US20140145024A1

US20140145024A1 - Ejectable aerodynamic cap for guided munition and guided munition comprising such a cap

Info

Publication number: US20140145024A1
Application number: US13/882,374
Authority: US
Inventors: Patrick Cohe; Fabien Moreau
Original assignee: TDA Armements SAS
Current assignee: TDA Armements SAS
Priority date: 2010-10-29
Filing date: 2011-10-25
Publication date: 2014-05-29
Also published as: WO2012055889A1; EP2633262A1; FR2966920A1; FR2966920B1

Abstract

An ejectable protective cap for controlled munition comprises a munition body of cylindrical form, having a front end comprising a central part directed toward a target. The cap comprises n portions distributed around a longitudinal axis, to cover the front end, n being an integer≧2, a cap portion having an edge in contact with an edge of a contiguous cap portion with it in a respective plane of assembly of two contiguous cap portions passing through the longitudinal axis, a pyrotechnic initiator for each cap portion comprising a pyrotechnic initiator body securely attached to the respective cap portion, a piston plunger that can slide in a seal-tight manner by one of its ends, the free other end in contact with the contiguous cap portion to separate, upon simultaneous activation of n pyrotechnic initiators, edges of the contiguous cap portions and release the front end of the munition body.

Description

The invention relates to the protective caps of homing heads of guided munitions and, more particularly, munitions of limited length.
Guided or controlled munitions, such as those of rocket or projectile or missile type, are equipped with optical and electronic guiding systems to ensure, after a flight phase followed by a target approach phase, a high level of reliability and accuracy of impact of the munition on the target.
For example, certain types of guided missiles or rockets are controlled using a laser beam. An optic of the missile detects the laser beam illuminating the target and a computer onboard the missile determines the flight parameters to reach the target.
Generally, the optical guidance system situated at the front end of the missile (nose or head of the missile), or of the controlled munition in a general case, that is to say at the end of the munition which is directed toward the target, comprises a protective cap, on the one hand to protect the optic of the homing head from impacts from bodies present in the air during the flight phase and, on the other hand, to avoid a rise in temperature of the missile control electronics associated with the optic of the homing head through the aerodynamic frictions of the munition head.
This cap can thus protect the optical guidance system of the munition, depending on the case, during a firing phase, for example, when passing through an opercule; during a ballistic phase, in the case of a rocket or a projectile; during a cruising phase, in the case of missiles.
After an approach phase (ballistic or cruising), the munition switches to the controlling guiding phase. To make this last phase operative, an ejection system has to be provided to release the emergent part of the optic from the homing head.
The ejectable protective caps of the prior art protecting the optics of the homing heads are not suited to munitions of limited length because of their large sizes.
To mitigate the drawbacks of the controlled munitions of the prior art, the invention proposes an ejectable protective cap for controlled munition comprising a munition body of cylindrical form of longitudinal axis ZZ′, having a front end of the munition body comprising a central part intended to be directed toward a target.
The cap comprises n cap portions C1, C2, . . . Ci, . . . Cn of the same forms, distributed about said longitudinal axis ZZ′, intended to cover the front end of the munition body, n being an integer number equal to or greater than 2, i being the rank of the cap portion, a cap portion Ci having at least one edge in contact with an edge of a cap portion which is contiguous with it in a respective plane of assembly of two contiguous cap portions passing through the longitudinal axis ZZ′, a pyrotechnic initiator for each cap portion, each of the pyrotechnic initiators comprising, along a longitudinal axis AA′, a pyrotechnic initiator body securely attached to the respective cap portion Ci, a piston plunger that can slide in a seal-tight manner by one of its ends, along said longitudinal axis AA′, the free other end of the piston plunger being in contact with the contiguous cap portion in order to separate, upon the simultaneous activation of the n pyrotechnic initiators, the edges in contact of the contiguous cap portions, from their respective planes of assembly and release the front end of the munition body.
Advantageously, each pyrotechnic initiator comprises an igniter between the pyrotechnic initiator body and the piston plunger to separate, upon its activation, the piston plunger from the body of the pyrotechnic initiator and exert a separation force F between the two contiguous cap portions.
In an embodiment of the cap according to the invention, n being equal to 2, the cap comprises two cap portions of symmetrical forms relative to a plane of assembly passing through the longitudinal axis ZZ′, the two cap portions being a bottom half-cap and a top half-cap.
In another embodiment, the two assembled half-caps intended to closely encompass the front end of the munition body, each comprise an outer surface wall in half-ovoid form of axis of revolution ZZ′ forming the external surface of the front of the munition.
