EP2827094B1 - Device for the controlled initiation of the deflagration of an explosive charge - Google Patents

Description

The invention relates to a device for the controlled initiation of the deflagration of an explosive charge, which is arranged in a sheath with non-constant diameter, comprising at least one extending in the region of the longitudinal axis of the explosive charge detonation cord, wherein the detonation cord is designed as an explosive charge core.

From the DE 100 08 914 C2 a dosable explosive charge for a warhead with two different ignition devices has become known. While the first ignition device detonatively initiates the explosive charge, the further, oppositely directed ignition device is designed such that at most a subdetonative initiation can take place. The use of at least one detonating cord for this purpose is also known from this. In practice, some problems have arisen which, in extreme cases, may lead to the termination of initiation or to complete detonation initiation.

The US 2012/0227609 A1 describes an ignition system with two different ignition devices. The first ignition device is conventionally designed for the detonative triggering of the explosive charge. The locally opposite second ignition device is dimensioned for a deflagrative initiation of the explosive charge. Since in this ignition system the same construction principle with opposite ignition points is used, from which the detonation waves run against each other, the already known deficiencies occur here as well.

The DE 10 2005 031 588 B3 discloses the preamble of independent claim 1 and shows a device for the controlled initiation of the deflagration of an explosive charge, which is arranged in a casing comprising at least one extending in the region of the longitudinal axis of the explosive charge Detonation cord, the detonation cord is designed as an explosive charge core. Other features of the detonation cord are not described.

On the other hand, the present invention has the object to develop an ignition device which is able to maintain a deflagrative initiation over the entire length of the explosive charge, without the deflagration reaction in the axial or radial direction passes into a burn, dies or turns into a detonation.

The object is achieved by the features of claim 1. This results in various design options, which are described in the other claims and allow an adaptation of this initiation to the local conditions in the explosive charge.

The explosive charge core can be fired from both ends as required. According to the invention, the transverse dimension of the explosive charge core is adapted to the course of the envelope in the longitudinal direction of the explosive charge. This can be done in stages or continuously so that the explosive charge core can be matched to any shape of the envelope.

Another adaptation option is that the charging of the explosive charge core over the length of the explosive charge core with respect to the type of explosive is homogeneously or locally differently adjustable. It can therefore be combined with each other to an explosive charge core if necessary, also different explosive types.

In order to consciously influence the transition from the detonating explosive core to the explosive charge, it is helpful if the explosive charge core of one Sheath or tube is surrounded. This jacket or tube may for example consist of a plastic layer or a fabric or a combination of the two. As a material for a sheath (jacket or tube) include textile fibers, plastics (polymers) such. As polyethylene, Kvlar, nylon, polypropylene but also wax into consideration.

The deflagrator, which is initiated in the smallest action mode alone, triggers a subdetonative reaction called deflagration. This happens, for example, by detonation of a detonation cord, whereby the hot reaction gases heat unreacted energetic material convectively. This continues through pores present in the explosive charge. It forms a multi-phase reaction zone out, in which the pressure and flame front, in contrast to the detonation are spatially separated from each other and can well propagate at different speeds. The reaction ultimately leads to an increase in pressure under which the explosive can also mechanically fail and crack and continue to propagate. The reaction rates also depend on the state of confinement of the explosive charge, i. Wall thickness and strength of the shell, from. The speed of the pressure front is in the range of the speed of sound of the explosive.

A stable deflagration results from the rate of energy dissipation compared to the rate of energy production, which is controlled by the detonation cord here. Here are some system influencing factors described and specific numbers / ranges for individual parameters where controlled deflagration occurs.

Insensitive explosive charges contain at least 10% of the plastic binder. The proportion of the explosive molecule, for which Hexogen, octogen, Fox-7 (1,1-diamino-2,2-dinitroethylene) and others, can be between 90 and 50%. Suitable binders include, inter alia, a two-component casting resin with hydroxyl-terminated polybutadiene (HTPB), but also silicone rubber, polyurethane rubber, polystyrene, Estan or nylon. The binder encapsulates the explosive crystals. Such a plastic-bound explosive charge basically has microscopically small pores as a result of the manufacturing process. These pores determine the porosity of the explosive charge and provide the necessary for the deflagration reaction free surface available. The porosities are typically in the single-digit percentage range. To increase the Blastdruckwirkung the explosive charge may additionally have coated or uncoated metal powder with particles such as aluminum, magnesium, titanium carbide or zirconium carbide. Here, a share of 15 to 25 mass percent is sought to optimize the blast pressure.

