Assembly of explosive charges with scalable explosive power

Abstract

An integral assembly of explosive charges and their associated priming devices, including a first explosive charge C1 made of a composition M1, coupled to at least one priming relay R1, the explosive charge C1 including in its volume at least one other explosive charge C2 made of a composition M2, each explosive charge C2 being coupled to a priming relay R2. The assembly is such that the critical diameter of the composition M1 of the explosive charge C1 is greater than the critical diameter of the composition M2 of the explosive charge C2. Each explosive charge C2 together with its priming relay R2 is arranged at a distance D from each priming relay R1, namely at a distance which is greater than the thickness of the number of cards corresponding to a negative detonability index test of the composition of the priming relay R1.

Description

FIELD OF THE INVENTION

[0001] The present invention concerns an assembly of explosive charges and their detonation priming devices. The assembly of explosive charges is designed to be integrated into the warhead of a munition with scalable explosive power.

[0002] A munition with scalable explosive power is understood to mean a munition capable of generating a detonation of predetermined non-zero power P1 in at least one first operating mode and of generating, in at least one other operating mode, a detonation of non-zero power P2 different from P1, each power P1 and P2 being estimated, for example, by its TNT equivalent.

[0003] A munition of this type is generally designed to be connected to a carrying platform, in particular an aircraft. It then constitutes an aerial weapon used to accurately hit ground targets such as bunkers or armored vehicles, with an explosive power adapted to avoid collateral effects, for example.STATE OF THE ART

[0004] Examples are known of munitions with scalable explosive power, i.e. capable of releasing all or part of their explosive energy on demand, depending on the more or less armored nature of the target and its immediate environment.

[0005] For example, international application WO 2011 / 135279 describes a munition comprising two coaxial cylindrical explosive charges, one internal and the other external, of the sleeve-candle type. In a first embodiment, the charges are each connected to a detonation priming device. Controlled priming of one or both firing devices enables either one or both explosive charges to be detonated, thereby controlling the explosive power of the munition. The two charges are separated by an inert material or a non-detonating energetic material. This interface material between the two explosive charges prevents detonation of the external charge when only the internal charge is detonated. This architecture therefore requires concentric stacking of two explosive charges separated by an attenuating material. In a second embodiment, the external charge has a diameter smaller than its critical detonation diameter. It is not coupled with a priming relay. The external charge, in the form of a sleeve enclosing the internal explosive charge in direct contact, has the sole function of reducing the sensitivity of the warhead to external stresses (fragments, bullets, etc.). Only the detonation of the internal charge is capable of influencing the detonation of the external charge. This type of warhead has a single operating mode.

[0006] Patent application FR-A-2599134 describes an explosive head with two concentric explosive charges separated by a trigger gap. A priming device enables either the external or internal charge to be primed. The expansion gap between the two charges is designed so that priming of the inner charge causes priming of the outer charge, and so that priming of the outer charge does not cause priming of the inner charge. These two modes of operation lead to a different spatial distribution of metal fragments in the wall of the explosive head. This architecture therefore requires a complex expansion gap to be created between the two explosive charges.

[0007] International application WO 2014 / 132004 describes a munition with scalable explosive power comprising a body extending in an axial direction and housing at least a first and a second explosive charge separated by a non-detonating element and a priming device. It further comprises a selector provided with a detonating part and adapted to move between at least a first and a second position, the selector being configured so that its detonating part couples the priming device to the first explosive charge in said first position and to the second explosive charge in said second position, one of the first and second explosive charges not being coupled to the priming device in at least one of the first and second positions. This architecture requires the munition to be divided into two parts, each containing an explosive charge and a moving part constituting the detonation initiation selector.

[0008] The skilled person is therefore always on the lookout for an explosive charge and its priming device that do not require any interface material, added cavity or non-standard priming device for a scalable power munition. In addition to these features, he is also looking for a munition whose explosive power can be modulated on more than two levels.

[0009] In the context of the present invention, it should be remembered that the critical diameter of an explosive composition corresponds to the minimum diameter below which the detonation of an explosive charge in this composition no longer propagates. This critical diameter is determined using cylindrical test specimens of variable section in an unconfined environment. The cylinder section with the largest surface area is detonated, and the critical detonation diameter is then determined by observing the surface area at which the detonation of the specimen is no longer propagated. This standard test, codified in the document “NATO STANAG 4170 and Allied Ordnance Publication 7, AOP-7 (Manual of Tests for Qualification of Explosive Materials for Military Use)” in an unconfined environment, measures a value specific to each explosive composition. The critical diameter is therefore a standard value of “surface sensitivity to a detonation wave”, which enables a relative classification of explosive compositions, but is not a dimensional parameter of a charge.

