This design of the liquid-cooling garment for NASA spacesuits allows the suit to remove metabolic heat from the human body more effectively, thereby increasing comfort and performance while reducing system mass. The garment is also more flexible, with fewer restrictions on body motion, and more effectively transfers thermal energy from the crewmember’s body to the external cooling unit. This improves the garment’s performance in terms of the maximum environment temperature in which it can keep a crewmember comfortable.
The garment uses flexible, highly thermally conductive sheet material (such as graphite), coupled with cooling water lines of improved thermal conductivity to transfer the thermal energy from the body to the liquid cooling lines more effectively. The conductive sheets can be layered differently, depending upon the heat loads, in order to provide flexibility, exceptional in-plane heat transfer, and good through-plane heat transfer. A metal foil, most likely aluminum, can be put between the graphite sheets and the external heat source/sink in order to both maximize through-plane heat transfer at the contact points, and to serve as a protection to the highly conductive sheets. Use of a wicking layer draws excess sweat away from the crewmember’s skin and the use of an outer elastic fabric ensures good thermal contact of the highly conductive underlayers with the skin.
This allows the current state of the art to be improved by having cooling lines that can be more widely spaced to improve suit flexibility and to reduce weight. Also, cooling liquid does not have to be as cold to achieve the same level of cooling. Specific areas on the human body can easily be targeted for greater or lesser cooling to match human physiology, a warmer external environment can be tolerated, and spatial uniformity of the cooling garment can be improved to reduce vasoconstriction limits.
Elements of this innovation can be applied to other embodiments to provide effective heat transfer over a flexible and surface-conformable fashion without the limitation of fluid freeze points.
This work was done by Warren P. Ruemmele, Grant C. Bue, and Evelyne Orndoff of Johnson Space Center and Henry Tang of Muniz Engineering. For more information, download the Technical Support Package (free white paper) at www.techbriefs.com/tsp under the Bio-Medical category. MSC-24189-1
This Brief includes a Technical Support Package (TSP).
Advanced Liquid-Cooling Garment Using Highly Thermally Conductive Sheets
(reference MSC-24189-1) is currently available for download from the TSP library.
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Overview
The document outlines the development of an Advanced Liquid-Cooling Garment utilizing highly thermally conductive sheets, aimed at improving the performance and comfort of astronauts and personnel in extreme environments. This innovation addresses limitations of the current state of the art (SOA) in thermal management systems, particularly in NASA space suits and similar applications in the Department of Defense (DoD) and commercial sectors.
The primary problem identified is the inefficiency of existing fluid cooling systems, which can lead to hot and cold spots, increased stiffness, and weight, ultimately affecting crew performance and comfort. The proposed solution involves the use of flexible, highly thermally conductive materials, such as graphite sheets, combined with improved thermal conductivity cooling water lines. This design allows for more effective heat transfer from the body to the cooling lines, enabling several advantages: wider spacing of cooling lines for enhanced suit flexibility, reduced weight, less reliance on extremely cold cooling liquids, targeted cooling for specific body areas, improved tolerance to warmer external environments, and greater spatial uniformity in cooling distribution.
The garment's unique features include a layered construction of conductive sheets to optimize both in-plane and through-plane heat transfer, the incorporation of a metal foil (likely aluminum) to enhance thermal contact and protect the conductive layers, a wicking layer to manage sweat, and an outer elastic fabric to ensure good thermal contact with the skin. These innovations collectively aim to maintain an acceptable temperature for the wearer by efficiently transferring metabolic heat away from the body.
The document also highlights the potential commercial applications of this technology, which could extend to surgical cooling vests, HAZMAT suits, combat fatigues, high-performance athletic wear, and fire suits for race car drivers. The anticipated development process is expected to be straightforward, supported by detailed thermal analysis and prototype testing to mitigate errors.
In summary, the Advanced Liquid-Cooling Garment represents a significant advancement in thermal management technology, promising to enhance comfort, performance, and safety for users in various high-stress environments.