In another embodiment, the two assembled half-caps comprise an internal surface of ovoid form covering the central part of the munition body connected to another internal surface of circular cylindrical form comprising a threading intended to produce a threaded link with the munition body, a circular edge to abut on a shoulder of the munition body when screwed onto the munition body.
In another embodiment, the two half-caps comprise, in the thickness of their wall, at the level of the other internal surface of circular cylindrical form, cells on either side of a plane Py at right angles to the plane of assembly passing through the axis ZZ′ for the insertion of the pyrotechnic initiators.
In another embodiment, the pyrotechnic initiator body comprises, in addition, an electrical connection pin intended to receive at least two electrical wires for the activation of the igniter.
In another embodiment, the pyrotechnic initiators are mounted head-to-tail on either side of a plane Py at right angles to the plane of assembly of the two half-caps and passing through the axis ZZ′.
In another embodiment, the bottom and top half-caps each comprise a respective edge in contact with one another in the plane of assembly.
In another embodiment, the bottom half-cap comprises, on its edge situated in the plane of assembly, a longitudinal groove that extends on either side of the axis ZZ′, the top half-cap comprising, symmetrically relative to said plane of assembly, on its edge situated in said plane of assembly a longitudinal tenon extending on either side of the axis ZZ′ of the same external dimensions as those of the longitudinal groove to form a fitting between the two half-caps of tenon/mortice type.
In another embodiment, the two half-caps are held together by a securing belt of circular cylindrical form of axis ZZ′, in a circular groove around two half-caps.
In another embodiment, the securing belt comprises, in the plane of assembly, on either side of the plane Py, embrittlement zones to provoke the rupture of said securing belt upon the separation of the half-caps by the action of the pyrotechnic initiators.
In an embodiment of the guided munition comprising the cap according to the invention, the central part of the munition body of cylindrical form on the axis ZZ′ is connected to the munition body by a circular cylindrical body of the same axis ZZ′ comprising a body threading intended for the screw-fastening of the cap onto the munition body and a rear part of the munition body comprising a shoulder in ring form of axis ZZ′ of tapered cone surface inscribed in a cone of generatrix Pe close to a perpendicular to the external surface of the munition body, at the level of said shoulder, the cap comprising an internal surface of ovoid form covering the central part of the munition body connected to another internal surface of circular cylindrical form comprising another threading of the same diameter as the body threading intended to produce a threaded link between the cap and the munition body, a circular edge of the same form as the shoulder of the munition body abutting on this shoulder when the cap is screwed onto the munition body.
In another embodiment of the munition, the shoulder comprises a groove in ring form of axis ZZ′, open on its tapered cone surface, containing an electrically insulating material, comprising, on said tapered cone surface, two annular tracks, of electrically conductive material, with axes of revolution that are the same as the axis ZZ′ for the electrical connection of the pyrotechnic initiators.
In another embodiment of the munition, the pyrotechnic initiator body also comprises an electrical connection pin intended to receive at least two electrical wires each equipped with a flexible contact in contact with a respective annular track in the shoulder of the munition body.
A main objective of the invention is to produce ejectable protective caps of small dimensions for guided munitions of limited length.
Another objective is to produce an aerodynamic cap that makes it possible to retain, after the ejection of the cap, an aerodynamic profile of the munition close to its profile before the ejection of the cap.

The invention will be better understood with the help of an exemplary embodiment of a guided munition comprising an ejectable cap according to the invention, with reference to indexed drawings in which:

FIG. 1 a shows a partial view in axial cross section of the front end of a controlled munition equipped with an ejectable protective cap according to the invention;

FIG. 1 b shows another partial view in axial cross section of the front end of the munition of FIG. 1 a;

FIG. 1 c represents a detail of the cross-sectional view of FIG. 1 a showing the power supply tracks of the pyrotechnic initiators of the cap;

FIG. 2 a shows a view in transversal cross section showing the pyrotechnic initiators of the controlled munition of FIG. 1 a;

FIG. 2 b shows a partial view in transversal cross section of one of the pyrotechnic initiators of the controlled munition of FIG. 1 a;

FIG. 3 a shows a front view of the munition of FIG. 1 a equipped with its ejectable cap;

FIG. 3 b shows a detail view of FIG. 3 a around the embrittlement zone of a cap securing belt;

FIG. 4 shows a partial view at the level of one of the pyrotechnic initiators upon the separation of the edges of the half-caps;

FIG. 5 shows a front view of the munition after ejection of the two half-caps with the pyrotechnic initiators;

FIG. 6 shows a view in transversal cross section of the munition body without the cap;

FIG. 7 shows a front view of an ejectable cap according to the invention produced from three contiguous cap portions C1, C2, C3, and;

FIG. 8 shows another exemplary embodiment of the ejectable cap according to the invention comprising four identical contiguous cap portions C1, C2, C3, C4.

