EP3029012A2 - Device for the controlled initiation of the deflagration of an explosive charge - Google Patents

Abstract

A device for triggering a subdetonative reaction, in particular a deflagration, an explosive charge of an active system can be adapted by measures to the configuration of the explosive charge and, if available, its envelope so far that a stable deflagration of the entire explosive charge is achieved.

Description

The invention relates to a device for the controlled initiation of a subdetonative reaction - in particular the deflagration - of an explosive charge arranged in a casing, comprising at least one explosive charge core extending in the region of the longitudinal axis of the explosive charge.

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.

In the DE 10 2012 006 044 B3 a cylindrical explosive charge is described with a shell having a parallel to the detonating cord arranged measuring device which detects the progress of the current deflagration.

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.

On the other hand, the present invention seeks 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 turns into a burn, dies out or turns into a detonation.

This should be done in such a robust manner that even in highly dammed-up systems (such as penetrators) and under extreme military environmental conditions (especially at very low and very high temperatures) the deflagration of the explosive charge is controlled and reliable.

The object is achieved in that the explosive charge has an explosive charge core, which is adaptable in its transverse dimensions of the radial course of the shell in the longitudinal direction of the explosive charge, and that its charge over the length of the explosive charge core with respect to the type of explosive is homogeneously or locally adjustable ,

This results in various design options, which are described in the other claims and allow adaptation of this initiation to the local conditions in the explosive charge.

It is advantageous that the transverse dimension of the explosive charge core is adaptable to the course of the shell 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.

By means of the charging of the explosive charge core over the length of the explosive charge core, which is homogeneously or locally differently adjustable with regard to the type of explosive, if necessary different types of explosive can be combined with one another to form an explosive charge core. Also suitable for an explosive charge core are comparatively high-energy (highly explosive) and / or sensitive CHNO-based explosives, such as, for example. Hexogen- or octogen-based explosive mixtures as well as RDX (cyclo-1,3,5-trimethylene-2,4,6-trinitramine, hexogen), HMX (cyclo-1,3,5,7-tetramethylene 2,4,6, 8-tetranitramine, octogen), PETN (pentaerythritol tetranitrate), HNS (hexanitrostilbene), FOX-7 (1,1-diamino-2,2-dinitroethylene), FOX-12 (guanyl urea dinitramide) or Mixtures of these. In addition, inert binders such as HTPB (hydroxyl-terminated polybutadiene), silicone rubber, polyurethane rubber, polystyrene, estane, nylon, wax and / or graphite may be used

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 explosive charge core is to be adapted to the size and shape of the explosive charge.

In order to prevent direct contact of the detonative reacting explosive core to the explosive charge and thus to dampen the shock wave during detonation of the explosive charge core, it is helpful if the explosive charge core is surrounded by a jacket or a tube. This jacket or tube can be made of a fabric, a composite material (GFK, CFRP, CRC or CFRC), a plastic or a combination thereof, for example. As a material for a jacket (jacket or tube) u. a. Textile fibers, plastics (polymers) such. As Kevlar, nylon, polyethylene, polypropylene, PTFE (Teflon), PVC, polystyrene, Plexiglas (acrylic glass) or polyurethane but also wax into consideration.

The wall thickness and the material of the shell or of the tube can be adapted to the radial course of the shell in the longitudinal direction of the explosive charge in stages or continuously.

With the deflagrator, which is initiated in the mode of least action alone, a subdetonative reaction is triggered. This is done in the exemplary embodiment by detonation of the explosive charge core, whereby the hot reaction gases convectively heat an unreacted energetic material. 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 Verdämmungszustand the explosive charge, ie wall thickness and strength of the shell from. The speed of the flame and pressure front is typically below the speed of sound of the explosive charge.

A stable deflagration results from the rate of energy dissipation compared to the energy production rate, which is controlled here by the explosive charge core. In the following, some system influence factors are described and concrete numbers / numbers ranges are given for individual parameters, in which a deflagration proceeds stably.

