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Life-support systems at modern spacecrafts are based on the reserves of different components and their partial physical and chemical regeneration. This permits cosmonauts to stay for a long time under space flight conditions (Valery Polyakov - 1 year and 4 months). At the same time, in many countries works are in progress on the creation of closed ecological life-support systems involving the use of biological objects of different phylogenetic levels (Mashinsky and Nechitailo, 1996). In the known ground-based ecological systems one to several thousands of biological species are used to support the human life functions. For instance, only Chlorella was used in the first 1-day experiment in Moscow in a closed biological system with the participation of a man, while in the two-year experiment in the Bioshere-2 complex in Arizona more than 4000 species were used (Alling and Nelson, 1993).

The primary source of potable water planned for the International Space Station will be generated from the reclamation of humidity condensate, urine, and hygiene waters. It is vital to crew health and performance that this reclaimed water be safe for human consumption, and that health risks associated with recycled water consumption be identified and quantified. Only recently has data been available on the chemical constituents in reclaimed waters generated in microgravity. Results for samples collected during Mir-21 reveal that both the reclaimed water and stored water are of potable quality, although the samples did not meet U.S. standards for total organic carbon (TOC), total phenols, and turbidity.

The reproductive ontogeny of ‘Super-Dwarf’ wheat grown on the space station Mir is chronicled from the vegetative phase through flower' development. Changes in the apical meristem associated with transition from the vegetative plhase to floral initiation and development of the reproductive spike were all typical of ‘Super Dwarf’ wheat up to the point of anthesis. Filament elongation, which characteristically occurs just prior to anthesis (during floral development stage 4) and moves the anthers through the stigmatic branches thus facilitating pollination, did not occur in the flowers of spikes grown on Mir. While pollen did form in the anthers, no evidence of pollination or fertilization was observed. Analysis of pollen idlentified abnormalities; the presence of only one nucleus in the pollen as opposed to the normal trinucleate condition is likely an important factor in the sterility observed in wheat grown on Mir.

Liquid and gas exchange within a particulate plant-rooting medium is likely to be altered in a microgravity environment. A difference in gravitational force can result in significant offsets in control parameters developed on earth for optimum plant growth, due to the shift in hydrostatic water distribution. The experiment being developed will examine the effects of variable gravity on water distribution and gas diffusion. We are developing and testing an automated gas diffusion measurement system for use on the International Space Station (ISS). To allow comparison of μg and 1g conditions, gas diffusion cell designs were horizontally oriented to minimize gravitational effects using 1) a ‘thin rectangular profile’ cell and 2) a cylindrical cell design for flight. Electronic solenoid valves provide air and water flow control while pressure transducers measure water and substrate potential.

This study compared the effect of increased CO2 partial pressure in atmosphere up to 30 mm Hg (i.e. hypercapnia) on the risk of decompression sickness (DCS) during decompressions simulating space extravehicular activity (EVA). Test subjects were exposed to a pressure 330, 308 and 261 mm Hg, breathed O2-CO2 gas mixture under experimental or 100% O2 control conditions. DCS symptoms (joint pains) developed in 32.7% (33/101) of control and 67.9% (72/106) of experimental exposures (p<0.05). This finding is of importance for delivering medical support during EVA.

A bioregenerative system model based on photosynthesis of unicellular algae has been created and studied. It includes man and microorganisms. The regeneration of substances vital for man in the model achieves 90%. Besides regeneration of atmosphere, water and partly food, a series of secondary functions is performed by the system. All functional characteristics were stabilized either at once or after some transitory period, and were close to the control. The environment formed in the system met biological needs of man. The system model is a transitory stage on the way of creating systems, more complex in structure and closure degree. It has a practical significance as a bioregenerative system and may be used in present-day astronautics practice.

A three country effort (U.S., Russia, and Bulgaria) has upgraded the plant growth facilities on the Mir Space Station and used the new facility to grow wheat for 90 days. The Svet plant-growth facility was reactivated and used in an initial experiment as part of the Shuttle/Mir program, August to November, 1995. The Svet system, used first to grow cabbage and radish during a 1990 experiment, was augmented by the addition of a U.S. developed Gas Exchange Measurement System (GEMS) that measures a range of environmental parameters plus transpiration, photosynthesis, and possibly respiration. Environmental parameters include cabin, chamber, root-zones, and leaf temperatures. Light levels, relative humidity, oxygen, and atmospheric pressure are also measured. High-accuracy water-vapor and carbon-dioxide concentrations and differences are measured using specially developed IRGA systems.

During 1995, we tested instruments and attempted a seed-to-seed experiment with Super-Dwarf wheat in the Russian Space Station Mir. Utah instrumentation included four IR gas analyzers (CO2 and H2O vapor, calculate photosynthesis, respiration, and transpiration) and sensors for air and leaf (IR) temperatures, O2, pressure, and substrate moisture (16 probes). Shortly after planting on August 14, three of six fluorescent lamp sets failed; another failed later. Plastic bags, necessary to measure gas exchange, were removed. Hence, gases were measured only in the cabin atmosphere. Other failures led to manual watering, control of lights, and data transmission. The 57 plants were sampled five times plus final harvest at 90 d. Samples and some equipment (including hard drives) were returned to earth on STS-74 (Nov. 20). Plants were disoriented and completely vegetative. Maintaining substrate moisture was challenging, but the moisture probes functioned well.

Potable- and hygiene-quality water will be supplied to crews on the International Space Station through the recovery and purification of spacecraft wastewaters, including humidity condensate, urine, and wash water. Contaminants released into the cabin air from human metabolism, hardware offgassing, flight experiments, and routine operations will be present in spacecraft humidity condensate; normal constituents of urine and bathing water will be present in urine and untreated wash water. This report describes results from detailed analyses of Mir reclaimed potable water, ground-supplied water, and humidity condensate. These results are being used to develop and test water recycling and monitoring systems for the International Space Station (ISS); to evaluate the efficiency of the Mir water processors; and to determine the potability of the recycled water on board.