Patent Publication Number: US-11662184-B2

Title: Device and method for mine disposal

Description:
TECHNICAL FIELD OF THE INVENTION 
     The invention relates to the field of projectiles and in particular to projectiles for mine disposal and to methods of using said projectiles. 
     BACKGROUND TO THE INVENTION 
     Mines can have a devastating impact on personnel, platforms, vehicles and other equipment. Therefore, in areas were mines have been deployed, it is important that they can be disposed of effectively so as to provide a safe path or area for personnel and vehicles to enter and operate. 
     Mines have been deployed in a wide variety of locations including surface and buried land mines as well as naval mines located in the ocean and other bodies of water. Naval mines in particular can be challenging to dispose of due to the added complexities of operating at sea. 
     Mapping or marking mined areas may be sufficient for some applications where it is possible to avoid the affected areas altogether. However, such measures may be insufficient where it is necessary for personnel or expensive equipment to enter the mined region. Where access to the mined area is desirable or necessary it is known that an explosive device may be used to detonate the mine. However, this method may require the storage, transit and deployment of an explosive device which may require expertise to operate and which may pose an additional safety risk and cost. 
     Therefore, it is an aim of the present invention to provide an alternative means for mine disposal. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the invention there is provided a projectile for piercing a casing of a mine containing an explosive material;
         the projectile comprising a projectile body having a nose portion and a tail portion wherein a longitudinal axis extends between the nose portion and the tail portion, the projectile body comprising a switch, and a first electrode and a second electrode;   wherein the switch is configured to control the closure of a circuit connecting the first electrode and the second electrode to a source of electrical energy; and   wherein the first electrode and the second electrode are separated by a separation distance such that in use an electrical discharge can flow between the first electrode and the second electrode, either through an explosive material contained within a mine, or through a material comprised between the electrodes or which is introduced between the electrodes in use, so as to cause the material to release energy so as to detonate an explosive material contained within a mine.       

     According to a second aspect of the invention there is provided, a method of mine disposal, the method comprising the steps of: (i) providing a projectile according to the first aspect of the invention; (ii) launching the projectile towards a mine; (iii) piercing the casing of the mine with the projectile; and (iii) applying a voltage between the first electrode and the second electrode of the projectile so as to cause an electrical discharge to flow between the first electrode and the second electrode either through an explosive material contained within a mine, or through a material comprised between the electrodes or which is introduced between the electrodes in use, so as to cause the material to release energy so as to detonate an explosive material contained within a mine. 
     The material comprised between the electrodes, or which may be introduced in use, is one that explodes or combusts when electricity is discharged through it. Examples include aluminium foil or salt water. Clearly a suitable amount should be used such that the electrical discharge to be delivered to it, will cause its temperature to rise appropriately so that it delivers an appropriately high amount of energy for initiating explosion of the explosive material contained within the mine. 
     Optionally, the nose portion is provided with a water ingress path arranged such that in use underwater, water can ingress to a location between the first and second electrodes, such that in use an electrical discharge can flow between the first electrode and the second electrode, through the water between the electrodes, to initiate the energetic material, to detonate an explosive material contained within a mine. This will be most effective when the water used is salt water. The salt water does not need to be provided by the user if the projectile is being used in a salt water environment, since the projectile will be immersed in salt water by virtue of its use, so the leak path enables an amount (i.e. controlled by the space available between the electrodes) quantity of the environmentally abundant salt water to ingress between the electrodes, and the amount is controlled such that the electrical discharge will cause that quantity of water to explode. 
     The first and second electrodes are separated by a separation distance such that, in use, once the projectile has pierced through the casing of the mine, and the electrodes are in contact with the explosive material, applying a suitable voltage and current into the electrodes causes an electrical discharge to flow between the two electrodes and through the explosive material (or energetic material if comprised in the projectile). For instance, in use, an electrical discharge may flow between the first electrode and the second electrode through an explosive material contained within a mine so as to initiate an explosive reaction. The electrical discharge may be caused by the electrical breakdown of the explosive material located in the region of the applied electrical field created between the two electrodes, resulting in the flow of plasma formed from ionised particles of the explosive material. Electrical breakdown of the explosive material may occur when the voltage applied between the electrodes causes (e.g. forms) an electric field in the explosive material which exceeds the breakdown voltage of the explosive material. The electrical discharge may overcome the Figure of Sensitivity of the explosive to detonate the mine. The electrical discharge may flow through the explosive material contained within the detonator and/or the explosive material of the main charge. The projectile is therefore capable of initiating, and thereby disposing of, a mine without the use of additional explosives. Therefore, projectile is particularly suitable as a mine disposal projectile. 
     In more difficult to access areas it can be particularly disadvantageous to transport and deploy explosive materials typically used during mine disposal. Therefore, the invention may be particularly advantageous for the disposal of mines located in terrain which may be difficult to access, for example, in the case of naval mines or underwater mines. 
