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Handling and processing human feces in space habitats is a major concern and needs to be addressed for the Crew Exploration Vehicle (CEV) as well as for future exploration activities. In order to ensure crew health and safety, feces should either be isolated in a dried form to prevent microbial activity, or be processed to yield a non-biohazardous product using a reliable technology. During laboratory testing of new feces processing technologies, use of “real” feces can impede progress due to practical issues such as safety and handling thereby limiting experimental investigations. The availability of a non-hazardous simulant or analogue of feces can overcome this limitation. Use of a simulant can speed up research and ensure a safe laboratory environment. At Ames Research Center, we have undertaken the task of developing human fecal simulants. In field investigations, human feces show wide variations in their chemical/physical composition.

The white rat, Rattus norvegicus has been used extensively in microgravity flights. Initial NASA flight experiments with rats supported the Shuttle Student Involvement Program (SSIP). Hardware to house the rats was called the Animal Enclosure Module (AEM). The AEM for the SSIP, fit into a middeck locker. Potatoes provided water; food bars, glued on the walls, provided nourishment. Waste was absorbed and odor and microbial growth controlled by sandwiched phosphoric acid treated charcoal and filter materials utilizing much of the technology employed in the Rodent Research Animal Holding Facility, a Spacelab piece of equipment. The SSIP AEM potato “watering” system succumbed to mold and had to be replaced by real water contained within plasma bags. A metal enclosure housed the plasma bags between two heavy springs which forced water through animal activated lixits.

Management of human feces and wastes is a major challenge in space vehicles due to the potential biohazards and malodorous compounds emanating during collection and storage of feces and wastes. To facilitate safe, yet realistic human waste management research, we have previously developed human fecal simulants for research activities. The odoriferous compounds in feces and wastes reduce the quality of life for astronauts, can reduce performance, and can even cause health problems. The major odoriferous compounds of concern belong to four groups of chemicals, volatile fatty acids, volatile sulfurous compounds, nitrogenous compounds and phenols. This paper attempts to review the problem of odor detection and odor control with advanced technology. There has been considerable progress in odor detection and control in the animal industry and in the dental profession.

A microwave powered solid waste stabilization and water recovery prototype was delivered to Ames Research Center through an SBIR Phase II contract awarded to Umpqua Research Company. The system uses a container capable of holding 5.7 dm3 volume of waste. The microwave power can be varied to operate either at full power (130 W) or in a variable mode from 0% and 100%. Experiments were conducted with different types of wastes (wet cloth, simulated feces/diarrheal wastes, wet trash and brine) at different levels of moisture content and dried under varying microwave power supply. This paper presents the experimental data. The results provide valuable insight into the different operation modes under which the prototype can be used to recover water from the wastes in a space environment. Further investigations and testing of the prototype are recommended.

Space Station Freedom will provide an opportunity to conduct long duration life sciences research on plants and animals in a microgravity environment. Studies will be able to determine the rate of change of various processes in animals, e.g., calcium loss from bones, muscle atrophy, etc., determine the effect of microgravity on plant respiration and transpiration, and assess the impact of the microgravity environment over multiple generations for both plants and animals. However, all of these processes may also be affected by the 5.3 mm Hg partial pressure of CO2 (7000 ppm) currently specified for Space Station Freedom. The specifications for the plant and animal habitats to be developed as part of the Centrifuge Facility require that the CO2 level for plants be controlled over the range of 0.23 -2.3 mm Hg (300 to 3000 ppm ± 10-50 ppm) and that the atmospheric composition (CO2 level) for rodents be ± 1 % of the cabin composition.

A Microwave Enhanced Freeze Drying Solid Waste (MEFDSW) processor was delivered to NASA-Ames Research Center by Umpqua Company having been funded through a Small Business Innovative Research Phase II program. The prototype hardware was tested for its performance characteristics and for its functionality with the primary focus being the removal of water from solid wastes. Water removal from wastes enables safe storage of wastes, prevents microbes from growing and propagating using the waste as a substrate and has potential for recovery and reuse of the water. Other objectives included measurements of the power usage and a preliminary estimate of the Equivalent System Mass (ESM) value. These values will be used for comparison with other candidate water removal technologies currently in development.

