Abstract
A stand-off breaching device (20) for breaching a barrier, comprising a housing (21), an explosive main charge (24) having a barrier-end (25) and a rear-end (26), a detonator (29), and means for initiating the detonator (27) when the explosive main charge (24) is at a preselected distance from a barrier. The detonator (29) is configured to detonate explosive main charge (24) at the rear-end (26) such that the resultant detonation wave propagates through the explosive main charge (24) towards the barrier-end (25) and the barrier being breached. This configuration provides more efficient transfer of explosively generated overpressure towards a barrier, thereby enabling the use of explosive main charges (24) with reduced mass, and the associated improvements in operator safety. The breaching device (20) is particularly suited to use in door breaching operations.
Claims
1. A stand-off breaching device for breaching a barrier, comprising a housing, an explosive main charge having a barrier-end and a rear-end, a detonator, and means for initiating the detonator when the explosive main charge is at a preselected distance from a barrier, wherein the detonator is configured to detonate the explosive main charge at the rear-end, such that in-use a barrier can be breached by an explosively generated overpressure.
2. The stand-off breaching device according to claim 1 wherein the explosive main charge is a conically formed explosive main charge having a substantially circular end and a cone-apex, the conically formed explosive main charge being arranged such that the substantially circular end is the barrier-end and the cone-apex is the rear-end.
3. The stand-off breaching device according to claim 2 wherein the cone-apex is a truncated cone-apex.
4. The stand-off breaching device according to claim 2 wherein the conically formed explosive main charge has an apex-angle in a range of 50 to 70 degrees.
5. The stand-off breaching device according to claim 2 wherein the conically formed explosive main charge further comprises a charge extension formed at the substantially circular end.
6. The stand-off breaching device according to claim 5 wherein the charge extension comprises an inverted truncated cone.
7. The stand-off breaching device according to claim 1 wherein the explosive main charge comprises a multi-point initiated explosive main charge.
8. The stand-off breaching device according to claim 1 wherein the means for initiating the detonator comprises a proximity sensor, the proximity sensor being configured to receive radiation of a predetermined wavelength.
9. The stand-off breaching device according to claim 8 wherein the proximity sensor is configured to transmit radiation of the predetermined wavelength.
10. The stand-off breaching device according to claim 9 wherein the proximity sensor further comprises an electronics module, the electronics module being configured to measure a signal-difference between a transmitted radiation of the predetermined wavelength and a received radiation of the predetermined wavelength, the signal-difference corresponding to a range-to-go.
11. The stand-off breaching device according to claim 10 wherein the electronics module is configured to output a first detonation signal when the range-to-go is less than or equal to the preselected distance.
12. The stand-off breaching device according to claim 11 wherein the preselected distance is between 50 mm and 250 mm.
13. The stand-off breaching device according to claim 11 wherein the means for initiating the detonator further comprises a safe-to-arm unit, the safe-to-arm unit being configured to allow detonation of the explosive main charge upon detecting at least a first post-launch criterion and a generation of the first detonation signal.
14. The stand-off breaching device according to claim 8 wherein the radiation of the predetermined wavelength is acoustic radiation with a wavelength, or range of wavelengths, between 20 kHz and 100 KHz.
15. The stand-off breaching device according to claim 8 wherein the radiation of the predetermined wavelength is electromagnetic radiation with a wavelength, or range of wavelengths, between 800 nm and 1200 nm.
16. The stand-off breaching device according to claim 1 wherein the detonator comprises a firing pin, firing pin actuator and a stab detonator.
17. The stand-off breaching device according to claim 1 further comprising an eject cartridge attached to the housing.
18. The stand-off breaching device according to claim 1 wherein the housing is substantially cylindrical and has a maximum diameter of 40 mm.
19. The stand-off breaching device according to claim 1 wherein the housing is formed from low fragment hazard materials.
20. The stand-off breaching device according to claim 1 further comprising a means for self-destruction.
21. The stand-off breaching device according to claim 1 wherein the explosive main charge has a mass of less than 50 g.
22. The stand-off breaching device according to claim 21 wherein the explosive main charge has a mass less than or equal to 20 g.
23. The stand-off breaching device according to claim 1 further comprising an on-board power supply.
24. The stand-off breaching device of claim 1, wherein the detonator is located adjacent to the rear end of the explosive charge.
