[C2H4 reducing facility for controlled ecological life support system].

OBJECTIVE: To develop an experimental facility for reducing C2H4 produced by plants' growing in the controlled ecological life support system (CELSS). METHOD: Based on technical parameters and performance requirements, project planning, design drawing, fabrication, and debug were conducted. Then, an experimental test for reducing C2H4 was done by measuring the content of C2H4 in gases between the inlet and the outlet of the facility. Its C2H4 decomposing capacity was evaluated. RESULT: The facility worked well, and the parameters, such as energy consumption, and volume, met the design requirements. The experimental test results demonstrated that the content of C2H4 was reduced from 0.034 mg/kg to below 0.010 mg/kg, under the condition that the relative humidity and velocity of flow of the inlet-gas was 20% and 1.0-3.0 L/min respectively, and power of the lamp was 48 W. Considering the composition and the content of the gas in the outlet of the facility, there was no harmful product to the plants, except CO2 and H2O. CONCLUSION: The facility has reasonable technical indices, and smooth and dependable performances. It can be used as a facility for decomposing C2H4 in plants growing system in CELSS.

[Progress of biological air filter (BAF) development in manned spacecraft cabin].

The contaminants originating from human metabolism, material off-gassing and waste processing, may influence human health and the growth and development of higher plants when they accumulate at some degree in the spacecraft cabin. So the contaminants concentrations must be controlled below the spacecraft maximum allowable concentration (SMAC). For the long manned space missions and planetary habitation, biological technique is available for the removal of the contaminants. The biological air filter, BAF, is a system that degrades the contaminants into carbon dioxide, water and salts. It holds many advantages such as small weight and volume, low power consumption, easy maintenance and good working performance under the condition of microgravity. Its wide application will be seen in the space field in near future.

[Development of a prototype of space vegetable-cultivating facility for ground-based experiments].

OBJECTIVE: To develop a ground-based experimental prototype of space vegetable-cultivating facility (GEPSVF), so as to solve the main key techniques related to higher plant cultivation in space environmental conditions, and to further lay a foundation for future development and application of the prototype of space vegetable-growing facility. METHOD: Based on detailed demonstration and design of technique plan, the blueprint design and machining of components, whole facility installment, debugging, trial operations and verification experiments were done. RESULT: The parameters in the growing chamber such as temperature, relative humidity, wind velocity, total pressure, O2 partial pressure, CO2 partial pressure and water content of the growing media were totally and effectively controlled; the light source was electronic fluorescent lamp; the average vegetable-producing output reached 60 g (fresh weight) d-1. CONCLUSION: The prototype could operate stably; its actual performance indexes achieved the expected ones basically; some of its operating principles can adapt to space microgravity condition. Therefore, the prototype is a good beginning for future development of space vegetable-producing facilities.

[Development of a special controlled-releasing long effect fertilizer used in controlled ecological life support system].

OBJECTIVE: To develop a special controlled-releasing long effect fertilizer (SCRLEF) for growing higher plant in controlled ecological life support system (CELSS). METHOD: First, a plan was designed. According to requirements, some original fertilizers were chosen and compounded in proper proportions, and a granule product was obtained and encapsulated in certain materials to form SCRLEF. Then, experiments were done by measuring the content and releasing-rate of the fertilizer, and cultivating plants with the fertilizer. RESULT: The fertilizer contains nutrients for plant growing, such as: N 18.0%, P2O5 14.3%, K2O 12.6%, Ca 2.6%, S 3.5%, Mg 0.12%, and other micro-nutrients. The granules of the SCRLEF are uniform in size with diameters form 2.5 mm to 4.0 mm. Under 20-25 degrees C, the cumulative amounts of released nutrients from the fertilizer in 10 d, 20 d, 30 d, 40 d, and 50 d, are 7.9%, 21.6%, 40.5%, 50.2%, 60.9% respectively, within 10 d, 20 d, 30 d, 40 d, 50 d. By cultivating lettuce with the fertilizer, we found that the vegetable could grow normally, and there wasn't any deficiency symptom in the plants within 45 d. CONCLUSION: The design consideration of the SCRLEF is reasonable. The fertilizer provides total nutrients for plant growing, and can be used to supply the required nutrients for the plants grown in the CELSS.

Selection of root-zone media for higher plant cultivation in space.

OBJECTIVE: To investigate the cultivating effects of several mineral matters used as root-zone media for higher plant growth in space. METHOD: Four kinds of artificial and natural mineral matters were used as plant root-zone media based on lots of investigation and analysis. Nutrient liquid was delivered into the media by a long capillary material, and roots of plants obtained nutrition and water from the media. The related parameters such as plant height and photosynthetic efficiency were measured and analyzed. RESULT: The growing effect in a mixture of coarse and fine ceramic particles with equal quantity proportion was the best, that in fine ceramic particles was the second best, that in clinoptilolite particles was the third and that in diorite particles was the last. CONCLUSION: The mixture of coarse and fine ceramic particles with equal quantity possesses not only fine capillary action, but also good aerating ability, and therefore is capable of being utilized as an effective root-zone media for higher plants intended to be grown in space.

[Development of a ground-based experimental facility for space waste material processing with microorganism].

OBJECTIVE: To develop a ground-based experimental facility for microorganism waste processing, which will be used to recover nutrient from plant inedible biomass essential for growth and development of plants. METHOD: After technical parameters and performance requirements were defined, planning demonstration, drawing design, fabrication, debug and plant inedible residue-biodegradation tests by microorganisms were conducted. RESULT: The facility worked well, and the parameters, such as energy consumption, volume and weight, met the design requirement. The water-treated quality and the ability of treating plant residual by microorganism were better than the demands. The ground-based results demonstrated that total organic carbon (TOC) degradation above 92.1%, and chemical oxygen demand (COD) reduction over 95.5% could be maintained. CONCLUSION: The facility has reasonable technical indexes, and smooth and reliable performances. Its major working principle is suitable for the demand of space conditions. It is capable of being utilized for biodegradation of plant inedible biomass in space.

[Progress in development and application of experimental facilities for life sciences on onboard the International Space Station].

The construction of the International Space Station (ISS) will be completed soon, and life sciences studies are important tasks to be carried out onboard. Therefore, various related facilities for life science flight experiments are being developed aimed at diverse objectives, and some of them were completed and passed ground-based simulation experiment or airplane parabolic flight tests, and to be arranged for implementation of spaceflight experiments. This article reviews comprehensively the recent progress in the development of various types of related experimental facilities and the onboard experiments, in the hope that it will provide reference for related fields of research.

[Selection of light source used for plant cultivation in controlled ecological life support system].

OBJECTIVE: To select suitable light source for higher plant cultivation in the controlled ecological life support system of the future space station. METHOD: The experiment was carried out in the Space Higher Plant Cultivation Ground-based Experimental Facility (SHPCGEF); four combinations of two red and blue light-emitting diode (LED) were utilized as light sources; soilless cultivation technique with porous ceramic tubes and porous ceramic particles was utilized in the growth system. RESULT: The plants grown under the shelf of pure red LED showed a lying-down state in early stage, and stood erect in later period with slender and long stems; the plants under various combinations of red and blue LED grew with nearly normal state, but the plants under the combination of 90% red and 10% blue LED possessed the best comprehensive indexes. CONCLUSION: The normal growth and development of plantlets needs two light sources of red and blue LED, and the combination of 90% red and 10% blue LED is the optimum one among those tested combinations.