Study of Recoverable Liquid Launch Vehicle Stage Separation Based on Equivalent Model of Large-Amplitude Liquid Slosh

In the process of stage separation of recoverable liquid launch vehicles, due to the large amount of remaining fuel in the storage tanks, the impact of liquid sloshing on separation safety must be considered. Considering the simplicity of the calculation and the practicality of the operation, the moving pulsating ball equivalent model (MPBM) of large amplitude liquid sloshing is introduced into the calculation of stage separation of launch vehicles. Considering the scenario of liquid leaving the wall of tanks, improvements have been made to the existing MPBM. Then, all external forces and moments are applied to the rigid body of the stages to get the translation and rotation dynamic equations of the two stages respectively. Based on the relative position of the two stages, the geometric shape of the interstage section, and the geometric shape of the second stage engines, the minimum clearance during the separation process can be determined to determine whether the separation process is safe. Finally, a brief analysis of parameter sensitivity is conducted.