Characterizing flow rate of the system for pressurant venting from pressure accumulators during the final phase of an upper stage flight

A math model has been proposed (and, accordingly, the software has been developed) for characterizing the flow rate of the system for venting the pressurant from connecting pressure accumulators (spherical tanks) during the final phase of flight after payload separation and prior to de-orbiting of the upper stage. The proposed computational model takes into account the flow of pressurant from one spherical tank to the other and equalization of parameters in spherical tanks during venting. The paper updates approaches to computations of critical flow from lines, computations of velocity factors and certain gas-dynamic functions, as well as writing the equation of state for spherical tanks. Based on the results of this work, the venting system flow rate was characterized using the presented model. The model can be used for preliminary engineering evaluations during various phases of the rocket and space hardware design cycle.