Base-region thermal environment and flow characteristics of liquid rocket in retro-propulsion re-entry process

Reusable liquid-propellant launch vehicles constitute a pivotal direction for future space transportation systems. During vertical re-entry of a rocket, the aft-mounted engines descend in an irregular configuration facing the freestream. The local thermal environment and flow characteristics are highly complex. A simulation study of the flow over a Falcon 9 v1.2 derived geometry was conducted for four representative re-entry phases: high-altitude powered deceleration, high-altitude aerodynamic deceleration, low-altitude aerodynamic deceleration, and low-altitude powered deceleration. The vehicle thermal environment is markedly transient and non-uniform: plume morphology evolves continuously with altitude and engine operating condition. Powered deceleration phases exhibit substantially stronger flow disturbances and heat-flux maxima than aerodynamic deceleration phases owing to intense plume-freestream coupling. Secondary combustion exerts a global thermal influence on the far-field plume at low altitude. Across the four characteristic stages, the peak heat flux persistently localizes at the nozzle lip and the aft-edge of the rocket base, reaching 380 kW/m², these data constitute a quantitative basis for engine thermal-protection design.