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The study of conceptual designs for a space suit Personal Life Support Subsystem (PLSS) at the Texas Engineering Experiment Station resulted in the recommendation to NASA of an evolution path from the existing PLSS to a long duration, low mass PLSS suitable for Martian missions. The replacement of the water sublimator cooling unit by a radiator-mechanical heat pump subsystem was one of the key technology upgrades for this evolution. The assessment was based on using a carbon radiator and mechanical heat pump. The “Lunar Noon” environment was used for sizing the system. The effect of lunar dust on the radiator and choice of refrigerant fluid were considered. A survey of previous work on high temperature heat pumps was made in order to estimate the maturation time for the heat pump technology. We concluded that a heat pump radiator using water as its cooling fluid was the best alternative.

Conceptual designs for a space suit Personal Life Support Subsystem (PLSS) were developed and assessed to determine if upgrading the system using new, emerging, or projected technologies to fulfill basic functions would result in mass, volume, or performance improvements. Technologies were identified to satisfy each of the functions of the PLSS in three environments (zero-g, Lunar, and Martian) and in three time frames (2006, 2010, and 2020). The viability of candidate technologies was evaluated using evaluation criteria such as safety, technology readiness, and reliability. System concepts (schematics) were developed for combinations of time frame and environment by assigning specific technologies to each of four key functions of the PLSS -- oxygen supply, waste removal, thermal control, and power. The PLSS concepts were evaluated using the ExtraVehicular Activity System Sizing Analysis Tool, software created by NASA to analyze integrated system mass, volume, power and thermal loads.

Sending humans to the moon and Mars in support of NASA’s Vision for Space Exploration (VSE) presents a variety of operational environments in which astronauts will need to wear a space suit, both inside the vehicle and during Extravehicular Activity (EVA). Four feasible suit architectures were proposed by NASA in terms of the number and type of suits needed to enable task performance in scenarios ranging from launch and entry operations to conducting EVA’s in microgravity and on planetary surfaces. This study was aimed at defining space suit operational and functional needs across the spectrum of mission elements called out in the VSE, identifying temporal and technical design drivers, and establishing appropriate trade variables with associated weighting factors for analyzing the proposed architecture options. Recommendations from the analysis are offered for consideration in selecting from the four options.