A Measure of Reliability and Information Quality in Redundant Systems

In the development of complex military electronic equipment, It is necessary to consider the effects of many interacting operational and design factors. For both the over-all weapon system, and for the electronic subsystems with which we are concerned, optimum trade-offs for such interdependent parameters as reliability, weight, accuracy, maintainability, cost, mission time, and target vulnerability must be determined. Considered individually, these parameters do not adequately describe the operational worth of equipment incorporating multiple redundancies and operating modes. Operational worth is the probability that a system will achieve success in performing its required functions, and is obviously a prime consideration in the planning and selection of systems for military applilcation. The inadequacy in describing operational worth in terms of its individual parameters was encountered in the synthesis of an optimum redundant configuration for the B-58 bombing-navigation system. To resolve this difficulty, operational worth models describing the interaction between parameters were developed and utilized by Sperry Gyroscope Company. These techniques enabled Sperry to design this bombing-navigation system to have a high operational worth and an inherent mission reliability in excess of 95 per cent. In this paper, the model for ``system worth,'' the interaction between reliability and information quality, is discussed.