Factors that Influence the Acceptance of New Aerospace Risk Assessment Techniques

Abstract

With the rise of new space missions such as NASA’s Dragonfly that will include a nuclear-powered rotorcraft for exploring Saturn’s icy moon, Titan, as well as deep space missions that cannot rely on solar power, new risk assessment strategies are needed that balance the need for safety against the impracticality of lifetime testing. Risk assessments for existing nuclear technologies and, more broadly, safety-critical systems can widely vary in approaches and outcomes, with significant cultural influences. Some safety-critical systems like driverless cars and surgical robots have been authorized to operate with little or highly questionable risk assessments. Others using well-established probabilistic-based risk assessment methods such as those used for Stirling-based convertors for Radioisotope Thermoelectric Generators have struggled to convince relevant agencies that risk is acceptable. Case studies show that risk-averse oversight groups tend to rely more on concepts of heritage for technology risk assessments, which is the existence of either observed data from actual or similar operational systems. While reliance in heritage may reduce risk, it can result in incremental, evolutionary technologies instead of revolutionary ones, in effect stifling innovation. This notion of heritage can also lead to a misperception of acceptable risk under the guise of a regulatory concept termed equivalence, which allows new technologies to be fielded based on erroneous technical comparisons, much like the Boeing 737 MAX. More work is needed to understand the interplay between probabilistic-based risk assessments, notions of equivalence and heritage, and the culture of oversight agencies.