Unveiling the System-of-Systems Complexity in Regenerative ECLSS: Insights from ISS

In regenerative Environmental Control and Life Support Systems (ECLSS), the intricate interconnectivity between subsystems is critical for ensuring sustainable life support in space habitats. This paper aims to provide a comprehensive analysis of ECLS subsystems by highlighting their interactions and dependencies within the larger system. While most studies focus on individual components or subsystems, the true complexity of ECLSS emerges at the system-of-systems level, where the connections between subsystems drive overall functionality and resilience. Due to the inherent complexity of ECLSS and its tightly coupled subsystems, understanding the holistic interdependence remains a challenge. This paper addresses this gap by using the International Space Station (ISS) as a case study, given its advanced regenerative ECLSS architecture. We walk through the major ECLS subsystems, deconstructing each one to examine its interdependencies, resource flows, potential failure modes, and backup mechanisms. For each subsystem, we explore subsystem decomposition: breaking down its components and functions, connections to other subsystems and resource exchanges, impacts of failures on interconnected subsystems, redundancy considerations and backup solutions in case of subsystem failure. An interconnectivity table will also be presented, illustrating the relationships between subsystems and how they contribute to the system-of-systems structure. This analysis provides new insights into the design, operation, and reliability of future regenerative ECLSS, with implications for long-duration missions and space habitat sustainability and exploration.