US20100269723A1

US20100269723A1 - Metal binders for thermobaric weapons

Info

Publication number: US20100269723A1
Application number: US11/504,808
Authority: US
Inventors: George D. Hugus; Edward W. Sheridan; George W. Brooks
Original assignee: Lockheed Martin Corp
Current assignee: Lockheed Martin Corp
Priority date: 2006-08-16
Filing date: 2006-08-16
Publication date: 2010-10-28

Abstract

A munition includes a penetrator casing; and a payload, the payload composed of an explosive material dispersed in a metallic binder material. Related methods are also described. A method is also provided that includes forming an energetic material, combining the energetic material with a metallic binder material to form a mixture, and shaping the mixture to form a composite structural munition component.

Description

FIELD OF THE DISCLOSURE

The present disclosure relates to explosive compositions for structural components of munitions. More specifically, the present disclosure relates to, at least in part, explosive energetic materials dispersed in a metallic matrix.

BACKGROUND

In the discussion that follows, reference is made to certain structures and/or methods. However, the following references should not be construed as an admission that these structures and/or methods constitute prior art. Applicant expressly reserves the right to demonstrate that such structures and/or methods do not qualify as prior art.
While munitions capable of hard target penetration utilize many specially designed components and sub-systems to deliver lethal energy to a target, they are substantially comprised of two key elements: 1) a warhead fill which stores and releases explosive energy into a target when triggered, and 2) a penetrator casing that contains the warhead fill and delivers the warhead intact into a hardened target. Many hardened (or buried) targets, once breached by a penetrator, demonstrate a particularly pronounced sensitivity to the blast from thermobaric warheads in relation to the effect from a high explosive warhead with comparable explosive energy content. Thermobaric warhead fills are typically composed of detonable energetic material blends that include high explosives, an oxidizer, a dispersed reactive metal power (often aluminum), and a polymeric binder that holds the energetic materials together. In order to maximize the penetrating capability of a warhead, four primary trades are made involving the shape of the penetrator nose, weight of the penetrator, impact velocity of the penetrator, and cross-sectional area of the penetrator. The achievable depth of penetration is considered to be proportional to the weight and to the impact velocity of the penetrator, but inversely proportional to its cross-sectional area. Often, the impact velocity is limited as in the case of dropped bombs, and cannot easily be increased for enhanced hard target penetration. The overall cross-sectional area of the munition (which includes both the penetrator casing and the energetic fill) can be reduced to facilitate penetration but a corresponding reduction in warhead capacity per unit length is then observed. A smaller cross-sectional area will also result in a reduced weight/reduced blast trade unless the weapon is lengthened, which may prevent its use on current and future weapon delivery platforms that have limited weapon storage capacity. When considering the weight of the penetrator munition in terms of its volume, the density of a steel alloy penetrator casing is typically 6.5 to 8.5 g/cm³, while the relatively low density warhead fill contained within it is perhaps 1.5-2.5 g/cm³, and the composite, or combined density falling somewhere in between. If the overall weapon weight per unit volume (i.e., density) were increased thus facilitating enhanced hard target penetration, and a tailored thermobaric energy release produced, hard target lethality can be optimized.
Thus, it would be advantageous to provide an improved munition which may address one or more of the above-mentioned concerns. Related publications include U.S. Pat. Nos. 3,961,576 and 6,679,960, the entire disclosure of each of these publications is incorporated herein by reference.

SUMMARY OF THE INVENTION

According to the present invention, there is provided a munition which possesses one or more of: improved target penetration, improved density characteristics, and improved thermobaric properties.
According to the present invention there is provided a munition comprising: a penetrator casing; and a payload, the payload comprising an explosive material dispersed in a metallic binder material.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The following detailed description of preferred embodiments can be read in connection with the accompanying drawings in which like numerals designate like elements and in which:

FIG. 1 is a longitudinal sectional view of a schematic illustration of a munition formed according to the principles of the present invention.

FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates a munition 10 formed according to the principles of the present invention, and according to one embodiment thereof. The munition illustrated in FIG. 1 can be in the form of a boosted penetrating bomb. The munition 10 may include a penetrator comprising a casing 12, as well as containing a payload 14, preferably in the form of an explosive medium. Optionally, a shaped charge liner or casing insert may be provided within the casing 12 (not shown). Other payloads may be used or included, for example, fragmenting bomblets, chemicals, incendiaries, and/or radioactive materials.
As illustrated in FIG. 2, the payload 14 generally comprises a metallic binder material 20 having a detonable explosive material 30 dispersed therein.
The binder material 20 can be formed from any suitable metal or combination of metals and/or alloys. According to one embodiment, the binder material 20 comprises a metal or alloy that when combined with the explosive component (or components), the pressure used to compact and densify the structure is of magnitude below that causing autoignition of the explosive materials. According to a further embodiment, the binder material 20 comprises one or more of: bismuth, lead, tin, aluminum, magnesium, titanium, gallium, indium, and alloys thereof. By way of non-limiting example, suitable binder alloys include (percentages are by mass): 52.2% In/45% Sn/1.8% Zn; 58% Bi/42% Sn; 60% Sn/40% Bi; 95% Bi/5% Sn; 55% Ge/45% Al; 88.3% AI/11.7% Si; 92.5% Al/7.5% Si; and 95% Al/5% Si. In addition, the binder material 20 may optionally include one or more reinforcing elements or additives. Thus, the binder material 20 may optionally include one or more of: an organic material, an inorganic material, a metastable intermolecular compound, and/or a hydride. By way of non-limiting example, one suitable additive could be a polymeric material that releases a gas upon thermal decomposition. The composite can also be reinforced by adding one or more of the following organic and/or inorganic reinforcements: continuous fibers, chopped fibers, whiskers, filaments, a structural preform, a woven fibrous material, a dispersed particulate, or a nonwoven fibrous material. Other suitable reinforcements are contemplated.
The binder material 20 of the present invention may be provided with any suitable density. For example, the binder material 20 of the present invention may be provided with the density of at least about 6.5 g/cm³, or at least about 8.5 g/cm³, or at least about 10.0 g/cm³. According to a further embodiment, the binder material 20 of the present invention is provided with a density of about 6.5 g/cm³to about 8.5 g/cm³, or about 6.5 g/cm³to about 14.0 g/cm³.
Component 30 may comprise any suitable explosive material. The explosive 30 can be formed from any suitable explosive composition. By way of non-limiting example, the high explosive composition can be a suitable explosive, such as: PBXN-109, PBX-108, PBXIH-135, AFX-757, PBXC-129, HAS-13, RDX, and Tritonal. The volumetric proportion of metal binder with respect to explosive material(s) may be in the range of 3-60%. The explosive material 30 may have any suitable morphology (i.e., powder, flake, crystal, etc.).
The payload 14 of the present invention can be formed according to any suitable method or technique.
Generally speaking, a suitable method for forming a payload of the present invention includes forming an explosive material, combining the energetic material with a metallic binder material to form a mixture, and shaping the combined explosive material and metallic binder material mixture to form a payload.
The mixture can be accomplished by any suitable technique, such as milling or blending. Additives or additional components can be added to the mixture. As noted above, such additives or additional components may comprise one or more of: an organic material, and inorganic material, a metastable intermolecular compound, and/or a hydride. In addition, one or more reinforcements may also be added. Such reinforcements may include organic and/or inorganic materials in the form of one or more of: continuous fibers, chopped fibers, whiskers, filaments, a structural preform, dispersed particulate, a woven fibrous material, or a nonwoven fibrous material. Optionally, the explosive material, the metallic binder material, the above-mentioned additives and/or the above-mentioned reinforcements can be treated in a manner that functionalizes the surface(s) thereof, thereby promoting wetting of the component(s) in the matrix of metallic binder. Such treatments are per se known in the art. For example, the particles can be coated with a material that imparts a favorable surface energy thereto.
This mixture can then be shaped thereby forming a payload having a desired geometrical configuration. The payload can be shaped by any suitable technique, such as molding or casting, pressing, forging, machining, cold isostatic pressing, or hot isostatic pressing. The payload component can be provided with any suitable geometry.
Alternatively, the mixture may be poured directly into a casing, optionally under a vacuum, and solidified therein.
There are number of potential applications for munitions formed according to principles of the present invention. Non-limiting exemplary weapons and/or weapons systems which may incorporate payloads or payload components formed according to the principles of the present invention include a BLU-109 warhead or other munition such as BLU-109/B, BLU-113, BLU-116, JASSM-1000, J-1000, and the JAST-1000.
Utilization of a metal binder as described herein as a replacement for polymeric binders can potentially introduce many attractive ballistic and thermobaric controls on the explosive behavior of the penetrator munition. For example, the metal binders may comprise alloys of relatively high density typically in the range of about 6.5 to 14.0 g/cm³(compared to polymeric binders which can be expected to have densities near 2.5 g/cm³). By replacing currently used polymeric binders with a metal binder, the overall weapon density will increase resulting in enhanced target penetration capability. Upon initiation of a thermobaric blast, metal binder particles will be propelled away from the warhead while suspended within the reacting high explosive reaction products. Metal binder particles will likely exhibit a desirable non-ideal behavior due to their high density and large molecular weights in the blast that lag in velocity (due to momentum effects) and temperature (due to heat transfer effects) behind the lighter weight gaseous explosive products such as Co, Co_e, N₂, and H₂O. This favorable non-ideal behavior suggests that the sharpness of the overpressure peak during the initial blast will be somewhat attenuated due to thermal and kinetic energy storage of released high explosive energy into the ejected metal binder particles. As the blast progresses, release of the kinetic and thermal energy stored in the metal binder particles will ideally result in an extension of the time at overpressure and enhanced damage to the target. Metal binders according to the present invention have fuel energies comparable to metals burning in oxygen such as zinc, iron, molybdenum, and tungsten, and as such, a given metal binder may effectively impart a significant afterburning component to the thermobaric blast, further extending the overpressure effect. Metal binders are compatible with organic materials, inorganic materials, reactive thin films, metastable intermolecular composites, hydrides, and combinations of all these energetic materials and are considered optional components of the present invention.
To facilitate a uniform dispersion of the explosive metal binder within the explosive warhead explosive matrix, the metal particles may be chemically functionalized in such a way that the surface energy between the metal binder particles and the high explosive is minimized promoting wet-out of the metal (if necessary).
Successful implementation of the above approach permits an enhanced trade-space involving warhead design, achievable hard target penetration, and lethality beyond which is available currently. There is reason to believe that implementation of the metal binder will also serve to aid in addressing the increasingly present insensitive munition requirements imposed on warhead designs.
All numbers expressing quantities of ingredients, constituents, reaction conditions, and so forth used in the specification are to be understood as being modified in all instances by the term “about”. Notwithstanding that the numerical ranges and parameters setting forth, the broad scope of the subject matter presented herein are approximations, the numerical values set forth are indicated as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective measurement techniques.
Although the present invention has been described in connection with preferred embodiments thereof, it will be appreciated by those skilled in the art that additions, deletions, modifications, and substitutions not specifically described may be made without department from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A munition comprising:

