GB2428083A

GB2428083A - Controlling the strength and direction of detonation of an explosive charge in a warhead

Info

Publication number: GB2428083A
Application number: GB0612415A
Authority: GB
Inventors: Werner Arnold
Original assignee: TDW Gesellschaft fuer Verteidigungstechnische Wirksysteme mbH
Current assignee: TDW Gesellschaft fuer Verteidigungstechnische Wirksysteme mbH
Priority date: 2005-07-06
Filing date: 2006-06-22
Publication date: 2007-01-17
Anticipated expiration: 2026-06-22
Also published as: GB2428083B; GB0612415D0; FR2888317A1; FR2890436A1; FR2888317B1; DE102005031588B3; FR2890436B1

Abstract

A compensating volume in the form of a cavity 2 is arranged inside the explosive charge 1 of a warhead. The warhead has different ignition devices of which one ZK2 is suitable for the detonation initiation and the second ZK1 effects a deflagration or mechanical breakdown of the explosive charge. Detonation cords 3 extend from the deflagration initiator ZK1 and surround the cavity 2. Upon deflagration initiation or mechanical breakdown the cavity 2 absorbs the broken-down explosive charge particles and fragments 10. In this way the strength of the detonation can be controlled and, by further refinements, its direction also. In a second embodiment, the region between the compensating volume 2 and the casing 4 of the warhead is divided into a number of sector-shaped compartments (8,Fig.9) which are filled with liquid explosive whereby each sector (8,Fig.9) has at least one passage (9,Fig.9) to the compensating volume 2. In a third embodiment, an expansion means is provided for forcing part of the explosive into the compensating volume 2 to render it incapable of ignition, before detonation is initiated, so as to adjust the force of the explosion.

Description

Adjustable charge for a warhead The invention relates to an explosive

charge for a warhead, such as a shell. Such charges generally have a first ignition chain, the power of which is designed for the detonation initiation of the explosive charge, and at least one further detonation means which is arranged at the other end with respect to the detonation initiation and which transmits energy to the explosive charge in an amount at most sufficient for the initiation of deflagration or non- explosive breakdown of the explosive charge.

Warheads today are increasingly adapted to the constantly changing conditions of use. Since the possible targets to be neutralised for weakening the enemy infrastructure are increasingly located in an urban environment, the warheads have to be designed so that the buildings in the immediate vicinity of the targets suffer as little damage as possible. The direction of effect in warheads is predetermined by the design. Thus, the only possible way of reducing collateral damage is to influence the power of the warhead or to focus in the direction of the target.

A warhead in which part of the explosive charge is broken down by deflagration with the aid of detonation cords arranged in the explosive charge is already known from DE 08 914 C2 by the applicant. The remaining part of the explosive charge is initiated with the aid of a further ignition chain. By determining the relative position of the ignition times with respect to one another, it is possible to set the power of the warhead within very wide ranges.

This arrangement has been tested and, according to the test results, is well suited to small warheads such as fragmentation charges with a calibre not substantially in 1, 2 excess of 100 nun. The casing of the warhead here should not have too thick a wall, so that the fragmentation mass to be accelerated does not become too large. However, it is not suitable for warheads with a large calibre and particularly not for penetrators or charges similar to penetrators, which necessarily have a strong and cohesive casing structure. The reason for this is that the explosive charge that is broken down by deflagration and is to be accelerated radially outwards by the ignited detonation cords is hindered in this by the solid casing of the warhead or penetrator. The same also occurs in warheads with a large calibre because of the inertia of the explosive mass itself. In these cases, the spread of deflagration is hindered and can result in the detonation transformation of the entire explosive charge.

DE 35 22 008 Al describes a warhead with a fragment- forming casing in which the explosive charge abuts as a cylindrical layer against the inside of the casing and thus forms a central cavity. This cavity is used to accommodate all missile components and missile propellants. There is no provision for influencing the power of the warhead or for deliberately setting a preferred direction of effect; nor was this an aim of the design at the time of developing the invention.