FIG. 1 a shows a partial view in axial cross section of the front end of a controlled munition equipped with an ejectable protective cap according to the invention.
FIG. 1 b shows another partial view in axial cross section of the front end of the munition of FIG. 1 a.
More specifically, FIG. 1 b is a view in cross section in a plane Py at right angles to the plane of assembly P1 passing through the axis ZZ′.
The protective cap comprises, in this exemplary embodiment, two cap portions C1, C2, i.e. n=2.
The munition of FIGS. 1 a and 1 b comprises a munition body 10 that has a front end 12 of said munition body 10 covered by the ejectable cap according to the invention. A central part 14 of the munition body 10 may comprise, for example, an optic of the homing head of the munition (not represented in the figures).
The ejectable cap according to the invention, in this embodiment, comprises two cap portions of symmetrical forms relative to a plane of assembly P1 passing through the longitudinal axis ZZ′ of the munition body. The two cap portions are a bottom half-cap C1 and a top half-cap C2.
The ejectable cap also comprises two pyrotechnic initiators, a right pyrotechnic initiator 20 and a left pyrotechnic initiator 22 for separating the two half-caps in the munition control/guiding phase.
The central part 14 of the munition body of cylindrical form on the axis ZZ′ is connected to the munition body 10 by a circular cylindrical body 26 of the same axis ZZ′ comprising a body threading 28 intended for the screw-fastening of the cap onto the munition body 10 and a rear part 24 of the munition body comprising a shoulder 30 in ring form of axis ZZ′ of a tapered cone surface inscribed in a cone of generatrix Pe close to a perpendicular to the external surface of the munition body, at the level of said shoulder 30.
The shoulder 30 comprises a groove 32 in ring form of axis ZZ′, open on its tapered cone surface, containing an electrically insulating material 34, comprising, on said tapered cone surface, two annular tracks a1, a2, of electrically conductive material, axes of revolution that are the same as the axis ZZ′ for the electrical connection of the pyrotechnic initiators of the cap.
FIG. 1 c represents a detail of the cross-sectional view of FIG. 1 a showing the power supply tracks of the pyrotechnic initiators of the cap.
The two half-caps C1, C2 assembled to form the ejectable cap of small dimensions according to the invention, as represented in FIGS. 1 a and 1 b, closely encompass the front end 12 of the munition body 10. The two half-caps each comprise an outer surface wall in half-ovoid form of axis of revolution ZZ′. The two assembled half-caps form the external surface 36 of the front of the munition.
Once the two half-caps C1, C2 are assembled, the resulting cap comprises an internal surface 40 of ovoid form covering the central part 14 of the munition body 10 connected to another internal surface 42 of circular cylindrical form comprising another threading 44 of the same diameter as the body threading 28 intended to produce a threaded link between the cap and the munition body 10.
The cap comprises a circular edge 48 of the same form as the shoulder 30 of the munition body 10 in order to abut on this shoulder 30 when the cap is screwed onto the munition body 10.
The two half-caps C1, C2 comprise, in the thickness of their wall, at the level of the other surface 42 of circular cylindrical form, cells 50, 52 on either side of the plane of assembly for the insertion of the pyrotechnic initiators 20, 22.
FIG. 2 a shows a view in transversal cross section showing the pyrotechnic initiators of the controlled munition of FIG. 1 a.
FIG. 2 b a partial view in transversal cross section of one of the pyrotechnic initiators of the controlled munition of FIG. 1 a.
The pyrotechnic initiators of FIGS. 2 a and 2 b are, in their embodiment, of igniter type. FIG. 2 b shows in particular a cross-sectional view of the right pyrotechnic initiator 20 along a plane Pz at right angles to the axis ZZ′ passing through the longitudinal axes AA′ of the right 20 and left 22 pyrotechnic initiators.
Each pyrotechnic initiator comprises, along its longitudinal axis AA′, a pyrotechnic initiator body 60 and a piston plunger 62 being able to slide in a seal-tight manner on the pyrotechnic initiator body 60 along the longitudinal axis AA′.
