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PRA - Public's Risk Assessment on Safety
Derek Lyons wrote: Yep, the ol' tunnel trio: Time, Distance, and Shielding One can never drive the risk to zero since that would require n levels of redundancy, n infinite. That's where "acceptable risk" comes in. The definition of "acceptable risk" is of course quite subjective. Yep. It's made worse when the perceived risk is driven by the assumption that "routine" = "safe as a nursery school". Or, in the case of Soviet submarines,"routine" = "as safe as a gulag".... Pat |
#12
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PRA - Public's Risk Assessment on Safety
Pat Flannery wrote in
: This is going to be a very difficult problem to solve...as it requires NASA to analyze failure modes that only manifest themselves when a perceived minor problem interacts with another perceived minor problem in an unanticipated way- maybe there should be a separate entity inside the agency, made up of top-quality engineers whose sole purpose is to locate such possible interactions, and issue "No-flights-till-fixed" orders when such a problem is found- to be effective, such a entity must not be beholden to NASA management in any way, so that the "keep quiet, and keep your job" mindset can be broken...if one were looking for some engineers to staff such a NASA department...then the engineers who were shooting those concerned e-mails back and forth about the damage to Columbia from the foam strike would be a good place to start. There is a danger from going too far the other way, however. "Paralysis by analysis." You can *always* find a reason not to fly. An organization so predisposed will not fly. -- JRF Reply-to address spam-proofed - to reply by E-mail, check "Organization" (I am not assimilated) and think one step ahead of IBM. |
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PRA - Public's Risk Assessment on Safety
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PRA - Public's Risk Assessment on Safety
And arguably the same is true post SRB ignition for Columbia. Sure
there were possibilities, but none with significant and elevated risks themselves. Worse yet, all of those hinge on early detection and decisive action. With regard to the in-flight decision-making, I agree with you. Hmmm..the largest piece of foam ever seen, hitting the TPS in contrast to the SRB for the previous flight, and potentially at a place for which no data existed? At least, somebody should have said - in particular, given the scant quantity and bad quality of tracking images - that there was insufficient knowledge to _exclude_ a safety of flight issue. Jan |
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PRA - Public's Risk Assessment on Safety
Jorge R. Frank wrote: There is a danger from going too far the other way, however. "Paralysis by analysis." You can *always* find a reason not to fly. An organization so predisposed will not fly. That's why I think that such a group should be made up of NASA veteran engineers....they would have the best chance of being able to analyze what constituted a real risk versus a simple annoying problem that could be addressed when time and budget allowed; we have had two near fatal single point problems regarding the Apollo spacecraft (Apollo 13's oxygen tank rupture, and the leaking RCS propellants on the Apollo from the ASTP leading to crew inhalation and failure of one of the three landing parachutes... in both cases these were things that could not have been foreseen before the launch....but in the case of Challenger, the gas leakage on the SRB was foreseen by the engineers who tried to have the launch stopped...only to be overruled by managment...in the case of Columbia, the engineers were probably concerned about foam shedding in regard to vehicle damage based on past experience; and very concerned once they saw the foam impact during ascent...but again their input (small that it was- they mainly talked among themselves about it; and that is very troubling in itself, as it indicates that they were, in their own opinion, outside the loop as to having real input into flight decisions on-orbit) didn't change the mission's flight profile in regards to trying to get a look at possible damage, or planning for a possible abnormal reentry (not that either of these would probably had any effect on the final outcome of the mission). The use of outside contractors for Shuttle mission support and between-mission maintenance makes the need for some sort of completely independent safety analysis doubly important in my opinion, as the support companies have a vested economic interest in maintaining a smooth flight schedule; both to avoid being penalized for poor performance, and to maintain their contracts- while receiving incentive rewards for on-time launches. This means that they have a possible conflict of interest in regards to the safety of launches, as it will be in their interest to regards to corporate profits to assure that the vehicle flies on time every time....even when there are possible flight safety concerns; whatever else one can say in regards to Boeing's foam strike analyze of damage to the Columbia, the simple fact remains that they were wrong....whatever else can say in regards to Lockheed/Martin's external tank, the fact remains that it was consistently shedding foam in larger or smaller pieces during virtually all flights; which under NASA's own guidelines for Shuttle safety was an unacceptable situation. Anyway, the CAIB has just started giving its report, so I'll wait to hear what they say. Pat |
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PRA - Public's Risk Assessment on Safety
"Jorge R. Frank" wrote:
There is a danger from going too far the other way, however. "Paralysis by analysis." You can *always* find a reason not to fly. An organization so predisposed will not fly. As a collory to this, I'd like to toss in an article of faith from the Navy; "Any inspection can always find something f****d up, no matter how competent the folks being inspected are". We firmly believed that the inspections teams searched through obscure regs and directives in order to have something, anything, to fry a crew. D. -- The STS-107 Columbia Loss FAQ can be found at the following URLs: Text-Only Version: http://www.io.com/~o_m/columbia_loss_faq.html Enhanced HTML Version: http://www.io.com/~o_m/columbia_loss_faq_x.html Corrections, comments, and additions should be e-mailed to , as well as posted to sci.space.history and sci.space.shuttle for discussion. |
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