[0010] Compositions can therefore be classified relatively according to their critical detonation diameter. For example, the critical diameter of an explosive composition of type B2514 (containing 14% polyurethane-based binder, 22% RDX; 24% ammonium perchlorate and 40% aluminum by weight) is about 30 mm, that of a composition of type ORA86 (containing 14% polyurethane-based binder and 86% HMX by weight) is 4 mm. In a confined environment (e.g. when the explosive is placed in a 3 to 4 mm metal structure), the measured critical diameter of the explosive composition is about a factor of 3 smaller than that determined in an unconfined environment using the standard procedure. Nevertheless, the relative ranking of the critical diameters for detonation in a confined environment of one composition versus another remains identical to that determined according to the standard test in an unconfined environment. In practice, an explosive charge C1 is usually detonated by a detonator coupled to a priming relay charge R1, or by another explosive charge C2 which is itself detonated. It is known to the skilled person that an explosive charge C1 can only be detonated if the diameter of the initiating relay R1 or of the charge C2 in contact with the explosive charge C1 is greater than the critical diameter of the composition of the explosive charge C1, determined by taking into account its geometric shape and confinement and operating conditions. In the remainder of this document, the practical critical detonation diameter of a charge is determined, by testing or by simulation, on a case-by-case basis according to its composition, the geometric shape of the charge (e.g. a square-section charge) and its structural confinement conditions.

[0011] The sensitivity test of the type “detonation priming through a barrier” called IAD (Detonation Aptitude Index) or “Card Gap Test” on a specimen of solid explosive composition is carried out in accordance with standard NF T 70-502 or NATO standard STANAG 4488 (“STANAG=Standardisation agreement”), available at URL: https: / / nso.nato.int / nso / nsdd / main / standards, and in particular its Annex B (“Intermediate scale gap test”). It consists in determining the reactivity of a specimen, made of an explosive substance, subjected on one of its faces to detonation by a priming relay through a barrier of cellulose acetate cards. The limit thickness of the barrier at which the detonation of a second relay placed in contact with the other face of the specimen is not initiated is determined. In the remainder of this document, the limit values for the thickness of detonation initiation through a barrier correspond to the IAD test described in the reference “intermediate scale gap test” of STANAG 4488, on an explosive sample with a diameter of 40 mm. Reference can also be made to patent application EP-A-477090, which refers to and describes this standard test. This thickness is typically 30 mm, corresponding to 150 cards of 0.2 mm, for industrial composite explosives such as PBXN109 (containing 16% polyurethane-based binder, 64% RDX and 20% aluminum by weight), ORA86 (containing 14% polyurethane-based binder and 86% HMX by weight), HBU88 (containing 12% polyurethane-based binder and 88% RDX by weight). The thickness determined by the IAD test is therefore a specific characteristic of a composition and enables explosive compositions to be classified from one another. When the barrier is not made of cellulose acetate cards, the detonation non-ignition limit thickness is different from that determined with cellulose acetate cards. When the barrier is an explosive block (which is not detonation-initiated, but acts solely as a barrier), the detonation non-ignition limit thickness of the explosive composition tested varies slightly from the standard value obtained with cellulose cards. The attenuation of the explosive wave is, in fact, slightly lower through a barrier made of an explosive block than through a barrier made of cellulose acetate cards, Nevertheless, the relative ranking of the detonation non-ignition limit thicknesses of one composition versus another remains identical to that determined according to the standard IAD test. In the remainder of this document, the practical D thickness (distance) setting the lower detonation non-ignition limit of an explosive composition is determined, by testing or simulation, on a case-by-case basis according to the composition of the explosive barrier material.

