Numerical analysis on thermal environment of reusable launch vehicle during supersonic retropropulsion

Developing reusable launch vehicles (RLV) is an effective way to significantly reduce space transportation costs. However, in the return stage of the vehicle, especially the supersonic retropropulsion (SRP), the first stage is partially submerged in the hot exhaust plume and faces severe convective heating at the base plate and sidewalls. As a rule of thumb, the layout of nozzles at the rocket base significantly affects the heat load. In order to evaluate the influence of heat load under different nozzle configurations during SRP (33 km–22 km), the thermal environment of RLV was studied through numerical investigation for three typical nozzle configurations. Using Reynolds-averaged Navier–Stokes equations (RANS)-based computational methods and the k−ω SST turbulence model, the flowfield is characterized at different trajectory points during retropropulsion. Results showed that the high heat flux is mainly concentrated in the baseplate's center area and the sidewall's near base area during SRP. In general, activating engines in the radial position is beneficial for the thermal protection system of a reusable launch vehicle while the thrust is identical. Base heating primarily results from high-temperature counterflows due to plume interactions, while sidewall heating is predominantly a result of high-temperature recirculation zones generated by plume-induced flow separation. During the supersonic retropropulsion phase, the 3-nozzle-180°, a non-closed nozzle configuration, has significantly lower heat loads on the baseplate and the sidewall than that of the 4-nozzle-90° and the 3-nozzle-120°. In addition, reducing the number of engines is also an effective solution under the same conditions of thrust. Studying the layout of the working engine without changing the original layout has important guiding significance for improving the reusability and safety factor of the RLV.