Development of a New Prebreathe Protocol for Future Spacecraft Atmospheres

As human space exploration sets its goal to venture beyond low Earth orbit, toward long-duration missions to the Moon and Mars, the need for faster and more efficient Extravehicular activity (EVA) preparation becomes increasingly critical. Current prebreathe procedures used on the International Space Station (ISS) can last up to four hours, making them impractical and unsustainable for frequent or emergency EVAs in future extraterrestrial environments. In order to enable faster and safer operations, as well as to avoid decompression sickness, new prebreathe protocols need to be studied and developed. Therefore, this thesis investigates the physiological processes in the human body that lead to decompression sickness, and explores new options to mitigate the current long preparations. The existing human model in the MATLAB-environment Virtual Habitat (V-HAB), called Detailed Human, was expanded to also include Nitrogen dissolution processes. Using this updated model, different simulations were performed to analyze the effects of cabin pressure, atmospheric composition, and physical activity on denitrogenation. Results show that specific and optimized combinations of atmospherics characteristics and exercise profiles can significantly shorten prebreathe protocols while assuring crew safety. These findings pave the way for the development of more efficient prebreathe protocols tailored for faster and more flexible EVA operations for future exploration missions.