[0012] It is to the inventors' credit that they have identified that the selection of the most suitable explosive compositions for an assembly of confined explosive charges can be made on the basis of standard test values. Indeed, although the values of the explosive properties of the charges depend in practice on their geometry, assembly and confinement, they remain in relative values identical to those measured in standard tests carried out on the compositions of the charges.SUMMARY OF THE INVENTION

[0013] The present invention concerns a monolithic assembly of explosive charges and their associated priming devices, intended for integration in the warhead of a munition with scalable explosive power. This assembly consists of an explosive charge, hereinafter referred to as C1, in an explosive composition M1 with a high critical detonation diameter Φ1, and at least one other explosive charge, hereinafter referred to as C2, in an explosive composition M2 with a low critical detonation diameter Φ2. These notions of “high” and “low” are relative in accordance with those characterized according to the standard test, and determined practically under the conditions of containment and assembly of the munition charges. The at least one other charge C2 is included in the volume of the explosive charge C1. Priming relays (each primed by a detonator) are coupled to the munition's explosive charges, at least one priming relay R1 for the charge C1 and one priming relay R2 for each charge C2. The dimensions of the charge C1 are such that detonation of the charge C1 in composition M1 with a high critical diameter by the at least one priming relay R1 results in detonation of the charge(s) C2 with a low critical diameter and of the priming relay(s) R2. Initiation of detonation of the low-critical-diameter charge(s) C2 by the priming relay(s) R2 does not result in detonation of the priming relay(s) R1 of the high-critical-diameter charge(s) C1. To achieve this, the charge(s) C2 and their priming relay R2 are arranged at a distance D from the priming relay(s) R1, the distance D being greater than the thickness of the number of cards corresponding to a negative IAD test of the composition of the priming relay R1. Such a distance does not lead to detonation of the priming relay R1, Advantageously, the dimensions of the charge(s) C2 are configured in such a way as to avoid any possible edge effect, during priming of said charge(s) C2, which could lead residually to a deflagration or detonation reaction of very localized zones of the charge C1. When the assembly comprises several charges C2 (at least 2 charges C2), each coupled to its priming relay R2, they are arranged at a distance d from each other greater than the thickness of the number of cards corresponding to a negative IAD test of the composition M2 of each of the charges C2 and the composition of their respective priming relay R2. Such a distance d between the charges C2 does not lead to the detonation of a charge C2 and its priming relay R2 through the influence of the detonation of one or more charges C2.

[0014] The invention therefore relates to a monolithic assembly of explosive charges and their associated priming devices, comprising a first charge C1 of explosive composition M1, coupled to at least one priming relay R1, said charge C1 including within its volume at least one other charge C2 of explosive composition M2, each charge C2 being coupled to a priming relay R2. The critical diameter Φ1 of the composition M1 in charge C1 is greater than the critical diameter Φ2 of the composition M2 in charge C2. The charge(s) C2, and its / their priming relay(s) R2, are each arranged at a distance D from the at least one priming relay R1 which is greater than the thickness of the number of cards corresponding to a negative IAD test of the composition of the priming relay(s) R1, which thickness is determined according to STANAG 4488. As mentioned above, the IAD test consists in determining the reactivity of a specimen made of explosive substance subjected on one of its faces to a detonation of a priming relay through a barrier made up of cards advantageously made of cellulose acetate. The number of cards forming this barrier for which there is no initiation of the detonation of a second relay placed in contact with the other face of the specimen constitutes the thickness referred to in the context of the present invention. Generally speaking, the charge C1, when detonated by its at least one priming relay R1, detonates the at least one charge C2 and its priming relay R2. The at least one charge C2, when initiated by its priming relay R2, does not detonate the at least one priming relay R1 and the charge C1. When the assembly contains several charges C2, a charge C2, when initiated by its priming relay R2, does not detonate the at least one other priming relay R2 and charge C2.

[0015] Generally speaking, the critical diameter Φ1 of the composition M1 of charge C1 is at least 2 times greater, for example at least 5 times greater, or even at least 20 times greater than the critical diameter Φ2 of the composition M2 of charge(s) C2.

[0016] Generally speaking, the number of cards corresponding to a negative IAD test of the composition M2 of a charge C2, of the composition of the priming relay R1, and of the composition of the priming relay R2 is between 135 and 240 cards, corresponding to a thickness of between 27 mm and 48 mm.

[0017] In a first mode of operation at high explosive power, the priming relay(s) R1 is (are) actuated and detonates the charge C1, leading by transmission to detonation of the at least one charge C2 and its priming relay R2. In this first operating mode, the priming relay(s) R2 may also be actuated simultaneously with the priming relay R1, without this providing any advantage.

