratulations.
How many tweets did Bridenstine send out during and after OFT?
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#387
by
ThomasGadd
on 29 Dec, 2019 16:55
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With the caveat that I only looked through the two Update threads for the SpaceX DM-1 flight, there are only three tweets on DM-1 from Bridenstine. That includes the formal, PR office composed on letterhead, post-launch congratulations.
How many tweets did Bridenstine send out during and after OFT?
You are comparing different things.
SpaceX DM-1 OFT flight was completely successful,
since then SpaceX's Flight Abort static fire event,
now Boeing's Starliner OFT issues.
NASA has learned to get in front of PR issues.
Look at the whining on this site SpaceX's Flight Abort static fire event.
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#388
by
JEF_300
on 29 Dec, 2019 19:07
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With the caveat that I only looked through the two Update threads for the SpaceX DM-1 flight, there are only three tweets on DM-1 from Bridenstine. That includes the formal, PR office composed on letterhead, post-launch congratulations.
How many tweets did Bridenstine send out during and after OFT?
You are comparing different things.
SpaceX DM-1 OFT flight was completely successful,
since then SpaceX's Flight Abort static fire event,
now Boeing's Starliner OFT issues.
NASA has learned to get in front of PR issues.
Look at the whining on this site SpaceX's Flight Abort static fire event.
I think the fact that this flight wsn't as successful is the main reason for any discrepancy in number of tweets...
which I guess is a statistic that matters.
Afterall, he also tweeted more about Soyuz MS-10 than other crewed Soyuz flights.
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#389
by
Comga
on 29 Dec, 2019 20:46
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So to get more praise from the Administrator one just has to mess up?
I don’t think that goes both ways.
Bridenstine heaped praises on the OFT recovery team in the desert after the successful landing, after tweeting out “Bullseye” despite a 1.4 km offset, but didn’t even tweet congratulations when Dragon touched down.
Look at the body posture in the post-launch press conferences.
For DM-1 Bridenstine had his arms folded across his chest. Classic distancing.
For OFT, particular when things were literally going sideways (spacecraft attitude control joke 😀) he was smiling, ebullient, and praiseworthy.
Somebody REALLY likes OFT.
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#390
by
Comga
on 29 Dec, 2019 20:47
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After landing, the Starliner ground team puts a custom cover over The capsule. It protects the outer surface, docking adapter, and forward sensors from the desert environment, but it leaves the hatch and interior exposed. They must have decided that desert dust, including salt from the dry lakebed, is not a significant issue.
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#391
by
b0objunior
on 29 Dec, 2019 20:58
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Please can we not go there. Jim did what he did, reading too much into this borders conspiracy theories.
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#392
by
OM72
on 29 Dec, 2019 20:59
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There is an environmental barrier around the hatch along with other precautions. Post-landing the vehicle powers down. Outside of getting the crew out and any time-sensitive payloads, reasons to access the interior is limited.
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#393
by
OM72
on 29 Dec, 2019 21:01
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Where did the 1.4 km number come from?
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#394
by
ThomasGadd
on 29 Dec, 2019 23:47
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Restating what I said earlier
ten months ago SpaceX DM-1 OFT flight was completely successful,
since then SpaceX's Flight Abort static fire event,
both providers are having different parachute issues,
now Boeing's Starliner OFT issues.
I think Administrator Bridenstine was not completely confident in this mission and was trying to set expectations.
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#395
by
OM72
on 30 Dec, 2019 03:09
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except there was a clearly identified problem THAT WAS IGNORED.
Ignored by the "right people". That was the point.
Again, scare tactics. You have no insight to claim such things.
You should, again, be ashamed that you are drumming up fear and doubt for your own personal forum/internet likes.
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#396
by
clongton
on 30 Dec, 2019 03:27
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except there was a clearly identified problem THAT WAS IGNORED.
Ignored by the "right people". That was the point.
Again, scare tactics. You have no insight to claim such things.
You should, again, be ashamed that you are drumming up fear and doubt for your own personal forum/internet likes.
