Explosive device deployment apparatus

Abstract

Explosive device deployment apparatus 2 comprises coupling means 5 to permit the apparatus 2 to be coupled to an aircraft 1 such as an unmanned aerial vehicle (UAV), in use. The apparatus 2 also inclu

Description

INVENTION The present invention relates to explosive device deployment apparatus, and particularly but not exclusively to apparatus and a system for deploying an explosive device for mine clearing. BACKGROUND TO THE INVENTION Minefields present a significant danger to military personnel and civilians. Current methods for minefield clearance are time-consuming, resource-intensive, and impact the pace of military operations. The mines also pose long-term threats to civilian populations if they are not cleared. Traditional methods of mine clearing include the use of ploughs, flails and / or rollers attached to armoured vehicles, such as armoured tractors. Recently, there has been a trend to make these vehicles autonomous to reduce the risk to operators of the vehicles having to enter a minefield being cleared. Other conventional methods include manual detection devices such as metal detectors or ground-penetrating radar. These conventional methods are effective but tend to be slow, costly, and require operators to remain in or near dangerous areas. Recently, alternative solutions to mine clearing have been proposed which use a single line charge fired from outside the minefield, for example using a rocket or other propellent. For example, the Abrams M58 Mine Clearing Line Charge (MICLIC). Similar systems to the MICLIC include the Giant Viper and Python mine clearing systems, which also use a line charge deployed from a specialist vehicle using a rocket. However, these rocket-based systems require specialist equipment including a rocket launcher to deploy the line charge using a rocket. This means there is limited access to these capabilities. They are also expensive and require bespoke training. In addition, these systems also have the disadvantage that they can only achieve straight line clearance, in the direction the rocket is aimed when launched from the rocket launcher. Also, their coverage is only as good as the operator’s aim. If the operator’s aim is off by only a few degrees, this error will be magnified at the remote end of the line charge, where the end of the line furthest from the launch site lands. This depending on the terrain, this can potentially result in the need to launch further lines charge(s) to ensure that the line charge lands on and clears the desired route through the mine field. STATEMENT OF INVENTION In accordance with a first aspect of the present invention, there is provided explosive device deployment apparatus, the apparatus comprising coupling means to permit the apparatus to be coupled to an aircraft, in use; a mounting device; a longitudinally extending member rotatably mounted on the mounting device, the longitudinally extending member adapted to have a flexible explosive device wound thereon; and wherein the coupling means is coupled to the mounting device. An advantage of the invention is that it provides apparatus for deploying a flexible explosive, for example, onto an area of ground to be cleared, using an aircraft. This permits a relatively accurate and controlled deployment of the explosive compared to existing systems. In one example of the invention, the apparatus may further comprise a clutch mechanism coupled between the longitudinally extending member and the mounting device, the clutch mechanism permitting relative rotation in one direction between the longitudinally extending member and the mounting device and preventing relative rotation in the opposite direction between the longitudinally extending member and the mounting device. An advantage of incorporating the clutch mechanism into the apparatus is that it can prevent accidental rotation of the longitudinally extending member in a direction opposite to the rotational direction for unwinding of the flexible explosive device, when the apparatus is in use. Preferably, the clutch mechanism comprises a first member having a curved surface; a second member having a generally saw-tooth profile; and a third member located between the first and second members, the third member being movable relative to the curved surface and the saw-tooth profile; and wherein the third member moves relative to the first and second members when the longitudinally extending member and the mounting device rotate relatively in the one direction, and the third member is engaged between the curved surface and the saw-tooth profile, when the longitudinally extending member and the mounting device attempt to rotate relatively in the opposite direction, to prevent relative rotation in the opposite direction. In one example of the invention, the clutch mechanism may comprise a sprag clutch. Typically, the mounting device may comprise an elongate member and the longitudinally extending member comprises an elongate hollow member rotatably mounted on the elongate member. The elongate member may form an axle on which the hollow member rotates. Preferably the elongate member extends within and more preferably along substantially the length of the hollow member. Preferably, the longitudinally extending member is tubular. The longitudinal axes of the elongate member and the longitudinally extending