Free-flight trim-angle predictions for the aeroassist flight experiment

Abstract

The aerodynamic coefficients and trim angle for an aerobrake at Mach numbers of 9.2 and 11.8 were found using a combination of experiment and computation. Free-flight tests were performed at NASA Ames Research Center's Hypervelocity Free-Flight Aerodynamic Facility, and the forebody pressure distribution was calculated using a three-dimensional Navier-Stokes code with an effective specific heat ratio. The computed drag, lift, and moments were used to prescribe the number of terms in the aerodynamic coefficient expansions and to specify values of the higher-order terms, and the experimental aerodynamic coefficients and trim angle were extracted from the experimental data. The experimental and computed aerodynamic coefficients and trim angles were in good agreement. The trim angle obtained from the free-flight tests, 14.7 deg, differed from the design trim angle, 17 deg, and from the Langley wind-tunnel results, 12 deg in air and 17 deg in CF4. These differences are attributable to real-gas effects.