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A cyclic two-step process is described which forms the basis for a simple and highly efficient air purification technology. Low molecular weight organic vapors are removed from contaminated airstreams by passage through an optimized sequence of sorbent media layers. The contaminant loaded sorbents are subsequently regenerated by thermal desorption into a low volume inert gas environment. A mixture of airborne organic contaminants consisting of acetone, 2-butanone, ethyl acetate, Freon-113 and methyl chloroform has been quantitatively removed from breathing quality air using this technique. The airborne concentrations of all contaminants have been reduced from initial Spacecraft Maximum Allowable Concentration (SMAC) levels to below the analytical limits of detection. No change in sorption efficiency was observed through multiple cycles of contaminant loading and sorbent regeneration via thermal desorption.

Space flight and related factors such as stress appear to have an adverse effect on astronauts' immune systems. The presence of potentially pathogenic microbes including several genera of fungi reported from spacecraft environment may be a cause of concern in such situations. In order to study the role of such organisms in causing opportunistic or allergic diseases in crewmembers, we have tried to develop an animal model. BALB/c mice were suspended upside down for varying periods of time to induce stress, and their lymphocyte functions were evaluated. These studies indicate that the stress resulted in lowered mitogen induced lymphocyte stimulation as represented by 3H-thymidine uptake. We have also studied the ability of these animals to respond to Aspergillus fumigatus spores. The results of the study clearly demonstrate a definite down-regulation in T-cell proliferation and a higher incidence of infection with A. fumigatus.

Small, highly polar organics such as urea, alcohols, acetone, and glycols are not easily removed by the International Space Station's Water Recovery System. The current design utilizes the Volatile Removal Assembly (VRA) which operates at 125°C to catalytically oxidize these contaminants. Since decomposition of these organics under milder conditions would be beneficial, several ambient temperature biocatalytic and catalytic processes were evaluated in our laboratory. Enzymatic oxidation and ambient temperature heterogeneous catalytic oxidation of these contaminants were explored. Oxidation of alcohols proceeded rapidly using alcohol oxidase; however, effective enzymes to degrade other contaminants except urea were not found. Importantly, both alcohols and glycols were efficiently oxidized at ambient temperature using a highly active, bimetallic noble metal catalyst.

Two simulated spacecraft water systems are being used to evaluate the effectiveness of iodine for controlling microbial contamination within such systems. An iodine concentration of about 2.0 mg/L is maintained in one system by passing ultrapure water through an iodinated ion exchange resin. Stainless steel coupons with electropolished and mechanically-polished sides are being used to monitor biofilm formation. Results after three years of operation show a single episode of significant bacterial growth in the iodinated system when the iodine level dropped to 1.9 mg/L. This growth was apparently controlled by replacing the iodinated ion exchange resin, thereby increasing the iodine level. The second batch of resin has remained effective in controlling microbial growth down to an iodine level of 1.0 mg/L. Scanning electron microscopy indicates that the iodine has impeded but may have not completely eliminated the formation of biofilm.

The ability of iodine to maintain microbial water quality in a simulated spacecraft water system is being studied. An iodine level of about 2.0 mg/L is maintained by passing ultrapure influent water through an iodinated ion exchange resin. Six liters are withdrawn daily and the chemical and microbial quality of the water is monitored regularly. Stainless steel coupons used to monitor biofilm formation are being analyzed by culture methods, epifluorescence microscopy, and scanning electron microscopy. Results from the first two years of operation show a single episode of high bacterial colony counts in the iodinated system. This growth was apparently controlled by replacing the iodinated ion exchange resin. Scanning electron microscopy indicates that the iodine has limited but not completely eliminated the formation of biofilm during the first two years of operation.

In 1985, the Man-Systems Division at the Johnson Space Center initiated a program for the development of a whole body shower suitable for operation in a microgravity environment. Supporting this development effort has been a systematic research program focused on four critical aspects of the design (i.e., human factors engineering, biomedical, mechanical, and electrical) and on the interfaces between the whole body shower system and the other systems to be aboard the Space Station (e.g., the water reclamation and air revitalization systems). A series of tests has been conducted to help define the design requirements for the whole body shower. Crew interface research has identified major design parameters related to enclosure configurations, consumable quantities, operation timelines, displays and controls, and shower and cleanup protocols.

