Space/Science — HabitableZone

Space/Science » in reply to re: Exactly on point

Standard practice is to design for the worst case scenario
Gary — (archived)

When designing an Entry, Descent and Landing (EDL) system it is impossible to come up with an exact solution. The physics involved is too complicated and there are too many unknowns, e.g. exact atmospheric density, entry angle, etc. Therefore a design approach based upon engineering approximations is used. The engineering approximations are inaccurate but their error bounds are known. When the heat shields were sized for Mars Exploration Rover (MER), it was known that all solutions of the engineering approximations within reasonable error bounds would yield successful landings. When I used the same methodology for Beagle-2, I discovered that most of the possible solutions resulted in failure. Beagle-2 was right on the hairy edge (actually slightly beyond the hairy edge). What frightened me about Beagle-2 was the miniscule probability of an extremely under funded, badly designed Mars lander actually working. Our arch-enemies, the "bean counters" would have slashed the budgets of all future Mars missions and then parroted back at us that if the British can do it for 10 cents on the dollar then so can we. The one fluke success of Beagle 2 would have resulted in many American spacecraft failing simply because they didn't hit the right part of the probability curve.

Gary

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