[0018] In a second operating mode with reduced explosive power, the at least one priming relay R1 is not primed and only the at least one priming relay R2 is actuated and detonates a charge C2 with which it is coupled. In this second operating mode, the charge C1 is not primed or is partially primed (for a part of its mass less than 100%) by influence to detonation or deflagration by the detonation of at least one charge C2. When the munition comprises several charges C2, each of which is coupled to a priming relay R2, these are generally all primed simultaneously. When the assembly comprises several charges C2, it is also possible for only one or some (at least one but not all) charges C2 to be primed. The explosive power of the second operating mode can therefore be modulated according to the number of charges C2 detonated. The number of charges C2 detonated can moreover determine the proportion by mass (less than 100%) of the charge C1 locally influenced by detonation or deflagration.

[0019] The assembly of charges of the invention is perfectly suited to equip a munition with scalable explosive power.

[0020] Table 1 summarizes these two operating modes.TABLE 1Detonation primingIgnition relay R1XCharge C1XNone or partialdetonation ordeflagrationPriming relay(s) R2XXCharge(s) C2XX

[0021] Unlike the assemblies of charges described in the prior art, the assemblies according to the invention do not require any interface material, added cavity or non-standard priming device. The principle adopted for the operation of the ammunition of the invention is based solely on the (different) detonation properties of the explosive compositions and their appropriate arrangement in the ammunition.BRIEF DESCRIPTION OF FIGURES

[0022] FIG. 1 shows an assembly in which a cylindrical charge C2, inserted in a cylindrical charged C1, is primed by a priming relay R2 in contact with the flush surface of the charge C2.

[0023] FIG. 2 shows an assembly in which a cylindrical charge C2, inserted into a cylindrical charge C1, is primed by a priming relay R2 inserted into the charge C1 in contact with the surface of the charge C2.

[0024] FIG. 3 shows an assembly in which 6 cylindrical charges C2 are arranged in a ring around the axis of a cylindrical charge C1.

[0025] FIG. 4 shows an assembly in which 4 cylindrical charges C2 are arranged in a ring around the axis of a cylindrical charge C1, with two priming relays R1 radially offset from the axis of symmetry of the cylindrical charge C1.

[0026] FIG. 5 shows an assembly in which a helical charge C2 with a circular cross-section is inserted into a cylindrical C1 charge.

[0027] FIG. 6 shows a view of the helical charge C2 with a circular cross-section shown in FIG. 5,

[0028] FIG. 7 shows an assembly in which a helical charge C2 with a square cross-section is inserted into a cylindrical charge C1.

[0029] FIG. 8 shows a loading view of the helical charge C2 with a square cross-section shown in FIG. 7.

[0030] FIG. 9 shows an assembly in which two helical charges C2 with circular cross-sections of the same diameter and radially offset by an angle π are inserted into a cylindrical charge C1.

[0031] FIG. 10 shows a view of the two helical charges C2 with a circular cross-section shown in FIG. 9.

[0032] FIG. 11 shows an assembly in which two helical charges C2 with circular cross-sections of different diameters and radially offset by an angle π are inserted into a cylindrical load C1.

[0033] FIG. 12 shows a view of the two helical charges C2 with circular cross-sections shown in FIG. 11.

[0034] FIG. 13 shows a photograph of an assembly in which 4 cylindrical charges C2 are inserted in a ring around the axis of a cylindrical load C1.

[0035] FIG. 14 shows table 2 in Annex B of standard STANAG 4488.DESCRIPTION OF THE INVENTION

[0036] The assembly of explosive charges of the invention comprises a cylindrical explosive charge C1 of diameter DC1, length LC1 (typically, diameter DC1~160 mm, length LC1~400 mm), in a composition M1 with a high critical detonation diameter Φ1, for example greater than or equal to 40 mm. According to a standard operating mode, this charge is detonated by at least one cylindrical priming relay R1 coupled to a detonator. This at least one cylindrical priming relay R1 has a diameter DR1 equal to or greater than the critical diameter 1 of the charge C1. This priming relay R1, by virtue of its diameter DR1 greater than or equal to the critical diameter Φ1 of the composition M1 of the charge C1, is therefore capable of detonating the charge C1 (DR1≥Φ1), The at least one priming relay R1 is in contact with a flat surface of the charge C1 via one of its faces. When it is single, it is generally centered on one face of the charge C1. The at least one priming relay R1 can be in simple external contact with one of the faces of the charge C1 or, more generally, inserted in contact in the charge C1 in a through channel (thus leaving free one of the faces of the priming relay R1 which can be coupled to an external detonator).

