Search Results

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 Six liters are withdrawn daily and the chemical and microbial quality of the water is monitored regularly.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.

Microbial proliferation in the STS potable water system is prevented by maintaining a 2-5 ppm iodine residual. The iodine is added to fuel cell water by an iodinated ion exchange resin in the Microbial Check Valve (MCV). Crew comments indicated excessive iodine in the potable water. To better define the problem, a method of in-flight iodine analysis was developed. Inflight analysis during STS-30 and STS-28 indicated iodine residuals were generally in the 9-13 ppm range. It was determined that the high iodine residual was caused by MCV influent temperatures in excess of 120 °F. This is well above the MCV operating range of 65-90 °F. The solution to this problem was to develop a resin suitable for the higher temperatures. Since 8 months were required to formulate a MCV resin suitable for the higher temperatures, a temporary solution was necessary. Two additional MCV's were installed on the chilled and ambient water lines leading into the galley to remove the excess iodine.

Recovery of oxygen (O2) from water will be needed on future long-duration manned space missions. Direct electrolysis of cabin water vapor into O2 and hydrogen (H2) offers the advantage of avoiding the phase change, separation and handling of liquid water in zero gravity. These considerations affect liquid electrolysis subsystems which are presently baselined for central O2 generation aboard the Space Station. This paper presents the results of a technology development program that Life Systems, Inc., in cooperation with the National Aeronautics and Space Administration (NASA) Johnson Space Center (JSC) has been undertaking. The goal of the program is to develop Water Vapor Electrolysis (WVE) hardware that can selectively be used as localized topping capability in areas of high metabolic activity without oversizing the central Air Revitalization System (ARS).

Humidity control is essential in the extravehicular mobility unit (EMU). Excessive humidity can lead to visor fogging; accumulation of water, which can block air flow through the vent loop and corrode system components; and uncomfortable conditions for the person inside the EMU, reducing productivity. This paper describes the development of a membrane-based process for dehumidifying the EMU. The membrane process promises to be smaller, lighter, and more energy efficient than the other technologies being considered for dehumidification, and it requires no expendables. The system employs novel dehydration membranes, which were tested for 90 days at conditions expected to be present in the EMU. The results of these tests indicate that membrane-based technology can effectively control humidity in the EMU.

The ability of iodine to control microbial contamination and biofilm formation in spacecraft water distribution systems is being studied. Two stainless steel water subsystems are being used. One subsystem has an iodine level of 2.5 mg/L maintained by an iodinated ion-exchange resin. The other subsystem has no iodine added. Stainless steel coupons are being removed from each system to monitor biofilm formation. Results from the first six months of operation indicate that 2.5 mg/L of iodine has limited the number of viable bacteria that can be recovered from the iodinated subsystem. Epifluorescence microscopy of the coupons taken from this subsystem, however, indicates some evidence of microbial colonization after 15 weeks of operation. Numerous bacteria have been continually recovered from both the water samples and the coupons taken from the noniodinated subsystem after only 3 weeks of operation.