     The projectile may be arranged such that, in use, it sufficiently pierces the casing of the mine such that the first electrode and the second electrode at least partially enter the body of the mine and the explosive material contained therein. Optionally, the projectile may be arranged such that one of, or advantageously both of, the first and the second electrodes fully enter the body of the mine. 
     The projectile body comprises a nose portion and a tail portion. The nose portion and the tail portion may be formed as a single component. Alternatively, the nose portion and the tail portion may be formed as separate components which are attached by any suitable attachment means. For example, the nose portion and the tail portion may be attached by, welding, adhesive, bolts or any combination thereof. 
     The length of the projectile body may be between 5 cm and 50 cm, more particularly between 10 cm and 30 cm in length. Optionally, the diameter of the projectile body may be between 1 cm and 10 cm, more particularly between 2 cm and 5 cm. 
     The projectile body may be optimised for piercing a particular material and/or thickness of mine casing. For example, the projectile body may be optimised to pierce a mine casing formed substantially from metal, plastic, glass fibre reinforced plastic or any combination thereof. Advantageously, the projectile may be optimised to pierce a mine casing having a thickness of between 2 mm and 60 mm, or more particularly between 5 mm and 30 mm, or even more particularly between 5 mm and 10 mm. 
     The shape of the nose portion and/or the tail portion, may be configured to improve the penetration of the projectile into the mine casing. For example, the projectile nose portion may be substantially flat, substantially stepped, substantially conical or substantially hemispherical in shape. Optionally, the surface of the nose portion and/or the tail portion may comprise a surface texture to improve penetration of the projectile through the mine casing, such as, one or more grooves, fins, blades or threads. 
     The nose portion may be formed from any material suitable for piercing a mine casing. For example, the nose portion may be at least partially formed from Tungsten or Hardened Steel or metal alloys. 
     Advantageously, the nose portion may comprise a detachable (E.g. or sacrificial) casing. The detachable casing may be optimised to reduce the coefficient of drag associated with passage of the projectile through a fluid, for example, through seawater. This may be particularly advantageous, for example, in the disposal of an underwater mine where it may be necessary for the projectile to travel some distance through a body of water before reaching a mine. 
     The detachable casing may be arranged to be detachable responsive to an impact between the projectile and a mine casing. For instance, the detachable casing may be frangible. Optionally the detachable casing may be arranged such that in use it breaks away upon impact of the projectile with the mine casing. Alternatively, the casing may be configured to detach in response to a trigger means, such as, a timer, a proximity sensor, a remotely operated switch, or any combination thereof. 
     The detachable casing may be formed from any suitable material, for example, plastic, glass reinforced plastic, metal, metal foil, ceramic, or any combination thereof. 
     The explosive material may be the main charge explosive and/or it may be the explosive material contained within the booster or detonator of the mine. The explosive material may be any suitable explosive material capable of detonation in response to an electrical discharge. For example, the explosive material may be a High Explosive, such as, TNT, RDX or PETN. 
     The first electrode and/or the second electrode may be positioned in whole or in part on the surface of the projectile body. The first and/or second electrode may be shaped to encourage contact of the explosive material with both electrodes (preferably complete contact covering all of at least one of the electrodes, preferably covering all of both electrodes) so as to ensure the current path within the explosive material (as opposed to air or other substances in the vicinity of the explosive material). In particular, positioning of at least one of the electrodes at least partially on the surface may enable the electrode(s) to more readily come into contact with the explosive material after the projectile penetrates the mine casing. 
     One of the first electrode or the second electrode may extend in whole or in part into the projectile body. More preferably, both of the first and the second electrodes may extend in whole or part of into the projectile body. By extending in whole or in part into the projectile body the electrode(s) may be at least partially protected by the projectile body during the penetration of the mine casing. 
     The portion of the first electrode which extends into the projectile body may be separated from the portion of the second electrode which extends into the projectile body by an insulator. The insulator may be any material, or composite material, suitable for electrically insulating the first and second electrodes, for example, plastic, glass, ceramic, wax, oil or any combination thereof. 
     Advantageously, the nose portion may comprise whole or part of one or both of the first electrode and the second electrode. For example, both of the electrodes may at least partially extend into the nose portion of the projectile. This arrangement is particularly advantageous where it is preferable that only the nose portion of the projectile body extends into the mine after piercing. 
     The nose portion may be formed from whole or part of one or both of the electrodes. Said electrode(s) may thereby readily come into contact with the explosive material upon piercing of the mine casing. 
