Hot Stage Seperation of Rockets Using Coupled CFD and Flight Mechanics Method

Kurzfassung

This work is to simulate the hot staging of a multistage launch vehicle using numerical methods. Due to the severe flight environment, the staging dynamics of the hot seperation is usually studied through statistical experiments on the ground during developing a rocket. The systematic flight tests are however extremely expensive and with high risk. The hot staging of the three-staged VLM-1 rocket, which is still in development, is studied in this work. A python program has been developed based on DLR TAU-code for the simulation of the hot rocket staging with multiple moving bodies. In the simulation, the governing equations of the flow are solved in the arbitrary Lagrangian-Eulerian system, in which the flight mechanics equations and the governing equations can be tightly coupled. Firstly, the aerodynamic effects of the trussed inter-stage structure have been numerically studied. The results show that, the trussed adapter increases the drag but has no significant effects on the lift and the moment of the rocket. Secondly, the modeling of the rocket plume, which is very difficult to be valided with experiment but the most important issue for the hot staging simulation, is discussed in detail. Three plume gas models with different thermochemical levels are evaluated in this work. A two-species-calorically-perfect-gas-model, which compromises well between the computation accuracy and efficiency, is proposed for the 6-DOF staging simulation. Finally, the staging dynamics of VLM-1 is systematically studied with the coupled 6-DOF simulations. The effects of the moving center of mass on the continuing-stage and the different plume gas models are evaluated, as well as the viscous effects. This work achieves the 6-DOF simulation of the hot rocket staging that rarely appears in literatures. Moreover, the crucial problems that dominate the fidelity of the simulation are studied in detail. With the developed method, the hot staging dynamics of VLM-1 can be investigated through numerical simulation, with which the requirements of the wind tunnel test, which is not only expensive but also with limited means, and the high-risk flight test can be significantly reduced.