For a detonation cord or an explosive charge core are relatively high-energy (highly explosive) and / or sensitive explosives such. As hexogen- or octogen-based explosives mixtures, and RDX, PETN, HMX, HNS or explosive mixtures thereof.

The detonating cord or detonating core should additionally have a fabric or plastic sheath which prevents direct contact with the explosive charge and results in damping of the shockwave upon detonation of the detonating cord or detonating core. In addition, the diameter of the explosive charge core can vary with non-constant sheath diameter and be adapted directly to this. The charging of the detonation cord is to be adapted to the size and shape of the explosive charge or cargo envelope.

In the presence of a charge envelope, the relevant parameters are the wall thickness, also in comparison to the charge diameter, and the material strength. These are expediently linked together via the static failure pressure. Above a specific limit pressure, more likely undesirable transitions into stronger reactions (Detonation-to-deflagration-transitions, DDTs) expected. Damping at the charge ends can be regulated by the aeration described below so that there is little difference between charges open at the ends (ie, the expansion rate and hence the pressure rate).

mit k = d_i /d_a , di als Innendurchmesser, da als Außendurchmesser und σ_max als Maximalspannung. Eine Verdämmung mit einem statischen Versagendruck kleiner als 2,6 kBar, typischerweise kleiner als 2,0 kBar, wird dabei, sofern die Initiierung optimal an die Ladungsabmessungen angepasst ist, als günstig angesehen, um eine kontrolliert ablaufende Deflagration zu gewährleisten. Im Gegensatz dazu können höhere Verdämmungswerte, insbesondere wenn keine ausreichende Belüftung vorhanden ist, Übergänge in stärkere Reaktionen (DDTs) begünstigen. Grundsätzlich kann die Belüftung durch Ladungsdeckel, Sollbruchstellen der Hülle und Bohrungen nachhaltig beeinflusst werden, sofern es sich um eine vollständig verdämmte Sprengladung handelt. Vorteilhaft ist die Belüftung insbesondere im Bereich der Initiierung, wo die Deflagrationsreaktion beginnt und hierdurch der Druck zuerst ansteigt. Eine permanente Entlüftung führt bei konstanter Initiierung über die Ladungslänge zu einer Druckrate, die zu einer stabilen Deflagrationsreaktion über den Ladungsradius führt. Diese Druckrate lässt sich indirekt über die Aufweitungsgeschwindigkeit der Ladungshülle messen. Als Hüllenmaterial eignen sich nicht nur Metalle wie Stahl, Aluminium, Titan oder entsprechende Legierungen, sondern auch Kunststoffe oder Komposit-Werkstoffe wie GFK oder CFK, sowie CRC oder CFRC. Damit wird eine geringere letale Wirkung erreicht, dagegen aber eine höhere Druckwelle.The failure pressure of a static load suspension is calculated by $$p_{\mathit{Max}}={\sigma }_{\mathit{Max}}\frac{1-k^2}{1+k^2}$$

with k = d _i / d _a , di as inner diameter, as outer diameter and σ _max as maximum stress. A stagnation with a static failure pressure of less than 2.6 kbar, typically less than 2.0 kbar, is considered favorable, provided the initiation is optimally adapted to the charge dimensions, in order to ensure controlled deflagration. In contrast, higher levels of damming, especially if there is insufficient ventilation, may favor transitions into stronger reactions (DDTs). Basically, the ventilation can be sustainably influenced by cargo cover, shell breakage and drilling, as long as it is a fully dammed explosive charge. Advantageously, the ventilation is especially in the area of initiation, where the deflagration reaction begins and thereby the pressure increases first. A permanent venting leads to a pressure rate with constant initiation over the charge length, which leads to a stable deflagration reaction over the charge radius. This pressure rate can be measured indirectly via the expansion rate of the cargo envelope. Suitable cladding materials are not only metals such as steel, aluminum, titanium or similar alloys, but also plastics or composite materials such as GRP or CFRP, as well as CRC or CFRC. This achieves a lower lethal effect, but a higher pressure wave.

