State Of The Art Engineering Aeroprediction Methods With Emphasis On New Semiempirical Techniques For Predicting Nonlinear Aerodynamics On Complete Missile Configurations

This report discusses the pros and cons of numerical, semiempirical and empirical aeroprediction codes and lists many state-of-the-art codes in use today. It then summarizes many of the more popular approximate analytical methods used in State-of-the-Art (SOTA) semiempirical aeroprediction codes. It also summarizes some recent new nonlinear semiempirical methods that allow more accurate calculation of static aerodynamics on complete missile configurations to higher angles of attack. Results of static aerodynamic calculations on complete missile configurations compared to wind tunnel data are shown for several configurations at various flight conditions. Calculations show the new nonlinear methods being far superior to some of the former linear technology when used at angles of attack greater than about 15 degrees. Aeroprediction codes, Nonlinear semiempirical methods, State-of-the-Art (SOTA) semiempirical aeroprediction codes, Static aerodynamic calculations.

A new version of the aeroprediction code (APC), the AP02, has been developed to address the requirements arising from advanced weapon concepts. The AP02 was formed by adding significant new technology and several productivity improvements to the previous version of the APC, the AP98. New technology added included 6 and 8 fin aerodynamics, improved nonlinear aerodynamics, improved pitch damping predictions, improved power-on base drag estimates, base-bleed effect on base drag estimation, improved axial force of nonaxisymmetric bodies and trailing-edge flap capability. Other improvements and productivity enhancements include an aerodynamic smoother, ballistic and three degree-of-freedom simulation modules as well as refinements for the pre- and post-processor for inputs and outputs of the AP02. Comparison of the predicted aerodynamics of the AP02 to AP98 and experimental data showed the AP02 to be slightly better than the AP98 in most cases that both codes would handle. However, due to the additional new technology incorporated into the AP02, many new options are available in the AP02 that are not available in the AP98. Therefore, the AP02 is more robust and, on average, is slightly more accurate than the AP98 in predicting aerodynamics of weapons.

A new semiempirical method has been developed to predict normal force, pitching moment, and center of pressure on missile configurations up to angles of attack of 30° The method is based on linear theory and slender body techniques at low angle of attack and uses wind tunnel data to derive nonlinear angle-of-attack corrections as angle of attack increaces. The new improved theories include body alone, wing alone, and body-wing and wing-body interference. While the new theory is databased, simple analytical formulas are derived that allow general use of the techniques. Comparison with the linearized approaches used in the former NSWCDD aeroprediction code shows singificant reductions in errors of aerodynamics above 5° to 10° angle of attack. Limited comparisons to other state-of-the-art engineering codes show the new theory to be as good as or better than anything known to be available for computing planar aerodynamics up to 30° angle of attack.

New and improved version of the Naval Surface Warfare Center, Dahlgren Division aeroprediction code (AP93) has been developed. The new code contains new technology that allows planar aerodynamics of axisymmetric solid rocket-type weapons to be computed with engineering accurately over the entire Mach number range and for angles of attack to 30 deg. New technology developed and included in the AP93 includes; A new engineering method to compute aeroheating information at a high Mach number; Extension of the second-order shock-expansion theory to include real-gas effects, including several new pressure prediction techniques; An improved body-alone nonlinear normal-force method; New methods for computing nonlinear aerodynamics of wing alone, wing body, and body wing due to angle of attack, and wing body due to control deflection; and a new base-dmg database and improved empirical base-drag estimation technique. ... Aeroprediction code (AP93), Planar aerodynamics, High mach number.