A Parametric Comparison of Microgravity and Macrogravity Habitat Design Elements

With human space exploration currently in a state of ux, it is challenging to develop critical human systems, such as habitats, in the absence of a speci c known destination. Systems for Earth analogue testing, such as the Habitat Demonstration Unit developed by NASA and evaluated in recent Desert RATS eld tests, have been tasked with representing everything from Mars and lunar habitats to microgravity habitats for use on missions to near-Earth objects or long-duration human servicing missions. Launch vehicles are no better known than destinations at the moment, and potential habitat designs range from 4.5 meter diameters for existing expendable launch vehicles to 7-10 meter diameters for speculative future heavy-lift vehicles. This paper attempts to take a step back from the plethora of habitat point designs under consideration, and examines human space habitats based on parametric models of size, mass, and function, with a primary goal of reaching an informed decision on the degree to which an Earth analogue habitat in full Earth gravity can meaningfully represent habitats in substantial reduced gravities (moon, Mars) or in microgravity (NEOs, cislunar space, Martian moons). Using basic geometry and physics, this paper identi es a standard habitat element as a right circular cylinder with ellipsoidal endcaps, and assesses pressurized and habitable volumes and surface areas in various con gurations. This changes based on the need to provide standing head height in macrogravity, and the equivalent head height for a neutral body posture in microgravity. This leads to di erences between vertical and horizontal con gurations of habitat layouts, which are extended from geometric expressions of volumes and areas to mass estimating relationships for habitat overall mass based on geometric con guration. Simple physical models are created to understand the fundamentals of human motion in reduced gravities, such as increase in jumping capability, inadvertent freeight due to excess energy in standard locomotion, and alternate designs for stairs, ladders, and other systems for moving between vertically stacked decks in alternate gravitational environments. This is one of the primary areas of fundamental di erence between reduced gravity and microgravity, as energy requirements for climbing become meaningless in microgravity. Finally, the paper begins the deliberation in the e ectiveness of available and potential Earth analogue environments for higher delity assessment of habitat functionality and the development of a validated data base on reduced gravity design rules. While the U.S. space program has learned a great deal about microgravity habitat and workstation design in the last 30 years of shuttle operations, we are still at the beginning in terms of long-term life on the Moon or Mars.