Re-entry rocket basic flow characteristics and thermal environment of different retro-propulsion modes

During the supersonic re-entry of multi-nozzle heavy rockets into the atmosphere, the basic flow state becomes increasingly complex due to the coupling effect between the retro-propulsion plumes and the freestream. A numerical method using the hybrid Reynolds-Averaged Navier-Stokes and Large Eddy Simulation (RES) method and discrete coordinate method is developed to accurately estimate the thermal environment. In addition, finite rate chemical kinetics is used to calculate the afterburning reactions. The numerical results agree well with wind tunnel data, which confirms the validity and accuracy of the numerical method. Computations are conducted for the heavy carrier rocket re-entry from 53.1 km to 39.5 km altitude with 180° angle of attack by using three different Supersonic Retro-Propulsion (SRP) modes. The numerical results reveal that these three SRP flow fields are all Short Penetration Models (SPM). As the re-entry altitudes decrease, both the plume-plume interaction and the plume-freestream interaction become weaker. The highest temperatures in the plume shear layers of the three SRP modes increase by 8.36%, 7.33% and 6.92% respectively after considering afterburning reactions, and all occur at a re-entry altitude of 39.5 km. As the rocket re-enters the atmosphere, the maximum heat flux on the rocket base plate of three SRP modes stabilizes at 290, 170 and 200 kW/m2 respectively, but the maximum heat flux on the side wall increases significantly. When the altitude declines to 39.5 km, the extreme heat flux of the three modes increase by 84.16%, 49.45% and 62.97% respectively compared to that at 53.1 km.