The pyrotechnic initiator body 60 comprises, on the side of the piston plunger 62, a cylindrical bush 64 having a cavity 65 and, in this cavity 65, an igniter 66 for releasing gases under pressure into the cavity 65.
The piston plunger 62 comprises, at one of its two ends, on the side of the pyrotechnic initiator body 60, a cylindrical wall 68 that can slide in a seal-tight manner over the cylindrical bush 64 of the pyrotechnic initiator and, at its free other end, a wall 69 sealing the piston plunger to form a chamber 70 between the piston plunger 62 and the cylindrical bush 64.
The cylindrical bush 64 comprises a passage 72 in the axis AA′ for the passage of the gases produced by the igniter 66 to the chamber 70 formed between the piston plunger 62 and the cylindrical bush 64.
The cylindrical bush 64 comprises a seal 80 on its periphery in a plane at right angles to the longitudinal axis AA′, in contact with an internal surface of the cylindrical wall 68 to obtain the piston plunger/cylindrical bush seal-tightness.
The pyrotechnic initiator body 60 also comprises an electrical connection pin 90 intended to receive at least two electrical wires 92 each equipped with a flexible contact 11,12 in contact with a respective annular track al, a2 in the shoulder 30 of the munition body.
Electronics embedded in the munition ensure the sending of electrical pulses over the annular tracks a1, a2, transmitted by the electrical wires 92 and the electrical connection pin 90, to activate the igniters 66 of the pyrotechnic initiators.
In this embodiment of the cap according to the invention, comprising two half-caps C1, C2, the pyrotechnic initiators 20, 22 are mounted head-to-tail on either side of the plane Py in the respective cells 50, 52 opening at the level of the plane P1, along the axes AA′ of the pyrotechnic initiators and on either side of said plane of assembly P1.
With the body 60 of one of the pyrotechnic initiators being securely attached in translation to a respective half-cap, its piston plunger 62 is securely attached in translation to the other half-cap. In the embodiment of FIG. 2 a, on one side of the plane Py, the body of the right pyrotechnic initiator 20 is securely attached in its cell 50 of the bottom half-cap C1, its piston plunger 62 is then securely attached in translation to the top half-cap C2 and, on the other side of the plane Py, the body of the left pyrotechnic initiator 22 being securely attached in its cell 52 of the top half-cap 22, its piston plunger 62 is then securely attached in translation to the bottom half-cap C1.
FIG. 3 a shows a front view of the munition of FIG. 1 a equipped with its ejectable cap.
The bottom C1 and top C2 half-caps each comprise a respective edge 100, 102 in contact with one another in the plane P1 sealing the ejectable cap of the munition.
The two half-caps are assembled together by a tenon/mortice-type fitting. To this end, the bottom half-cap C1 comprises, on its edge 100 situated in the plane of assembly P1, a longitudinal groove 110 extending on either side of the axis ZZ′. The top half-cap C2 comprises, symmetrically relative to the plane of assembly P1, on its edge 102 situated in said plane of assembly P1, a longitudinal tenon 112 extending on either side of the axis ZZ′ of the same external dimensions as those of the longitudinal groove 100 to form a tenon/mortice-type fitting (see FIGS. 1 a and 1 b). This type of fitting also ensures a perfect hermetic seal for the cap.
The two half-caps C1, C2 are secured together to form the cap according to the invention by a securing belt 120 around the cap at the level of the other internal surface 42 of circular cylindrical form of the cap. To this end, the half-caps include a circular groove 130, with dimensions identical to those of the securing belt, around the axis ZZ′. The securing belt 120, inserted into the circular groove 130, is linked to the two half-caps by bonding. The two half-caps thus bound by the securing belt are secured to the munition body by the threaded link (threadings 28, 44).
The securing belt 120 comprises, in the plane of assembly P1, on either side of the plane Py, embrittlement zones 140 to produce its rupture upon the separation of the half-caps by the action of the pyrotechnic initiators.
FIG. 3 b shows a detail view of FIG. 3 a around the embrittlement zone of the cap securing belt.
There now follows an explanation of the principle of the ejection of the cap according to the invention.
