Developing Status and Analysis on Fluid Management Technology of Rocket Cryogenic Upper Stage

The technical characteristics of rocket upper stages at home and abroad are compared,and key cryogenic fluid management techniques are summarized and present. The space thermal insulation techniques,on-orbit gas-liquid separation techniques,on-orbit venting techniques associated with cryogenic propellant are reviewed and analyzed. It is pointed out that applying up-to-date thermal insulation techniques,the cryogenic propellant could be stored safely for longer time and thus the upper stage could provide a wider application range. Besides,use of thermal insulation,structure optimization design of upper stage,and fluid management techniques comprehensively is beneficial to reduce the boil-off of cryogenic propellant in space. Comparatively,metal screen capillary gas-liquid separation device is more suitable for the pure-liquid acquisition of cryogenic liquid,especially in liquid hydrogen tank. Moreover,traditional thermodynamic venting system(TVS)could realize the purpose of pure-gas venting in space,but extra propellant boil-off is yielded. Instead, a passive TVS could be suggested for the gas venting of cryogenic tank. In a word,more attention should be given in the researches on fluid science and management techniques of liquid hydrogen in space,and liquid hydrogen/liquid oxygen propellant upper stage should be developed as soon as possible.