     One or both of the first and the second electrodes may be arranged such that the electrode(s) is/are projectable away from the projectile body. For example, one or both of the first and the second electrodes may be arranged such that the electrode(s) is/are projected away from the projectile body responsive to the piercing a mine casing. Optionally, one or both of the first and the second electrodes may be located at or beneath the surface of the projectile body and arranged such that the electrode(s) is/are projected away from the projectile body responsive to the piercing a mine casing. This arrangement may protect the electrode(s) from damage during impact with the mine and/or penetration of the mine casing. By projecting the electrode(s) away from the projectile body, such that they extend away from the projectile body and into the explosive, this may ensure the electrodes become further embedded within the explosive material with the advantage of ensuring the current path through the target explosive but may increase the separation distance between the electrodes. This may increase the distance that the electrical discharge travels through the explosive material, which would require increased voltage to exceed the minimum breakdown voltage required for the initiation of the explosive material in question. 
     The electrode(s) may be projected away from the projectile body by any suitable means, for example, an actuator, such as, a mechanical, pneumatic or hydraulic actuator. One or both of the electrodes may be deformable, such that, in use, the impact of the projectile with the mine casing causes one or both of the electrodes to contact a portion of the projectile body resulting in deformation of the electrode(s) such that the electrode(s) extend away from the projectile body. 
     The first electrode and the second electrode may be a transmission line such as planar or coaxially arranged about the longitudinal axis. This arrangement may allow for a particularly compact arrangement of the projectile. For instance, one of the electrodes may form a central core electrode about which a second tubular electrode is arranged. Preferably, there may be a tubular insulating material arranged between the coaxially arranged electrodes. Each of the coaxially arranged electrodes may extend along whole or part of the longitudinal axis of the projectile body. For example, the one of the electrodes may form a central core electrode, wherein a portion of the central electrode forms the nose portion of the projectile body. Advantageously one, or both, of the tubular electrodes may form a portion of the outer surface of the projectile body. 
     Advantageously, the first electrode and the second electrode may be separated along the longitudinal axis of the projectile by the separation distance. For example, the one of the electrodes may be located in the nose portion and the other electrode may be located in the tail portion. 
     The electrodes may be formed of any suitable conductive material, for example, the electrodes may be formed from copper, tungsten, steel, titanium, brass, silver, chromium, chromium alloy, or other metal alloys, or platinum, preferably chromium or chromium alloy. 
     The first electrode and the second electrode are arranged so as to be connectable to a source of electrical energy. One or both of the electrode(s) may be arranged so as to be permanently attachable to the source of electrical energy, for example, by welding, (e.g. threaded) bolts or other suitable means. Advantageously, one or both of the electrodes may be arranged so as to be temporarily attachable to the source of electrical energy. One or both of the electrodes may comprise an electrical connector for attaching the electrode(s) to a source of electrical energy. For example, the electrical connector may form one portion of an inter-engaging fixing. The other portion of the inter-engaging fixing may be associated with the source of electrical energy. Such inter-engaging fixings may be, for example, plug and socket connectors or ring/spade terminals. The electrical connector may comprise an integral portion of the electrode or may be a separate component attached to the electrode(s). 
     The application of the voltage may be controlled such that it occurs when the electrodes are embedded within the explosive material of the mine. Advantageously, the projectile may comprise a switch configured to connect the first electrode and the second electrode to a source of electrical energy. The switch may be used to control the closure of a circuit connecting the first electrode and the second electrode to a source of electrical energy. Advantageously, the switch may be arranged so as to be remotely controlled. The switch may be a thin insulating layer of metal oxide that activates when the electrical breakdown of the thin layer is reached. The switch may comprise a timer. The timer may be configured to control the timing of the operation of the switch. The switch typically connects one electrode in a controlled fashion (i.e. selectively connects the electrode to the source of electrical energy), and may be arranged to connect other electrode continuously (or alternatively it may connect both electrodes in a controlled fashion). Whilst the source of electrical energy is preferably comprised as part of the projectile (e.g. as part of or within the tail of the projectile), it may alternatively be separate or may be part of a launcher for the projectile, however in the latter cases, the user should connect the projectile to the source of electrical energy via cabling (E.g. two insulated wires, typically bound as a single cable). 
     Advantageously, the switch may comprise a sensor configured to sense the piercing of a mine casing by the projectile. Thereby, the switch may be operated upon sensing the piercing of a mine casing by the projectile 
     The switch may comprise a first switch element and a second switch element, wherein the first switch element and the second switch element are separated along the longitudinal axis by a switch distance, and wherein the switch is compressible along the longitudinal axis such that in use impact of the projectile body with a mine casing causes relative movement between the first element and the second element along the longitudinal axis such that the switch distance is reduced causing the switch to be triggered. For example, the first switch element and the second switch element may be the first and second plates of a spark gap. The spark gap may be compressible along the longitudinal axis such that in use impact of the projectile with the casing of a mine causes the first plate and the second plate to move towards one other along the longitudinal axis. Thereby, the distance between the two spark gap plates may be reduced sufficiently that a current may flow between them in the form of a discharge. 