25. A barrier breaching system comprising the stand-off breaching device of claim 1 and a launcher, the launcher being suitable for firing the stand-off breaching device towards a barrier.
26. A method of breaching a barrier, the method comprising the steps of: a) Providing a stand-off breaching device comprising a housing, an explosive main charge having a barrier-end and a rear-end, a detonator, and means for initiating the detonator when the explosive main charge is at a preselected distance from a barrier, wherein the detonator is configured to detonate the explosive main charge at the rear-end; b) Locating the stand-off breaching device proximal to the barrier, such that the barrier-end is in facing relations with the barrier and is at the preselected distance from the barrier; and then c) Initiating the detonator using the means for initiating, thereby generating an explosively generated overpressure; such that the barrier is breached by the explosively generated overpressure.
27. An explosive main charge for use in stand-off barrier breaching, comprising a conically formed explosive charge having a substantially circular end and a cone-apex, such that in-use the explosive main charge is arrangeable to have the substantially circular end facing a barrier to be breached, such that the main charge is configured to detonate at the cone-apex to generate an overpressure directed towards the barrier, wherein the explosive main charge further comprises a charge extension extending from the substantially circular end, such that in-use the overpressure directed towards the barrier has a predetermined pressure profile.
28. The explosive main charge of claim 27, wherein the charge extension comprises an inverted truncated cone extending from the substantially circular end.
29. The explosive main charge of claim 28, wherein the inverted truncated cone has a maximum diameter equal to a diameter of the substantially circular end.
30. The explosive main charge of claim 29, wherein the cone-apex of the conically formed explosive charge is a truncated cone apex.
31. The explosive main charge of claim 30, wherein the charge extension further comprises a cylindrical part located between the conically formed explosive charge and the inverted truncated cone.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) Embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings, in which:
(2) FIG. 1 shows a cross-sectional view of a representation of a prior art stand-off breaching round comprising an impact fuze;
(3) FIG. 2 shows a cross-sectional view of a representation of an embodiment of the invention comprising a cylindrical explosive main charge;
(4) FIG. 3 shows a cross-sectional view of a representation of an embodiment of the invention comprising a conically formed explosive main charge;
(5) FIG. 4 shows an illustration of an embodiment of the invention being deployed, the embodiment comprising a proximity sensor, the proximity sensor itself comprising a transceiver;
(6) FIG. 5a shows an illustration of a door barrier being breached without fragmentation;
(7) FIG. 5b shows an illustration of a door barrier being breached with fragmentation;
(8) FIG. 6a shows an illustration of an embodiment of a conically formed explosive main charge with a charge extension, in expanded view;
(9) FIG. 6b shows an illustration of the conically formed explosive main charge of FIG. 6a in perspective view; and
(10) FIG. 7 shows an illustration of an embodiment of a multi-point initiated explosive main charge.
DETAILED DESCRIPTION
(11) FIG. 1 shows a cross-sectional view of a representation of a prior art stand-off breaching round 10 comprising an impact fuze 17. The breaching round 10 comprises a housing 11 and contained within the housing 11 is an explosive main charge 14 with barrier-end 15 and rear-end 16. Attached to the rear of housing 11 is an eject cartridge 18. When deployed the breaching round 10 must impact a barrier to detonate. Upon impact the impact fuze 17 detonates the explosive main charge 14 at the barrier-end 15. The point of detonation of the explosive main charge 14 is typically in the middle (concentric) of the barrier-end 15 of main charge 14. This is particularly inefficient as the detonation must propagate through the explosive main charge 14 towards the rear-end 16 i.e. away from the barrier being breached and towards the user of the breaching device. Furthermore radial over-pressures (parallel to the face of the barrier-end 15) are generated upon detonation, wasting further blast energy. The explosive main charge 14 will typically therefore have a relatively large mass of between 45 g and 100 g to compensate for these inefficiencies. The stand-off breaching device 10 may impact a barrier slightly off axis (i.e. barrier-end 15 may not be perfectly parallel with the plane of the barrier upon impact). As a result, radial over pressures may cause undesirable fragmentation of the barrier back towards the user, forcing the user to stand-off from the barrier at distances in the region of 10-15 m.