[0037] According to a first embodiment, at least one (usually several) cylindrical explosive charge C2 of diameter DC2 (typically DC2~20 mm) and length LC2 is included in the volume of charge C1. The length LC2 is less than or equal to the length LC1 of the charge C1 (LC2≤LC1). The diameter DC2 of charge C2 is smaller than that DC1 of charge C1. The axis of said at least one charge C2 is colinear with that of the charge C1, and is radially offset from said at least one priming relay R1, so as to be disposed at a radial distance from the priming relay(s) R1 greater than the thickness of the number of cards corresponding to a negative IAD test of the composition of the priming relay(s) R1. Said at least one charge C2 can be flush (FIG. 1) at least on one side with the surface of the charge C1 so that it can be coupled with an external priming relay R2. It can also be inserted (FIG. 2 and FIG. 3) into the charge C1, leaving a free volume to accommodate an ignition relay R2 in the charge C1. This priming relay R2 (coupled to a detonator) with diameter DR2 is therefore in contact with a free surface of the C2 charge. The diameter DR2 of the priming relay R2 is greater than or equal to the critical diameter Φ2 of the composition M2 and less than the critical diameter Φ1 of the composition M1. A priming relay R2 of diameter DR2 is therefore able to detonate a charge C2 without priming the charge C1. The at least one charge C2 and its priming relay R2 are arranged in the volume of the charge C1 in such a way that their detonation does not cause that of the priming relay R1 designed to prime the charge C1. To achieve this, the at least one charge C2 and its priming relay R2 are positioned at a distance D from the ignition relay R1 at which they are not likely to ignite the priming relay R1. This distance D is defined on a case-by-case basis depending on the explosive compositions but is greater than the thickness of the number of cards leading to a negative result for the IAD test of the composition of the priming relay R1. As a general rule, the compositions of the priming relays R1 and R2 are identical, and possibly also identical to that of the charge(s) C2. When the assembly contains several charges C2, a charge C2, when primed by its priming relay R2, does not detonate the at least one other priming relay R2 and charge C2. To achieve this, the charges C2 coupled to their priming relay R2 are arranged at a distance d from each other at which they are not likely to prime another charge C2 and its priming relay R2. This distance d is defined on a case-by-case basis depending on the explosive compositions but is greater than the thickness of the number of cards leading to a negative result for the IAD test of the composition M2 of each of the charges C2 and that of their respective priming relay R2, a thickness which is determined in accordance with STANAG 4488.

[0038] The maximum explosive power in the second operating mode (priming of one or more charges C2) of the first embodiment is limited by the maximum number of charges C2. Indeed, for geometrical reasons, the number of charges C2 inserted in the charge C1 is necessarily small, typically around 6 at most for a 160 mm diameter charge C1 [FIG. 3], in order to respect a distance D to the priming relay(s) R1. The explosive mass of the charges C2 is thus limited, and consequently the maximum explosive power of the second mode of operation, particularly when the detonation of the charges C2 does not partially detonate or deflagrate the charge C1, is also limited.

[0039] Advantageously, when the assembly comprises several cylindrical charges C2, these are arranged in a ring around the axis of symmetry of the cylindrical charge C1, The various charges C2 (inserted into the C1 charge) can alternatively be arranged radially to one another in a ring. When the assembly comprises n charges C2 (n is advantageously an integer ranging from 2 to 6), said charges are arranged radially at an angle of 2π / n to each other. When the assembly comprises several cylindrical charges C2, the priming relay R1 in contact with the charge C1 can be offset from the axis of symmetry of the charge so as not to be located in a zone of possible detonation wave concentration of the charges C2. It is then advisable to place at least one other priming relay R1 in contact with the charge C1 to ensure homogeneous detonation.

[0040] Throughout the description and the embodiments described, a cylindrical charge C2 can, under the same conditions, be replaced by a rectangular parallelepiped charge C2. Thus, the invention in particular relates to an assembly as defined above, in which said at least one other explosive charge C2 is rectangular parallelepipedal and has an axis of symmetry colinear with the axis of symmetry of the explosive charge C1.

