Mc Drag A Computer Program For Estimating The Drag Coefficients Of Projectiles

MC DRAG - a Computer Program for Estimating the Drag Coefficients of Projectiles

This report presents a FORTRAN program "MC DRAG" for estimating a projectile's zero-yaw drag coefficient from the given values of certain size and shape parameters. The results are valid over a Mach number range of 0.5 to 5 and a projectile diameter range of 4 to 400 millimetres. A user's guide and a FORTRAN listing of MC DRAG is provided. The program is applied to three illustrative examples: (1) an experimental low-drag small arms bullet, the 5. 56mm BRL-1 design; (2) a 55mm scale model of the Minuteman re-entry stage vehicle; (3) the 155mm long-range artillery shell M549. The MC DRAG program estimates drag coefficient to within 3% error at supersonic speeds, 11% error at transonic speeds, and 6% error at subsonic speeds.

SANDRAG

A design method is presented for calculating the flow field and drag of bodies of revolution at zero angle of attack in incompressible flow. The body pressure distribution, viscous shear stress, and boundary layer separation point are calculated by a combination of potential flow method and boundary layer techniques. The portential solution is obtained by modeling the body with an axial distribution of source/sink elements who strengths very linearly along their length. Both the laminar and turbulent boundary layer solutions use momentum integral techniques which have been modified to account for the effects of surface roughness. An existing technique for estimating the location of transition was also modified to include surface roughness. Empirical correlations are developed to estimate the base pressure coefficient on a wide variety of geometries. Body surface pressure distributions and drag predictions are compared with experimental data for artillery projectiles, conical, and flared bodies. Very good agreement between the present method and experiment is obtained.

Scientific and Technical Aerospace Reports