It is therefore an object of the invention to provide a method that is equally suitable both for large calibres, i.e. significantly greater than 100 mm in diameter, and for penetrators and preferably also enables focussing in the radial direction onto a possible target.

According to the invention, as defined in claim 1, at least one compensating volume for compensating for the reduction in the density of the explosive charge that occurs upon deflagration initiation is arranged in the central region of the explosive charge, and the.

detonation means are arranged between the compensatirrg volume and the casing of the warhead and are at a ncinimum. ..

spacing from the first ignition chain. The detonation means are preferably constructed as detonation cords.

This enables the deflagration to spread inwards to the desired extent and in unhindered manner after its initiation. The compensating volume is expediently arranged rotationally symmetrically about the main axis of the explosive charge, particularly in the case of cylindrical explosive charges. Deflagration refers in

summary to all effects which do not result in the

detonation transformation of the explosive charge, i.e. including effects such as those in which the explosive charge is broken down "mechanically" without chemical reaction.

The deflagration initiation can be advantageously influenced by using damping layers which surround the detonation cords on all sides.

To increase the detonation power, the compensating volume can also be filled with an explosive charge that has a substantially lower density than the bulk material of the explosive charge itself, thus likewise ensuring compensation upon deflagration initiation of the explosive charge. As an alternative to this, it is also possible for the entire explosive charge to comprise an explosive with a correspondingly lower density than a conventional explosive. The necessary reduction in the density is achieved in that the explosive has pores or in that the explosive is foamed in the course of the casting process.

To achieve focussing in addition to controlling the power, it has proven effective to arrange further punctiform or linear detonation means in the region of the casing of the warhead, which are initiated at the optimum time in dependence on the ignition times of the ignition devices already present. * 4

A further advantageous construction of the invention has the detonation cords arranged at a spacing from the casing that is substantially smaller than the spacing of the detonation cords from the compensating volume, and strip-shaped passive devices extending along the detonation cords for the distribution of forces, arranged between the detonation cords and the casing, the strips being made of metal or plastics material. it is thus possible to achieve a wider distribution of the acceleration forces acting on the casing from the inside.

The above-mentioned arrangement also enables only part of the detonation cords to be ignited, whereby the corresponding part of the fragmentforming casing can be removed. This procedure reduces the overall power of the explosive charge, improves focussing on the target and considerably reduces the effect on objects facing it.

In another aspect of the invention at least one compensating volume is arranged in the central region of the explosive charge and the region between the compensating volume and the casing of the warhead is subdivided into a plurality of sector-shaped volumina or compartments which are filled with liquid explosive.

Each sector has at least one passage to the compensating volume and can be acted upon by gas pressure. The passage here can be constructed as required either as a releasable opening or as a controllable opening, for example as a valve. This enables a propulsion pressure, which may be present in any case, to be used to transfer the liquid explosive rapidly into the central compensating volume.

This arrangement also enables at least part of the contents of a plurality of sectors to be discharged into the central compensating volume. It is advantageously possible to take into account here that a sector containing liquid explosive does not have to be fully emptied in order for it to be neutralised. Partial

-I

emptying is generally sufficient to reduce the power of this sector considerably.

Finally, it is proposed that the initiation of the sectors be effected by way of a common ignition device or that at least one of the volumina have a separate ignition device in order to enable a focussing effect to be achieved by direct or time-delayed ignition.

For a better understanding of the invention, embodiments of it will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 shows a longitudinal section through a perletrator with detonation cords and a central compensating volume; Fig. 2 shows a penetrator according to Fig. 1 with a partially broken-down explosive charge; Fig. 3 shows a portion of a fragmentation charge with detonation cords; Fig. 4 shows a portion of a fragmentation charge with an additional exPlosive charge of lower density; Fig. .5 shows a portion of a fragmentation charge with an explosive charge with a lower density; Fig. 6 shows the focussing effect using peripheral initiation; Fig. 7 shows a portion of a fragmentation charge with detonation cords and a device for the distribution of forces; Fig. 8 shows a portion of a fragmentation charge and a partially exploded casing; and Fig. 9 shows a portion of a fragmentation charge with sectors filled with liquid explosive.

