Reentry flow and aerothermal characteristics of a retro-propulsive booster

Abstract

Retro-propulsion of a rocket booster is a topic of rising interest where companies are striving to develop reusable launchers in order to reduce cost, environmental impact and turnover time. Understanding the loads on the nozzles during reentry is key to be able to design and produce nozzles capable to reliably be used multiple times. During the project a tool was developed based
on CAD and flight data of a Falcon 9 based rocket. A case was set up and simulated with the help of computational fluid dynamics (CFD) and chemical models in order to understand the flow behaviour and thermal loading on and near the nozzles during two flight altitudes with- and without retro-propulsion. The results concluded that without retro-propulsion, the most exposed area, with highest heat transfer coefficient (HTC) and heat flux, are the throats of the nozzles due to a recirculation within the nozzle cluster stagnating the flow at that region. While with retro-propulsion, the thermal loads were similar in magnitude for start and end burn with local high values at the exit of the nozzles. The major thermal loads during retro-propulsion where due to expansion of the exhaust hitting the nozzle walls due to plume-plume interaction.