[0041] A second embodiment of the invention increases the maximum explosive power of the second operating mode.

[0042] This second design incorporates the geometric and operating features of the first design, with the exception of the geometry of the at least one charge C2.

[0043] In the second embodiment, the at least one cylindrical charge C2 of the first embodiment is replaced by a helical charge C2. Such a charge can have a circular or any other cross-section (square, rectangular . . . ), advantageously with a circular or square cross-section. Its linear length LC2 corresponds to the length of the longitudinal axis of the helix plus the axial length of its curved end fitting up to the priming relay R2. The helix of diameter DHC2<DC1 is radially circumscribed in the charge C1. The following features of the first embodiment are retained for the second embodiment with respect to the charges C1 and C2 and the priming relays R1 and R2;

[0044] DR1 priming relay diameter ≥Φ1 critical diameter of the composition of the C1 charge,

[0045] critical diameter Φ2 of the composition M2 of the charge C2<critical diameter Φ1 of the composition M1 of the charge C1,

[0046] diameter of the priming relay DR2≥critical diameter Φ2 of the composition of the helical charge C2 and less than the critical diameter Φ1 of the composition of the charge C1,

[0047] distance D from the helical charge C2 and the priming relay R2 to R1>thickness of the number of cards leading to a negative result for the IAD test of the composition of priming relay R1,

[0048] distance d between coupled helical charges C2 with their priming relay R2>thickness of the number of cards leading to a negative result for the IAD test of the composition M2 of each of the charges C2 and that of their respective priming relay R2.

[0049] Each helical charge C2 is arranged so that the axis of the helix coincides with the axis of the charge C1. The helix is wound around the axis of the charge C1 in such a way that the helical charge C2 and the priming relay R2 are at a distance D from the priming relay R1 (distance D at which they are not likely, when detonated, to ignite the priming relay R1).

[0050] When several (=n, preferably n is an integer from 2 to 6) concentric helical charges C2 of the same DHC2 helix diameter are present, the helices of the n helical charges C2 are radially offset by an angle 2π / n. It is also possible for several helical charges C2 with different DHC2 helix diameters to be arranged concentrically. This latter configuration is particularly suitable for C1 charges with a large diameter DC1. It is also possible for the helix of at least one helical charge C2 to have a variable pitch along its axis.

[0051] The coils of the helix(es) constituting the helical charge(s) C2 are spaced edge-to-edge by a distance D′ sufficiently large to avoid neighbouring priming between helix(es). The detonation of a helical charge C2 therefore propagates only along the trajectory of its helix. This distance D′ is defined on a case-by-case basis depending on the explosive compositions but is greater than the thickness of the number of cards leading to a negative result for the IAD test of the composition of the helical charge(s) C2. This thickness is typically 30 mm, corresponding to 150 cards of 0.2 mm for composite explosives such as PBXN109, ORA86, HBU88.

[0052] The assemblies of charges including at least one helical charge C2 can be obtained by an additive process or by successive casting in demountable nesting moulds.

[0053] An example of the higher explosive power achieved in the second operating mode with an assembly according to the second embodiment, compared with the first embodiment, is given below for information.

[0054] A cylindrical charge C2 with diameter DC2=20 mm and length LC2=340 mm has a volume of 107 cm3. A helical charge C2 with 6 coils of diameter DHC2=120 mm, circular cross-section of diameter DC2=20 mm, spaced 50 mm apart (D′=30 mm edge-to-edge), and axial length LC2=300 mm added to a curved extension connecting 40 mm in axis length to the R2 priming relay has a volume of 1055 cm3. A helical charge C2 of this type therefore has a volume (and therefore a mass) around 10 times greater than that of a C2 cylindrical charge ensuring a greater explosive power than that of a C2 charge.

[0055] In a third embodiment, the assembly of charges comprises a charge C1, at least one cylindrical charge C2 and at least one helical charge C2. The characteristic geometric inter-charge and C2 charge relationships with the priming relay R1 described above for the first two embodiments are retained.

[0056] As indicated above, throughout the description and the described embodiments, a cylindrical charge C2 can be replaced by a rectangular parallelepiped charge C2 under the same conditions.

