Stability analysis of elastic launch vehicles with fuel sloshing in planar flight using a BEM-FEM model

A numerical model is developed for investigation of coupled dynamics of fuel contained elastic launch vehicles in planar atmospheric flight. Finite element method along with the linear quasi-steady piston aerodynamic theory is used for developing an aeroelastic model. A reduced order boundary element model is used for modeling the liquid sloshing in tanks. The interaction of sloshing and aeroelasticity is studied using stability analysis of the coupled system. Results show that the slosh–aeroelastic coupling in an elastic launch vehicle occurs for low tank filling ratios and may lead to decreasing the system damping. Due to more interactions between the slosh and rigid body modes, larger damping values of the rigid body mode and lower slosh frequencies are found for an elastic vehicle compared with a rigid vehicle. It is also shown that the slosh–aeroelastic interaction is increased as the slosh inherent damping decreases.