My "own personal forum/internet likes"? Are you kidding? I could really care less if I got any likes at all. I don't need or want any "likes". I don't give a rat's ass about any of that crap. I can't remember if I have ever looked to see if I got any, because I really don't care. I speak my mind and if someone likes or doesn't like what I say well that's on them and has zero effect on me.
And it's not scare tactics. It's established fact. Challenger should not have launched. The "right people" were advised strongly not to launch. They were told by the engineers that the temperature was below the safe minimum. Yet they decided to launch anyway. Why? Schedule pressure. I've felt that kind of pressure. It can be unbelievably brutal at times. All I said was I hoped today's batch of the "right people" wouldn't succumb to that kind of pressure the way others have in the past. That is not a scare tactic. It's a prayer.
And I never indicated that I was some kind of expert on Starliner, from one of your earlier posts. I've no idea where that came from.
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#397
by
SoftwareDude
on 30 Dec, 2019 03:51
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Regarding Starliner's failure to reach orbit. There is some information that allows us to guess a little about how Starliner's software works. This is only an educated guess.
First some events seemed to happen on time and others did not. It sounds like there are multiple timers in use.
Another piece of information is that, for things to work, RCS eliminating dead space and OMT burn, events are synchronized across multiple timers. This brings up several questions:
1. The RCS system went into dead space elimination without the OMT firing means that there is no master state machine providing events to subsystem state machines. Is this true? In other words, how was the RCS acting as if OMT was firing when it wasn't unless they are separate and not communicating?
2. Does this mean multiple software platforms having to synchronize?
3. Does this mean multiple software systems running os different hardware stacks?
If the answers to 1,2, and 3 is true then did Boeing cobble Starliner out of at least some existing controllers?
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#398
by
edzieba
on 30 Dec, 2019 08:20
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My bet would be that there are both reactive (measure spacecraft state, go to new state, proceed once net state achieved, etc) and timer-based sequences (something along the lines of a "some gunk covered all the sensors somehow so we need an purely inertial backup" sequence), along with some form of quorum voting, and Starliner found itself in an edge-case where those disagreed sufficiently to jump about in the sequence but agreed sufficiently for some portions of the sequence to still be valid. That would explain how with a MET 11 hours out Starliner still proceeded through several post-seperation events normally, but ended up stuck simultaneously in two different states: oriented in a late post-burn attitude, but with the RCS in the mid-burn pointing mode. If there were multiple systems that had decided that neither of these states was 'not wrong' but unable to agree on the 'right' sequence step to proceed to Starliner would be crippled without manual intervention.
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#399
by
woods170
on 30 Dec, 2019 08:52
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except there was a clearly identified problem THAT WAS IGNORED.
Ignored by the "right people". That was the point.
Again, scare tactics. You have no insight to claim such things.
You should, again, be ashamed that you are drumming up fear and doubt for your own personal forum/internet likes.
My "own personal forum/internet likes"? Are you kidding? I could really care less if I got any likes at all. I don't need or want any "likes". I don't give a rat's ass about any of that crap. I can't remember if I have ever looked to see if I got any, because I really don't care. I speak my mind and if someone likes or doesn't like what I say well that's on them and has zero effect on me.
And it's not scare tactics. It's established fact. Challenger should not have launched. The "right people" were advised strongly not to launch. They were told by the engineers that the temperature was below the safe minimum. Yet they decided to launch anyway. Why? Schedule pressure. I've felt that kind of pressure. It can be unbelievably brutal at times. All I said was I hoped today's batch of the "right people" wouldn't succumb to that kind of pressure the way others have in the past. That is not a scare tactic. It's a prayer.
And I never indicated that I was some kind of expert on Starliner, from one of your earlier posts. I've no idea where that came from.
Emphasis mine.
Chuck is entirely correct. Just read the final report of the Rogers Commission's investigation into the Challenger accident:
https://spaceflight.nasa.gov/outreach/SignificantIncidents/assets/rogers_commission_report.pdfIt clearly spells out that substantial pressure from top NASA management, to meet flight schedules, is what cost the lives of 7 US astronauts.
As such, Chuck raising the red flag with regards to CCP schedule pressure is fully and wholly justified IMO.
