Defining the Required Net Habitable Volume for Long-Duration Exploration Missions

—As the National Aeronautics and Space Administration continues planning for long-duration space missions, specifically to Mars, it will be necessary to understand the requirements for a “transit habitat”, the element that the crew will live in as they travel to and from Mars. In particular, understanding of volume requirements for the transit habitat is of significant importance because the volume is a first order driver of the habitat size and mass, and therefore the propulsion and propellant requirements for future Mars missions. Despite this importance, there is significant uncertainty regarding how much habitable volume is required to support the crew on these missions. Prior studies provide valuable background, but their focus has largely been on investigating historical analogs in order to develop parametric sizing formulas. Other research has focused on specific drivers of habitat volume and stressors to the crew. However, there has been limited focus on establishing a comprehensive minimum required habitable volume based on crew activity needs and crew health requirements. This paper will describe a detailed effort to establish the minimum required net habitable volume for a Mars Transit Habitat employing a bottom-up methodology. The process used to establish volumetric requirements involves the definition of a set of specific “crew functions” and the assignment of required volumes to each function. This type of bottom-up approach is the most accurate method to establish required habitat volume and is specifically recommended by the NASA Chief Medical Officer for future space missions. The authors established a taxonomy of crew functions that could be required during a Mars transit. These functions include direct operational activities, such as command and control or system maintenance, habitation activities, such as eating and sleeping, or