a penetrator casing having a first density; and

a payload, the payload comprising a explosive material dispersed in a metallic binder material having a second density;

wherein the second density is at least as great as the first density.

2. The warhead of claim 1, wherein the metallic binder has a density of at least 6.5 g/cm³.

3. The warhead of claim 1, wherein the metallic binder has a density of about 6.5 to 14.0 g/cm³.

4. The warhead of claim 1, wherein the metallic binder material comprises one or more of bismuth, lead, tin, indium, or alloys thereof.

5. The munition of claim 1, wherein the explosive material is flaked, powdered, or crystallized.

6. The munition of claim 1, wherein the payload additionally comprises one or more of: an organic material, and inorganic material, a metastable intermolecular composite, or a metal hydride.

7. The munition of claim 1, wherein the payload is reinforced with one or more reinforcements comprising organic or inorganic materials in the form of: chopped fibers, whiskers, a structural preform, a woven fibrous material, a nonwoven fibrous material, or a dispersed particulate.

8. The munition of claim 7, wherein at least one of the explosive materials, the metallic binder material, and the one or more reinforcements are surface treated to promote wetting.

9. The munition of claim 1, wherein the munition comprises a warhead, and the penetrator casing is at least partially filled with the payload.

10. A method comprising:

forming an explosive material;

combining the explosive energetic material with a metallic binder material to form a mixture; and

introducing the mixture into the interior of a penetrator casing.

11. The method of claim 10, wherein the metallic binder has a density of at least about 6.5 g/cm³.

12. The method of claim 10, wherein the metallic binder has a density of about 6.5 g/cm³to about 14.0 g/cm³.

13. The method of claim 10, wherein the metallic binder material comprises of one more of bismuth, lead, tin, indium, and alloys thereof.

14. The method of claim 10, further comprising adding one or more of the following to the mixture: an organic material, and inorganic material, a metastable intermolecular composite, or a hydride.

15. The method of claim 10, further comprising adding one or more reinforcements of organic or inorganic materials in the form of: chopped fibers, whiskers, a structural preform, a woven fibrous material, a nonwoven fibrous material, or a dispersed particulate.

16. The method of claim 10, further comprising treating the surface of at least one of the explosive materials, the metallic binder material, and the one or more reinforcements in order to promote wetting.

17. The method of claim 13, further comprising shaping the mixture prior to introducing it into the penetrator casing.