     Advantageously, the projectile may comprise a retaining means for retaining the projectile partially within the casing of a mine. For instance, it may be desirable to control the proportion of the projectile body which penetrates the mine casing. This may provide a convenient means for ensuring that the projectile does not exit the mine prior to detonation. Advantageously, the retaining means may form part of the tail portion of the projectile body. 
     Optionally, the projectile may be arranged such that in use only the nose portion of the projectile body penetrates into the mine casing after piercing. For instance, the tail portion may comprise components which, by remaining external to the mine, may be protected from impact damage. 
     The retaining means may comprise a flange projecting from the projectile body. For example, the flange may comprise an external rim or collar projecting from the projectile body. 
     Advantageously, the projectile may further comprise a source of electrical energy. Advantageously, the source of electrical energy may be integral to the projectile body. Alternatively, source of electrical energy may be separate from the projectile body. The source of electrical energy may be electrically connected to the projectile by wires. For example, the wires may be between 1 meter and 50 meters in length. 
     The source of electrical energy may be any suitable energy source. For example, the source of energy may comprise a capacitor or battery. 
     Optionally, the source of electrical energy may comprise a magnet arranged to move through a coil of wire where the impact causes the magnet to travel through the wire inducing a current in it that may be a high voltage. 
     Advantageously, the source of electrical energy may comprise a piezoelectric material. For instance, the piezoelectric material may be arranged such that in use when the projectile impacts with a mine the piezoelectric material undergoes mechanical stress resulting in the generation of electrical energy. For example, the piezoelectric material may be a piezoelectric crystal. 
     The source of electrical energy may comprise a capacitor. The capacitor may be arranged to charge or discharge responsive to the penetration of a mine casing by the projectile and may be remotely discharged by an external stimulus such as a detectable oscillating wave of a specific frequency or set of frequencies in the local environment that is received as a command to charge the capacitor or activate a switch to discharge the capacitor. If a remote trigger is used, the projectile needs to incorporate a receiver, sensitive to a predetermined signal (acoustic or electric/electronic) able to detect the signal and trigger the electrical discharge. Additionally or alternatively a time delay circuit may be incorporated to provide control over the timing of the electrical discharge. 
     The energy source may be optimised to supply a voltage across the separation distance between the electrodes sufficient to cause an electrical breakdown for a particular explosive material or range of explosive materials. For example, the energy source may be arranged to supply between 1,000 to 30,000 volts per mm across the separation distance between the electrodes. 
     Optionally, the projectile may comprise a means for charging the energy source. For example, the means for charging the energy source may comprise an integral battery with a high voltage charging circuit. 
     Advantageously, the separation distance between the electrodes may be in the range of 0.1 mm to 5 cm, more advantageously in the range of 0.1 mm to 5 mm. 
     The projectile body may comprise a damping means for damping internal oscillations resulting from the impact with a mine. For example, the damping means may be arranged to damp internal oscillations of one or more of the integral power source, electronic circuitry, the switch, the first electrode, the second electrode, and the means for charging the energy source, or any combination thereof. For instance, the damping means may comprise a hydraulic damper or a mechanical damper. Optionally, the damping means may comprise a spring. Advantageously, the damping means may comprise, for example, a cavity comprising a compressible fluid such as air or a liquid such as oil or silicone. Advantageously, the damping means may comprise a cavity comprising a wax or highly viscous material. The material may be optimised to change state in use from a solid to a liquid in response to the shock or heating of the projectile body upon impact (for instance the material may be granular/pelleted rather than liquid prior to use). For instance, the projectile body may comprise one or more through holes through which the wax may flow out of the projectile body when in a liquid state. 
     The electrodes may be treated to form a thin layer of oxide that with a high voltage stress structure, such as a protrusion from a flat surface that may be pointed or spherical or any shape with an asymmetry that encourages an electric field gradient over its cross section, can act as a high voltage breakdown switch with an operating switch voltage proportional to the thickness, homogeneity and smoothness of the oxide layer. This may form part of a triggering system whereby a capacitor supplying the switch may have an operating voltage that exceeds the switch voltage, which as the capacitor becomes charged reaches the switch voltage where the charge crosses the switch and forms a current path through the medium between the electrodes, which may be a high explosive material that initiates by the electrical current path passing through it or may be a material that exhibits energetic properties under sufficient pulse power conditions, such as aluminium foils or wires with oxidising fuel such as water and plastic or commercially available non-explosive energetics such as METAFEX. Preferably the energetic material is not an explosive, but is a material that explodes when sufficient electrical discharge is passed through it (an example being aluminium foil). This has the advantage of increasing reliability without worsening handling safety. 
     The complete disposal of the mine may be achieved by direct or in-direct initiation of electrical discharge such as pulse power or high voltage alternating current. As direct initiation by method of pulse power may require control of the contact of target high explosive material between the electrodes to ensure a current path through the material, in-direct initiation may make use of a non-explosive energetic material(s) or compound(s) such as metal foil or wires and compounds thereof that may initiate the target high explosive within the mine through sympathetic explosion due to the initiation of the non-explosive energetic material which may provide an advantage in reliability, cost of manufacture or electrical energy storage requirements within the dart. 
