Parametric Analysis of Internal Heat Transfer for Full-Body Radiative-Cooled Space Suit Concepts

The metabolic heat produced by astronauts working in their space suits must be removed from the space suit system to avoid overheating, while also ensuring sufficient insulation in cold environments to avoid undercooling. Traditional space suits achieve this through an insulated space suit, a liquid-cooling garment to collect the heat, and a central heat sink in the PLSS backpack. A novel design aims to reduce the mass and reliance on consumables of such a system by utilizing the entire external space suit surface as a radiator. A variable emissivity (VE) coating on the suit exterior provides a method to control the environmental heat flux and maintain thermal comfort for the astronaut within. Previous studies of this concept have shown promising results and possible methods of implementation but neglected the heat transfer within the suit. These internal heat paths, from astronaut to external suit radiator are characterized in this paper. The range of metabolic heat loads that can be maintained in comfortable steady-states is evaluated in Martian and Lunar environments. The evaluation considers a full day in each of the environs, including seasonal differences between summer and winter on Mars. Both gas pressure and mechanical counterpressure suit architectures are considered and characterized separately since the functionality of the two inherently changes the way heat can be transferred within. Due to a large number of unknowns in this suit design, the characterization is supplemented with a sensitivity analysis of the overall performance to variations in key parameters. Results show that nominal heat loads of 300 W can be maintained in comfortable steady-states in nearly all scenarios. Additionally, a substantial impact on performance by the contact conduction between astronaut skin and suit interior is identified in the GP architecture. Other key factors include the suit conductivity and range of the variable emissivity technology.