Drag Behavior of Inflatable Reentry Vehicle in Transonic Regime

Abstract

The drag coefficient for inflatable reentry vehicles shows discrepancies between a wind tunnel experiment and a flight test in a transonic regime. These discrepancies exist in the drag decrease behavior in the transonic regime and local minimum values of drag above the sonic speed in a wind tunnel. Hence, the present paper focuses on uncovering the reasons and mechanisms behind the same and investigates transonic flowfields around a vehicle by using a transonic wind tunnel and the computational fluid dynamics approach. Several test models with diameters ranging from 56 to 96 mm are used to quantitatively evaluate the effects of scale and a sting attached on the rear. Aerodynamic coefficients, pressures at the rear of the model, and density-gradient distributions are measured for operation conditions of freestream Mach numbers ranging between 0.8 and 1.3. In addition, detailed distributions of the flowfield properties are clarified using the computational fluid dynamics method, which is validated by the experimental data. The results indicate that a sting behind the test models reduces the steep drag decrease at transonic speeds and that shock waves reflected on the test-section walls of the wind tunnel result in local minimum values at supersonic speeds.