Insensitive, cast explosive charges contain at least 10% of the plastic binder. The proportion of the explosive molecule for which RDX (cyclo-1,3,5-trimethylene-2,4,6-trinitramine, hexogen), HMX (cyclo-1,3,5,7-tetramethylene 2,4,6, 8-tetranitramine, octogen), NTO (5-nitro-1,2,4-triazole-3-one), FOX-7 (1,1-diamino-2,2-dinitroethylene), FOX-12 (guanyl urea dinitramide) and others can range between 90 and 50%. As a binder is suitable u. a. a two-component casting resin with hydroxyl-terminated polybutadiene (HTPB), but also silicone rubber, polyurethane rubber, polystyrene, Estan or nylon. In the binder matrix, the granular explosive crystals are encapsulated. 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, i. well below five percent. To increase the blast-pressure effect, the explosive charge may additionally be applied over coated or uncoated metal powders with particles, e.g. of aluminum, magnesium, zirconium, titanium, tungsten, titanium carbide or zirconium carbide. In this case, a share of typically 15 to 25 mass percent is sought, provided the blast pressure is to be optimized. To increase the blast pressure, the explosive charge may also be enriched with up to 20 percent ammonium perchlorate (AP).

mit ρ₀ als Dichte, U als Schockgeschwindigkeit, c₀ als Bulk-Schallgeschwindigkeit, s als Steigung und u als Partikelgeschwindigkeit. Der Schockdruck ergibt sich dann mit $$\mathrm{P}={\mathrm{\rho }}_{\mathrm{0}}•\mathrm{U}•\mathrm{u}=\mathrm{Z}•\mathrm{u}$$

To avoid a shock-initiated detonation of the explosive charge, it is expedient if the explosive charge a comparatively low Shock sensitivity. For this purpose, the materials of the explosive charge core and its enclosing jacket or tube should be chosen with their Hugonioteigenschaften such that the shock impedance of the shell / tube leads to a significant reduction of the grazing detonation pressure of the explosive charge core. The shock impedance Z can be determined with the known formula $$\mathrm{Z}={\mathrm{\rho }}_{\mathrm{0}}•\mathrm{U}={\mathrm{\rho }}_{\mathrm{0}}\left({\mathrm{c}}_{\mathrm{0}}+\mathrm{s}•\mathrm{u}\right)$$

with ρ ₀ as density, U as shock velocity, c ₀ as bulk sound velocity, s as slope and u as particle velocity. The shock pressure then results with $$\mathrm{P}={\mathrm{\rho }}_{\mathrm{0}}•\mathrm{U}•\mathrm{u}=\mathrm{Z}•\mathrm{u}$$

Conveniently, the resulting pressure at the interface of the damping material to the explosive charge should be below the shock initiation pressure. In addition, a critical diameter for a shock-initiated detonation of the explosive charge, which is at least 5 mm, typically more than 10 mm, is also favorable.

In order to promote an ignition of the explosive charge by hot spots due to the weak shock wave and the hot reaction gases, the explosive charge should have a relatively low Selbstentzündzungstemperatur. It should be less than 230 ° C and typically be well below 200 ° C. Nevertheless, it should be large enough not to negatively impact the insensitivity of the explosive charge during thermal stimuli such as slow-cook-off and fast-cook-off tests.

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, it is more likely that undesirable transitions into stronger detonation-to-deflation (DDT) reactions are expected. Damping at the charge ends can be regulated by the venting described below so that there are hardly any differences to open charges at the ends. This shows up then in similar expansion rates of the cargo envelope and thus pressure rates due to the reaction of the explosive charge.

mit $$k=d_i/d_a,$$

d_i als Innendurchmesser, d_a als Außendurchmesser und σ_max als Maximalspannung. Eine Verdämmung mit einem statischen Versagendruck kleiner als 6,0 kbar, typischerweise kleiner als 2,6 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 Entlüftung vorhanden ist, Übergänge in stärkere Reaktionen (DDTs) begünstigen. Grundsätzlich kann die Entlüftung durch Ladungsdeckel, Sollbruchstellen der Hülle und Bohrungen nachhaltig beeinflusst werden, sofern es sich um eine vollständig verdämmte Sprengladung handelt. Vorteilhaft ist die Entlüftung insbesondere im Bereich der Initiierung, wo die Deflagrationsreaktion beginnt und hierdurch der Druck zuerst ansteigt.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 $$k=d_i/d_a.$$

d _i as inner diameter, d _a as outer diameter and σ _max as maximum stress. A stowage with a static failure pressure of less than 6.0 kbar, typically less than 2.6 kbar, is considered favorable, provided that the initiation is optimally adapted to the charge dimensions, in order to ensure a controlled deflagration. In contrast, higher levels of damming, especially if there is insufficient deaeration, may favor transitions into stronger reactions (DDTs). Basically, the vent can be sustainably influenced by cargo cover, breaking points of the shell and drilling, as long as it is a completely dammed explosive charge. Advantageously, the vent is especially in the area of initiation, where the deflagration reaction begins and thereby the pressure increases first.

