Explosive firing train with a single explosive transfer interface

Abstract

An EFI or LEEFI provides enhanced detonation energy sufficient to directly detonate a main charge to improve the reliability and ease the qualification of an explosive firing train. This is accomplished by forming the EFI's output charge from an explosive material typically used as a booster explosive (e.g., PBXN-5, CH-6 and Composition A5) rather than a primary explosive and making the diameter of the output charge greater than the diameter of the barrel thus increasing the total mass of the output charge. The explosive firing train now requires only a single explosive transfer interface. For use in military grade munitions, the EFI's casing is formed with one or more vent holes radially adjacent the output charge.

Claims

1. An explosive firing train, comprising: an explosive foil initiator (EFI); a main charge; and a single explosive transfer interface on the main charge, wherein the EFI includes a circuit positioned in the bottom of a lower casing with a plurality of leads extending therethrough and a barrel having a through hole and an output charge positioned in an upper casing against and substantially aligned with the barrel through hole, a diameter D.sub.oc of the output charge being greater than a diameter D.sub.b of the barrel, said output charge having a lower detonation threshold and explosive energy than the main charge; wherein in response to an electric stimulus, the circuit accelerates a flyer plate through the barrel's through hole to impact and detonate the output charge, which in turn impacts the single explosive transfer interface to detonate the main charge.

2. The explosive firing train of claim 1, wherein plasma from a foil on the circuit drives another thin plastic or metal foil to create the flyer plate.

3. The explosive firing train of claim 1, where D.sub.oc is at least 2D.sub.b.

4. The explosive firing train of claim 3, wherein D.sub.b is between 0.5 inches and 1 inch and D.sub.oc is between 1 and 3 inches.

5. The explosive firing train of claim 3, wherein a diameter Due is between 2.8 and 3 inches.

6. The explosive firing train of claim 1, where in the output charge is selected from one of PBXN-5, CH-6 and Composition A5.

7. The explosive firing train of claim 1, wherein the output charge is not HNS or RSI-007.

8. The explosive firing train of claim 1, wherein the main charge is selected and the output charge is not selected from PBXN-9, LX-14, PBXN-110, PBXN-109 or PBXN-112.

9. The explosive firing train of claim 1, wherein the output charge has a detonation threshold of between 1 to 3 Gpa of shock pressure.

10. The explosive firing train of claim 9, wherein the output charge when detonated reaches a detonation pressure of between 27 to 38 Gpa and a detonation velocity of between 8,100 to 10,000 m/s.

11. The explosive firing train of claim 1, wherein the upper casing includes one or more radial vent holes.

12. The explosive firing train of claim 1, wherein only a single output charge resides in the upper casing.

13. An explosive firing train, comprising: an explosive foil initiator (EFI); a main charge having a fuze well with an inner diameter of 3 inches; and a single explosive transfer interface on the main charge, wherein the EFI includes a circuit positioned in the bottom of a lower casing with a plurality of leads extending therethrough and a barrel having a through hole and an output charge positioned in an upper casing against and substantially aligned with the barrel through hole, a diameter D.sub.oc of the output charge being greater than a diameter D.sub.b of the barrel, said output charge having a lower detonation threshold and explosive energy than the main charge; wherein a diameter Duc of the upper casing is between 2.8 and 3.0 inches and D.sub.oc>=5*D.sub.b wherein in response to an electric stimulus, the circuit accelerates a flyer plate through the barrel's through hole to impact and detonate the output charge, which in turn impacts the single explosive transfer interface to detonate the main charge; wherein said output charge has a detonation threshold of 1 to 3 Gpa of shock pressure and when detonated reaches a detonation pressure of 27 to 38 Gpa and a detonation velocity of 8,100 to 10,000 m/s.

14. The explosive firing train of claim 13, wherein plasma from a foil on the circuit drives another thin plastic or metal foil to create the flyer plate.

15. The explosive firing train of claim 13, where in the output charge is selected from one of PBXN-5, CH-6 and Composition A5.

16. The explosive firing train of claim 13, wherein the output charge is not HNS and RSI-007.

17. The explosive firing train of claim 13, wherein the upper casing includes one or more radial vent holes.

18. The explosive firing train of claim 13, wherein main charge has a fuze well with an inner diameter of 3 inches, wherein the upper casing has a diameter Duc between 2.8 and less than 3 inches, wherein D.sub.oc>=5*D.sub.b.

19. The explosive firing train of claim 13, wherein the upper casing includes one or more radial vent holes.

20. The explosive firing train of claim 13, wherein the main charge is selected and the output charge is not selected from one of PBXN-9, LX-14, PBXN-110, PBXN-109 or PBXN-112.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1, as described above, illustrates an embodiment of an explosive firing train;

(2) FIG. 2, as described above, illustrates the detonation energies and detonation thresholds of the primary explosive, booster explosive and main charge;

(3) FIG. 3, as described above, is a section view of a conventional EFI;

(4) FIG. 4, as described above, is a perspective view of a fuze booster;

(5) FIGS. 5A-5B are different section views of an embodiment of an EFI designed to enhance detonation energy;

(6) FIG. 6 illustrates an embodiment of an explosive train having a single explosive transfer interface between the EFI and the main charge; and

(7) FIG. 7 illustrates the detonation energies and detonation thresholds of the EFI's output charge and main charge.

