Evaluation and Improvements to the Aeroprediction Code Based on Recent Test Data

Abstract

The 1998 (AP98) and prior versions of the U.S.NavalSurfaceWarfare Center, DahlgrenDivisionAeroprediction Code are based primarily on slender body and perturbation theories at low angle of attack and empirical constants that represent the nonlinear aerodynamics as a function of angle of attack, Mach number, aspect and taper ratio, and othermissile geometric parameters. The primary database on which these empirical nonlinear constants were derived was based on the NASA/Tri-Service component database taken in the 1970s. This database was limited in body radius to wing semispan plus body radius ratios of 0.5. A more recent database taken by NASA and the formerMcDonnell DouglasCorporation investigated other values of the parameter: body radius to wing semispan plus body radius ratio of 0.25, 0.33, and 0.5. As a result of this new database, the empirical constants in the AP98 that represent many of the aerodynamic nonlinearities were Ž ne tuned. This Ž ne tuning, along with other minor improvements, has shown the average normal force coefŽ cient errors to be reduced by anywhere from 10 to over 40% on various missile conŽ gurations. The largest reductions in error were for conŽ gurations where the AP98 average accuracy was the worst. These new improved empirical constants will be a part of the next planned release of the aeroprediction code in 2002 (AP02). The AP98 average error on normal force coefŽ cient of § 10% will, therefore, be somewhat better for the AP02.