[0057] The invention will be illustrated by means of the following examples, which are given by way of illustration.Example 1

[0058] FIG. 3 shows an example of the configuration of an assembly of explosive charges according to the first embodiment. The geometric values shown are representative of those that would be suitable for a composite explosive charge of the PBXN109, ORA86, or HBU88 type. The assembly comprises a priming relay R1 (DR1=40 mm, LR1=60 mm) inserted coaxially and centred in the C1 charge (DC1=160 mm, LC1=400 mm). The assembly also includes 6 cylindrical charges C2 (DC2=20 mm, LC2=400 mm) colinear with the axis of charge C1, each coupled to a priming relay R2 (DR2=20 mm, LR2=60 mm). These charges C2 and priming relays R2 are arranged radially in a ring at a distance D from the priming relay R1.

[0059] Due to a possible concentration of the detonation waves from the charges C2 and their priming relay R2 in the centre of the assembly, it may be necessary to increase the distance D (defined by the IAD test of the composition of the priming relay R1) by, for example, misaligning the priming relay R1 with the centre of symmetry of the charges C2. FIG. 4 thus shows a configuration comprising two priming relays R1 offset from the axis of symmetry of the charges C2. Four charges C2 and their priming relays R2 are located radially at a distance D from the two priming relays R1.Example 2

[0060] FIG. 5 shows an example of an assembly of explosive charges according to the second embodiment, with a charge C1 including a helical charge C2. The geometric values shown are representative of those that would be suitable for a composite explosive assembly of the PBXN109, ORA86, or HBU88 type. The assembly comprises a priming relay R1 (DR1=40 mm, LR1=60 mm) inserted coaxially centred in the charge C1 (DC1=160 mm, LC1=400 mm). The helical charge C2 has a diameter DHC2=120 mm, is circular in cross-section with a diameter DC2=20 mm, and has an axial length LC2=285 mm (5 coils of 50 mm pitch+35 mm axial length for the curved connection to the priming relay R2). The helix axis of helical charge C2 is coaxial with the axis of charge C1. The helical charge C2 is coupled to a priming relay R2 (DR2=20 mm, LR2=60 mm). For this example, the length of the helical charge C2 added to that of the priming relay R2 is less than the length of the charge C1. This does not preclude it being equal to the length of charge C1 in another variant. The helical charge C2 and the priming relay R2 are arranged radially at a distance D from the priming relay R1. The distance D′ between the centre of the coils avoids transmission of proximity detonation between the coils of the helical charge C2.

[0061] FIG. 6 shows a helical charge C2 fitted with its priming relay R2, identical to that included in the charge C1 shown in FIG. 5.

[0062] FIG. 7 shows an example similar to that in FIG. 5, except that the cross-section of the helical charge C2 is square.

[0063] FIG. 8 shows a view of the single square-section helical charge C2 fitted with its priming relay R2.

[0064] FIG. 9 shows an example of charge according to the invention, with two helical charges C2a and C2b, of cross-section DC2=20 mm and diameter DHC2=120 mm, offset by an angle x. The distance between the coils of charge C2a and charge C2b is 100 mm, thus ensuring an edge-to-edge distance D′ between the coils of the two charges C2a and C2b. The number of coils is 3 for charges C2a and C2b. In the configuration shown in FIG. 9, the length LC2 of the helix of charges C2a and C2b added to that of their priming relays R2a and R2b is equal to the length of charge C1.

[0065] FIG. 10 shows a view of only the two helical charges C2a and C2b and their priming relay R2 from FIG. 9.

[0066] FIG. 11 shows a charge C1 with a large diameter DC1=400 mm and length LC1=400 mm, comprising two concentric helical charges C2a and C2b with diameter DHC2a=120 mm and diameter DHC2b=240 mm. Charges C2a and C2b have the same circular cross-section with a diameter DC2=20 mm, and the same axial length LC2=285 mm (5 coils with 50 mm pitch+35 mm axial length for the curved connection to the priming relay R2). The axis of the helices of charges C2a and C2b is coaxial with the axis of the charge C1.

