Analyses of Cryogenic Propellant Tank Pressurization based upon Ground Experiments

Abstract

The pressurization system of cryogenic propellant rockets requires on-board pressurant gas. The objective of this study was to analyze the influence of the pressurant gas temperature on the required pressurant gas mass in terms of lowering the launcher mass. First, ground experiments were performed in order to investigate the pressurization process with regard to the influence of the pressurant gas inlet temperature. Second, a system study for the cryogenic upper stage of a small Two Stage to Orbit (TSTO) launch vehicle was performed with focus on the influence of the pressurant gas temperature on the propellant management system mass. One important experimental result is that for evaporated propellant as pressurant gas, the maximum applicable gas temperature is best for reducing the needed pressurant gas, but on condition that all pressurization lines are chilled down. Moreover, the use of helium is very advantageous with regard to lowering the pressurant gas mass. Also significant is that an immediate pressure drop occurred after the pressurization end. The conclusion drawn from the system analysis is that an increased evaporated propellant and helium pressurant gas temperature resulted in a decrease of the total propellant management system mass, despite the application of external helium vessels.