     The nose portion may be shaped in a way as to permit or encourage the flow of high explosive material onto the electrodes during or after penetration of the nose into the mine case. This may advantageously provide a means for ensuring the current path of the high voltage discharge passes through the explosive material. 
     The projectile may be powered for penetrating means without propellant and instead by high pressure gas and may be powered using differential relative pressures to generate the force needed to penetrate the mine case by positioning the relative pressure chamber(s) about the projectiles longitudinal axis in a way that allows the free movement of the projectile forward on release of the high pressure gas. The gas may be stored in a chamber that is attachable or unattached to the projectile body either in-front or behind the nose and tail portion of the projectile and may be pierced to release the pressure or may be controlled by a valve mechanism. The pressure(s) may be held in potential until a remote means of activation such a remotely operated switch or triggering mechanism. 
     One of the penetrating electrodes may be a high temperature metal, such as Tungsten or alloys of the same, which may be heated by the energy source to exceed the FOI of heat for the explosive material within the mine. The high temperature metal may be heated by an alternating current supplied by the energy source. 
     The projectile may electrically couple to the target system case to deliver a pulse power discharge or high voltage signal to the electronics that may be connected to the target system case for the purpose of electrical grounding of the target system electronics. This may damage the target system electronics rendering it in-operable or reduce its function or cause mission abort. 
     The projectile may discharge within the case to induce electrical currents within the mine electronics by means of a pulse power discharge or high voltage signal that may influence or damage the target system electronics rendering it in-operable or reduce its function or cause mission abort. 
     The tail portion generally has a larger cross section than the nose portion with respect to the longitudinal axis, being at least double that of the nose portion (preferably at least four times greater, preferably at least 8 times greater). This enables the projectile to project the electrodes into a mine casing, and to have a suitably powerful (i.e. large) source of electrical energy within it, but without requiring such a high projectile velocity as would be required to project the source of electrical energy into the mine casing. This also reduces the required structural strength of the projectile body, and amount of propellant required to accelerate it. Generally the nose and tail portions are separated by a sleeve, which may advantageously be generally conical, such as to reduce the sudden-ness of deceleration when the tail portion impacts the mine casing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described, purely by way of example, with reference to the accompanying drawings, in which; 
         FIG.  1   a    shows a side elevation cross sectional illustration of a first embodiment of a projectile according to a first aspect of the invention; 
         FIG.  1   b    shows a side elevation illustration of a first embodiment of a projectile according to a first aspect of the invention; 
         FIG.  2   a    shows a side elevation cross sectional illustration of a further embodiment of a mine disposal projectile according to a first aspect of the invention; 
         FIG.  2   b    shows a side elevation cross sectional illustration of a further embodiment of a projectile according to a first aspect of the invention when in use; 
         FIG.  3   a    shows a side elevation cross sectional illustration of a further embodiment of a projectile according to a first aspect of the invention; 
         FIG.  3   b    shows a side elevation cross sectional illustration of a further embodiment of a projectile according to a first aspect of the invention when in use; 
         FIG.  4   a    shows a side elevation cross sectional illustration of a further embodiment of a projectile according to a first aspect of the invention; 
         FIG.  4   b    shows a side elevation cross sectional illustration of a further embodiment of a projectile according to a first aspect of the invention when in use; 
         FIG.  5   a    shows a side elevation cross sectional illustration of a further embodiment of a projectile according to a first aspect of the invention; 
         FIG.  5   b    shows a side elevation cross sectional illustration of a further embodiment of a projectile according to a first aspect of the invention when in use; 
         FIG.  6   a    shows a side elevation cross sectional illustration of a further embodiment of a projectile according to a first aspect of the invention; 
         FIG.  6   b    shows a side elevation cross sectional illustration of a further embodiment of a projectile according to a first aspect of the invention when in use; and 
         FIG.  7    shows a flow diagram illustrating a method according to a second aspect of the invention. 
     
    
    
     The drawings are for illustrative purposes only and are not to scale. 
