Comparison modeling of system reliability for future NASA projects

A National Aeronautics and Space Administration (NASA) supported Reliability, Maintainability, and Availability (RMA) analysis team developed a RMA analysis me thodology that uses cut set and importance measure analyses to compare model proposed avionics computing architectures. In this paper we will present an effective and efficient application of the RMA analysis methodology for importance measures that includes Reliability Block Diagram (RBD) Analysis, Comparison modeling, Cut Set Analysis, and Importance Measure Analysis. In addition, we will also demonstrate that integrating RMA early in the system design process is a key and fundamental decision metric that supports design selection. The RMA analysis methodology presented in this paper and applied to the avionics architectures enhances the usual way of predicting the need for redundancy based on failure rat es or subject matter expert opinion. Typically, RBDs and minimal cut sets along with the Fussell-Vesely (FV) method is used to calculate importance measures are calculated for each functional element in the architecture [1]. This paper presents an application of the FV importance measures and presents it as a methodology for using importance measures in success space to compare architectures. These importance measures are used to identify which functional element is most likely to cause a system failure, thus, quickly identifying the path to increase the overall system reliability by either procuring more reliable functional elements or adding redundancy [2]. This methodology that used RBD analysis, cut set analysis, and the FV importance measures allowed the avionics design team to better understand and compare the vulnerabilities in each scenario of the architectures. It also enabled the design team to address the deficiencies in the design architectures more efficiently, while balancing the need to design for optimum weight and space allocations.