Optimal Cooling Garment Design Based on Analysis, Modeling, and Testing
The thermal conductance of liquid cooling garments can limit the performance of future space suits that must provide thermal control and comfort in new and challenging environments. New design approaches can help design future suits for optimal performance. These approaches can build on extensive work that has been done developing and validating analysis, data, and modeling software for heat and moisture transport in garments for the design of terrestrial chemical/biological protective gear. The analysis is based on fundamental physics of heat and moisture transport in textiles and convective transport inside the garment ensemble, coupled with models of human thermoregulation characterizing metabolic heating, sweating, and respiration. The analysis and modeling methods have been validated through extensive testing of materials, fabrics, and garment components. Design models have been formulated that use the analysis methods to calculate performance of garment ensembles. Inputs to the models include garment definition (materials, fit, closures), environmental conditions, subject anatomy, activity rate and level of exertion, and mission parameters. Outputs include rates of heat and moisture transport throughout the garment system, cooling and evaporation from the wearer’s skin, and temperatures and relative humidity levels throughout the garment system. These models help designers screen and iterate design alternatives, explore “what if” scenarios, reduce the need for expensive full system testing, and lead to greater confidence that designs are optimized with respect to cost, weight, and performance. This paper describes the basic design methods, data and models; how these elements are applied to garment design; and how they can be used to improve the performance of future space suits. Use of these design methods could guide materials selection, testing, data assessment, and optimal garment design for future liquid cooling and ventilation garments. The payoff would be improved thermal conductance and comfort of future LCVGs, thus maximizing astronaut performance.