member may be aligned with each other, preferably are substantially parallel to each other and more preferably are substantially coincident. Alternatively, the mounting device may comprise two mounting members, the longitudinally extending member rotatably mounted on the mounting members and between the mounting members. Typically, the longitudinally extending member has a length of at least 4 metres and preferably, at least 5 metres. Preferably, the coupling means comprises a linear member coupled to the coupling device. Preferably, the coupling means comprises two linear members, the linear members coupled to the mounting device at, or adjacent to, opposite ends of the longitudinally extending member. Part or all of the linear member or linear members may be flexible. For example, they may comprise wire or rope, which may be metallic or non-metallic. In accordance with a second aspect of the present invention, there is provided a mine clearing system comprising an aircraft and apparatus according to the first aspect, the apparatus being coupled to the aircraft by the coupling means. Preferably, the aircraft is an unmanned aircraft, which is preferably remotely operated. The unmanned aircraft may be a drone, such as a copter drone. Typically, the system further comprises a flexible explosive device wound onto the longitudinally extending member. Preferably, the flexible explosive device is linearly extending. The flexible explosive device may comprise at least one of a linear explosive and a sheet explosive. In one example of the invention, the flexible explosive device comprises a two-dimensional mesh of linear explosive. Alternatively, or in addition, the flexible explosive may comprise a sheet explosive. Typically, the flexible explosive comprises a chemical explosive, such as at least one of: pentaerythritol tetranitrate explosive (PETN); octahydro-1,3,5,7-tetranitro- 1,3,5,7-tetrazocine (also known as octogen or high melting explosive) (HMX); and hexahydro-1,3,5-trinitro-1,3,5-triazine (also known as cyclonite or hexogen explosive) (RDX). Preferably, the two-dimensional mesh of linear explosive comprises a number of first lengths of linear explosive aligned with each other in a first direction; a number of second lengths of linear explosive aligned with each other in a second direction, the second direction being orientated transverse to the first direction so that the number of second lengths cross the number of first lengths; and a number of cord securing mechanisms, the cord securing mechanism securing the first lengths to the second lengths at each location where the first and second lengths cross each other. The cord securing mechanisms may be formed from plastic, for example, by a moulding or 3D printing process. Typically, each cord securing mechanism comprises a female portion having a first engagement formation and a male portion having a complementary second engagement formation, the female portion being adapted to receive a first length and a second length and the male portion being received by the female portion so that the first and second engagement formations engage with each other to retain the male portion in the female portion and to retain the first and second lengths within the female portion. The linear explosive may comprise detonating cord. In accordance with a third aspect of the present invention, there is provided a flexible explosive device comprising a two-dimensional mesh of linear explosive. Preferably, the flexible explosive device comprises a number of first lengths of linear explosive aligned with each other and being orientated in a first direction; a number of second lengths of linear explosive aligned with each other and being orientated in a second direction, the second direction being transverse to the first direction so that the number of second lengths cross the number of first lengths; and a number of securing mechanisms, one securing mechanism securing one of the first lengths to one of the second lengths at each location where the first and second lengths cross each other. In one example of the invention, the two-dimensional mesh may be formed from a single length of linear explosive, the first and second lengths being portions of the single length. Preferably, the securing mechanisms are fabricated from a plastics material. Typically, where the securing mechanisms secure the first lengths to the second lengths, the first and second lengths are urged into contact with each other at each location where the first and second lengths cross each other. Preferably, the flexible explosive device further comprises a flexible sheet of a non-metallic material located on one side of the flexible explosive device and extending across the flexible explosive device in both the first and second directions. Typically, the sheet of non-metallic material covers substantially all of the one side of the flexible explosive device. The sheet may be perforated. The perforations may be coincident with openings of the mesh. The flexible sheet may comprise at least one of: a plastics material; a synthetic composite material; carbon fibre; an ultra-high molecularweight polyethylene fibre; and a para-aramid fibre. Preferably, the flexible explosive device may be for use with the apparatus according to the first aspect or for use with the system according to the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made