Spacelab-J was an international Spacelab mission with numerous innovative Japanese and American materials and life science experiments. Two of the Spacelab-J experiments were designed over a period of more than a decade by a team from NASA-Ames Research Center. The Frog Embryology Experiment investigated and is helping to resolve a century-long quandary on the effects of gravity on amphibian development. The Autogenic Feedback Training Experiment, flown on Spacelab-J as part of a multi-mission investigation, studied the effects of Autogenic Feedback Therapy on limiting the effects of Space Motion Sickness on astronauts. Both experiments employed the use of a wide variety of specially designed hardware to achieve the experiment objectives.

Waste Management Systems (WMSs) designed for use aboard long-term spacecraft missions and within Lunar and planetary habitations must reduce volume and recover useful resources from solid wastes, as well as impart chemical and microbial stability to stored wastes. Many WMS processes produce high concentrations of toxic emissions that can periodically overwhelm Trace Contaminant Control Systems (TCCSs) designed to handle nominal atmospheric contaminants. A prototype Catalytic Oxidation System (COS) has been developed for this contingency, and when mated to different WMS processes, will treat these toxic emissions on an as-needed basis. The COS reactor utilizes a platinum and ruthenium bimetallic catalyst supported on mesoporous zirconia that is highly active and oxidizes at relatively low temperature a wide variety of volatile organic compounds (VOCs) and inorganic toxic emissions produced by WMS processes.

Several solid waste management (SWM) systems currently under development for spacecraft deployment result in the production of a variety of toxic gaseous contaminants. Examples include the Plastic Melt Waste Compactor (PMWC) at NASA - Ames Research Center1, the Oxidation/Pyrolysis system at Advanced Fuel Research2, and the Microwave Powered Solid Waste Stabilization and Water Recovery (MWSWS&WR) System at UMPQUA Research Company (URC). The current International Space Station (ISS) airborne contaminant removal system, the Trace Contaminant Control Subassembly (TCCS), is designed to efficiently process nominal airborne contaminants in spacecraft cabin air. However, the TCCS has no capability to periodically process the highly concentrated toxic vapors of variable composition, which are generated during solid waste processing, without significant modifications.

The inedible portion of plant biomass in closed regenerative life support systems must be reprocessed producing recyclable by-products such as carbon dioxide, sugars, and other useful organic species. High solids biomass slurries containing up to 27 wt% were successfully prepared in a stirred batch reactor and then pumped using a single piston valveless pump. Wheat straw, potato, and tomato crop residues were acid hydrolyzed using 1.2 wt% sulfuric acid at 180°C and 1.2 MPa for 0.75-1.5 hours. Viscosity for a 25 wt% acid hydrolyzed wheat straw emulsion (Bingham-plastic) was 6.5 centipoise at 3 cm/sec and 25°C.

The effects of acoustic levels in manned space vehicles was not thoroughly appreciated until the STS 40 mission, Spacelab Life Sciences 1 (June, 1991). Previous to that mission, waivers were submitted and equipment operated without overwhelming effect on ongoing flight activities. The factors of multiple pieces of noise producing equipment operating simultaneously, operating in the vicinity of crew sleep stations, and operating for this long of a mission (10 days) became relevant in crew tolerance, fatigue, communication, and permanent shifts in hearing thresholds. Because this was a life sciences mission, accurate instrument measurements were obtained of acoustic levels in the middeck, flight deck and spacelab during flight and physiological measurements were obtained from the crew members during all phases of the mission. Due to the STS 40 results, a Spacelab/Payloads Acoustics Working Group (SPAWG) was formed post flight to address acceptable acoustic limits.