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 Six liters are withdrawn daily and the chemical and microbial quality of the water is monitored regularly.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

Future long duration manned space missions will require regenerative Life support subsystems which operate efficiently and reliably with minimum attendance from the crew. An essential prerequisite to achieving this goal is the development of highly reliable controllers to control the various life support processes, to monitor subsystem performance, and to provide automatic shutdown of a process when out of tolerance conditions persist. While life support controller designs have improved dramatically over the years, it is now no Longer good enough to continue a philosophy where the only result of the fault monitoring process is to provide an automatic shutdown of the subsystem.

The crew of a manned Mars mission will be unavoidably exposed to galactic cosmic ray (GCR) flux. If one employs conventional radiological health practices involving absorbed dose(D), dose-equivalents (H), and LET-depen-dent quality factors (Q)2, the Mars mission crew shielded by 2 g/cm All could receive about 0.7 Sv in a 460-day mission at solar minimum. However three-fourths of this dose-equivalent in free space is contributed by high LET heavy ions (Z ≥ 3) and target fragments with average Q of 10.3 and 20, respectively. Such high quality factors for these particles may be inappropriate. Moreover, in a 460-day mission less than half of the nuclei in the body of an astronaut will have been traversed by a single heavy particle. The entire concept of D/Q/H as applied to GCR must be reconsidered.

The Environmental Health System (EHS) and Health Maintenance Facility (HMF) on Space Station Freedom will require a comprehensive microbiology capability. This requirement entails the development of an automated system to perform microbial identifications on isolates from a variety of environmental and clinical sources and, when required, to perform antimicrobial sensitivity testing. The unit currently undergoing development and testing is the Automated Microbiology System II (AMS II) built by Vitek Systems, Inc. The AMS II has successfully completed 12 months of laboratory testing and evaluation for compatibility with microgravity operation. The AMS II is a promising technology for use on Space Station Freedom.

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.

The NASA Lyndon B. Johnson Space Center (JSC) Life Sciences Space Station Program (LSSSP) will support the NASA goal of expanding human presence beyond the Earth into the solar system. The Biomedical Research Project (BmRP) is a major element of the LSSSP and is planning an onboard laboratory for studying the effects of microgravity on humans. During the Space Station era, the major emphasis for the BmRP is to identify and quantify the effects of reduced gravitational forces on humans and, if necessary, to develop methods and techniques which counteract or modify these effects to promote man's long-term health and productivity while working in space and upon return to Earth. A status of current science, technical, and programmatic planning activities that are being conducted at JSC to define BmRP requirements for the Space Station Program is presented herein.