by way of example only to the accompanying drawings, in which: Figure 1A is a schematic of view of a copter drone with deployment apparatus and a mesh explosive wound onto the deployment apparatus; Figure 1B is a more detailed schematic view illustrating the attachment of the deployment apparatus to the copter drone; Figure 2 is a schematic cross-sectional view of an optional one-way clutch mechanism for use in the deployment apparatus shown in Figures 1A and 1B; Figure 3 is a side view of a plastic connector for use in fabricating an explosive mesh; Figure 4 is a plan view of the plastic connector; Figure 5 is a perspective view of the plastic connector; Figure 6 is a schematic view showing deployment of the explosive mesh using the apparatus and drone shown in Figures 1A and 1B; Figure 7 is a schematic view showing the explosive mesh after deployment but before detonation; and Figure 8 is schematic showing the explosive mesh being detonated after deployment. DESCRIPTION OF PREFERRED EMBODIMENTS Figures 1A and 1B are schematic views of a drone 1 with explosive mesh deployment apparatus 2 mounted to and suspended from the drone 1 by means of a support 4 and wires 5. The deployment apparatus 2 has an explosive mesh 3 wound on to it. The explosive mesh 3 is particularly useful for assisting to clear ground mines, such as antipersonnel mines, anti-vehicle mines and improvised explosive devices (lEDs) and can be deployed onto an area of ground to be cleared using the deployment apparatus 2 and the drone 1, as explained in more detail below. The drone 1 is typically a drone that is capable of hovering, for example a copter drone, such as a hex copter, as depicted in Figure 1. However, any suitable drone or unmanned aerial vehicle (UAV) could be used provided that it has sufficient power to lift the deployment apparatus 2 with a payload of explosive mesh 3 and a flight endurance time sufficient to deploy the explosive mesh 3 and return to base. It is also possible to use a manned aerial vehicle instead of the drone 1. However, it is desirable to use a drone or UAV to reduce the risk to operating personnel, as explained in more detail below. The deployment apparatus 2 comprises an axle 6 on which is rotatably mounted a hollow sleeve 7. The hollow sleeve 7 is typically fabricated from a material with a low weight to strength ratio, such as carbon fibre. Two wires 5 are attached to the axle 6 with an end of each wire 5 attached to one end of the axle 6. The opposite ends of the wires 5 are attached to a mounting point 4 on the drone 1, so that the deployment apparatus is suspended from the drone 1 via the mounting point 4. The sleeve 7 can be any suitable length depending on the width of the mesh explosive to be deployed. However, in a preferred embodiment the sleeve 7 has a length of at least 5 metres to enable a 5 metre wide explosive mesh 3 to be wound onto the sleeve 7. Preferably the sleeve 7 has a length of from 5 m to 6 m and more preferably has a length of from 5.25 m to 5.5 m. Optionally, a one-way clutch mechanism 10, such as a sprag clutch, may be mounted between the hollow sleeve 7 and the axle 6, as shown in Figure 2. The clutch mechanism 10 permits the sleeve 7 to rotate relative to the axle 6 in the direction of the arrow 11 but prevents rotation of the sleeve 7 relative to the axle 6 in the opposite direction, indicated by the arrow 12. The clutch mechanism comprises a profiled ring 13 mounted on the axle 6 for rotation with the axle 6. The profiled ring 13 has a number of ramp profiles 14 on its external circumference. A roller 15 is located between each ramp profile 14 and the internal surface of the sleeve 7, so that there is a roller 15 for each ramp profile 14. The ramp profiles 14 are configured such that the gap between the surface of each ramp profile 14 and the internal surface of the sleeve 7 reduces along the length of each ramp profile 14. The gap between the internal surface of the sleeve 7 and the surface of each ramp profile 14 at its widest point is wider than the diameter of the rollers 15. The gap between the internal surface of the sleeve 7 and the surface of each ramp profile 14 at its narrowest point is narrower than the diameter of the rollers 15. Hence, if the apparatus 2 includes the one-way clutch mechanism 10, when the sleeve 7 rotates in the direction of the arrow 11, the rollers 15 move to the section of the ramp profiles 14 with the largest gap enabling the sleeve 7 to rotate relative to the axle 6. However, if the sleeve 7 tries to rotate in the opposite direction (that is, in the direction of the arrow 12), the rollers 15 are urged by the internal surface of the sleeve 7 towards the section of the ramp profiles 14 with the narrowest gap, causing the rollers 15 to jam between the ramp profiles 14 and the internal surface of the sleeve 7, thereby preventing relative rotation between the sleeve 7 and the axle 6 in the direction of the arrow 12. This feature can be useful in preventing inadvertent rotation of the sleeve 7 in a direction opposite to the direction of rotation for unwinding the mesh 3 from the sleeve 7. The explosive mesh 3 is fabricated from a linear explosive, which can be conventional detonating cord filled with one or more of a number of conventional chemical explosives. For example, the linear explosive may comprise one or more of a number of different