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It has been proposed to use plants as elements of biologically-based life support systems for long-term space missions. Three roles have been brought forth for plants in this application: recycling of water, regeneration of air and production of food. This report discusses recycling of water and presents data from investigations of plant transpiration water quality. Aqueous nutrient solution was applied to several plant species and transpired water collected. Our findings indicated that this water typically contained 0.3-6 ppm of total organic carbon, which meets hygiene water standards for NASA's space applications. It suggests that this method could be developed to achieve potable water standards.

Experience with reclaimed and recycled life support testbeds is necessary to identify problems unique to this new class of spacecraft systems. Current research and engineering testbeds necessary for advanced Space Station Freedom, moonbase, interplanetary travel and Mars/Phobos mission and base are large, complex, costly and rare. We report a small, simple, flexible and affordable experimental research and engineering testbed for biologically contaminated or enhanced physical chemical and biological water/air reclamation and recycling systems. Experience with this and similar testbeds is necessary to understand and rationally develop safe, stable, deployable, larger biological reclamation/recycle life support systems for terrestrial and extraterrestrial uses.

U.S. space missions have to this point used water either made on board or carried from Earth and discarded after use. For Space Station Freedom, long duration life support will include air and water recycling using a series of physical-chemical subsystems. The Environmental Control and Life Support System (ECLSS) designed for this application must be tested extensively at all stages of hardware maturity. Human test subjects are required to conduct some of these tests, and the risks associated with the use of development hardware must be addressed. Federal guidelines for protection of human subjects require careful consideration of risks and potential benefits by an Institutional Review Board (IRB)before and during testing. This paper reviews the ethical principles guiding this consideration, details the problems and uncertainties inherent in current hardware testing, and presents an incremental approach to risk assessment for ECLSS testing.

Iodine is a flight-proven disinfectant which because of its unique properties, will probably be used on the Space Station and future manned spaceflight applications. However, present knowledge of and experience with iodination is insufficient to assess crew safety when used in conjunction with reclamation or recycle systems, especially if the reclaimed water is consumed.