--- Randall Clague <[EMAIL PROTECTED]> wrote: > You put blowout panels in your tanks. You need a > mechanism to blow > them out in an emergency. But you need to be damn > sure they don't > blow out at any other time, or it will BE an > emergency. The > damn-sure-they-don't has to have many times the > reliability of the > damn-sure-they-do, since hopefully you have few > emergencies where you > have to use the blowout panels. So you have to put > a lot of > reliability in the vehicle somewhere - why not in > the engines? Which > you will use every time you fly, in contrast to the > blowout panels > which hopefully you will never use.
I can think of one possible explanation. I don't think it's quite what Pierce is thinking, but here goes... In order to have a catastrophic explosion, you could design a system so that failures X and Y both have to happen. If only one or neither happens, the vehicle is intact, and your population density * impact area is low - hopefully below 1E-6. An explosive failure would drive this far up, say to 1, but the probability of that is P(X_fail) * P(Y_fail) - so, 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), then you've demonstrated that 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. You could get away with only 100 test flights if you design it so that systems X, Y, and Z would all have to fail for an explosion - say, X being the valves that keep propellant and oxidizer from mixing in large quantities at any moment, Y being relief valves (not explosive blowout panels, to avoid igniting the fuel) rigged to open if said mixture is detected (say, if the pressure is not what it should be given expected fuel and oxidizer use at a given time), and Z being some system to prevent ignition that far back of the nozzle. It's not designed - and therefore theoretical - reliability, but proven reliability. Or am I misreading what the AST means by "proven"? _______________________________________________ ERPS-list mailing list [EMAIL PROTECTED] http://lists.erps.org/mailman/listinfo/erps-list