chemical explosives, such as pentaerythritol tetranitrate explosive (PETN), octahydro-1,3,5,7-tetranitro- 1,3,5,7-tetrazocine (also known as octogen or high melting explosive) (HMX) and hexahydro-1,3,5-trinitro-1,3,5-triazine (also known as cyclonite or hexogen explosive) (RDX). Any other suitable explosives may also be used in addition or instead of these explosives. As shown in Figure 1A, the explosive mesh 3 comprises a number of longitudinal lengths 8 of detonating cord and a number of cross lengths 9 of detonating cord. Where the cross lengths cross each longitudinal length 8, the respective cross length 9 and longitudinal length 8 are secured together using a connector 30. Hence, there is a connector 30 at each crossing point of the longitudinal and cross lengths 8, 9. In Figure 1A only two connectors 30 are shown for reasons of clarity. The connector 30 is shown in more detail in Figures 3 to 5 and comprises a male member 31 having an external thread 32 and a female member 33 having a recess 34 with an internal thread 35, which receives the threaded male member 31. As shown in Figures 4 and 5, the male member has a hexagonal formation 37 formed on end 36. This enables a suitable tool to be engaged to be engaged with the end 36 to rotate the male member 31 to screw it into the recess 34 in the female member 33. In the connector 30 the hexagonal formation 37 is recessed into the end 36. Preferably, the connectors 30 are formed from a plastics material, such as polyethylene or polypropylene. The male and female members 31, 33 may be formed by a moulding process, such as injection moulding, by a 3D printing process, or by any other suitable forming technique. The female member 33 has four slots 38, 39 formed in the side wall, these consist of two shallow slots 38 and two deeper slots 39. The slots 38, 39 are preferably spaced equidistantly around the circumference of the side wall at substantially 90 degrees from each other, with the shallow slots 38 opposite each other and the deeper slots 39 opposite each other. Hence, each shallow slot 38 has a deeper slot 39 as its nearest neighbour and each deeper slot 39 has a shallow slot 38 as its nearest neighbour. The slots 38, 39 extend through the side wall of the female member 33 to the internal recess 34. The slots 39 extend further down the side wall of the female member 33 than the slots 38. To fabricate the explosive mesh 3, a number of longitudinal lengths 8 of detonating cord are laid out at a desired spacing and so that the lengths 8 are generally parallel to each other and a number of cross lengths 9 of detonating cord are laid across the longitudinal lengths so that the cross lengths 9 are also generally parallel to each other. The cross lengths 9 are laid across the longitudinal lengths 9 preferably so that the cross lengths are perpendicular to the longitudinal lengths 8. At each crossing point of a longitudinal length 9 with a cross length 8, one of the lengths 8, 9 is inserted into one of the pair of slots 38, 39 and the other of the lengths 8, 9 is inserted into the other of the pair of slots 38, 39, so that the lengths 8, 9 cross each other within the recess 34 of the female member 33. The male member is then screwed into the female member and tightened, using an appropriate tool on the hexagonal formation 37, to clamp the lengths 8, 9 between end 41 of the male member 31 and bottom 42 of the recess 34. This clamping of the lengths 8, 9 between the male member and the female member presses the lengths 8, 9 together at the crossing point of the lengths 8, 9 within the connector 30. A connector 30 is installed at each crossing point of the lengths 8, 9 to fabricate the mesh. The number of longitudinal lengths 8 depends on the desired gap size of the mesh and the desired width of the mesh and can be altered to suit different requirements. However, in one example, the mesh 3 is fabricated to have a width of 5 metres. 5 metres is a useful width as it permits large vehicles, such as tanks to pass along a path cleared by the mesh 3. The number of cross lengths 9 also depends on the desired gap size of the mesh and on the length of the mesh 3. The longer the length of mesh required, the more cross lengths 9 will be required for a given mesh gap size. Operational use of the drone 1, the apparatus 2 and the mesh 3 is depicted in Figures 6 to 8. In use, the explosive mesh 3 is wound onto the sleeve 7 and the deployment apparatus 2 coupled to the drone 1 by means of the wires 5. In a safe area of ground 47 outside the area of ground to be cleared of mines (a mine field) 48, the drone 1, deployment apparatus 2 and the explosive mesh 3 are placed on the ground. Loose end 45 of the explosive mesh 3 is secured to the ground using a number of anchors 46. Typically, the anchors are plastic. The anchors 46 may take the form of pegs that are pushed into the ground to secure the end 45 to the ground. After the loose end 45 of the mesh 3 is secured, an operator launches the drone 1, which takes off carrying the deployment apparatus 2. As the drone 1 rises off the ground or a launch vehicle, the sleeve 7 rotates relative to the axle 6 to enable the mesh 3 to be unrolled from the sleeve. The operator then flies the drone 1 over the ground to be cleared 48 following the direction of the desired path or route 49 to be cleared. As the drone flies forward over the path 49 to be