Abstract: Structural analysis of rockets entails conversion of aerodynamic loads into structural loads.The transformation method of pressure interpolation can ensure the equivalence of the local loads, meanwhile requiring the shape of the structural model to be consistent with that of the aerodynamic model.However, the structural model usually retains only the main load-bearing structures while neglecting the fairing and other surface details.To solve this problem, this paper proposes a hybrid fluid-to-solid load conversion method based on pressure interpolation and force equivalence.For the rocket model with protuberance on its surface, comparison of the distances between a certain aerodynamic pressure point and the center point of its nearby structural elements to the rocket axis can be conducted to judge whether the structural model near the aerodynamic pressure point is consistent with the aerodynamic model in shape, thereby differentiating the consistent and inconsistent areas on the surface of the structural model.Then the pressure interpolation method is used for the area with the consistent shape, while the force equivalent method is adopted for that with the inconsistent shape.The calculation results of a rocket model show that both the errors of the resultant force and moment before and after the load conversion are smaller than 3%.This method exhibits good engineering applicability potential with characteristics such as wide application range and automatic conversion process.

Key words: pressure interpolation, spline interpolation, force equivalent method, launch vehicle structure, fluid-to-solid load conversion