Liquid propellant analogy technique in dynamic modeling of launch vehicle

The coupling effects among lateral mode, longitudinal mode and torsional mode of a launch vehicle cannot be taken into account in traditional dynamic analysis using lateral beam model and longitudinal spring-mass model individually. To deal with the problem, propellant analogy methods based on beam model are proposed and coupled mass-matrix of liquid propellant is constructed through additional mass in the present study. Then an integrated model of launch vehicle for free vibration analysis is established, by which research on the interactions between longitudinal and lateral modes, longitudinal and torsional modes of the launch vehicle can be implemented. Numerical examples for tandem tanks validate the present method and its necessity.