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Old 06-06-2017, 08:34 PM
scr4 scr4 is offline
Join Date: Aug 1999
Location: Alabama
Posts: 14,121
Originally Posted by Chronos View Post
Wouldn't the fact that it's lasted so much longer than its designed mission suggest that it's poorly engineered? That probably means that they could have made it cheaper while still accomplishing all of their goals.
It was designed to work in space for 11 years: almost 7 years enroute + 4 years of science observations. (Plus years of testing on the ground, probably.) So it's only 10 years beyond its design life - not even twice as long.

Also, when you're talking about reliability - if you design something so that there's a 99% chance of it surviving for 10 years, there's probably a 98% chance of it surviving for 20 years. Though of course, some things do have finite life determined by wear of moving parts, degradation from radiation, etc., and can't be thought of in terms of mean time between failure.