Experimental Investigation of Minimum Cabin Sizes at Varying Gravity Levels

The return to the development of near-term human exploration missions beyond low Earth orbit has necessitated renewed investigation of low size, low mass, and cost-effective human spacecraft. However, very little experimental data on the effects of smaller cabin sizes on crew performance exists, and that which does is mainly focused on micro-gravity habitation in low Earth orbit and thus not directly extensible to the Moon or Mars. The focus of this research is to experimentally analyze the impact of reducing habitat size on crew performance to determine the minimum effective habitat volume for future manned spacecraft. This paper summarizes ongoing research being conducted by the University of Maryland Space Systems Laboratory with support from the NASA X-Hab program to investigate minimum effective habitat and spacecraft sizing, as well as results and conclusions to date for crew effectiveness within restricted cabin volumes under short-term, high-workload testing conditions. Utilizing modular resizable habitat mockups, tests in habitats ranging from 5 to 25 m3 were conducted in simulated micro, Lunar, and Martian gravities through underwater testing with body-segmented ballasting, as well as a surface Earth-gravity control. The impact of size and configuration on crew effectiveness was measured by timed habitat translations, which are compared along with qualitative data to arrive at spacecraft sizing conclusions. While the underwater environment prevents long-duration studies, thus not allowing for analysis of the psychological impacts of smaller habitat sizes, the short-term, high-workload human effectiveness in varying gravity environments provides new insights into the sizing of future manned spacecraft designs.