cleared, the weight of the mesh 3 and the end 45 anchored to the ground, rotate the sleeve 7 relative to the axle 6, pulling the explosive mesh of the sleeve 7 so that it is deployed on the ground following the path to be cleared. During the deployment, the operator can alter the direction of the drone as required. This enables the mesh 3 to be deployed along a specific path or route 49 that does not need to be a straight line. This may be particularly useful when clearing sloping ground, such as on the sides of hills or to avoid particular areas, such as buildings, rivers or forested areas. When all the mesh 3 has been unrolled from the sleeve 7, the non-anchored end of the mesh 3 falls off the sleeve 7 and drops to the ground, thereby completing the deployment of the mesh 3 across the desired route 49 through the mine field 48. The operator then returns the drone 1 and the apparatus 2 (without the mesh 3) to the safe area. After the drone 1 has been returned, a conventional safety fuse is connected to the explosive mesh and set, and the operator together with any other personnel retreat to a safe distance before detonating the mesh 3 using the safety fuse. As an alternative to a safety fuse, it is possible that the mesh 3 (or indeed any other flexible explosive used) may be detonated electrically, such as by using a conventional electrically initiated detonator. Detonation 50 of the mesh 3 clears any mines or lEDs in or on the ground below where the mesh is laid (or at least the vast majority of them) by detonating them or damaging them so as to be inoperative, thereby rendering the ground that was covered by the mesh (that is, the route 49) safe. Depending on the particular circumstances, after detonation of the mesh 3, it may be desirable to then use ground-based mine clearance equipment to confirm that all mines have been cleared from the desired route 49 and / or to deploy and detonate a further mesh 3 to ensure that as many mines as possible are cleared from the route 49. It is possible that the deployment of the mesh 3 may accidentally trigger a mine or I ED. Therefore, the drone 1 is flown at a safe height above the ground while deploying the mesh 3. The apparatus 2 can be reused and a further length of mesh 3 wound onto the sleeve 7 to be deployed using the drone 1 and apparatus 2, to clear a further area of ground within the mine field 48 or another mine field. As an alternative to an explosive mesh 3 fabricated from a linear explosive, it is possible that sheet explosive could be used instead of the mesh 3. In this case the sheet explosive would be wound onto the sleeve 7 and deployed in the same manner as for the mesh 3. In a further alternative, a layer of non-explosive sheet material could be placed on top of the mesh 3 or other explosive. Typically, the sheet material would be secured to the mesh 3 and preferably, would be a non-metallic material. For example, the sheet material could be a fabric formed from one or more of a plastics material; a synthetic composite material; carbon fibre; an ultra-high molecular weight polyethylene fibre (such as Dyneema®); and a para-aramid fibre (such as Kevlar®). An advantage of providing the layer of non-explosive sheet material on top of the mesh 3 or other explosive is that it may help to reduce friction and rubbing of the mesh 3 against itself as it is wound onto the sleeve 7 and during deployment. Use of a sheet material that is resistant to explosions, such as materials of ultra-high molecular weight polyethylene fibre and / or a para-aramid fibre, has the advantage that it may help to direct the explosion from the mesh 3 (or other explosive) into the ground, thereby improving the efficacy of the detonation of the mesh 3 for clearing ground and / or reducing the amount of explosive required to effectively clear the ground. Advantages of the invention include that the drone 1, the apparatus 2 and the sleeve 7 are reusable. It does not require expensive, large-scale or expensive machinery and equipment. It enables a mine clearing process to be performed without personnel having to enter the area to be cleared and permits paths to be cleared across a mined area of ground which are not a straight line by flying the drone 1 to deploy the mesh 3 in a non-straight line. In addition, as the drone 1 and the apparatus 2 are relatively small and light, they can be relatively easily deployed to an area of ground to be cleared and are not dependent on the type of vehicle used to transport and deploy it. In other words, the apparatus and system are vehicle agnostic. This means that non-specialised vehicles can be used for deployment to the vicinity of a mine field 48. For example, light-weight military vehicles or non-military vehicles can be used for transport and deployment, including infantry fighting vehicles, military tactical vehicles, military light utility vehicles, light 5 military vehicles or non-military vehicles, such as cars, trucks, pick-ups or off-road cars. If there is insufficient space within the vehicle for the apparatus 2, the apparatus 2 may be stored or transported by mounting on the side or top of the vehicle. The embodiments described above are provided by way of example only, and various changes and modifications will be apparent to persons skilled in the art without 10 departing from the scope of the present invention as defined by the appended claims.

