An improved approach for tank purge modeling

Many launch support processes use helium gas to purge rocket propellant tanks and fill lines to rid them of hazardous contaminants. As an example, the purge of the Space Shuttle's External Tank used approximately 1,100kg of helium. With the rising cost of helium, initiatives are underway to examine methods to reduce helium consumption. Current helium purge processes have not been optimized using physics-based models, but rather use historical ‘rules of thumb’. To develop a more accurate and useful model of the tank purge process, computational fluid dynamics simulations of several tank configurations were completed and used as the basis for the development of an algebraic model of the purge process. The computationally efficient algebraic model of the purge process compares well with a detailed transient, three-dimensional computational fluid dynamics (CFD) simulation as well as with experimental data from two external tank purges. ► This work examines a tank purge prior to filling with cryogenic propellant. ► Maximum and minimum limiting conditions for a tank purge are identified. ► An algebraic model is developed to examine tank purge. ► Experimental data from external tank purge is compared with algebraic model. ► Detailed CFD results of ET purge are also compared with the algebraic model.