Coupled Simulation of CFD and Flight Mechanics with a Two-Species-Gas-Model for the Hot Staging of a Multistage Rocket

Abstract

The hot staging dynamics of a multistage rocket is studied using the coupled simulation of Computational Fluid Dynamics (CFD) and Flight Mechanics (FM). In the coupled simulations, the free-stream is modeled as "cold air" and the exhausted plume from the continuing-stage-motor is modeled with an equivalent calorically-perfect-gas that approximates the properties of the plume at the nozzle exit. The Navier-Stokes equations in the coupled simulations are time-accurately solved in moving system, with which the Flight Mechanics equations can be fully coupled. The Chimera mesh technique is utilized to deal with the relative motions of the separated stages. A few representative staging cases with different initial flight conditions of the rocket are studied with the coupled simulation. Based on the simulation results, the staging dynamics of the rocket are finally analyzed. Nomenclature CFD = computational fluid dynamics DN = diameter of nozzle dt = time step size FM = flight mechanics P 1 = chamber pressure of the motor, Pa R = gas constant, J/K mol  Sep = separation distance, m t = time, s 3D = three dimensional I I I I O x y z  = inertial coordinate system = translational velocities in the staging coordinate system, m/s NP Z = nozzle-to-plate distance, m  = the ratio of specific heats 1 PhD Student, Department Spacecraft, Lilienthalplatz 7, 38108 Braunschweig, Germany, AIAA student member.