Downselection of Miniature X-Ray System for Spaceflight Applications

The inclusion of a handheld, portable x-ray system is hypothesized to improve the management of crew health during long-duration spaceflight missions. A ground demonstration was performed with three such miniature x-ray systems to determine the full capabilities of the technology within the context of a spaceflight environment and to evaluate its suitability for flight certification. Criteria developed during this demonstration were used to select the most suitable system to recommend for flight. The scope of the demonstration was defined with input from NASA flight surgeons, engineers, and operations experts. This scope was intentionally broad to support the identification of both clinical and nonclinical applications of the system and also to establish evaluation criteria for recommending the most appropriate system for a future flight demonstration. Considerations within scope included x-ray hardware design, clinical diagnostic capability, engineering failure analysis, and in-space science applications. The ground demonstration identified many distinct selection criteria to quantify these applications. These selection criteria were then condensed to 20 key figures of merit, allowing for uniform comparison between criteria and strong comprehension of the study by stakeholders. System scores for each figure of merit were obtained from ground demonstration data. Project stakeholders used pairwise rating to weight figures of merit by relative importance for different mission profiles (a space-station demonstration mission and a long-duration mission to Mars). The top system was then determined by summing the weighted scores for each system under consideration. The resulting recommendation for a portable x-ray system to include in spaceflight missions is robust to variations in scoring and weighting of the figures of merit. Rather than recommending the system with the smallest mass and volume, this process recommends the x-ray system that provides the most clinical capability. This highlights the impact of using pairwise weighting to support decision making in a trade study with many complex criteria. Stakeholder weighting identifies the most important decision-making criteria for the system under evaluation, concluding the ground demonstration effort with a recommendation of the portable x-ray system hypothesized to best improve health management and to reduce the most risk during a long-duration spaceflight mission.