The invention is Concerned with arranging a central compensating volume 2 inside the explosive charge 1, as explained with reference to the embodiments illustrated in the drawings. The invention is not restricted here to the examples; these are instead intended to demonstrate the spectrum of possible applications In Figure 1, a longitudinal section through a penetrator with a reinforced casing 4 is shown as an example. The penetrator has a generally elongate form, most of the length of which is occupied by the explosive. A first ignition chain ZIL, for deflagration, is arranged at the rear of the penetrator, and a second chain ZK2, for detonation, near the front end.

A central compensating volume or cavity 2 is arranged along the main axis 5 of the penetrator starting from the first chain ZIG. Detonation cords 3 extend from the deflagration initiator ZK and surround the compensating volume 2, distributed evenly over the circumference at a predetermined spacing, and are completely embedded in the explosive charge. However, the compensating volume 2 and the detonation cords 3 do not quite reach the ignition chain ZK2 of the explosive charge, so as to ensure the reliable initiation of the explosive charge over its entire cross-section Depending on the shockwave sensitivity of the explosive charge 1 used, the detonation cords 3 can be surrounded by one or more damping layers 3a, as shown in Figure 3.

The detonation cords 3 are Controlled by way of a fuse device SV of the first ignition chain ZK1 and initiated at a point in time t1. After an adjustable time-delay, which determines the extent to which the explosive charge is broken down mechanically by deflagration, the charge is ignited at time t2 by means of the second ignition chain ZK2 which can likewise be controlled by way of the same fuse device SV.

By choosing the time delay t2-t1, it is possible to break down any part of the explosive charge and for the rest to undergo detonation transformation. it is thus possible to configure the charge so that it can be measured or adapted in power according to the target. In Figure 2, this procedure is shown with reference to the exemplary embodiment of a penetrator. This clearly shows that the compensating volume 2 absorbs the broken-down explosive charge particles and fragments 10 after the common initiation of the detonation cords 3. The relative volumes of the explosive charge 1 on the one hand and the compensating volume 2 on the other have to be designed so that the breakdown and the resultant reduction in the density of the explosive charge can no longer excite detonation transformation Thus the cavity or cavities should be big enough to ensure that the overall density is lower than this threshold. The dimensions are in turn dependent on the choice of explosive charge. For the explosive charges in question, the minimum density from which the charge is no longer capable of detonation is known in each case. The size chosen for the compensating volume 2 is dependent on this density; the maximum quantity of explosive charge that can be integrated in the warhead is derived indirectly from this. Insensitive explosive charges which, at the same time, can be easily broken down are chosen for the warhead. If the explosive charge and detonation cords are designed and adapted accordingly, it is possible for the entire charge to be broken down without detonating. A purely chemical reaction is prevented here, since this would considerably reduce the desired effect owing to the quantity of reaction gases generated.

The method according to the invention is not restricted to penetrators alone, but can be used for all possible types of pressure or fragmentation charges. As an example, Figure 3 shows a portion of a fragmentation charge with a metal casing 4 without notches. it is equally possible to use a notched casing at this point for controlled fragment formation. Finally, the casing 4 can comprise pre-formed fragments and/or can be of a multi-layered construction, The method can even be used in pressure charges without a solid casing.

The loss of power owing to the compensating volume is Only slight for a practical design, since that proportion of the explosive charge which is located in the immediate vicinity of the casing is chiefly responsible for the acceleration of the fragments. The further away the charge is from the casing, the less it contributes to its acceleration.