In-flight contamination control has been an important concern of NASA since the first manned missions. Previous experience has shown that uncontrolled growth of bacteria and fungi can have a detrimental effect on both the health of the crew and the proper operation of flight hardware. It is therefore imperative to develop a safe, effective method of microbial control. Spacecraft application dictates a more stringent set of requirements for biocide selection than is usually necessary for terrestrial situations. Toxicity of the biocide is the driving factor for disinfectant choice in spacecraft. This concern greatly reduces the number and types of chemical agents that can be used as disinfectants. Currently, four biocide candidates (hydrogen peroxide, quaternary ammonium compounds, iodine, glutaraldehyde) are being evaluated as potential surface disinfectants for Space Station Freedom.

We evaluated the ability of a 3% (8800 μM) solution of hydrogen peroxide to kill 12 strains of bacteria and 12 strains of fungi. A 1:4 dilution of 3% H2O2, equivalent to 1100 μM, was lethal to all the tested strains. If the situation calls for a nonaggressive disinfectant without residue or toxic aftereffects, 3% H2O2 seems an ideal choice.

Controlling microbial growth and biofilm formation in spacecraft water-distribution systems is necessary to protect the health of the crew. Methods to decontaminate the water system in flight may be needed to support long-term missions. We evaluated the ability of iodine and ozone to kill attached bacteria and remove biofilms formed on stainless steel coupons. The biofilms were developed by placing the coupons in a manifold attached to the effluent line of a simulated spacecraft water-distribution system. After biofilms were established, the coupons were removed and placed in a treatment manifold in a separate water treatment system where they were exposed to the chemical treatments for various periods. Disinfection efficiency over time was measured by counting the bacteria that could be recovered from the coupons using a sonication and plate count technique. Scanning electron microscopy was also used to determine whether the treatments actually removed the biofilm.

The active control of problematic microbial populations aboard spacecraft, and within future lunar and planetary habitats is a fundamental Advanced Life Support (ALS) requirement to ensure the long-term protection of crewmembers from infectious disease, and to shield materials and equipment from biofouling and biodegradation. The development of effective antimicrobial coatings and materials is an important first step towards achieving this goal and was the focus of our research. A variety of materials were coated with antibacterial and antifungal agents using covalent linkages. Substrates included both granular media and materials of construction. Granular media may be employed to reduce the number of viable microorganisms within flowing aqueous streams, to inhibit the colonization and formation of biofilms within piping, tubing and instrumentation, and to amplify the biocidal activity of low aqueous iodine concentrations.

This paper provides an assessment of functional characteristics needed in the microbial water analysis system being developed for Space Station. Available technology is reviewed with respect to performing microbial monitoring, isolation, or identification functions. An integrated system composed of three different technologies is presented.

Novel mesoporous bimetallic oxidation catalysts are described, which are currently under development for the deep oxidation (mineralization) of aqueous organic contaminants in wastewater produced on-board manned spacecraft, and lunar and planetary habitats. The goal of the ongoing development program is to produce catalysts capable of organic contaminant mineralization near ambient temperature. Such a development will significantly reduce Equivalent System Mass (ESM) for the ISS Water Processor Assembly (WPA), which must operate at 135°C to convert organic carbon to CO2 and carboxylic acids. Improvements in catalyst performance were achieved due to the unique structural characteristics of mesoporous materials, which include a three-dimensional network of partially ordered interconnected mesopores (5-25 nm).

Weightlessness, cosmic radiation and other space flight related conditions may adversely impact the physiology and immune status of the crew. Since microorganisms will surely be present in space habitats, the effects of space on microbial metabolic and physiologic functions will depend upon environmental conditions, types of organisms, and the duration of the flight. Because humans will conduct long-duration space missions, space microbiology must address the effect of alterations in microbial function during space flight. Even innocuous microorganisms and endogenous flora may become etiologic agents for disease during long missions. The microbial population in the closed environments of spacecraft may also become a source of toxic metabolites or the biodegradation of materials. This paper reviews studies concerning microbial behavior in closed environments, simulated microgravity, and actual space flight.

To mitigate risk to crew health, the microbial surveillance of the quality of potable water sources of the International Space Station (ISS) has been ongoing since before the arrival of the first permanent crew. These water sources have included stored ground-supplied water, water produced by the Shuttle fuel cells during flight, and ISS humidity condensate that is reclaimed and processed. In-flight monitoring was accomplished using a self-contained filtering system designed to allow bacterial growth and enumeration during flight. Upon return to Earth, microbial isolates were identified using 16S ribosomal gene sequencing. While the predominant isolates were common Gram negative bacteria including Ralstonia eutropha, Methylobacterium fujisawaense, and Sphingomonas paucimobilis, opportunistic pathogens such as Stenotrophomonas maltophilia and Pseudomonas aeruginosa were also isolated.

