Force Measurements in Hypervelocity Flows with an Acceleration Compensated Strain Gage Balance

Abstract

Force and moment measurements are performed on a 6-inch Apollo shaped capsule in the LENS I and 48-Inch reflected shock tunnels at CUBRC in cold hypersonic nitrogen flows and for high enthalpy flows (10 MJ/kg) of air, nitrogen, pure oxygen and a 50%-50% oxygen-argon mixture. Measurements with an acceleration compensated flexured strain gage force balance are compared with non-equilibrium Navier-Stokes computations. For the low enthalpy nitrogen runs, axial and normal force coefficients are within 2% of the numerical predictions whereas the pitching moment is under-predicted by 10%. Excellent agreement within 0.5% for the lift-to-drag ratio is achieved. For the first time, the effect of thermodynamic and chemical non-equilibrium on the force and moment coefficients is measured on a reentry capsule in a reflected shock tunnel and compared with state of the art numerical simulations. Both computations and experiments show an increase in the axial force, normal force and pitching moment coefficients and a decrease in the lift-to-drag ratio.