(12) FIG. 2 shows a cross-sectional view of a representation of an embodiment of the stand-off breaching device of the invention 20. The stand-off breaching device 20 comprises a housing 21 containing a cylindrical explosive main charge 24 with a barrier-end 25 and a rear-end 26. The housing 21 also contains means for initiating the detonator in the form of a proximity sensor 27. The cylindrical explosive main charge 24, in contrast with the prior art, is detonated at the rear-end 26 by detonator 29. Also provided as part of the means for initiating the detonator, is the safe-to-arm unit 28. The detonator 29 is shown as being electrically connected by electrical wire 30 to the proximity sensor 27, such that when the proximity sensor 27 determines the stand-off breaching device 20 is in sufficient proximity to the barrier to be breached (less than or equal to a preselected distance), the detonator 29 can be triggered and detonate the explosive main charge 24. An on-board power supply is not visible in the figure. The stand-off breaching device 20 further comprises an eject cartridge 31. Advantageously by detonating the explosive main charge 24 at the rear-end 26, the detonation propagates from the rear-end 26 through the explosive main charge 24 towards the breaching end 25, and towards the barrier being breached. As a result the explosively generated overpressure from explosive main charge 24 is more efficiently delivered to the barrier to achieve the breaching effect.
(13) FIG. 3 shows a cross-sectional view of a representation of an embodiment of the invention 32 comprising a conically formed explosive main charge 36. The stand-off breaching device 32 comprises a housing 33 manufactured from a non-metallic material such as nylon or glass reinforced plastic, thereby minimising any fragmentation hazard when the breaching device 32 is used. The conically formed explosive main charge 36 has a substantially circular end as the breaching-end 37 and a truncated cone apex as the rear-end 38. The shape of the main charge 36 has been formed by pressing an explosive material into the conical recess formed between rear-end 38 and breaching-end 37. The conically formed explosive main charge 36 in this embodiment has an apex-angle of 60 degrees. The explosive main charge 36 is detonated at the rear-end 38 and therefore the detonation propagates towards the barrier-end 37 and the barrier being breached. Furthermore, the radial overpressures (wasted energy) are reduced owing to the conical design. As a result, the envisaged mass of the main charge 36 is less than 20 g. The proximity sensor 39 of FIG. 3 comprises an ultrasonic transceiver 40 (for instance a ProWave 400EP250 transceiver) and electronics module 42 (for instance a PIC12LF1822). The on-board power supply 41 is electrically connected to electronics module 42, the electronics module 42 then being electrically connected to transceiver 40 and detonator 44. A safe-to-arm unit 43 is provided that comprises a rotor onto which the stab detonator of detonator 44 is positioned. The rotor is purely mechanical in operation and therefore requires no electrical power. In this particular embodiment, when the stand-off breaching device is launched, the device rotates owing to a rifling effect from the launch apparatus. The rotation exerts a force on stab detonator of detonator 44. The force causes the rotor of safe-to-arm unit to rotate into alignment with firing pin of detonator 44, where it is subsequently locked into position. Therefore when a sufficient number of rotations of the stand-off breaching round have elapsed, the breaching device is ‘armed’ and will detonate when a first detonation signal is generated. During use of breaching device 32, the transceiver 40 constantly transmits towards a barrier to be breached, and receives therefrom, ultrasonic radiation of predetermined wavelength. The electronics module 42 then measures a signal-difference between the transmitted radiation of predetermined wavelength and the received radiation of predetermined wavelength, the signal-difference corresponding to range-to-go. When the range-to-go decreases below a preselected distance, the electronics module 42 generates a first detonation signal and transmits it electrically along electrical wires 46 to the firing pin actuator of detonator 44. The electronics module 42 may calculate the range-to-go based on reading in data from the transceiver 40 when operating in a pulsed transmit/receive mode. For instance, a 4 kHz operating frequency for transceiver 40 would provide 800 samples of data over a 15 m range with −0.2 second flight time, thereby achieving a range fidelity of 1.8 cm. The detonator 44 is a firing pin and firing pin actuator. The firing pin actuator is connected by electrical wires 46 to the proximity sensor 39. The firing pin actuator is a piston actuator and upon receiving the first detonation signal along electrical wire 46, a propellant charge is initiated in the piston actuator via a bridge wire, thereby driving the piston actuator and the firing pin of detonator 44 towards the now aligned stab detonator of detonator 44. As a result of the detonator receiving the first detonation signal (and the resultant stab detonation), the explosive main charge 36 is detonated at the rear-end 38.
