In response to the challenge of sintering silicon carbide ceramic into complex part,which limits it application in certain mechanical seal,a design was developed that integrates silicon carbide ring with metal component to create a mechanical sealed with intricate structure.Type tests and durability tests were designed and conducted in the context of urine processor assembly for space stations,the test results indicate that the static liquid leakage rate of mosaic type mechanical seal did not exceed 0.88 mL/h under a pressure differential of 50 kPa,and the dynamic liquid leakage rate did not exceed 0.47 mL/h at a rotational speed of 400 r/min.The vibration and impact qualification tests of dynamic environment were conducted under the conditions of mechanical seals installed.There was no change in sealing performance observed before and after the tests.Following that,a 4 500-hour durability test was performed in pretreated urine.The results showed good sealing performance.After the test,the mechanical seals were disassembled and checked.the installation and appearance of ceramic rings were found to be in good condition,with no visible corrosion or wear.The results suggest that this integrated structure meets the requirements for complex mechanical structures and can operate stably over extended periods under acidic and corrosive liquid conditions.

Objective To develop space vegetable cultivation facility(SVCF)and apply to the cultivation of several fruit and vegetable plants on China Space Station.Methods Through conducting experiments and development of regenerative plant cultivation substrate,active water supply,nutrient supply based on controlled-release fertilizer,LED light environment regulation,modular design and development of various functional units of the SVCF,as well as system integration and testing,plant full cycle cultivation verification,the development of the SVCF(also known as Space Vegetable Garden)has been completed.Through the cultivation on-orbit of three vegetables and one fruit plants,the feasibility of cultivation methods with regenerative substrate was tested and the growth characteristics of several plants were studied.Results The facility worked normally,which can supply water actively,detect substrate parameters including water content and conductivity,and adjust the height according to the plant lighting requirement.All performance indicators of the SVCF meet the cultivation requirements of different fruit and vegetable.Three types of lettuce plants("shengcaiwang","hongye","meiluo")and one tomato plants("honglei")were cultivated from seeding to harvest on-orbit.The lettuce and tomato plants grew well.Astronauts participated in the cultivation and management of lettuce and tomato plants,picking and consuming lettuce leaves(about 900 g,fresh weight)and tomato fruit.The tomato seeds were preserved after harvest and returned to earth.The seeds(second generation)was sowed and cultivated on earth.The growth characteristics will be studied and compared with the tomato plants on-orbit.Conclusion The facility performance meets the requirements of several fruit and vegetable plants cultivation on-orbit.The cultivated lettuce and tomato plants grew well.Astronauts picked and consumed lettuce leaves and tomato fruits.The results laid an important technique foundation for the continuous production of multiple types of fruit and vegetable plants on-orbit.