Surface Vehicle Atmospheric Considerations for Moon to Mars Exploration
NASA and its Artemis commercial providers are continuing to address and mitigate flammability concerns at planned vehicle atmospheres on the lunar surface. Challenges include close integration between materials flammability, ignition control, fire mitigation, human physiology and performance, and spacesuit mobility and performance. Past NASA recommendations for vehicle atmospheres identified some of these challenges as open work, but they were not funded through completion. In winter 2022, NASA created a team dedicated to this problem, including all relevant stakeholders, to develop a strategy to quantify the integrated issue, reduce the severity of its impacts, and, if needed, provide alternative options to program management. This paper outlines key discussions, assumptions, interdependencies, analysis, and testing that led to the exploration atmosphere team’s findings and recommendation of an optimized vehicle atmosphere and approach for early surface missions. These efforts not only shape the path to flight certification for those surface missions, but will improve the development and certification processes through updated materials flammability standards, vehicle configuration constraints, fire barrier effectiveness, ignition guidelines, and partial gravity impacts on flammability. Additionally, recent vehicle and spacesuit design efforts have allowed the team to challenge long-standing norms and assumptions to potentially provide more mission flexibility through improved fire suppression, elevated spacesuit operating pressures, and advanced vehicle environmental control systems. The team has also identified areas where standards or guidelines are insufficient for cumulative mission decompression sickness risk and partial gravity compensation factors. These efforts will lay the groundwork for future surface elements and missions to follow a similar process, reducing development time and flammability risk while providing clear guidance on a path to certification.