(14) FIG. 4 shows an illustration of an embodiment of the stand-off breaching device 51 being used. The breaching device 51 undergoes three phases of deployment. In the ‘launch phase’ a user orientates a launcher 50 towards a barrier to be breached 55 at a particular stand-off distance. The breaching device 51 is ejected from the launcher 50 through use of an eject cartridge (not shown). Upon launch a safe-to-arm unit of breaching device 51 detects at least a first post-launch criterion and ‘arms’ the breaching device 51. The breaching device 51 then enters the ‘sensing phase’ wherein a proximity sensor (not shown) in breaching device 51 transmits radiation of predetermined wavelength 52 and receives said radiation 53 after it is reflected from barrier 55. An electronics module (not shown) inside the proximity sensor processes the transmitted and received radiation and calculates the range-to-go to the barrier 55. When the range-to-go drops below a particular value (the preselected distance), the breaching device 51 enters the terminal phase of deployment. In the terminal phase the electronics module in the proximity sensor generates a first detonation signal. The first detonation signal is received by the detonator of breaching device 51, thereby resulting in detonation of the explosive main charge of breaching device 51. The point of detonation of the explosive main charge is at the rear-end of the charge, therefore the detonation wave (and explosive shockwave 54) propagates towards barrier 55, achieving the desired breaching effect. In different embodiments of the invention, the proximity sensor of breaching device 51 does not transmit radiation of predetermined wavelength 52. Instead the launcher 50 transmits the radiation of the predetermined wavelength 52, with the proximity sensor of breaching device 51 receiving the reflected radiation of predetermined wavelength 53 only.
(15) FIG. 5a shows an illustration of the barrier breaching effect delivered by embodiments of the stand-off breaching device. Part of a door frame 60 and door 61 is shown with handle 62 and locking mechanism 63. The door 61 has been deformed sufficiently along edge 64 so as to disengage locking mechanism 63 from door frame 60. The breaching effect has not resulted in fragmentation of the door 61. In contrast, FIG. 5b shows an illustration of the barrier breaching effect of some prior art impact breaching rounds. Door frame 70 and door 71 are shown, with door 71 featuring an aperture 73 that has been blasted through the door 71 as a result of the detonation of an impact fuze based breaching round. Door 71 would have fragmented upon creation of aperture 73, presenting a hazard to persons or equipment. Embodiments of the invention allow for deformation and forcing open of a barrier, whilst minimising fragmentation of the barrier and therefore minimising risk of harm to the user of the invention.
(16) FIG. 6a provides an illustration of an explosive main charge 80 in expanded view. The explosive main charge 80 comprises a truncated conically formed charge 81 having a rear-end 82 and a barrier-end 83. Extending from the barrier-end 83 is a charge extension comprising a cylindrical part 84 and an inverted truncated cone part 85. FIG. 6b shows the explosive main charge 80 in perspective view. The truncated conically formed charge 81, cylindrical part 84 and inverted cone part 85 are shown as distinct parts, but may be a single pressed explosive charge. Cylindrical part 84 may not be present in some embodiments, and the dimensions and cone apex angles shown in the diagram are illustrative only, and not intended to be limiting.
(17) FIG. 7 provides an illustration of a multi-point initiated explosive main charge 90. The explosive main charge 90 comprises a cylindrical part 91 with barrier-end 92 highlighted for clarity. A central point of detonation 93 is provided with stems 94 to transfer the detonation to points 95a, 95b, 95c and 95d on cylindrical charge part 91. The detonation of cylindrical charge part 91 occurs substantially simultaneously at the multiple positions 95a-d. The central point of detonation 93, stems 94, and cylindrical part 91 comprise explosive material, however each may be encased in suited environmental protection (such as low fragment hazard plastic.
(18) Whilst the embodiments of the invention described comprise proximity sensing, other types of fuzing can be used in the means for initiating the detonator, such as impact fuzes. Impact fuzing can be achieved by providing an extension on the housing that impacts the barrier first, thereby decelerating the stand-off breaching device, said deceleration causing mechanical movement of a pin into a stab detonator, for instance. At the point of detonation the explosive main charge will be at a preselected distance from the barrier as defined by the length of the extension of the housing. The explosive main charge may comprise a number of different explosive compositions, for instance plastic explosive or an aluminised explosive fill may be used.