During the phase of approach of the munition toward the target, the optic of the homing head of the munition, at the front of the munition body, is protected by the ejectable cap.
In the approach to the target, a final guided phase of the munition begins. In this last phase, the cap has to be ejected.
Just before the guiding/control phase of the munition, an electrical pulse is sent by electronics embedded in the munition to the two pyrotechnic initiators 20, 22 via the two annular tracks a1, a2 and the flexible contacts 11, 12 of the electrical wires 92 of the pyrotechnic initiators (see FIG. 2). This electrical pulse simultaneously initiates the igniters 66 of the two pyrotechnic initiators positioned head-to-tail in the half-caps as represented in FIG. 2 a.
The igniters 66 then generate gases under a pressure in the cavity 65 of the respective cylindrical bushes 64.
The gases arrive under pressure through the passages 72 in the chambers 70 of the two pyrotechnic initiators 20, 22. The pressure of the gases tends to increase the volume of the chambers 70 (height D of the chamber) very rapidly moving the piston plunger 62 away from the body 60 of the pyrotechnic initiator. The pistons and the bodies of the pyrotechnic initiators being securely attached to their respective half-caps produce forces F separating the two half-caps to the point of rupture, at the level of the embrittlement zones 140, of the securing belt 120.
FIG. 4 shows a partial view at the level of one of the pyrotechnic initiators at the time of the separation of the edges of the half-caps.
Since the two half-caps are no longer secured by the securing belt 120, they are ejected to the sides of the munition at right angles to the axis of the munition.
The separation of the two half-caps by the pyrotechnic initiators also allows for the high-speed inrush of air into the opening in the plane P1 that appears through the separation of the edges 100, 102 of the two half-caps, which facilitates their ejection.
In the case of munitions which revolve on themselves (roll), the components generated by the centrifugal force also participate in the ejection of the two half-caps.
After the ejection of the half-caps, the munition once again has an aerodynamic profile very close to its initial profile prior to injection.
In the case of a scored munition, with strong acceleration, the direction of the threading 28, 44 will be oriented in a preferential direction, that it to say that the angular acceleration of the munition will be exerted in the direction which favors the tightening of the cap onto the munition body.
In the case of a munition with strong axial acceleration, the inclined bearing of the cap on the inclined shoulder 30 generates force components toward the center of the munition which advantageously makes it possible to keep the two half-caps sealed bearing on their plane of assembly P1.
In another embodiment of the cap according to the invention, the igniters can be reinforced with a complementary charge.
FIG. 5 shows a front view of the munition after ejection of the two half-caps with the pyrotechnic initiators. FIG. 6 shows a view in transversal cross section of the munition body without the cap.
The ejectable cap of small dimensions according to the invention makes it possible to protect the optic of the homing head of the guided munition until the ejection of the cap portions, but also during storage and logistics phases and during the other operational (tactical) phases.
The embodiment of the ejectable cap described previously is not limiting and the number n of cap portions can be greater than 2. For example, FIG. 7 shows a front view of an ejectable cap according to the invention produced from three identical contiguous cap portions C1, C2, C3 (n=3) distributed around the axis ZZ′ assembled on planes of assembly P1, P2, P3 at 120 degrees.
FIG. 8 shows another exemplary embodiment of the ejectable cap according to the invention comprising four identical contiguous cap portions C1, C2, C3, C4 assembled on planes of assembly P1, P2 at 90 degrees.
A main advantage of the ejectable cap according to the invention is that it incorporates its own pyrotechnic ejection system, essentially the pyrotechnic initiators. The cap with its pyrotechnic ejection system are independent of the munition. The integration of the cap with the munition is carried out at the last moment, at the time of use of the munition, which confers on it an additional safety aspect.

