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Terraforming of Mars is the long-term goal of colonization of Mars. However, this process is likely to be a very slow process and conservative estimates involving a synergetic, technocentric approach suggest that it may take around 10,000 years before the planet can be parallel to that of Earth and where humans can live in open systems (Fogg, 1995). Hence, for the foreseeable future, any missions will require habitation within small confined habitats with high biomass to atmospheric mass ratios, thereby requiring that all wastes be recycled. Processing of the wastes will ensure predictability and reliability of the ecosystem and reduce resupply logistics. Solid wastes, though smaller in volume and mass than the liquid wastes, contain more than 90% of the essential elements required by humans and plants.

The future of manned space exploration will be determined through a process which balances the innate need of humanity to explore its surroundings and the costs associated with accomplishing these goals. For NASA this balance is derived from economics and budgetary constraints that hold it accountable for the expenditure of public funds. These budgetary realities demand a reduction in cost and expenditures of exploration and research activities. For missions venturing out to the edge of habitability, the development of cost effective life support approaches will have a significant influence on mission viability. Over the past several years a variety of mission scenarios for Lunar and Mars missions have been developed. The most promising of these attempt to provide basic mission requirements at a minimum cost. As a result these missions are extremely power limited.

For wastewater treatment applications, membrane processes are known to provide excellent treatment but are subject to failure due to membrane fouling. The Direct Osmotic Concentration (DOC) system evaluated in this study provides a membrane based primary treatment process capable of overcoming this problem. A full scale test apparatus containing full scale test module membrane cells has been developed and has undergone preliminary testing that provides a basis for comparison with other primary water recycle process concepts. This study confirms and extends the initial testing of this hardware and determines the required improvements to the existing test mo dules. These improvements, in addition to future testing, are intended to complete the validation of the concept and mature the hardware to the point that human rated test equipment design and development can be based directly on the test module derived data.

NASA is currently developing two new human rated launch systems. They are the Crew Exploration Vehicle (CEV) and the Lunar Surface Access Module (LSAM). Both of these spacecraft will require new life support systems to support the crew. These life support systems can also be designed to reduce the mass required to keep humans alive in space. Water accounts for about 80% of the mass required to keep a person alive. As a result recycling water offers a high return on investment. Recycling water can also increase mission safety by providing an emergency supply of drinking water. This paper evaluates the potential benefits of two wastewater treatment technologies that have been designed to reduce the mass of the CEV and LSAM missions. For a 3 day CEV mission to the International Space Station (ISS) this approach could reduce the mass required to provide drinking water by 65% when compared to stored water. For an 18 day Lunar mission a mass savings of 70% is possible.

Direct osmotic concentration (DOC) has been identified as a potential wastewater treatment process for potable reuse in advanced life support systems (ALSS). As a result, further development of the DOC process is being supported by a NASA Rapid Technology Development Team (RTDT) program. DOC is an integrated membrane system combining three unique membrane separation processes including forward osmosis (FO), membrane distillation (MD), and reverse osmosis (RO) that is designed to treat separate wastewater streams comprising hygiene wastewater, humidity condensate, and urine. An aqueous phase catalytic oxidation (APCO) process is incorporated as post treatment for the product water. In an ongoing effort to improve the DOC process and make it fully autonomous, further development of the three membrane technologies is being pursued.

This study introduces new concepts in the function and placement of membrane based water treatment processes in Exploration Life Support (ELS) System design. These differences are in both form and function and have the potential to radically alter the current paradigms of thought within the ELS research community with regards to the limitations of conventional membrane water treatment. More importantly, they have the potential to change the placement of water processing by quite literally moving it “out of the box”, or in the case of ELS, the standard rack volume. Two possible systems, extremely small scale personal urine treatment and recycle (CEV Lightweight Contingency Water Treatment) and a similar but scaled up habitat wall embedded membrane water treatment pouch, are used to demonstrate the concepts involved.