Numerical and Experimental Analysis of Grid Fin Aerodynamic Performance for China's Next Generation LOX/LCH4 Reusable Launch Vehicle "ZQ-3"
- Paper ID
95081
- DOI
- author
- company
LandSpace Technology Corporation Ltd.
- country
China
- year
2025
- abstract
Zhuque-3 (ZQ-3) is China's next generation liquid-fueled reusable launch vehicle powered by liquid methane and liquid oxygen (methalox), currently being developed by \textit{LandSpace Technology Co., Ltd}, a commercial space launch provider based in Beijing. This study investigates the grid fin aerodynamic effectiveness on the first stage of ZQ-3 launcher during the return phase. The first stage of ZQ-3 is equipped with nine Tianque-12 (TQ-12) engines at vehicle base and four grid fins near the interstage section. Unlike during the ascent phase, in the re-entry and return phase, the atmospheric freestream is directed towards the engine nozzles. Without engine exhaust plumes, the leading edge geometry of the engine nozzles results in complex aerodynamic characteristics, including flow separation and shock waves. Grid fins are critical aerodynamic control surfaces that enable effective vehicle re-entry and subsequent vertical landing through fin deflection. Optimizing the grid number, fin size, and web thickness is essential for achieving strong control capabilities while minimizing structural weight. This research employed computational fluid dynamics (CFD) simulations and wind tunnel tests to analyze the aerodynamic performance of grid fins with different web thicknesses under a range of freestream conditions, including Mach numbers from 0.9 to 4, angles of attack from $0^\circ$ to $20^\circ$, and sideslip angles from $0^\circ$ to $8^\circ$. A 1:50 scale model of the ZQ-3 first stage, with a grid fin web thickness of 0.3~mm, was used in the wind tunnel tests conducted in a test section with a cross-sectional area of 1.2$\times$1.2~m$^2$. The results demonstrate a good agreement between the numerical simulations and the experimental data, highlighting the significant impact of grid fin web thickness on aerodynamic control characteristics. Specifically, thicker grid fins lead to higher axial force coefficients and reduced sensitivity in the pitching moment coefficient, thereby resulting in decreased control effectiveness, particularly in transonic flow regimes. These findings provide valuable insights for optimizing reusable launch vehicles and understanding the aerodynamic control characteristics of grid fins during the vertical landing phase in complex flow environments.