One of the proposed methods for monitoring the microbial quality of the water supply aboard the International Space Station is membrane filtration. We adapted this method for space flight by using an off-the-shelf filter unit developed by Millipore. This sealed unit allows liquid to be filtered through a 0.45 μm cellulose acetate filter that sits atop an absorbent pad to which growth medium is added. We combined a tetrazolium dye with R2A medium to allow microbial colonies to be seen easily, and modified the medium to remain stable over 70 weeks at 25°C. This hardware was assembled and tested in the laboratory and during parabolic flight; a modified version was then flown on STS-66. After the STS-66 mission, a back-up plastic syringe and an all-metal syringe pump were added to the kit, and the hardware was used successfully to evaluate water quality aboard the Russian Mir space station.

With the restructure and funding changes for Space Station Freedom, the Environmental Health System (EHS)/Microbiology Subsystem revised its scheduling and operational requirements for component hardware. The function of the Microbiology Subsystem is to monitor the environmental quality of air, water, and internal surfaces and, in part, crew health on board Space Station. Its critical role shall be the identification of microbial contaminants in the environment that may cause system degradation, produce unsanitary or pathogenic conditions, or reduce crew and mission effectiveness. EHS/Microbiology operations and equipment shall be introduced in concert with a phased assembly sequence, from Man Tended Capability (MTC) through Permanently Manned Capability (PMC). Effective Microbiology operations and subsystem components will assure a safe, habitable, and useful spacecraft environment for life sciences research and long-term manned exploration.

The Crew Health System (CHeCS) plays a pivotal role in monitoring the life-support activities that maintain space station environmental quality and crew safety. Sampling hardware will be used in specific protocols to monitor the microbial dynamics of the closed spacecraft environment. NASA flight experience, ground-based studies, consultations with clinical and environmental microbiologists, and panel discussions with experts in engineering, flight-crew operations, microbiology, toxicology, and water quality systems all have been integral to the revision of in-flight microbial standards. The new standards for air and internal surfaces differentiate between bacterial and fungal loads, unlike previous standards that relied on total microbial counts. Microorganisms that must not be present in air or water or on surfaces also are listed.

Clinical-microbiological investigations are an important aspect of the crew health stabilization program. To ensure that space crews have neither active nor latent infections, clinical specimens, including throat and nasal swabs and urine samples, are collected at 10 days (L-10) and 2 days (L-2) before launch, and immediately after landing (L+0). All samples are examined for the presence of bacteria and fungi. In addition, fecal samples are collected at L-10 and examined for bacteria, fungi and parasites. This paper describes clinical-microbiological findings from 144 astronauts participating in 25 Space Shuttle missions spanning STS-26 to STS-50. The spectrum of microbiological findings from the specimens included 25 bacterial and 11 fungal species. Among the bacteria isolated most frequently were Staphylococcus aureus, Enterobacter aerogenes, Enterococcus faecalis, Escherichia coli, Proteus mirabilis and Streptococcus agalactiae.

A microgravity whole body shower (WBS) and a waste water recovery system (WWRS) were used in a closed loop test at the Johnson Space Center. The WWRS process involved chemical pretreatment, phase change distillation and post-treatment. A preprototype Thermoelectric Integrated Hollow Fiber Membrane Evaporation Subsystem (TIMES) was used for distillation after pretreatment and the post-treatment was accomplished with activated carbon, mixed ion exchange resin beds and microbial check valve (MCV) iodine bactericide dispensing units. The purposes of this test were to evaluate a NASA approved Shuttle soap for whole body showering comfort; evaluate the effects of the shower water on the WBS and the TIMES; and evaluate purification qualities of the recovered water in a closed loop operation.

Environmental monitoring of microbial contaminants is important for crew health and assessing functionality of engineering systems. Routine monitoring of air and surfaces on the International Space Station found Staphylococcus spp. to be the most common bacterial species whereas Aspergillus spp. were the most common fungi. The levels of microbial contaminants in the air and surfaces were typically low and within the acceptability limits. Bacterial levels in the potable water from the hot water port were uniformly low. Levels in water from the warm port and the SVO-ZV water distribution system exceeded acceptability limits on occasion. Methylobacterium spp. And Ralstonia spp. were the bacteria most commonly isolated from the potable water systems. The space environment, stress, and other factors may also diminish the host immune system. The status of antimicrobial functions of neutrophils and monocytes was determined by flow cytometry.