Modeling and Simulation Method for Ejection Dynamics of Multi-stage Cylinders of Rockets

The accurate and efficient modeling of buffer and the reproduction of the stress stiffening characteristics of ejection cylinder generated by the pressure variable topology of low-pressure chamber are the key to improving the reliability of multi-stage cylinders ejection dynamics simulation. A new type of multi-turn side-by-side hula-hoop buffer device is proposed. A dynamic equivalent model of buffer based on the elastoplastic spring is constructed using the Chebyshev iteration method. The modal analysis and axial compression buckling analysis of cylinder under the conditions of different internal pressures are compared to verify the significant stress stiffening effect of the cylinder. Thus, a variable topology spatial load mapping technology with additional virtual concentrated force is developed to effectively simulate the variable topology surface loading process of the low-pressure chamber pressure during the deployment of multi-stage cylinders in the ejection process, and an ejection dynamics model of multi-stage cylinders is constructed. The simulated results show that the proposed buffer model can well reflect the mechanical characteristics of buffer under repeated impacts. There are significant differences in the dynamic simulation results of the variable topology internal pressure loading and the cases with and without internal pressure. Moreover, the simulated results of the variable topology internal pressure loading model is highly consistent with the experimental results, which confirms that the influence of the cylinder's stress stiffening effect on the launch performance cannot be ignored. The variable topology spatial load mapping technology with additional virtual concentrated force and the equivalent modeling of buffer's elastoplastic spring are the necessary prerequisites to ensure the reliability of the simulation results of multi-stage cylinders ejection.