Influence of ECLSS Performance on Spacecraft Habitability

Space habitats for human missions shall keep the crew alive, healthy, happy and productive. Together, these attributes inform habitability, "How well does the space habitat meet crew physiological, psychological, and resource needs throughout the mission?" First and foremost, the Environmental Control and Life Support System (ECLSS) must provide for crew metabolic inputs and manage their outputs. Sustenance of human life, i.e. "keep the crew alive", demands that these be met. ECLSS performance and efficacy also influence crew physical and behavioral health which in turn may affect productivity. For these reasons, habitability management requires active real-time assessment of ECLSS performance. In this paper, we define habitability parameters and organize them according to their categorical influence on "alive, healthy, happy and productive." Paramount among these are ECLSS design and operational parameters, factors affecting crew safety, and space habitat facilities and features that accommodate the crew. We discuss, assess and rank each for inclusion in a habitability index that will characterize the overall health of the space habitat. We then recommend a subset of habitability parameters to quantify ECLSS robustness.