A numerical technique for simulating the separation dynamics of strap-on boosters jettisoned in the dense atmosphere is presented. Six-degree-of-freedom, rigid-body equations of motion are integrated into the three-dimensional unsteady Navier-Stokes solution procedure to determine the dynamic motions of strap-ons. An automated chimera overset grid technique is introduced to achieve maximum efficiency for multibody dynamic motion, and a domain division technique is implemented in order to reduce the computational cost required to find interpolation points in the chimera grids. The flow solver is validated by comparing the computed results around the Titan IV launch vehicle with experimental data. The complete analysis process is then applied to the H-II launch vehicle, a major rocket in Japan's space program, and the KSR-III sounding rocket, a three-stage vehicle being developed in Korea. From the analyses separation trajectories of strap-on boosters are predicted, and aerodynamic characteristics around the vehicles at each time interval are examined. And separation-impulse devices, generally introduced for safe separation of strap-ons, are properly modeled, and the guideline map of additional jettisoning force and moment for safe separation is presented. References: 14
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