In charge designs in which only a relatively small compensating volume 2 would be necessary, it is alternatively possible to use a volume that is greater than the necessary amount. According to Figure 4, this volume is filled with an explosive charge 2a having a lower density. This method can then always be used when the explosive charges are not too large or are not too heavily insulated, so that the deflagrating explosive charge can expand inwards and outwards.

As an alternative to this, it is also possible for the entire charge volume to be filled with an explosive charge la of a lower density, as shown in Figure 5.

Lower explosive charge densities can be achieved for example using specifically incorporated pores or by foaming the still-liquid explosive charge in the course of the casting process. it is moreover possible to incorporate one or more further detonation cords 3b in the region near to the main axis.

The use of purely electronic fuse devices also enables several detonators to be controlled simultaneously. In such cases, it is also possible to use flat foil igniters, also known as EFI (Exploding Foil Initiators), which Only require a small installation volume. Figure 6 shows a possible use of these EFIs with reference to a fragmentation charge with compensating volunie 2 and additional peripheral initiation points 6. In the case of the peripheral initiation, the detonation wave according to Figure 6 extends around to both sides of the compensating volume 2 so that it then meets again on the opposite side (arrow). This superimposition of detonation waves results in a local excess pressure (the so-called "Dautriche effect"), as a result of which the fragments there are accelerated more greatly and therefore have more power. It is thus also possible within the scope of the construction of the invention to effect radial focussing of the power in addition to the isotropic measurability of the charge.

A further embodiment of the invention is illustrated in Figure 7 with reference to a portion of a fragmentation charge. In this case, the detonation cords 3 are located further out than in the above-mentioned examples, i.e. on an imaginary circle with a larger radius. In addition, strip-shaped passive devices 7 are arranged to extend along the detonation cords 3 for the distribution of forces, between the detonation cords 3 and the casing 4.

These strip-shaped devices are made of plastics material or metal and, as a result of the dispersion of the detonation pressure of the detonation cords, effect a distribution of the acceleration forces over a relatively large region of the casing 4. A central compensating volume 2 will generally be provided.

It is also an option to ignite only part of the detonation cords 3, as shown by way of example in Figure 8. Here, the two upper detonation cords were ignited and thus the adlacent part of the fragment- forming casing was removed before the main charge was initiated by the ignition chain ZK2 illustrated in Figures 1. and 2. It is thus possible to achieve a global power reduction on the one hand, whilst also focussing the power in the direction of the target on the other, with the power acting on a collateral target on the opposite side being significantly reduced at the same time.

The use of any suitable combination of the possibilities and methods illustrated results in good flexibility of the warhead both In terms of the measurable isotropic effect and also in terms of the focusability and the consequent reduction in collateral damage. The embodiments described below increase this flexibility further.

Figure 9 shows a warhead in simplified form, which likewise has a central compensating volume 2. Deviating from the embodiments described above, the main charge here comprises separate explosive sectors 8. The explosive itself is in a liquid aggregate state.

Explosives of this type are known and used. Each sector has one or more initially closed passages 9 as a Supply path to the central compensating volume 2. The passages 9 can be opened in different ways. It is possible to use valves which are opened individually or in groups. If the warhead IS transported by a missile, it is possible to use the supplied propulsion pressure to accelerate the exit of the liquid explosive considerably when a valve is opened. It is also Conceivable to introduce the propulsion pressure directly into one or more selected sectors, in which case a bursting membrane used instead of a valve breaks or tears when a particular pressure level is exceeded and opens the path to the compensating volume 2. Further possible designs for this, for example the detonation opening of the passages 9, are conceivable according to the principle of the invention.

As shown on the right-hand side of Figure 9, ignition is effected by means of an ignition chain which acts on an explosive charge disc manufactured in a conventional manner as a pressed or cast explosive charge. Ignition of the ignition chain results in a focussed fragmentation and blast effect when the proposed methods are used.

It is additionally possible to open the passages 9 of a plurality of sectors 8 at the same time. The compensating volume has to have the appropriate dimensions for this. It is necessary to take into account here that a sector 8 with liquid explosive only has to be partially emptied since this is generally sufficient to eliminate the fragmentajo power of the relevant sector.

