Experimental Investigation of Minimum Required Cabin Sizing in Varying Gravity Levels

With the renewed emphasis on near-term human exploration beyond low Earth orbit, there is a reemphasized priority on the timely and cost-effective development of human spacecraft to support the planned missions. While smaller systems are less expensive to develop, there is little or no experimental data on the impact of smaller habitats on human performance. What data exists is primarily from microgravity experience; there is no meaningful flight data on crew performance in restricted volumes for operations on the Moon or Mars. This paper summarizes ongoing research in the University of Maryland Space Systems Laboratory under the support of the NASA X-Hab program to experimentally investigate the minimum effective cabin sizing and layout for critical elements of the space architecture, including launch and entry vehicles, surface ascent/descent vehicles, on-orbit and surface habitats, and pressurized rovers. Through the design and development of a modular resizable habitat mockup, tests of crew operations including nominal mission operations, maintenance and repair tasks, logistics management, and food preparation are assessed as a function of cabin volume, length/diameter ratio, and horizontal vs. vertical orientation of the cylindrical pressure vessels. Tests focus on various configurations with habitable volumes between 5 and 22 cubic meters, and crew sizes ranging from 2-4. While initial plans included significant laboratory testing, dealing with safety restrictions due to the COVID epidemic has caused a change to almost entirely underwater testing, which allows the use of body segment ballasting to simulate microgravity, lunar, and Mars gravity levels. While the use of the underwater simulation environment precludes long-duration studies such as those performed in analogue field sites, the ability to repeat activities in varying habitat configurations at differing gravitations provides new insight into future spacecraft cabin/habitat design.