DETAILED DESCRIPTION

(8) During testing and qualification of conventional EFI components and explosive firing trains, it was discovered that an EFI's flyer plate delivered sufficient energy (shock pressure and duration) to reliably initiate the fuze booster. This was an unexpected result. Conventional wisdom was that a highly sensitive primary explosive was required to initiate the explosive firing train. The 3-stage explosive firing train is well-established and accepted practice to safely and reliably detonate high explosives. Because these primary explosives are typically expensive, only a small amount sufficient to generate enough energy to initiate the fuze booster was used.

(9) The present disclosure provides an EFI or LEEFI, both referred to herein as an EFI, that provides enhanced detonation energy sufficient to directly detonate a main charge to improve the reliability and case the qualification of an explosive fire train. This is accomplished by forming the EFI's output charge from an explosive material typically used as a booster explosive rather than a primary explosive and making the diameter of the output charge greater than the diameter of the barrel thus increasing the total mass and detonation energy of the output charge. Elimination of an explosive transfer interface from the explosive firing train is highly desirable. For use in military grade munitions, the EFI's casing is formed with one or more vent holes radially adjacent the output charge.

(10) Referring now to FIGS. 5A-5B, an enhanced detonation energy EFI 500 includes a lower casing 502 having diameter Die and an upper casing 504 having a diameter Due. The casings are typically metal. A circuit or EFI chip 506 is positioned in the bottom of the lower casing with a plurality of leads 508 extending therethrough. A barrel 510 having a through hole 512 is positioned on top of the circuit. An output charge 514 is positioned in the upper casing against and substantially aligned with the barrel through hole 512. In a preferred embodiment, the EFI includes only a single output charge 514. An IM liner 515 may be positioned around output charge 514. The diameter D.sub.oc of the output charge is greater than the diameter D.sub.b of the barrel. In response to an electric stimulus, the circuit propels a flyer through the barrel's through hole to impact and detonate the output charge 514.

(11) In an embodiment, the output charge diameter D.sub.oc is at least 2 the barrel diameter D.sub.b. The barrel diameter D.sub.b may be 0.25 to 0.5 and the output charge diameter D.sub.oc may be 1 to 3. Conventional military grade explosives include a fuze well that has a 3 diameter. For these explosives the diameter of the upper casing Due would be just slightly less than 3 (e.g. 2.8 to 2.95) and at least 5 the barrel diameter to provide the required radial gapping.

(12) In an embodiment, the output charge has the detonation threshold and explosive energy characteristics of a conventional booster explosive. The detonation threshold is in a range between 1 to 3 Gpa (Giga Pascals) of shock pressure and the explosive energy is defined by a detonation pressure in a range between 27 to 38 Gpa and a detonation velocity in a range between 8,100 to 10,000 m/s. The output charge may be selected from one of PBXN-5, CH-6 and Composition A5. The output charge is not a conventional primary explosive such as HNS, RSI-007 or a main charge such as PBXN-9, LX-14, PBXN-110, PBXN-109 and PBXN-112. In certain embodiments, the upper casing is provided with one or more vent holes 516 that expose the IM liner 515.

(13) Referring now to FIG. 6, an embodiment of an explosive firing train includes 600 an enhanced detonation energy EFI 602, a main charge 604 and a single explosive transfer interface 606 on the main charge. Main charge 604 includes an axial fuze well 608 that is standardly 3 in diameter for military explosives. The EFI 602 is positioned in the fuze well with a small axial and radial gapping between the EFI's upper casing and the inner walls of the fuze well to define the single explosive transfer interface. The EFI's upper casing diameter, hence barrel diameter, is slightly less than 3 inches to provide the proper gapping. One or more vent holes are formed in the EFI's upper casing adjacent the radial gap. Alternately, the EFI 602 could be positioned to initiate the main charge in a solely axial or solely radial configuration with a single explosive transfer interface.

(14) Referring now to FIGS. 6 and 7, in response to an electric stimulus, the EFI 602 propels a flyer through the barrel's through hole to impact and detonate the output charge, which in turn impacts the single explosive transfer interface 606 to detonate the main charge 604. The flyer plate impacts the EFI output charge with sufficient detonation energy E1, exceeding the output charge's detonation threshold T1, to detonate the output charge. In turn, the detonation wave from the EFI's output charge impacts the single explosive transfer interface 606 with sufficient detonation energy E2, exceeding the main charge's detonation threshold T2, to detonate the main charge.

(15) While several illustrative embodiments of the disclosure have been shown and described, numerous variations and alternate embodiments will occur to those skilled in the art. Such variations and alternate embodiments are contemplated, and can be made without departing from the spirit and scope of the disclosure as defined in the appended claims.