Claims

1. An ejectable protective cap for controlled munition comprising a munition body of cylindrical form of longitudinal axis ZZ′, having a front end of the munition body comprising a central part intended to be directed toward a target, comprising:

n cap portions C1, C2, . . . Ci, . . . Cn of the same forms, distributed around said longitudinal axis ZZ′, intended to cover the front end of the munition body, n being an integer number equal to or greater than 2, i being the rank of the cap portion, a cap portion Ci having at least one edge in contact with an edge of a cap portion which is contiguous with it in a respective plane of assembly of two contiguous cap portions passing through the longitudinal axis ZZ′, a pyrotechnic initiator for each cap portion, each of the pyrotechnic initiators comprising, along a longitudinal axis AA′, a pyrotechnic initiator body securely attached to the respective cap portion Ci, a piston plunger being able to slide in a seal-tight manner by one of its ends, along said longitudinal axis AA′, the free other end of the piston plunger being in contact with the contiguous cap portion to separate, upon the simultaneous activation of the n pyrotechnic initiators, the edges in contact of the contiguous cap portions, from their respective planes of assembly and release the front end of the munition body.

2. The ejectable protective cap as claimed in claim 1, wherein each pyrotechnic initiator comprises an igniter between the pyrotechnic initiator body and the piston plunger to separate, upon its activation, the piston plunger from the body of the pyrotechnic initiator and exert a separation force F between the two contiguous cap portions.

3. The ejectable protective cap as claimed in claim 1, wherein, n being equal to 2, it comprises two cap portions of symmetrical forms relative to a plane of assembly passing through the longitudinal axis ZZ′, the two cap portions being a bottom half-cap and a top half-cap.

4. The ejectable protective cap as claimed in claim 3, wherein the two assembled half-caps intended to closely encompass the front end of the munition body, each comprise an outer surface wall in half-ovoid form of axis of revolution ZZ′ forming the external surface of the front of the munition.

5. The ejectable protective cap as claimed in claim 4, wherein the two assembled half-caps comprise an internal surface of ovoid form covering the central part of the munition body connected to another internal surface of circular cylindrical form comprising a threading (44) intended to produce a threaded link with the munition body, a circular edge to abut on a shoulder of the munition body when screwed onto the munition body.

6. The ejectable protective cap as claimed in claim 5, wherein the two half-caps comprise, in the thickness of their wall, at the level of the other internal surface of circular cylindrical form, cells on either side of a plane Py at right angles to a plane P1 of assembly passing through the axis ZZ′ for the insertion of the pyrotechnic initiators.

7. The ejectable protective cap as claimed in claim 2, wherein the pyrotechnic initiator body comprises, in addition, an electrical connection pin intended to receive at least two electrical wires for the activation of the igniter.

8. The ejectable protective cap as claimed in claim 3, wherein the pyrotechnic initiators are mounted head-to-tail on either side of a plane Py at right angles to the plane of assembly of the two half-caps and passing through the axis ZZ′.

9. The ejectable protective cap as claimed in claim 3, wherein the bottom and top half-caps each comprise a respective edge in contact with one another in the plane of assembly.

10. The ejectable protective cap as claimed in claim 9, wherein the bottom half-cap comprises, on its edge situated in the plane of assembly, a longitudinal groove that extends on either side of the axis ZZ′, the top half-cap comprising, symmetrically relative to said plane of assembly, on its edge situated in said plane of assembly a longitudinal tenon extending on either side of the axis ZZ′ of the same external dimensions as those of the longitudinal groove (110) to form a fitting between the two half-caps of tenon/mortice type.

11. The ejectable protective cap as claimed in claim 3, wherein the two half-caps are held together by a securing belt of circular cylindrical form of axis ZZ′, in a circular groove around two half-caps.

12. The ejectable protective cap as claimed in claim 11, wherein the securing belt comprises, in the plane of assembly, on either side of the plane Py, embrittlement zones to provoke the rupture of said securing belt upon the separation of the half-caps by the action of the pyrotechnic initiators.

13. A guided munition, further comprising an ejectable protective cap as claimed in claim 1.

14. The guided munition as claimed in claim 13, wherein the central part of the munition body of cylindrical form on the axis ZZ′ is connected to the munition body by a circular cylindrical body of the same axis ZZ′ comprising a body threading intended for the screw-fastening of the cap onto the munition body and a rear part of the munition body comprising a shoulder in ring form of axis ZZ′ of tapered cone surface inscribed in a cone of generatrix Pe close to a perpendicular to the external surface of the munition body, at the level of said shoulder, the cap comprising an internal surface 40 of ovoid form covering the central part of the munition body connected to another internal surface of circular cylindrical form comprising another threading of the same diameter as the body threading intended to produce a threaded link between the cap and the munition body, a circular edge of the same form as the shoulder of the munition body abutting on this shoulder when the cap is screwed onto the munition body.

15. The guided munition as claimed in claim 14, wherein the shoulder comprises a groove in ring form of axis ZZ′, open on its tapered cone surface, containing an electrically insulating material, comprising, on said tapered cone surface, two annular tracks, of electrically conductive material, with axes of revolution that are the same as the axis ZZ′ for the electrical connection of the pyrotechnic initiators.

16. The guided munition as claimed in claim 15, wherein the pyrotechnic initiator body also comprises an electrical connection pin intended to receive at least two electrical wires each equipped with a flexible contact in contact with a respective annular track in the shoulder of the munition body.