Numerical study on the aerodynamics of a rocket fairing half in the continuum regime of the reentry process
FENG Rui1,2, LIU Yu1,2, ZHANG Zhang1,2, HE Qingsong1,2, WU Zhuo1,2, TENG Haishan1,2, JIA He1,2
1. Beijing Institute of Space Mechanics & Electricity, Beijing 100094, China; 2. Laboratory of Aerospace Entry, Descent and Landing Technology, China Aerospace Science and Technology Corporation, Beijing 100094, China
Abstract:[Objective] Recently, a trend has been developed toward the high-density launches of launch rockets, and unprecedented attention has been paid to the impact zone safety of rocket's separated fairings. Great pressure on controlling the environmental safety of the rocket's fairing half results from the low accuracy and large uncertainty in reentry trajectory calculation using the traditional mass point ballistic model. The main reason for the difficulty in reliably calculating the reentry ballistics of the fairing half is the lack of comprehensive studies on the half fairing's aerodynamic characteristics under various reentry flight conditions. This study aims to deal with the problem of reliable prediction of the reentry impact point of fairing half after separation from the launch vehicle. By using the computational fluid dynamics (CFD) approach, a comprehensive study is conducted here on the aerodynamics of the fairing half of a common rocket in the continuum regime of its reentry process. The incoming flow parameters for multiple computational conditions are extracted from the measured ballistic data of a certain flight mission. The calculation of various conditions is set and controlled by a parametric automated script. To obtain the relevant aerodynamic coefficients, the steady-state numerical solution for three-dimensional Reynolds-averaged Navier-Stokes (RANS) equations is obtained using the finite volume method. The Roe scheme and the implicite lower-upper symmetric Gauss-Seidel (LU-SGS) solution algorithms are used to obtain the discretization solution of the flow control equations. A numerical model uses an unstructured mesh structure, with a total mesh number approximating 15 million, and generates enough prismatic layers on the surface. The turbulence model is a two-equation realizable k-ε model. Aerodynamic coefficients of the fairing half were obtained under various flight conditions, where the Mach number varied from 0.20 to 5.95, while the angle of attack (AOA) varied from 0° to 360°. Numerical results indicated that:1) Two trim angles of attack existed in the supersonic and hypersonic regions, with the first trim AOA ranging from 85° to 97° and the second trim AOA ranging from 256° to 254°. 2) Similarly, two trim angles of attack existed in the transonic and subsonic regions, with the first trim AOA ranging from 85° to 88° and the second trim AOA ranging from 259° to 252°. 3) Whether in the supersonic or transonic region, the fairing half behaved statically stabled at its first trim AOA in axial roll direction at 0° roll angle but non-statically stabled at the second trim AOA. 4) Adjusting the position of the center of mass of the fairing half along its axial direction could effectively change its trim AOA, which led to a significant change in the lift-to-drag ratio in turn. However, adjusting the position of the center of mass along its radial direction had little effect on the trim AOA and the lift and drag characteristics. By utilizing the obtained database of aerodynamic coefficients, the 6-degrees-of-freedom reentry model for the fairing half can be achieved, helping improve the prediction accuracy of the impact area significantly. In the hypersonic region, the difference in the aerodynamic coefficients under the same AOA condition is below 15%, indicating that in the continuum region, when the Mach number is greater than 5.95, the required aerodynamic coefficients for the ballistic reentry analysis are similar to those of Mach number is 5.95. Due to the obvious differences in the aerodynamic coefficients in the transonic or subsonic region, the required aerodynamic coefficients for the ballistic reentry analysis can be interpolated from the obtained database. The trim AOA and the corresponding lift-to-drag ratio can be effectively changed by adjusting the position of the center of mass of the fairing half along its axial direction, thus adjusting or controlling the impact point within a certain range.
冯瑞, 刘宇, 张章, 何青松, 吴卓, 滕海山, 贾贺. 火箭整流罩半罩再入过程连续流区气动特性数值研究[J]. 清华大学学报(自然科学版), 2023, 63(3): 414-422.
FENG Rui, LIU Yu, ZHANG Zhang, HE Qingsong, WU Zhuo, TENG Haishan, JIA He. Numerical study on the aerodynamics of a rocket fairing half in the continuum regime of the reentry process. Journal of Tsinghua University(Science and Technology), 2023, 63(3): 414-422.
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