Application of risk assessment for the NASA Vision for Space Exploration

Many quantitative reliability analyses and risk assessments of space systems have been criticized for unrealistic results. One reason for this may be that the analysis usually assumes that systems are mature. Unfortunately, limited budgets reduce the flight rates for systems to a level where maturity is never reached before a new design is proffered. If quantitative studies are to be depended upon for programmatic decisions, new methods must be applied to improve the usefulness and credibility of the analysis. Probabilistic risk analysis is becoming an integral part of decision making for NASA's Vision for Space Exploration (VSE). Since the Exploration Systems Architecture Study (ESAS), a number of high-level trade studies have been performed to evaluate options concerning NASA's architecture to support the transportation needs of the international space station and lunar missions including potential lunar bases. The risk analysis described here blended heritage information from existing systems and design features to create models that reflected mature reliability and assessed the effects of the flight manifest on maturing risk critical systems. This paper describes a multiple mission campaign model that illustrates the need for incorporating maturity into quantitative reliability and risk assessments.