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One important piece of data to correlate with that: how many times previously had engineers issued similar warnings for launches that then proceeded fine? Warn

by T-hawk 8y ago

One important piece of data to correlate with that: how many times previously had engineers issued similar warnings for launches that then proceeded fine? Warning fatigue is a thing and reasonable to wonder whether that happened at all here.

mehrdadn 8y ago
Yeah, very true. I did wonder about that a bit, and also how dire the previous warnings were, if any. "It's going to blow up" sounds like something that a good engineer shouldn't be saying very often about successful flights.
londons_explore 8y ago
In some working environments issuing a warning is enough to get you off the hook for something going wrong, so it might be that nearly every flight had a warning so the engineers were never responsible...
- deelowe 8y ago
  Look up Bob Ebeling. He definitely knew it wouldn't survive.
- freeopinion 8y ago
  These were not throw away warnings. These were fervent efforts to stop the launch. This wasn't somebody trying to protect their job. This was somebody risking their job.
InclinedPlane 8y ago
It was a specific warning about the vulnerability of the O-ring seals in low temperatures (precisely the mechanism of failure that doomed the Challenger). It was an unusual, specific, and high profile warning which was effectively overruled by NASA management. The guidance was to avoid launching in such low temperatures, the response was: "My God, Thiokol. When do you want me to launch? Next April?" That from Lawrence Mulloy at NASA MSFC. This is a pretty clearcut case and nothing like "warning fatigue".
- nashashmi 8y ago
  Maybe it wasn't warning fatigue then. It might be overthinking fatigue. I guess missions have gotten delayed before for so many reasons and this time they just got tired of "doing it again."
  - InclinedPlane 8y ago
    This is a well studied problem, it wasn't overthinking, it was "go fever", specifically in the form of "Normalization of Deviance" [1]. Morton-Thiokol and NASA set criteria for safety margins on the Shuttle system. And the Shuttle kept on violating those safety margins again and again. Instead of grounding the fleet or studying the problem further or attempting to ameliorate the problem the safety margins were loosened, deviance was normalized, unsafe operations were normalized. And those who called out the legitimate safety problems with the Shuttle were harassed and derided because their views differed from the orthodoxy (that a Shuttle loss was a 1 in 100,000 probability) and got in the way of their goals (the high flight rate of dozens of launches per year that were necessary for the Shuttle system to meet its promises). Later analysis of the Shuttle system [2] has indicated several other potential key failure modes that could have caused a loss of vehicle and crew, especially during the early flights. Not just the SRBs and the thermal protection system (the weaknesses which doomed Challenger and Columbia) but other systems such as the APUs, SSMEs, flight software, etc. led to a risk of catastrophic loss as high as 1 in 10 during the first several years of flights, 1 in 20 around the Challenger disaster period, 1 in 50 during the return to flight period after Challenger, and about 1.1-1.3% during the post-Columbia period. 1: https://en.wikibooks.org/wiki/Professionalism/Diane_Vaughan_and_the_normalization_of_deviance https://en.wikibooks.org/wiki/Professionalism/Diane_Vaughan_... 2: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110004917.pdf https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/201100...
    - Gibbon1 8y ago
      > that a Shuttle loss was a 1 in 100,000 probability I'm not sure how anyone could say that with a straight face. Serious events happen with commercial aircraft at a rate of about 1 in 1M. Figure that a rocket is inherently 100X more dangerous. And that the lack of repetitive experience with rockets bumps the risk another 1:100. Meaning you build a lot of aircraft and fly them all the time you get good at knowing where the design holes are. Also consider that each serious failure when mitigated improves the odds of the rest of the fleet. You don't get that when you're only flying a dozen flights a year. Est risk: 1X10-6 X 100 X 100 gives 1% chance of loss. Notable the Apollo program flew 15 flights 3 had serious failures[1][2] and 1 near loss event (Apollo 13). For consideration the Saturn V was a well tested conservative design which the Shuttle was not. [1] Apollo 6 and 13 had early engine shut downs due to failures of the S-II engines. [2] Apollo 12 lightning strike took out the command module computer.

