Guided Munitions Protected by an Aerodynamic Cap

Abstract

In the field of steered munitions intended to destroy a target after at least one flight phase followed by a target approach phase, a munition comprises a munition body of cylindrical shape of longitudinal axis having, on the same side as a front end of the munition which is the end intended to be directed toward the target, a front body comprising an optic of a guidance device that guides said munition toward the target, a cap for protecting the optic, secured to the munition body, characterized in that the protective cap comprises at least one recess having a pyrotechnic device intended to destroy said protective cap so as to free the optic and make the munition guidance device operational during the target approach phase. Application: steered or guided munitions such as those of the rocket or projectile type, or missiles.

1 . A steered munition intended to destroy a target after at least one flight phase followed by a target approach phase, said munition comprising: a munition body of cylindrical shape of longitudinal axis ZZ′ having, on the same side as a front end of the munition which is the end intended to be directed toward the target, a front body comprising an optic of a guidance device that guides said munition toward the target, a cap for protecting the optic, secured to the munition body,
 the protective cap, in the shape of an ogive of axis of revolution XX′ coincident with the longitudinal axis ZZ′, being made of a material that can be shattered into multiple fragments, comprising at least one recess forming at least one cavity containing a pyrotechnic device intended to supply propulsive energy directly to the walls of the cavity to shatter the protective cap into multiple fragments, in order to free the optic and make the munition guidance device operational during the target approach phase. 
 
     
     
         2 . The steered munition as claimed in  claim 1 , wherein the protective cap comprises walls having weakening grooves so as to promote regions along which said walls rupture when the protective cap is being destroyed. 
     
     
         3 . The steered munition as claimed in  claim 1 , further comprising, between the protective cap and the front body of the munition body, a shield that protects the optic of the guidance device. 
     
     
         4 . The steered munition as claimed in  claim 3 , wherein the protective shield comprises a shield body of circular cylindrical rounded shape having two main faces and a circular edge of axis coaxial with the longitudinal axis ZZ′, the rounded shape of the shield body conforming to the shape of the surface of the front body of the munition body. 
     
     
         5 . The steered munition as claimed in  claim 1 , further comprising a clamping band that secures the protective cap to the munition body, the clamping band comprising, on the same side as the front end of the munition, a circular edge of tapering shape. 
     
     
         6 . The steered munition as claimed in  claim 1 , wherein the surface of the front body, of rounded shape, has no discontinuity and no roughness so that it exhibits a continuous aerodynamic profile. 
     
     
         7 . The steered munition as claimed in  claim 1 , wherein the front body of the munition body comprises, on the same side as the front end, a front body part of circular cylindrical shape of diameter D 1 , of axis of revolution collinear with the longitudinal axis ZZ′, the front body part comprising a munition front body wall of rounded shape including the optic of the guidance device, the rounded portion of the munition front body wall being directed toward the front end to give the munition a continuous aerodynamic shape when it has been rid of the protective cap. 
     
     
         8 . The steered munition as claimed in  claim 7 , wherein the protective cap, in the shape of an ogive, of axis of revolution XX′, comprises a first recess opening onto a second recess of circular cylindrical shape of diameter equal to the diameter D 1  of the front body part of the munition, the first recess of the cap forming, with the rounded-shaped front body wall, centered on the longitudinal axis ZZ′, a first cavity containing the protective shield. 
     
     
         9 . The steered munition as claimed in  claim 1 , wherein the pyrotechnic device comprises a propulsive charge and an igniter, the igniter comprising electrical contacts for activating it. 
     
     
         10 . The steered munition as claimed in  claim 9 , wherein the first cavity contains the pyrotechnic device. 
     
     
         11 . The steered munition as claimed in  claim 9 , wherein the protective shield comprises, near its circular edge, a support for supporting the igniter in a plane parallel to the longitudinal axis ZZ′, the igniter support acting as a spoiler intended to generate a transverse force when it is subjected to the aerodynamic forces as the cap is being destroyed, and as out-of-balance weight in the case of a munition that spins on itself. 
     
