Analysis of active pressurization methods for a cryogenic propellant tank

A numerical study was conducted on active pressurization methods of a cryogenic liquid hydrogen tank used in the upper stage of a space launch vehicle. SINDA/FLUINT program which integrates complex flow and conjugate heat transfer problem was used for the study. The study encompasses four different ullage pressure control schemes and brings out the merits and demerits of each, considering output parameters such as pressurant mass requirement, pressurant temperature and tank pressure variations. The model was validated with fight-recorded data of ullage pressure. Each scheme is unique in the manner of their coupling between the pressurization system components like heat exchanger, control valves and active control orifices. The study shows that pressurant temperature and, consequently, the heat exchanger configuration is critical in maintaining the tank pressure within the required levels.