Overall reliability of multiply redundant systems

[Ed Whitacre]

I am trying 1-to find the equations to calculate the total system reliability of a system made up of multiply redundant identical strings. 2- Inversely, knowing the required end reliability to calculate the required reliability of each paralell string
Thanks - Ed

[Arai.M]

The system reliability of a system with N identical redundant units is:

Rs(t) = 1-(1-Ri(t))^N

Solving for Ri(t) gives

Ri(t) = 1 - log(1-Rs(t)) / N

Arai