Modeling of Propellant Tank Pressurization

Accurate modeling of propellant tank pressurization is an essential element of the prediction of rocket performance. This is the case even more so for hybrid rockets that use a self-pressurizing oxidizer because the thrust produced by the motor is dependent on oxidizer tank pressure. Described herein is a real fluid, quasi-phase equilibrium thermodynamic propellant tank model that is applicable to a broad range of propellants including those that are highly volatile and/or cryogenic. The model has been validated by comparison with the measured results of cold-flow blow-down tests of a self-pressurizing nitrous oxide system. Data from one of the cold-flow tests showed evidence of stratification within the oxidizer tank during the blow down. It was found that accurate modeling of the propellant evaporation rate is a crucial element in the prediction of the propellant expulsion process.