[0067] FIG. 12 shows a view of only the helical charges C2a and C2b and their priming relay R2 from FIG. 11.Example 3

[0068] Example 3 illustrates the operation of an assembly of explosive charges according to the first embodiment. The cylindrical charge C1 (DC1=90 mm, LC1=100 mm) is made of composition B2514 (containing in percentage by weight 14% polyurethane-based binder, 22% RDX, 24% ammonium perchlorate and 40% aluminum), The critical diameter of this B2514 composition is about 40 mm. The assembly also includes 4 cylindrical C2 charges (DC2=10 mm, LC2=100 mm) colinear with the axis of charge C1. These charges C2 are made of composition ORA86 (containing in percentage by weight 14% polyurethane-based binder and 86% HMX). The critical diameter and IAD thickness of this ORA86 composition are respectively about 4 mm and about 32 mm (160 cellulose acetate cards). Each charge C2 is coupled to a priming relay R2 (DR2=10 mm, LR2=16 mm) made of a Formex® composition marketed by the company Eurenco. These charges C2 inserted in the charge C1 are arranged radially at an angle of 90° to each other on a ring 50 mm in diameter. FIG. 13 shows a photograph of one face of the assembly of explosive charges of the instant Example 3. The photograph shows the explosive charge C1 in light grey and the 4 explosive charges C2 in white. Detonation power is measured by air overpressure at a distance of 4 m from the assembly of explosive charges. Full detonation of the assembly of explosive charges C1 and C2 results in an air overpressure of about 650 mbar at 4 m. Detonation of a single explosive charge C2 results in an air overpressure measured at 4 m of 160 mbar.

[0069] Under the same conditions, the detonation of two explosive charges C2 offset by an angle π results in an air overpressure measured at 4 m of 270 mbar. Detonation of 3 explosive charges C2 results in an air overpressure measured at 4 m of 390 mbar.

Claims

1. A monolithic assembly of explosive charges and their associated priming devices, comprising a first cylindrical explosive charge C1 of a composition M1, coupled to at least one priming relay R1, said explosive charge C1 including in its volume at least one other explosive charge C2 of a composition M2, each explosive charge C2 being coupled to a priming relay R2, in which assembly the critical diameter Φ1 of the composition M1 of the explosive charge C1 is greater than the critical diameter Φ2 of the composition M2 of the at least one other explosive charge C2, and in which each explosive charge C2 and its priming relay R2 is arranged at a distance D from each priming relay R1, the distance D being greater than the thickness of the number of cards corresponding to a negative Detonation Aptitude Index (IAD) test of the composition of the priming relay(s) R1, said thickness being determined in accordance with NATO standard STANAG 4488.

2. The assembly according to claim 1, wherein said at least one further explosive charge C2 is cylindrical, has an axis of symmetry colinear with the axis of symmetry of the explosive charge C1, and is radially offset from said at least one priming relay R1.

3. The assembly according to claim 1, comprising a plurality of cylindrical explosive charges C2 arranged in a ring around the axis of symmetry of the explosive charge C1.

4. The assembly according to claim 1, comprising n cylindrical explosive charges C2 arranged radially on a ring with an angle of 2π / n between them.

5. The assembly according claim 1, wherein said at least one other explosive charge C2 is rectangular parallelepipedal and has an axis of symmetry colinear with the axis of symmetry of the explosive charge C1.

6. The assembly according claim 1, comprising n concentric helical explosive charges C2 whose helices are radially offset by an angle 2π / n.

7. The assembly according to claim 5, comprising 2 to 6 helical explosive charges C2.

8. The assembly according to claim 6, wherein the helical explosive charges have an identical helix diameter.

9. The assembly according to claim 6, wherein the helical explosive charges have a different helix diameter.

10. The assembly according to claim 1, wherein each explosive charge C2 is helical with a circular or square surface, the axis of each helix coinciding with the axis of symmetry of the explosive charge C1, the distance between the coils of each helix being greater than the thickness of the number of cards corresponding to a negative IAD test of the composition M2 of each explosive charge C2, which thickness is determined according to NATO standard STANAG 4488.

11. The assembly according to claim 1, comprising a plurality of explosive charges C2 coupled to their priming relay R2 and arranged between them at a distance d greater than the thickness of the number of cards corresponding to a negative IAD test of the M2 composition of each charge C2 and that of their priming relay R2, which thickness is determined according to NATO standard STANAG 4488.

12. The assembly according to claim 1, wherein said at least one other explosive charge C2 comprises at least one cylindrical charge and at least one helical charge.

13. An explosive ammunition containing an assembly of explosive charges according to claim 1.

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