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Adequate rejection of a variety of inorganic and organic compounds is necessary if reverse osmosis (RO) and nanofiltration (NF) membranes are to be used for space mission wastewater reuse. Three ersatz space mission wastewaters having different pH, conductivities, and amounts of organic compounds were tested to determine the membrane flux and the solute rejection for five RO and two NF membranes that are commercially available. The results show that the rejection of ions depend upon the solution pH which influences electrostatic repulsion, while for organic solutes the removal depends mainly upon the solute radius and molecular structure. In addition, the rejection of dissolved organic carbon depends upon the composition of the wastewater. The ratio of solute radius (ri,s) to effective membrane pore radius (rp) can be employed to predict the rejection of ions and organic compounds.

A critical function of life support systems on board manned spacecraft is to continuously revitalize the ambient air and to maintain its proper composition throughout the duration of the mission. This involves gaseous processes that need continuous monitoring. Sound traveling through a gas propagates at different speeds and attenuates to different degrees depending upon the composition of the gas. We previously justified conceptually the operation of a real-time gaseous process control monitor for gas mixtures based on acoustic attenuation and phase velocity. In the present study, on the theory front, we have refined a non-empirical model of acoustic propagation in polyatomic gases based on quantum mechanics and the kinetic theory of gases.

Energy-efficient and low temperature water treatment is desirable for long-term space missions. A Microbial Fuel Cell (MFC) is a hybrid between a fuel cell and a biological reactor that has a potential to make water treatment an energy-generating (not consuming) process. Microorganisms in a MFC biodegrade contaminants and exchange electrons with the fuel cell electrodes, generating electricity at ambient temperature. To test the feasibility of MFC as an energy-generating and water treatment process, we constructed a single-compartment MFC to generate electricity from acetate. Three MFC electrodes were connected to a potentiostat as follows: the working electrode was a graphite rod with 0.312″OD connected to a wire using silver epoxy; the reference electrode was a standard silver-silver chloride reference electrode; and the auxiliary electrode was a membrane electrode assembly consisting of Nafion-117 and VUIcan XC-72 with standard platinum loading of 0.5 mg/cm2.

A promising technology for recycling wastewater on long term space missions is rotating reverse osmosis (RO). Rotating RO utilizes Taylor vortices, a flow structure in the annulus of the device, that provide increased transport of the water through the RO membrane compared to conventional RO systems. A high pressure rotating RO filter and fluid circuit have been designed and fabricated for use in long term tests. Preliminary results indicate that an increase in the operating pressure by a factor of three can improve the flux by a factor of four while maintaining high rejection of the contaminants.

Reverse Osmosis (RO) is a compact process for the removal of ionic and organic pollutants from space mission wastewater. However, flux decline and rejection deterioration due to concentration polarization and membrane fouling hinders the application of RO technology. In this study, a rotating cylindrical RO membrane system is investigated as a novel method to reduce concentration polarization for space mission wastewater recovery. The model developed for rotating RO [1] allows the prediction of flux and pollutant rejection over a wide range of design and operation parameters. The model matches the experimental results from a lab-scale rotating RO very well. Operating parameters such as rotational speed and transmembrane pressure play an important role in determining the flux and rejection in rotating RO. A rotational speed sufficient to generate Taylor vortices in the annulus is essential to maintain high flux as well as high rejection.

Variations in fuel composition can cause non-optimal natural gas engine performance and may affect engine durability. The sound speed in natural gas can be used as a measure of fuel quality, since it changes with the molecular weight of the gas. Sound speeds measured for twelve gas compositions matched theory. Based on over 6700 gas compositions, the sound speed correlates well with percent methane, percent non-methane hydrocarbons, density, and methane number. Moderate correlation results for the air-fuel ratio, hydrogen-to-carbon ratio, Wobbe index, and lower flammability limit. A sound speed sensor could provide input for engine control based on the quality of the natural gas.

Automotive design projects offer an outstanding opportunity for students to obtain practical experience in engineering design. Over the last three years student groups have competed in one such project, The Natural Gas Vehicle Challenge, which involved converting a pickup truck to be fueled by natural gas. This paper reports a survey of faculty advisors involved with the project at the competing universities. Fifteen students were typically involved in the project at each university participating in the competition. Five or six were usually “key” to the project. Usually faculty advisors had a research interest in automotive engineering or alternate fuels, and they often incorporated the project into a design course. Although the funding level for such a design project varied substantially, the typical funding level for one year was about $25,000, most of which came from local sponsors.