     DETAILED DESCRIPTION 
       FIGS.  1   a  and  1   b    show an illustration of an embodiment of the first aspect of the invention. A projectile  101  is shown, having a projectile body  102  comprising a nose portion  103  and a tail portion (not shown). In this embodiment the projectile body is approximately 10 cm the length (along the longitudinal axis) and has a diameter of approximately 3 cm. A first electrode  105  extends the length of the projectile, with a first portion of the first electrode  105  forming the nose portion  103  and a second portion of the first electrode  105  extending internally along the length of the tail portion (not shown). The nose portion  104  is substantially conical in shape. A second electrode  106  is tubular in shape and is arranged coaxially about a portion of the length of the first electrode  105 . The second electrode  106  forms the outer surface of the tail portion  104  of the projectile body  102 . In this embodiment the first and second electrodes are formed from tungsten. An insulator  107  is arranged between the first electrode  105  and the second electrode  106  along the length of the tail portion  104 . In this embodiment, the insulator  107  is a ceramic, for example, Boron Nitride or Cubic Zirconia, but insulator  107  could equally be another suitable insulating material, for example, a plastic, such as, PTFE or ABS. The first electrode and the second electrode are separated along the longitudinal axis by distance A, which in this embodiment is approximately 2 mm in distance. such that an electrical discharge can flow between the first electrode  105  and the second electrode  106 , for example in the direction indicated by arrow B. The surface of the first electrode  105  and the second electrode  106  are arranged so as to be connectable to a source of electrical energy by welding. 
       FIGS.  2   a  and  2   b    show an illustration of a different embodiment of the first aspect of the invention. A projectile  201  is shown, having a projectile body  202  comprising a nose portion  203  and a tail portion (not shown). A first electrode  205  extends the length of the projectile, with a first portion of the first electrode  205  forming the nose portion  203  and a second portion of the first electrode  205  extending internally along the length of the tail portion (not shown). The nose portion  204  is substantially conical in shape. A second electrode  206  is tubular in shape and is arranged coaxially about a portion of the length of the first electrode  205 . The second electrode  206  forms the outer surface of the tail portion (not shown) of the projectile body  202 . An insulator  207  is arranged between the first electrode  205  and the second electrode  206  along the length of the tail portion (not shown). The first electrode and the second electrode are separated along the longitudinal axis such that an electrical discharge (not shown) can flow between the first electrode  105  and the second electrode  106 . In  FIG.  2   b    the projectile  201  is shown partially embedded within the mine  209  (partially shown) having penetrated the mine casing  210  (partially shown). The second electrode  206  is deformable such that on penetration of the mine casing a portion of the second electrode  208  contacts the insulator  207  so as to deform the portion of the second electrode  208  away from the projectile body and into the explosive material  211 . Therefore, the separation distance through which the electrical discharge can flow is increased. The surface of the first electrode  205  and the second electrode  206  are arranged so as to be connectable to a source of electrical energy by welding. 
       FIGS.  3   a  and  3   b    show an illustration of a further embodiment of the first aspect of the invention. A projectile  301  is shown, having a projectile body  302  comprising a nose portion  303  and a tail portion (not shown). A first electrode  305  extends the length of the projectile, with a first portion of the first electrode  305  forming the nose portion  303  and a second portion of the first electrode  305  extending internally along the length of the tail portion (not shown). The nose portion  304  is substantially conical in shape. A second electrode  306  is tubular in shape and is arranged coaxially about a portion of the length of the first electrode  305 . The second electrode  306  forms the outer surface of the tail portion (not shown) of the projectile body  302 . An insulator  307  is arranged between the first electrode  305  and the second electrode  306  along the length of the tail portion (not shown). The first electrode and the second electrode are separated along the longitudinal axis such that an electrical discharge (not shown) can flow between the first electrode  305  and the second electrode  306 . The tail portion (not shown) has a flange  312  located at the opposing end from the nose portion  303 . The flange  312  has a diameter greater than the rest of the projectile body  302 . In  FIG.  3   b   , the projectile  301  is shown partially embedded within the mine  309  (partially shown) having penetrated the mine casing  310  (partially shown). The flange  312  has controlled the degree of penetration of the projectile body  302  such that the nose portion  302  and a portion of the tail portion (not shown) have penetrated the mine casing  310  and are located internally to the mine  309 . A portion of the tail portion (not shown) remains external to the mine. The surface of the first electrode  305  and the second electrode  306  are arranged so as to be connectable to a source of electrical energy by welding. 
