Analysis Classes for Space Exploration Reliability Assessments

Understanding and effectively communicating the spectrum of risk and reliability analysis classes is critical for an analyst to contribute to a team working on developmental space exploration architecture, mission, vehicle, or technology design. The proper characterization of class prior to the risk and reliability analysis can help calibrate stakeholder expectations with regard to required data inputs as well as anticipated outputs and insights. It can also help in the elicitation of data and cooperative participation from technical experts. This analysis class spectrum is bound on the bottom by low fidelity analyses conducted early in design definition cycles when designers and decision makers are looking for qualitative differences in design options to help discriminate, from a risk standpoint, and incorporate inherent safety into a design. At the other end of this spectrum, classic reliability assessment tools are applied to well defined or even operational hardware. These component level reliability analyses use Probabilistic Risk Assessment (PRA), Failure Mode and Effects Analysis (FMEA), and Hazard Analysis (HA) methodologies to quantify system level reliability values with relatively high confidence. For example, the risk and reliability analysis performed during the early definition of exploration architectures such as the Mars Architecture is significantly different from the analysis performed in support of an existing vehicle such as the Space Shuttle. Levels of design definition, requirement refinement, speed of design iterations, and available system data determine where on this spectrum an analysis will fall as shown in Figure 1. The proper classification and corresponding analysis type is critical to successfully adding value to design iterations.