Claims

Claims 1. An explosive charge (1) for a warhead with an explosion ignition

chain (ZK2), the power of which is designed for the detonation initiation of the explosive charge, and at least one further detonation means (ZK1; 3) which is arranged to act from the opposite end of the charge from the start of the detonation initiation and the energy of which that can be transmitted to the explosive charge is at most sufficient for a deflagration initiation of the explosive charge, characterised in that at least one compensating volume (2) for allowing for the reduction in the density of the explosive charge that occurs upon deflagration initiation is arranged in the central region of the explosive charge (1), and in that the deflagration detonation means (ZK1; 3) are arranged at least in part between the compensating volume (2) and the casing (4) of the warhead with a predetermined spacing (D) from the explosion ignition chain (ZK2).
2. An explosive charge according to claim 1, in which the compensating volume (2) is a single cavity arranged rotationally symmetrically about the main axis (5) of the explosive charge (1)
3. An explosive charge according to claim 1 or 2, in which the compensating volume (2) is filled with an explosive material (2a) which has a lower density than the main explosive charge (1).
4. An explosive charge according to claim 1 or 2, in which the explosive charge (la) comprises an explosive charge of a lower density.
5. An explosive charge according to claim 4, in which the explosive charge (la) has pores or is foamed.
6. An explosive charge according to any preceding claim, in which at least one further detonation means (6) is arranged in the region of the casing (4).
7. An explosive charge according to any preceding claim, in which the deflagration detonation means include detonation cords (3).
8. An explosive charge according to claim 7, in which the detonation cords (3) are surrounded by a damping layer (3a).
9. An explosive charge according to claim 7 or 8, in which the detonation cords (3) are arranged at a spacing from the casing (4) that IS substantially smaller than the spacing of the detonation cords from the compensating volume (2), and in that at least one strip-shaped passive device extending along the detonation cords (3) for the distribution of forces (7) is arranged between the detonation cords (3) and the casing (4)
10. An explosive charge according to claim 9, in which the or each device for the distribution of forces (7) is made of plastics material or metal.
11. An explosive charge according to any of claims 7 to 10, including means for igniting only that part of the detonation cords (3) which faces the direction of the target.
12. An explosive charge for a cylindrical warhead with an ignition chain (ZK), the power of which is designed for the detonation initiation of the explosive charge, characterised in that at least one compensating volume (2) is arranged in the central region of the explosive charge (1) and in that the region between the compensating volume (2) and the casing (4) of the warhead is sub-divided into a plurality of sector-shaped compartments (8) which are filled with liquid explosive, each sector (8) having at least one passage (9) to the compensating volume (2).
13. An explosive charge according to claim 12, in which the passage (9) is controllable or is Constructed as a bursting membrane.
14. An explosive charge according to claim 12 or 13, in which at least part of the contents of a plurality of sectors (8) can be simultaneously transferred into the compensating volume (2).
15. An explosive charge according to any of claims 12 to 14, in which at least one sector (8) can be acted upon by gas pressure.
16. An explosive charge according to any of claims 12 to 15, in which the initiation of the sectors (8) is effected by way of a common ignition device (ZK).
17. An explosive charge according to any of claims 12 to 15, in which at least one of the compartments (8) has a separate ignition device.
18. An explosive charge substantially &S described herein with reference to the attached drawings.
19. An explosive charge for a cylindrical warhead with an explosive mass (1) and an ignition chain (ZK2; ZK) whose power is designed for the detonation initiation of the explosive mass, characterised in that at least one compensating volume (2) is arranged in the central region of the explosive charge (1) and expansion means (3; 9) are provided for forcing part of the explosive mass into the compensating volume (2) so as to render it incapable of ignition, before the detonation is initiated, in order to adjust the force of the explosion.
20. A warhead including an explosive charge according to any preceding claim.