Three subcooled methods

including the subcooled technology of heat transfer

pumping down decompression and injecting cooled helium for cryogenic propellants were summarized. By comparing advantages and disadvantages of three methods

the subcooled technology of pumping down decompression was recommended to be used on the entire loading process of ground. Based on thermodynamics theory

expressions of consumption

refrigeration capacity

pumping down time and lowest pumping speed were derived for the subcooled technology of pumping down decompression. The researches showed that consumption of cryogenic propellants was mainly used for its temperature drop

then the proportion for offsetting external leakage heat and special heat of tank material was very small

for instance

the relative consumption of its temperature drop

special heat of tank material

and external leakage heat for liquid hydrogen was 10.94%，0.38%，0.098%

respectively. The arithmetic accurately calculating consumption of cryogenic propellants was recommended to reduce launch costs of launch vehicle and enhance utilization of cryogenic propellants. Compared with the exiting formula

its relative error was 18%.