For planetary applications, the space suit insulation has unique requirements because it must perform in a dynamic mode to protect humans in the harsh dust, pressure and temperature environments. Since the presence of a gaseous planetary atmosphere adds significant thermal conductance to the suit insulation, the current mu lti-layer flexible insulation designed for vacuum applications is not suitable in reduced pressure planetary environments such as that of Mars. Therefore a feasibility study has been conducted at NASA to identify the most promising insulation concepts that can be developed to provide an acceptable suit insulation. Insulation concepts surveyed include foams , microspheres , microfibers, and vacuum jackets. The feasibility study includes a literature survey of potential concepts, an evaluation of test results for initial insulation concepts , and a development philosophy to be pursued as a res ult of the initial testing and conceptual surveys . The recommended focus is on rnicrofibers due to the versatility of fiber structure configurations , the wide ch oice of fiber materials avail able , the maturity of the fiber processing ind ustry , and past experience wi h fibers in insu lation applications.
INTRODUCTIONHEAT BALANCE FOR SUITED CREWMEMBERTo better understand the effect of insulation on the su ited crewmember, an overall heat balance must first be presented , along with a breakdown of the individual heat contributions. Figure 1 shows the overall heat balance terms. The heat input term is the heat generated within the crewmember enclosure, or Qgen , consisting of metabolic heat and equipment loads. Heat output terms are the heat removed by the thermal control system, or Qtes , an(:l the heat lost to the environment through the insulation and suit enclosure, or Qsuit-leak.
Luis A. Trevino and Evelyne S. Orndoff
NASA Johnson Space CenterThe heat loads can further be sub-divided into individual thermal environment contributions, as shown in Figure 2. Here the Qsuit-Ieak term has been replaced by three terms. The absorbed thermal radiation , or Qabs, is that due to the net solar and infrared radiation absorbed by the outer surfaces of the EMU. Of importance in this term are the solar absorption property , Ct, and the infrared absorption property , E, of the outer suit materials. A second term is the emitted radiation from the suit surface, or Qemitted, which also involves the infrared absorption property E. Finally , in a gaseous environment such as on Mars, a third term is the heat lost to the gas, or Qlost-to-gas . The gas term in tum