       FIGS.  4   a  and  4   b    show an illustration of a further embodiment of the first aspect of the invention. A projectile  401  is shown, having a projectile body  402  comprising a nose portion  403  and a tail portion  404 . A first electrode  405  extends from the tip of the nose portion  403  of the projectile body  402  internally along a portion of the length or the tail portion  404 . The tip of the nose portion  404  is formed from a portion of the first electrode  405 . The nose portion  404  is substantially cylindrical in shape. A second electrode  406 , being tubular in shape, is arranged coaxially about a portion the first electrode  405 . The second electrode  406  forms a portion of the outer surface of the nose portion  403  of the projectile body  402 . An insulator  407  is arranged between the first electrode  405  and the second electrode  406  along a portion of length of the tail portion  404 . The first electrode  405  and the second electrode  406  are separated along the longitudinal axis such that an electrical discharge (not shown) can flow between the first electrode  405  and the second electrode  406 . The projectile  401  comprises and integral source of electrical energy, in the form of a capacitor  413 . The capacitor  413  is charged using the integral battery  414  which is controlled by the integral battery control module  415 . The capacitor is electrically connected to the second electrode  406  via the tail portion casing  418 . The capacitor is arranged in the tail portion  404  between a first cavity  416  and a second cavity  417 . The first and second cavities  416 ,  417  are filled with air. A compressible crumple ring  418  is located between the capacitor  409  and a keel  419 . The keel  419  comprises a conductive switch element  420  to which the first electrode  405  is electrically connected. The capacitor is movable along the longitudinal axis of the tail portion  404  responsive to the penetration of the mine casing  410  by the projectile  401 . Upon penetration of the mine casing  410  the capacitor  413  moves along the longitudinal axis towards the nose portion  403  by compressing the crumple ring  418 . As the capacitor  413  moves towards the nose portion  403  the first cavity  416  becomes reduced in volume and the second cavity  417  becomes increased in volume. Air can pass from the first cavity  416  to the second cavity  417  through channels around the outer edge of the capacitor (not shown). During impact with the mine casing the air transfer between the first and second cavities  416 ,  417  produces a damping effect reducing the impact stress on the capacitor  413 . The movement of the capacitor  413  towards the nose portion  403  closes the distance between the switch element  417  and the capacitor  413  enabling an electrical current to pass from the capacitor  413  to the switch element  417  and along the length of the first electrode  405  thereby electrically connecting the capacitor to the second electrode  406 . As second electrode becomes electrically connected to the capacitor an electrical discharge flows between the first electrode  406  and the second electrode  407  through the explosive material  411 . 
     The tail portion  404  has a diameter greater than the nose portion  403  of the projectile body  402 . The tail portion  404  thereby acts as a retaining means controlling the degree of penetration of the projectile  401  into the mine  409 .  FIG.  4   b    shows the projectile  401  partially embedded within the mine  409  (partially shown) having penetrated the mine casing  410  (partially shown). The degree of penetration of the projectile body  402  in controlled such that the nose portion  402  has penetrated the mine casing  410  and is located internally to the mine  409  and the tail portion  404 , being of greater diameter than the nose portion,  403  remains external to the mine  409 . 
       FIGS.  5   a  and  5   b    show an illustration of a further embodiment of the first aspect of the invention. A projectile  501  is shown, having a projectile body  502  comprising a nose portion  503  and a tail portion  504 . A first electrode  505  extends from the tip of the nose portion  503  of the projectile body  502  internally along a portion of the length or the tail portion  504 . The tip of the nose portion  504  is formed from a portion of the first electrode  505 . The nose portion  504  is substantially cylindrical in shape. A second electrode  506 , being tubular in shape, is arranged coaxially about a portion the first electrode  505 . The second electrode  506  forms a portion of the outer surface of the nose portion  503  of the projectile body  502 . The second electrode  506  extends internally along a portion of the length or the tail portion  504 . An insulator  507  is arranged between the first electrode  505  and the second electrode  506  along a portion of the length of the nose and the tail portions  503 ,  504 . The first electrode  505  and the second electrode  506  are separated along the longitudinal axis such that an electrical discharge (not shown) can flow between the first electrode  505  and the second electrode  506 . The projectile  501  comprises and integral source of electrical energy, in the form of a capacitor  513 . The capacitor  513  is charged using an integral battery  514  which is controlled by the integral battery control module  515 . The first electrode  505  extends internally into the capacitor  513  and is thereby electrically connected to the capacitor. The second electrode  506  is partially arranged coaxially about the outer surface of the capacitor  515  and is thereby electrically connected to the capacitor. The capacitor is arranged in the tail portion  504  between a first cavity  516  and a second cavity  517  (which may form a combined cavity, or may be a pair of distinguishable differential pressure chambers). The first and second cavities  516 ,  517  may be filled with a compressible or incompressible medium (such as paraffin wax, silicone or air). The capacitor is movable along the longitudinal axis of the tail portion  504  responsive to the penetration of the mine casing  510  by the projectile  501 . Upon penetration of the mine casing  510  the capacitor  513  moves along the longitudinal axis towards the nose portion  503  by compressing the wax located in the first cavity  516 . During impact, heating of the projectile causes the wax to become at least partially molten. Holes (not shown) are provided in the tail portion casing  522  through which the wax located in the first cavity can flow and escape the mine projectile casing. The compression and evacuation of the wax from the first cavity  516  produces a damping effect reducing the impact stress on the capacitor  513  and any associated electronics. 
     The second electrode  506  is deformable such that on penetration of the mine casing, as the capacitor  513  moves towards the nose portion  503 , a portion of the second electrode  508  contacts the insulator  507  deforming the portion of the second electrode  508  away from the projectile body  502  and into the explosive material  511 . Therefore, the electrodes form an electrical current path through the explosive material. 
