Mission success with components not as good as new

It is shown how the probability of mission success can be determined for cases of components which are not as good as new at the beginning of a mission and are not repaired during the mission. After a short definition of the appropriate conditional distribution functions of components lives, a few typical examples of plausible missions for redundant systems are discussed. Among these are such that are time-critical or—concerning flights—space-critical. Since only (advanced) probabilistic reasoning is used, there are no limitations as to the types of life distributions.