Fig.1:

die Radiallänge einer Sprengladung in Relation zur Aufladung eines Sprengladungskerns;

Fig.2:

ein Ausführungsbeispiel einer erfindungsgemäßen Vorrichtung bei der Verwendung in einem bekannten Wirksystem;

Fig.3:

Beispiele möglicher Querschnitte von Sprengladungskernen.

An embodiment is shown in the drawing and will be described in more detail below. Show it:

Fig.1:

the radial length of an explosive charge in relation to the charging of an explosive charge core;

Figure 2:

an embodiment of a device according to the invention when used in a known active system;

Figure 3:

Examples of possible cross sections of explosive charge cores.

In the FIG. 1 vertically the inner radius (radial length) is applied from the central axis to the inner wall of the shell and horizontally the appropriate charge of an explosive core for this purpose. Within the dashed lines a controlled deflagration is achieved. Above the dashed lines the deflagration dies and below it goes uncontrolled into a detonation.

In the FIG. 2 is a section through an active system shown, which is filled within the envelope HÜ except for a slender cavity in the region of the longitudinal axis LA with explosive SP. This unspecified cavity serves to receive the explosive charge core SK. The explosive charge core extends from a first ignition device Z1 at the tip of the active system to a further ignition device Z2 at the rear of the active system. Both ignition devices can be used to initiate the explosive charge core.

According to the invention, the explosive charge core SK is divided into a plurality of sections A1, A2, A3. Depending on the requirements of the active system, the division may also make sense in fewer or more sections. Each of these sections corresponds to charging of the explosive charge core SK adapted to this section. It is also possible to adjust the course of charging according to the course of the envelope HÜ such that the Charging decreases to a higher value in the middle range towards the end.

Typical values have already been determined for charges in the different ranges, which are promising. Thus, charging in section A1 can be in the value range 30 to 50 g / m, in the second range A2 in the value range 50 to 70 g / m and finally in the third range A3 in the value range 70 to 100 g / m.

Another option is the choice of the cross section of the explosive charge core SK. This can be designed, for example, rectangular, round oval, half round, depending on the need for adjustment, as in FIG. 3 is shown.

Due to the customization options, an explosive charge core can be applied to almost any shape and size of warhead and other active system. Another advantage is the significant reduction of

Initial speed of the splitter discharged from the shell. Another advantage is the significant reduction of the maximum blast pressure.

Claims (9)

1. Device for the controller initiation of the deflagration of an explosive charge, which is arranged in a casing of a diameter that is not constant, comprising at least one detonating cord running in the region of the longitudinal axis of the explosive charge, the detonating cord being configured as a core of the explosive charge, characterized in that the transverse dimension of the core of the explosive charge is adapted to the shape of the casing in the longitudinal direction of the explosive charge.
2. Device according to Claim 1, characterized in that the core of the explosive charge can be initiated at each end as a matter of choice.
3. Device according to Claim 1, characterized in that the charge of the core of the explosive charge is adapted with respect to its form to the shape of the casing in the longitudinal direction of the explosive charge.
4. Device according to Claim 1, characterised in that the charge of the core of the explosive charge is set to be homogeneous or to differ locally with respect to the type of explosive over the length of the core of the explosive charge.
5. Device according to Claim 4, characterized in that the explosive is arranged in the core of the explosive charge in particular with its density and/or its composition in percentage terms taken into consideration.
6. Device according to Claim 1, characterized in that the core of the explosive charge is surrounded by a sheath.
7. Device according to Claim 6, characterized in that the sheath consists of a woven fabric and/or of plastic.
8. Device according to Claim 1, characterized in that the core of the explosive charge is surrounded by a tube.
9. Device according to Claim 8, characterized in that the tube consists of a woven fabric and/or of plastic.

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