Numerical approach for radiative-heat-transfer of a reusable liquid-propellant launch vehicle

The radiative heat flux of the plume from reusable rockets is a critical parameter during the launch and return processes. This paper proposes a method for calculating radiative heat flux with higher accuracy than previously reported for a recoverable nine-engine liquid-propellant rocket. Based on the Radiative Transfer Equation (RTE), this study employs the discrete transfer method to solve the transient RTE problem using physical properties to describe the problem while avoiding the need to directly solve mathematical equations. The proposed method can effectively determine the radiative heat flux of the flow field and is applicable to problems involving various geometries. Calculations reveal that during the ascent phase of the rocket, the radiative heat flux at the base of the vehicle reaches its maximum in the initial stages of the lift-off, reaching a maximum of ~50 kW/m², which is 2.24 times the maximum value during the return phase. During the deceleration stage of re-entry into the atmosphere, the maximum radiative heat flux recorded on the sidewall of the rocket is 29.1 kW/m²; the maximum heat flux on the bottom surface is approximately 22.3 kW/m², accounting for 76.6% of that on the rocket’s sidewall. This provides a basis for the thermal protection design of the rocket’s bottom and walls as well as for the thermal management of cryogenic propellant tanks. Future research will involve ground engine testing and flight experiments to further validate the proposed model.