Modeling a highly reliable fault-tolerant guidance, navigation, and control system for long duration manned spacecraft

The use of a reliability modeling simulation tool to evaluate the reliability of a hypercube multiprocessor which is a candidate architecture for guidance, navigation, and control systems for long-duration manned spacecraft is described. The simulation tool was used to evaluate homogeneous Markovian, nonhomogeneous Markovian, and non-Markovian models of the hypercube. The study focuses on the effect of assuming Weibull decreasing component failure rates compared to the usual assumption of constant component failure rates. The effect of the use of cold spares on system reliability under the assumption of both constant and Weibull decreasing failure rates is also examined. The authors discuss simulation applied to discrete-state reliability models and the role that importance sampling can play. The results obtained from the models under the differing assumptions about failure rate behavior are presented