SMART: A propositional logic-based trade analysis and risk assessment tool for a complex mission

This paper introduces a new trade analysis software called the Space Mission Architecture and Risk Analysis Tool (SMART). This tool supports a high-level system trade study on a complex mission, such as a potential Mars Sample Return (MSR) mission, in an intuitive and quantitative manner. In a complex mission, a common approach to increase the probability of success is to have redundancy and prepare backups. Quantitatively evaluating the utility of adding redundancy to a system is important but not straightforward, particularly when the failure of parallel subsystems are correlated. SMART offers the unique capability of handling correlated redundancies and accurately evaluating the probability of mission success as well as its sensitivity to the reliability of mission components. It can also perform Monte-Carlo analysis to find the confidence interval of the success probability, total mission cost, and total mass. Additionally, SMART provides a GUI interface based on Matlab/Simulink that allows users to graphically define mission architecture as well as the logical relationship between mission components and outcomes. These analysis capabilities enable to answer questions such as: “for a given upper bound on total cost and mass, on which subsystem should we implement redundancy to maximize the chance of mission success?” Although the focus of SMART is high-level trade analysis, it also provides an interface to detailed models of mission components, allowing to perform an integrated analysis that covers from low-level details to high-level architecture. The analysis capabilities are enabled by our unique propositional logic-based approach. SMART translates the graphical mission model to a propositional logic representation through symbolic computation. We demonstrate SMART´s analysis capabilities on a MSR model as well as a model of a fictional mission.