by T-hawk 8y ago

mehrdadn 8y ago

Yeah, very true. I did wonder about that a bit, and also how dire the previous warnings were, if any. "It's going to blow up" sounds like something that a good engineer shouldn't be saying very often about successful flights.

londons_explore 8y ago

In some working environments issuing a warning is enough to get you off the hook for something going wrong, so it might be that nearly every flight had a warning so the engineers were never responsible...

deelowe 8y ago
Look up Bob Ebeling. He definitely knew it wouldn't survive.
freeopinion 8y ago
These were not throw away warnings. These were fervent efforts to stop the launch. This wasn't somebody trying to protect their job. This was somebody risking their job.

InclinedPlane 8y ago

It was a specific warning about the vulnerability of the O-ring seals in low temperatures (precisely the mechanism of failure that doomed the Challenger). It was an unusual, specific, and high profile warning which was effectively overruled by NASA management. The guidance was to avoid launching in such low temperatures, the response was: "My God, Thiokol. When do you want me to launch? Next April?" That from Lawrence Mulloy at NASA MSFC. This is a pretty clearcut case and nothing like "warning fatigue".

nashashmi 8y ago
Maybe it wasn't warning fatigue then. It might be overthinking fatigue. I guess missions have gotten delayed before for so many reasons and this time they just got tired of "doing it again."
- InclinedPlane 8y ago
  This is a well studied problem, it wasn't overthinking, it was "go fever", specifically in the form of "Normalization of Deviance" [1]. Morton-Thiokol and NASA set criteria for safety margins on the Shuttle system. And the Shuttle kept on violating those safety margins again and again. Instead of grounding the fleet or studying the problem further or attempting to ameliorate the problem the safety margins were loosened, deviance was normalized, unsafe operations were normalized. And those who called out the legitimate safety problems with the Shuttle were harassed and derided because their views differed from the orthodoxy (that a Shuttle loss was a 1 in 100,000 probability) and got in the way of their goals (the high flight rate of dozens of launches per year that were necessary for the Shuttle system to meet its promises). Later analysis of the Shuttle system [2] has indicated several other potential key failure modes that could have caused a loss of vehicle and crew, especially during the early flights. Not just the SRBs and the thermal protection system (the weaknesses which doomed Challenger and Columbia) but other systems such as the APUs, SSMEs, flight software, etc. led to a risk of catastrophic loss as high as 1 in 10 during the first several years of flights, 1 in 20 around the Challenger disaster period, 1 in 50 during the return to flight period after Challenger, and about 1.1-1.3% during the post-Columbia period. 1: https://en.wikibooks.org/wiki/Professionalism/Diane_Vaughan_and_the_normalization_of_deviance https://en.wikibooks.org/wiki/Professionalism/Diane_Vaughan_... 2: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110004917.pdf https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/201100...
  - Gibbon1 8y ago
    > that a Shuttle loss was a 1 in 100,000 probability I'm not sure how anyone could say that with a straight face. Serious events happen with commercial aircraft at a rate of about 1 in 1M. Figure that a rocket is inherently 100X more dangerous. And that the lack of repetitive experience with rockets bumps the risk another 1:100. Meaning you build a lot of aircraft and fly them all the time you get good at knowing where the design holes are. Also consider that each serious failure when mitigated improves the odds of the rest of the fleet. You don't get that when you're only flying a dozen flights a year. Est risk: 1X10-6 X 100 X 100 gives 1% chance of loss. Notable the Apollo program flew 15 flights 3 had serious failures[1][2] and 1 near loss event (Apollo 13). For consideration the Saturn V was a well tested conservative design which the Shuttle was not. [1] Apollo 6 and 13 had early engine shut downs due to failures of the S-II engines. [2] Apollo 12 lightning strike took out the command module computer.