Qualitative reliability growth — An affordability screening approach

The Orion program, the United States' next generation crewed spacecraft, was tasked with providing reliability growth analysis at the component level. With more than four-hundred unique Orion components, there are far too many to perform traditional or quantitative reliability growth assessments given the limited analytical resources. In order to provide decision-makers with insights into the risk of early Orion flights however, a qualitative reliability growth analysis was employed. Qualitative reliability growth uses engineering judgment based on ordinal scales [1] to estimate the growth expected between early test flights and the mature Orion vehicle. The goal of this type of growth analysis is to identify the top drivers affecting the reliability growth of the vehicle. Hence, qualitative reliability growth analysis is an affordability screening exercise that focuses limited resources by highlighting key reliability growth opportunities. Qualitative reliability growth analysis was applied to the first test flight of the Orion vehicle. The effort identified several risk groupings composed of twenty components that warrant further scrutiny using quantitative or conventional reliability growth techniques.