Claims

1. Explosive device deployment apparatus, the apparatus comprising coupling means to permit the apparatus to be coupled to an aircraft, in use; a mounting member; a longitudinally extending member rotatably mounted on the mounting member, the longitudinally extending member adapted to have a flexible explosive device wound thereon; and wherein the coupling means is coupled to the mounting member.

2. Apparatus according to claim 1, further comprising a clutch mechanism coupled between the longitudinally extending member and the mounting member, the clutch mechanism permitting relative rotation in one direction between the longitudinally extending member and the mounting member and preventing relative rotation in the opposite direction between the longitudinally extending member and the mounting member.

3. Apparatus according to claim 2, wherein the clutch mechanism comprises a first member having a curved surface; a second member having a generally saw-tooth profile; and a third member located between the first and second members, the third member being movable relative to the curved surface and the saw-tooth profile; and wherein the third member moves relative to the first and second members when the longitudinally extending member and the mounting member rotate relatively in the one direction, and the third member is engaged between the curved surface and the saw-tooth profile when the longitudinally extending member and the mounting member attempt to rotate relatively in the opposite direction to prevent relative rotation in the opposite direction.

4. A mine clearing system comprising an aircraft and apparatus according to any of claims 1 to 3, the apparatus being coupled to the aircraft by the coupling means.

5. A mine clearing system according to claim 4, wherein the aircraft is an unmanned aircraft.

6. A mine clearing system according to claim 5, wherein the unmanned aircraft is remotely operated.

7. A mine clearing system according to any of claims 4 to 6, further comprising a linearly extending flexible explosive device.

8. A mine clearing system according to claim 7, wherein the linearly extending flexible explosive device comprises at least one of a linear explosive and a sheet explosive.

9. A mine clearing system according to claim 7 or claim 8, wherein the linearly extending flexible explosive device comprises a two-dimensional mesh of linear explosive.

10. A mine clearing system according to claims 7 to 9, further comprising a number of first lengths of linear explosive aligned with each other in a first direction; a number of second lengths of linear explosive aligned with each other in a second direction, the second direction being orientated transverse to the first direction so that the number of second lengths cross the number of first lengths; and a number of cord securing mechanisms, one cord securing mechanism securing the first lengths to the second lengths at each location where the first and second lengths cross each other.

11. A mine clearing system according to any of claims 7 to 10, wherein the linear explosive comprises detonating cord.

12. A flexible explosive device comprising a two-dimensional mesh of linear explosive.

13. A flexible explosive device according to claim 12, further comprising a number of first lengths of linear explosive aligned with each other and being orientated in a first direction; a number of second lengths of linear explosive aligned with each other and being orientated in a second direction, the second direction being transverse to the first direction so that the number of second lengths cross the number of first lengths; and a number of securing mechanisms, one securing mechanism securing one of the first lengths to one of the second lengths at each location where the first and second lengths cross each other.

14. A flexible explosive device according to claim 13, wherein the securing mechanisms are fabricated from a plastics material.

15. A flexible explosive device according to claim 13 or claim 14, wherein when the securing mechanisms secure the first lengths to the second lengths, the firstand second lengths are forced into contact with each other at a number of locations where the first and second lengths cross each other.

16. A flexible explosive device according to claim 15, wherein the first and second lengths are forced into contact with each other at each location where the first and second lengths cross each other and are secured together by one of the securing mechanisms.

17. A flexible explosive device according to any of claims 12 to 16, further comprising a flexible sheet of a non-metallic material located on one side of the flexible explosive device and extending across the flexible explosive device in both the first and second directions.

18. A flexible explosive device according to claim 17, wherein the sheet of non-metallic material covers substantially all of the one side of the flexible explosive device.

19. A flexible explosive device according to claim 17 or claim 18, wherein the sheet is perforated.

20. A flexible explosive device according to claim 19, wherein there are perforations in the sheet that are coincident with openings in the mesh.

21. A flexible explosive device according to any of claims 17 to 20, wherein the flexible sheet comprises at least one of: a plastics material; a synthetic composite material; carbon fibre; an ultra-high molecular weight polyethylene fibre; and a para-aramid fibre.

22. A flexible explosive device according to any of claims 12 to 21, for use with the apparatus according to any of claims 1 to 3, or for use with the system according to any of claims 4 to 22.s

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