Effect of forward-facing concavity on the aerodynamic and aerothermodynamic characteristics of an atmospheric Re-entry vehicle

Aerodynamic heating and drag remain the two foremost factors to consider in the design of a re-entry vehicle. Mitigating the aero-heating effects is paramount for re-entry vehicles decelerating higher up in the atmosphere at hypersonic speeds. Re-entry vehicles use either propulsive forces, drag, or a combined effect of both to their advantage in order to dissipate speed. Furthermore, the ballistic coefficient, another critical parameter in determining the re-entry trajectory, is constantly optimized to lower values, meaning optimal re-entry with reduced aerothermal loads imposed upon the vehicle. The current computational study involves a design modification of the existing ORION CEV crew module, introducing a concavity on the heat shield of the re-entry vehicle-the forward-facing concavity. Six 2-dimensional spline curves were constructed to create six concavities at the nose of the vehicle based on the d/D ratios, where d is the height of the concavity measured from the axis of symmetry, and D is the depth of the concavity measured from the nose of the baseline model. The effect of these forward-facing concavities on aerodynamic and thermodynamic parameters, such as drag coefficient, ballistic coefficient, mean shock standoff distance (MSSD), and heat flux distribution, is investigated at varying Mach numbers of 1.4, 3, 6, and 7 at 0 degrees angle of attack. Furthermore, the monostability characteristics have been evaluated as well. From the analyses, comparing with the baseline model, M6 (d/D = 2.9) has the highest increment in drag of about 15 %. Model M3 (d/D = 0.97) has the maximum increment in MSSD of about 52.2 %. At higher Mach numbers, there is a reduction in nose heat flux at the cost of an increased peak. There is a 6 % reduction in heat flux over the entire heat shield for M6.