On Fri, 30 May 2003 14:19:33 -0700 (PDT), Adrian Tymes <[EMAIL PROTECTED]> wrote:
>In order to have a catastrophic explosion, you could >design a system so that failures X and Y both have to >happen. Oddly phrased - sounds like you want to have a catastrophic explosion...but that objection is trivial. My non-trivial objection, which I'm apparently not making clear, is: the whole point here is, something fails. Almost by definition, you designed and built it not to fail. Therefore, if it fails, it is not doing what it was designed and built to do. Its having failed, then, how can you be confident that it failed in such a way as to preclude an explosion unless some other thing also fails? If you knew the failure modes that well, you'd mitigate them. The very fact that something goes wrong STRONGLY suggests you didn't know it would. >if you can >demonstrate that P(X_fail) and P(Y_fail) are each at >most 1E-3 (say, run 1000 test flights in which neither >X nor Y fail) You need 2998 flights to demonstrate that with 95% confidence. >P(X_fail) * P(Y_fail) is less than 1E-6, so >P(X_fail) * P(Y_fail) * population_density * >impact_area(explosive_failure) < 1E-6...which is the >criteria for getting a launch license. Er... 1E-6 is the launch license threshold probability for killing any one person. Overall public EC is 30E-6. >It's not designed - and therefore theoretical - >reliability, but proven reliability. Or am I >misreading what the AST means by "proven"? AST does not use the word "proven." They use the word "unproven," and they refuse to define it. That little dig aside, they are very interested in real world flight test data, and their answers last week were very sensible (to the extent the requirements were under AST's control). -R -- "We've all heard that a million monkeys banging on a million typewriters will eventually reproduce the entire works of Shakespeare. Now, thanks to the Internet, we know this is not true." -- Robert Wilensky, UC Berkeley _______________________________________________ ERPS-list mailing list [EMAIL PROTECTED] http://lists.erps.org/mailman/listinfo/erps-list
