Computational and experimental evaluation of sonic boom from a HTV-2 type hypersonic boost gliding vehicle with high-enthalpy inlet conditions

Understanding sonic booms and their dependence on vehicle geometry and operation conditions is paramount to the development of future low-boom hypersonic aircraft. In this study, the sonic boom of a HTV-2 type boost gliding vehicle (BGV) traveling at hypersonic speeds (M_∞ > 5) was studied. Fifteen distinct cases of varying Mach number (Mach 6.5 or Mach 8) and varying angles of attack (-5°, 0°, or 5°) were tested in CUBRC’s LENS 48-Inch Tunnel and simulated with the US3D computational fluid dynamics (CFD) solver. These cases build upon our 2024 study with the same BGV configuration [1], but the key differences are as follows: 1) a new off-body pressure measurement rail was paired with sensors calibrated for the 0-1 psi range to significantly reduce measurement uncertainty, 2) higher inlet enthalpy conditions were used to better model the realistic hypersonic flight conditions, and 3) the inclusion of the off-body measurement device was included in CFD to compare with experiment results and CFD without the measurement device. The pressure signature was read at a radial distance of 0.3 meters from the BGV, and the overpressure data (which characterizes the sonic boom signature) was examined. It was found that the vehicle’s lift force impacts the location and intensity of the overpressure signature. Results of CFD simulations with the new rail aligned well with the experimental results. The resulting overpressure values with and without the rail were compared. The well-known reflection amplification factor of two is consistently found in the CFD results, but the experiment results were typically a little higher between 2 and 3. Additionally, due to the high freestream Mach number, the leading shock caused by the pressure rail is also found to have noticeable impact on the measured sonic boom signature, including the refraction of the incident shock (the bending of the shock) and the magnitude amplification of the enhancement factor (due to the pressure rise behind the leading shock). As a combined effect, the maximum overpressure with the rail is typically slightly greater than twice of that without the rail. This investigation of a hypersonic booms was successful through shock tunnel testing and CFD simulations.