Reliability tool for initial quantified functional risk and hazard analysis

Execution of NASA's Vision for Space Exploration through Project Constellation involves the integration of multiple mission architecture and vehicle design teams. One of these is the Altair Lunar Lander Design Team, which had chosen to approach the vehicle development through a process of risk-informed design. Following the "de minimus" concept, a single string minimally functional vehicle that can perform all the mission requirements was created as a baseline design. This exercise, performed by the Altair Design Team, ensured the minimal mass vehicle would fit within the design constraints and established what mass margin would be available for enhancement of the design. The design team, with the help of an outside contractor, developed a risk model to identify risk drivers for Loss of Mission (LOM) and Loss of Crew (LOC). The team then used the model to identify and evaluate design alternatives, which informed project managers about adding design features (mass) to the vehicle in order to reduce the risk. The following paper discusses the development of this model and the logic, which provided the support to component and system level probability estimates of LOM and LOC for the Altair Design Reference Mission (DRM) and alternate system configurations. Analyses of the risk results provided the design team with vital feedback regarding the relatively high- risk systems within the vehicle. This allowed for critical improvements to the design through "differences that make a difference." Overall modeling transparency and speed of analysis were considered essential to proper model development. The Altair Design Team was aided in choosing options that would provide greatest improvement in mission success and crew safety for a given mass. In a six-week period, 26 design trades were performed and 125 options were analyzed. The model was developed to reflect the mission requirements and vehicle design for the next generation Lunar Lander. However, the logic behind the reliability study can be used to evaluate other, similar systems or missions.