F - Mech Eng,Light,Heat,Weapons – 42 – B
Patent
F - Mech Eng,Light,Heat,Weapons
42
B
F42B 14/06 (2006.01) F42B 12/06 (2006.01)
Patent
CA 2127914
ABSTRACT A fin stabilized subcaliber projectile is subject to aerodynamic drag during night along the trajectory to its target. Under this influence its velocity decays accordingly. For kinetic energy armor piercing projectiles its effectiveness depends primarily on the impact velocity at the target. The reduction of the aerodynamic drag and induced decay of the projectile velocity is the subject of this invention. The aerodynamic drag in supersonic flight is the sum of pressure and wave drag and skin friction drag of the various projectile components such as the slender projectile nose, the high fineness ratio cylindrical body and the fin assembly needed for projectile stabilization. An additive aerodynamic drag is induced by a section of threads or a group of annular grooves arranged on the cylindrical body of the subcaliber projectile engaging a mating configuration provided on the interior of the metallic base of the discarding sabot. To minimize the drag of the acceleration-transmitting interface, whether annular grooves or threads, its length has to be as short as possible and be determined by the force to be transmitted and the dynamic strength properties of the mating sabot. The latter are less than those of the high density, high strength projectile material such as sintered tungsten alloy or depleted uranium alloy and therefore are the basis for the structural design. Limiting the length of the structural interface will reduce its pressure and wave drag, in addition, proper placement of the structural interface on the cylindrical body of the projectile can reduce the skin friction drag. Locating the structural interface aft of the point where natural transition of the laminar boundary layer to turbulent boundary layer occurs and/or at a station immediately ahead of the fin assembly will provide maximum benefit from the low friction coefficient of laminar boundary layer. Projectile velocity measurements over a range of 2000 meters have demonstrated the effectiveness of the inventions by a substantial reduction of the velocity decay.
Christenson Craig L.
Feldmann Fritz K.
Griffith Paul J.
Macrae & Co.
Oerlikon-Contraves Pyrotec Ag
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