Influence of failure propagation on mission abort policy in heterogeneous warm standby systems

In many life-critical applications (e.g., spacecraft, aircrafts and chemical reactors), accomplishing a specified mission or aborting mission objectives in the case of certain condition being met to survive the system are both crucial. While conventional reliability models have typically focused only on evaluating the mission success probability, few of recent research addressed effects of mission aborts and studied system survivability. However, these works fail to consider propagated failures that can make significant contributions to the mission failure and may affect the optimal mission abort policy adopted for the system. In this paper, we suggest a numerical method for addressing effects of failure propagations in analyzing the mission success probability (MSP) and system survivability (SS) of 1-out-of-N warm standby systems subject to mission abort. The system may be heterogeneous, composed of components with different standby modes, and different performance and failure time distribution parameters. Both the activation sequence of those heterogeneous components and the adopted mission abort policy can affect the system performance metrics greatly. Therefore, we make further contributions by formulating and solving optimization problems that find the optimal mission abort policy for systems with any given component activation sequence or the optimal combination of mission abort policy and component activation sequence, maximizing the MSP while satisfying a desired SS level. Examples are provided to demonstrate influence of propagated failures on system performance and optimization solutions. Examples also show that the optimal abort policy determined can achieve a good balance between MSP and SS taking into account failure propagation.