Study of Sweepback Angles Criterion for Reusable Hypersonic Vehicle

At hypersonic speed, severe aerodynamic heating is observed, and temperatures are too high to cool by radiation cooling; active cooling such as ablative cooling is helpful in this situation. The Thermal Protection System (TPS) consists of a layer of an ablative material, followed by an insulating material to lower the temperature at the inside wall of the lifting body. The surface area (considering the inside volume of the vehicle constant) of the TPS plays a vital role in heat transfer to the vehicle and heat transferred through the vehicle body. The minimum area sweepback angle (Λ_Area-min) is the function of the principal radius (R) and the ratio of the principal radii of the forward bi-curvature stagnation surface (R/r). The Λ_Area-min = 80° is obtained for R = 2 m and R/r = 2. The aerothermal analysis of the lifting body is of fundamental interest while designing the TPS. A Computational Fluid Dynamics (CFD) simulation of a two-dimensional (2D) lifting body against thermally perfect air in a hypersonic region (Mach number, M > 5) is carried out for M = 5–9 to obtain a heat-transfer-minimized sweepback angle (Λ_HT-min), at which heat transfer to the vehicle is minimum. The simulation was carried out at an altitude H = 35 km and zero angle of attack for cruise conditions. Results show that Λ_HT-min = 80° for all M (= 5–9, in this study) at all locations of Sweepback Leading Edge (SBLE).