Assessing complex failure scenarios of on-board distributed systems using a Markov chain

Vulnerability reduction is an important topic during the design of naval ships because they are designed to operate in hostile environments and because their on-board distributed systems are becoming increasingly complex. The vulnerability needs to be addressed in the early design stages already, in order to prevent expensive or time-consuming modifications in later, more detailed design stages. However, most existing methods for assessing the vulnerability are better suited for more detailed design stages. Furthermore, existing methods often rely on pre-defined damage scenarios, while damage–or system failure in general–may also occur in ways that were not expected beforehand. This paper proposes a method that addresses these gaps. This is done by incorporating several additions to an existing vulnerability method that has been developed by the authors, using a Markov chain. With this method, there is no longer a need for modelling individual hits or failure scenarios. The additions are illustrated by two test cases. In the first one, a notional Ocean-going Patrol Vessel is considered, and damage is related to physical locations in the ship. The second test case considers a chilled water distribution system in more detail, with failures modelled independent from the physical architecture. The quantitative nature of the results provide an indication of the generic, overall vulnerability of the distributed systems, which is meant to be used in the early design stages for identifying trade-offs and prioritising capabilities.