     
         12 . The steered munition as claimed in  claim 8 , wherein the protective cap further comprises, on the same side as the front end, a third recess of cylindrical shape of axis collinear with the longitudinal axis ZZ′, and separated from the first recess by a dividing wall in a plane perpendicular to the longitudinal axis ZZ′, the third recess being closed by a nose cone to form a second cavity containing the pyrotechnic device intended to destroy the protective cap. 
     
     
         13 . The steered munition as claimed in  claim 4 , wherein the protective shield comprises, near its circular edge, a spoiler intended to generate a transverse force on the shield body when it is subjected to the aerodynamic forces and to cause it to be ejected from the body of the munition, said spoiler also acting as an out-of-balance weight in the case of a munition that spins on itself. 
     
     
         14 . The steered munition as claimed in  claim 1 , wherein the protective cap comprises a cap connection part extended by a cap end ring having a cap edge of diameter D 5  greater than the outside diameter D 4  of the cap connection part so as to form a first cap shoulder so that the clamping band can prevent translational movement of the cap along the longitudinal axis ZZ′ on the front body of the munition body. 
     
     
         15 . The steered munition as claimed in  claim 9 , further comprising two layers of electric conductors intended to activate the igniter:
 a first layer having one end bonded to one of the main faces of the shield on the same side as the front body of the munition body, a central part bonded to the other main face of the shield on the same side as the first recess of the cap, the other end of the first layer, in the first cavity being electrically connected to the electrical contacts for the activation of the igniter, the first layer passing from one main face of the shield to the other along a groove on the edge of said shield,   a second layer of electric conductors, on the same side as the munition body, in electrical contact with the end of the first layer on the same side of the front body of the munition body.   
     
     
         16 . The steered munition as claimed in  claim 7 , wherein the front body part is extended toward the rear body of the munition by an intermediate body of circular cylindrical shape of the same axis of revolution ZZ′ as, and of diameter D 2  greater than the diameter D 1  of, the front body part, so as to form a first body shoulder, the intermediate body being extended by the rear body of the munition of diameter D 3  greater than the diameter D 2  of said intermediate body, so as to form a second body shoulder. 
     
     
         17 . The steered munition as claimed in  claim 16 , wherein the protective cap, secured to the body of the munition by the clamping band, comprises a cap central part of conical or ogive shape extended, on its larger-diameter side, by a cap connection part that connects the cap to the munition body, of circular cylindrical shape, of outside diameter D 4  smaller than the diameter D 2  of the intermediate body, the cap connection part being extended by a cap end ring having a cap edge of diameter D 5  greater than the outside diameter D 4  of the cap connection part and less than the diameter D 2  of the intermediate body so as to form a first cap shoulder intended to prevent translational movement of the cap. 
     
     
         18 . The steered munition as claimed in  claim 17 , wherein the cap edge and the first body shoulder each have a respective hole for the insertion of a pin that angularly indexes the cap and the munition body, the internal wall of the first recess of the cap comprising a tooth inserted in the groove situated on the circular edge of the protective shield, the angular indexing pin and the tooth inserted in the groove of the protective shield providing electrical contact between the two layers and orienting the spoiler of said protective shield at an advantageous clearance angle. 
     
     
         19 . The steered munition as claimed in  claim 18 , wherein the cap comprises a series of longitudinal weakening grooves along the walls of the first and second recesses, these grooves being evenly distributed about the axis of revolution XX′ of the cap, the cap further comprising a circular weakening groove along the periphery of its external surface some distance from the cap edge such that said circular weakening groove is located at the tapering end of the clamping band when the cap is mounted on the munition body. 
     
     
         20 . The steered munition as claimed in  claim 19 , wherein the cap comprises another circular weakening groove along the periphery of the internal surface of the cap formed by the wall of the second recess, some distance from the cap edge such that said other weakening groove is located at the end, of diameter D 1 , of the front body part on the side of the front body wall when the cap is mounted on the munition body, the axis XX′ of the protective cap then coinciding with the longitudinal axis ZZ′ of the munition.