--- Randall Clague <[EMAIL PROTECTED]> wrote: > 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.
Thinko: in order *not* to have... > 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. True, but it is possible to know some things. For instance, an explosion will not occur without fuel, oxygen, and ignition source (heat, spark, whatever). So, if you can keep those three things separate, you know you won't get an explosion. Of course, a rocket is all about combining them controllably, but just so long as not too much of them get together at any one time... > >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. Eh? 1000 runs where X does not fail, therefore P(X_fail) < 1/1000. Ditto Y. These just happen to be the same 1000 runs. > >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. I thought 1E-6 was the threshold for a single launch, while 30E-6 was the threshold for a group of launches. My calculations here were for a single flight. _______________________________________________ ERPS-list mailing list [EMAIL PROTECTED] http://lists.erps.org/mailman/listinfo/erps-list
