The overset/Chimera algorithm for structured grids and Favre-averaged Navier-Stokes equations were employed to solve the flow field.Tstion gas jets
were considered in this simulation.Atime profile boundary was employed to simulate the unsteady flow in the tail off duration of the booster.The separating trajectory was ultimately achieved by solving the 6DOF(six degree of freedom) motion models with certain constraints.Moreover
the influence of engine-jet on booster separation was studied.The work provides a reference for accurately simulating the trajectory and attitude of rocket booster.