Reentry flow and aerothermal characteristics of a retro-propulsive booster

Paper in proceeding, 2025

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.