As a shell material, for example, not only metals such as steel, aluminum, titanium or corresponding alloys, but also plastics or composite materials such as GRP or CFRP, and CRC or CFRC are. This achieves a lower lethal effect, but a higher pressure wave. Finally, when using non-metallic shell materials, the effect is limited to blast overpressure and heat, both rapidly decreasing with distance from the reaction site.

• 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;
• Fig.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 stable deflagration is achieved. Above the dashed lines, the deflagration goes into a combustion reaction and / or dies completely and below it goes unchecked in a stronger reaction as a partial or complete 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 the course of the charge to adapt according to the course of the envelope HÜ such that the charge decreases towards a higher value in the middle region towards the end again.

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 70 g / m, in the second range A2 in the value range 50 to 90 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.

mit p als Dichte und D als Reaktionsgeschwindigkeit, zumeist der Detonationsgeschwindigkeit, der Sprengladung. Bei der Deflagration lässt sich infolge der signifikant geringeren Reaktionsgeschwindigkeiten und Reaktionsdrücke die Leistung damit auf 5 bis 15 Prozent im Vergleich zur detonativen Umsetzung der Sprengladung reduzieren.Another advantage is the significant reduction in the initial velocity of the splinters emitted from the shell. Another advantage is the significant reduction of the maximum blast pressure. This can be easily characterized by estimating the performance of an explosive charge $$\mathrm{\rho }•{\mathrm{D}}^{\mathrm{2}}/\mathrm{4}$$

with p as density and D as reaction speed, mostly the detonation speed, the explosive charge. Due to the significantly lower reaction rates and reaction pressures, deflagration reduces performance by 5 to 15 percent compared to detonating the explosive charge.

Claims (15)

Device for the controlled initiation of a subdetonative reaction - in particular a deflagration - of an explosive charge which may be arranged in an envelope, comprising at least one explosive charge core extending in the region of the longitudinal axis of the explosive charge, characterized in that the transverse dimension of the explosive charge core is adaptable to the radial course of the envelope in the longitudinal direction of the explosive charge, - 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. Apparatus according to claim 1, characterized in that the charging of the explosive charge core is adaptable in terms of their shape to the radial course of the shell in the longitudinal direction of the explosive charge. Apparatus according to claim 1, characterized in that the explosive, taking into account its density and / or its percentage composition in the explosive charge core can be arranged. Apparatus according to claim 3, characterized in that for the explosive charge core mixtures of explosive molecules according to claim 4 and inert binder such as HTPB, silicone rubber, polyurethane rubber, polystyrene, Estan, nylon, wax and / or graphite are used. Apparatus according to claim 3, characterized in that the detonation velocity of the explosive charge core is ideally just as large or slightly smaller than the detonation velocity of the explosive charge. Apparatus according to claim 3, characterized in that the autoignition temperature of the explosive charge core is below 230 ° C and typically below 200 ° C. Apparatus according to claim 1, characterized in that the transverse dimensions of the explosive charge core are considerably smaller than the diameter of the explosive charge and their ratio is between 1/10 and 1/30. Apparatus according to claim 1, characterized in that the explosive charge core is surrounded by a jacket. Apparatus according to claim 8, characterized in that the wall thickness and / or the material of the jacket in shape is adapted to the course of the shell in the longitudinal direction of the explosive charge. Apparatus according to claim 8, characterized in that the wall thickness of the shell are of the order of magnitude of the transverse dimensions of the explosive charge core and fall below this typically. Apparatus according to claim 1, characterized in that the explosive charge core is surrounded by a tube. Apparatus according to claim 11, characterized in that the wall thickness and / or the material of the tube in shape is adapted to the course of the shell in the longitudinal direction of the explosive charge. Apparatus according to claim 11, characterized in that the wall thickness of the tube are of the order of magnitude of the transverse dimensions of the explosive charge core and fall below this typically. Apparatus according to claim 1, characterized in that a cast explosive charge with a CHNO-based explosive molecule such as RDX, HMX, NTO, FOX-7 or FOX-12, encapsulated in an inert binder such as HTPB, silicone rubber, polyurethane rubber, polystyrene, Estan or nylon , And / or additionally metal powder of aluminum, magnesium, zirconium, titanium, tungsten, titanium carbide, zirconium carbide and / or ammonium perchlorate (AP) consists. Apparatus according to claim 1, characterized in that the explosive charge is surrounded by a shell of metals such as steel, aluminum, titanium or corresponding alloys or plastics or composite materials such as GRP or CFK and CRC or CFRC and the ratio of the shell mass to the explosive charge mass (M / C ) is between 1.0 and 8.0 and the shell static failure pressure is below 6 kbar, typically below 2.6 kbar.

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