     The tail portion  504  has a diameter greater than the nose portion  503  of the projectile body  502 . The tail portion  504  thereby acts as a retaining means controlling the degree of penetration of the projectile  501  into the mine  509 .  FIG.  5   b    shows the projectile  501  partially embedded within the mine  509  (partially shown) having penetrated the mine casing  510  (partially shown). The degree of penetration of the projectile body  502  is controlled such that the nose portion  502  has penetrated the mine casing  510  and is located internally to the mine  509  and the tail portion  504 , being of greater diameter than the nose portion,  503  remains external to the mine  509 . 
       FIGS.  6   a  and  6   b    show an illustration of a further embodiment of the first aspect of the invention. A projectile  601  is shown, having a projectile body  602  comprising a nose portion  603  and a tail portion  604 . Except where stated like parts in  FIGS.  6   a  and  6   b    match those in the embodiment shown in  FIGS.  5   a    and  6   b.    
     First electrode  605  and second electrode  606  extend forward through the nose portion  603 . In this embodiment an outer wall of the nose portion (or in this case also of the projectile body) forms the second electrodes  606 . A conduction path is established (in event that there is a dielectric surrounding the nose portion) between the pointed tip of second electrode  606  and the circular tip of first electrode  605 , but otherwise are separated by an insulator  607 . The first electrode  605  and the second electrode  606  are separated along the longitudinal axis such that an electrical discharge (not shown) can flow between the first electrode  605  and the second electrode  606 . 
     The projectile  601  comprises and integral source of electrical energy, in the form of a capacitor  613 . The capacitor  613  is charged using an integral battery  614  which is controlled by an integral battery control module (not shown). The first electrode  605  is connected to the capacitor  613  by a sliding electrical connection  618 , and is thereby electrically connected to the capacitor. The second electrode  606  is connected to the capacitor only in the event that the capacitor slides within a cavity within the tail portion  604  forwards to connect to pressure/touch or sliding electrical connector  619 . 
     The cavity may be filled with a compressible or incompressible medium (such as paraffin wax, silicone or air) so long as this does not prevent electricity flowing across the two connectors  618  and  619 . The capacitor is movable along the longitudinal axis of the tail portion  604  responsive to the penetration of the mine casing  610  by the projectile  601 . Upon penetration of the mine casing  610  the capacitor  613  moves along the longitudinal axis towards the nose portion  603  (e.g. by compressing/displacing the substance/wax) located in the cavity. If a wax or wax-like substance is used then during impact, heating/heating/shear forces caused by the projectile causes the wax (or other substance) to become at least partially molten. Holes (not shown) are provided in the tail portion casing  622  through which the wax located in the cavity can flow and escape the mine projectile casing. The compression and evacuation of the wax from the cavity produces a damping effect reducing the impact stress on the capacitor  613  and any associated circuitry/electronics that may slide along with it. 
     The tail portion  604  has a diameter greater than the nose portion  603  of the projectile body  602 . The tail portion  604  thereby acts as a retaining means controlling the degree of penetration of the projectile  601  into the mine  609 .  FIG.  6   b    shows the projectile  601  partially embedded within the mine  609  (partially shown) having penetrated the mine casing  610  (partially shown). The degree of penetration of the projectile body  602  is controlled such that the nose portion  602  has penetrated the mine casing  610  and is located internally to the mine  609  and the tail portion  604 , being of greater diameter than the nose portion,  603  remains external to the mine  609 . 
     The nose portion  603  shows a space in front of the central electrode, behind the penetrating tip (which in any embodiment could be a dense and hard penetrating material such as tungsten). In the case that the first electrode is cylindrical around the second electrode then this is a cavity which could filled with the aforementioned energetic material. Alternatively if the first electrode is not cylindrical, but rather perhaps in the form of two rods either side of the second electrode, then the space will become filled with the explosive within the mine. In the case that another material such as salt water is used, this may be introduced between the electrodes during use, either by the user or by immersing the projectile into the material (water, typically salt water). In this case the nose portion has an ingress path (not shown) to allow the material to ingress between the electrodes. 
     Note that the term ‘between’ relates to the path that an electrical discharge would take between the two electrodes—if there is an insulator in the way of a straight line electrical discharge, then the discharge path will instead go around the insulator and this path should be considered to be between the electrodes irrespective of it not being a straight path. 
       FIG.  7    shows an illustration of a further embodiment of the first aspect of the invention. A projectile is provided according to a first aspect of the invention ( 630 ) as illustrated in the embodiment of  FIGS.  2   a  and  2   b   . The projectile is launched from a launch tube towards a mine ( 631 ). The casing of the mine is pierced by the projectile ( 632 ) such that the projectile is partially embedded within the mine as shown in the embodiment of  FIG.  2   a   . A voltage is applied between the first electrode and the second electrode of the projectile wherein the voltage is of sufficient magnitude to so as to cause an electrical discharge to flow between the first electrode and the second electrode through the explosive material of the mine so as to initiate an explosive reaction. ( 633 ).