Assessment of Two Fast Codes used for Preliminary Aerodynamic Design of Guided Projectiles
Final technical rept.
ARMY BALLISTIC RESEARCH LAB ABERDEEN PROVING GROUND MD
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Two missile aerodynamic prediction fast codes, namely NSWCAP and Missile-DATCOM, have been applied to the geometry of the guided, gun-launched Copperhead projectile. Assessment of the two codes was made in comparison with wind tunnel and free-flight range test data. Two configurations were considered for computation the launch configuration body-tail in the Mach range of 0.5 to 1.8 and the maneuvering configuration body-wing-tail in the Mach range of 0.3 to 0.95. Results show reasonable agreement for the drag coefficient, C sub D, and show very large disagreements for both C sub N sub alpha and C sub M sub alpha. The incapability of both codes to include body slots and fin gap effects seems to have contributed largely to these differences. The dynamic derivatives C sub l sub p and C sub M sub q C sub M sub alpha are not adequately estimated by the NSWCAP code, and are not calculated in the DATCOM code. For the coefficients actually computed, the DATCOM code results were slightly more accurate than those of the NSWCAP code. Both codes lack the determination of the explicit effects of control surface deflection angles on the aerodynamic coefficients. Development is needed for the determination if both codes are to be used for predictions for guided projectiles. Several areas of improvements in both codes are identified.
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