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Automatic thermal comfort control for the minimum consumables PLSS is undertaken using several control approaches. Accuracy and performance of the strategies using feedforward, feedback, and gain scheduling are evaluated through simulation, highlighting their advantages and limitations. Implementation issues, consumable usage, and the provision for the extension of these control strategies to the cryogenic PLSS are addressed.

Automatic thermal control (ATC) was investigated for implementation into a spacesuit to provide thermal neutrality to the astronaut through a range of activity levels. Two different control concepts were evaluated and compared for their ability to maintain subject thermal comfort. Six test subjects, who were involved in a series of three tests, walked on a treadmill following specific metabolic profiles while wearing the Mark III spacesuit in ambient environmental conditions. Results show that individual subject comfort was effectively provided by both algorithms over a broad range of metabolic activity. ATC appears to be highly effective in providing efficient, “hands-off” thermal regulation requiring minimal instrumentation. Final selection of an algorithm to be implemented in an advanced spacesuit system will require testing in dynamic thermal environments and consideration of technology for advancement in instrumentation and controller performance.

The use of the Wissler Human Thermoregulation model has been demonstrated for various aspects of the design of liquid cooling garment (LCG) temperature control. Thermal performance of the LCG under various conditions and the simulation of control schemes have been studied. The benefits of the study arise during the design of an automatic control scheme for the LCG when numerous control algorithms and scenarios can be evaluated without costly and time-consuming experimentation.

Reclamation of purified water from waste water will be a necessity for self-sufficiency on Lunar and Martian outposts. Biological waste water treatment is advantageous because it has low temperature, low pressure, and low power requirements. Four different media were tested for use as biological growth substrates in bench-top aerobic trickling filter bioreactors in the Hybrid Regenerative Water Recovery Lab at Johnson Space Center. The four media tested included a mixture of open skeleton polypropylene spheres and cylinders, ceramic berl saddles, solid glass beads, and small rocks. The media were tested to characterize the organism inoculation rate; the steady state performance; the response to system upsets; and the column characteristics like flooding and channeling. Results indicate that the ceramic berl saddles performed best with respect to inoculation rate, steady state performance, and response to system upsets.