Modelling Diversity in Redundant Systems: Case Study of Space Systems

Diversity plays an essential role in increasing reliability of redundant systems, however in safety and mission critical applications. The onboard computer of satellites and the flight computer of aircrafts, which are ultra-reliable system, utilizes various hardware platforms for their redundant architecture to resolve the common cause failure problem. Furthermore, the software is also developed by separate teams based on different software platforms to mitigate the specification and design flaws, and implementation mistakes. This paper focuses on modelling diversity of redundant systems using Markov reliability analyzing method. The proposed scheme is explored in two types of applications: mission critical applications (with long mission time) and safety critical applications (with short mission time). Analytical and simulation results show the effectiveness of diversity in increasing the reliability of these systems. Since about ten percent of all failures appear as common cause failures, which restrict reliability improvement through similar redundant modules, achieving ultra-reliable necessitate to consider diversity in these systems