Patent Application
20240174581
This patent application is generally directed to pyrotechnic expendable countermeasure decoy flares, and more particularly to ignition systems for pyrotechnic countermeasure decoy flares.
Conventional pyrotechnic infrared (IR) expendable countermeasures, such as decoy flares, are used in aircraft self-protection systems as a deployable expendable munition to counter an infrared homing surface-to-air missile, air-to-air missile, or other heat-seeking weapon. Decoy flares commonly include a pyrotechnic composition based on magnesium or another hot-burning powdered metal composition, with combustion/burning temperatures equal to or hotter than engine exhaust or other components of the aircraft. The aim is to make the IR-guided missile seek out the more attractive heat signature from the flare rather than the aircraft's engines or hot components. The countermeasure flares typically include ignition systems configured to ignite or otherwise activate the pyrotechnic and/or propellant materials within the countermeasure once deployed from the aircraft.
Ignition systems often utilize electrically initiated expulsion or impulse cartridges that eject the expendable from the aircraft dispensing system and contain features that ignite an expendable flare ignition material, such as an igniter pellet upon exit from the dispenser system. This ignition pellet, in turn, quickly generates flame and hot gas that propagates ignition to the body of the expendable or countermeasure flare assembly. Some conventional compositions for the ignition material, however, are susceptible to degradation by moisture exposure or intrusion, which can result in poor aging characteristics and reduced performance of the countermeasure, including complete failure and non-transfer of the ignition train to the expendable, rendering it totally ineffective. There is a need for an ignition system with an ignition composition, which may be in the form of an igniter pellet or pellets, that are sufficiently durable and insensitive to moisture and other conditions that can cause ignition delays and propagation failures associated with aging, storage, application, system interaction, and environmental issues.
Embodiments of the igniter pellets and related compositions for decoy countermeasures introduced herein may be better understood by referring to the following Detailed Description in conjunction with the accompanying drawings, in which like reference numerals indicate identical or functionally similar elements.
The headings provided herein are for convenience only and do not necessarily affect the scope or meaning of the claimed embodiments. Further, the drawings have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be expanded or reduced to help improve the understanding of the embodiments. While the disclosed technology is amenable to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and are described in detail below. The intention, however, is not to limit the embodiments described. The embodiments are intended to cover all modifications, equivalents, and alternatives falling within the scope of the embodiments.
The present technology provides ignition compounds and igniter pellets for use with deployable expendable countermeasures, such as IR decoy flares or other ignitable countermeasures, and associated methods that overcome drawbacks of the prior art and provide other benefits. Examples of the technology introduced above will now be described in further detail. The following description provides specific details for a thorough understanding and enabling description of these examples. One skilled in the relevant art will understand, however, that the techniques discussed herein may be practiced without many of these details. Likewise, one skilled in the relevant art will also understand that the technology can include many other features not described in detail herein. Additionally, some well-known structures or functions may not be shown or described in detail below so as to avoid unnecessarily obscuring the relevant description. For purposes of simplicity of discussion, the technology may be described herein with reference to top and bottom, upper and lower, above and below, and/or left or right relative to the spatial orientation of the embodiment(s) shown in the figures. It is to be understood that the technology, however, can be moved to and used in different spatial orientations without changing the structure of the system.
The terminology used below is to be interpreted in its broadest reasonable manner, even though it is being used in conjunction with a detailed description of some specific examples of the embodiments. Indeed, some terms may even be emphasized below; however, any terminology intended to be interpreted in any restricted manner will be overtly and specifically defined as such in this section.
In at least one embodiment, the technology disclosed herein provides an igniter pellet for use with an expendable countermeasure assembly having an igniter assembly with an igniter pyrotechnic pellet receptacle therein. The igniter pellet has a first layer formed by a first composition comprising a mixture of a first fuel material that includes Boron, a first oxidizer material that includes Bismuth Oxide and/or Potassium Perchlorate, a granular matrix binder holding the fuel material and the oxidizer material together, wherein the first composition is insensitive to ambient moisture. The igniter pellet has a second layer formed by a second composition different than the first composition. The second composition comprises a second fuel material that includes Magnesium, a second oxidizer that includes Polytetrafluoroethylene, and a binder material that includes a fluoropolymer elastomer. The second layer is configured to be contained in the pellet receptacle and covered by the first layer so that the second layer is isolated and protected from ambient moisture by the moisture insensitive first layer.
Another embodiment of the present technology provides a method of forming an igniter pellet for use with an expendable countermeasure flare assembly having an igniter assembly with an igniter pellet receptacle therein. The method includes forming a moisture-insensitive first ignition composition for a first layer of the igniter pellet by dissolving a first rubber-based binder in a polar solvent to form a binder solution. The binder solution is mixed with a first fuel material that includes Boron, and a first oxidizer material that includes Bismuth Oxide and/or Potassium Perchlorate to form a first mixture. A low boiling point non-polar solvent is added to the mixture and precipitating the binder from the mixture to form a coagulation composition. The coagulation composition is converted to a first moldable granular composition. The method also includes providing a second ignition composition that comprises a mixture of Magnesium, Polytetrafluoroethylene and a fluoropolymer elastomer binder. The first and second ignition compositions are positioned into the pellet receptacle of the igniter assembly slider, wherein the first composition forms a first layer, and the second composition forms a second layer that is covered and isolated from ambient moisture by the first layer.
Another embodiment of the present technology provides a deployable expendable infrared countermeasure assembly that has a body portion with a payload portion and a base portion. A deployable, ignitable payload is contained in the final configured countermeasure flare assembly. An impulse cartridge is coupled to the base of the outer case of the expendable. The impulse cartridge comprises an electrical initiator adjacent to a pyrotechnic output charge suitable for payload jettison and ignition train transfer to the expendable. The ignition pellet of the igniter contained in the expandable countermeasure flare assembly has a first layer formed by a first composition comprising a mixture of a first fuel material that includes Boron, a first oxidizer material that includes Bismuth Oxide and Potassium Perchlorate, and a granular matrix binder holding the fuel material and the oxidizer material together. The first composition is insensitive to ambient moisture. A second layer is formed by a second composition different than the first composition. The second composition comprising a second fuel material that includes Magnesium, a second oxidizer that includes Polytetrafluoroethylene, and a binder material that includes a fluoropolymer elastomer. The second layer is configured to be fully contained in the flare igniter assembly and covered by the first layer so that the first layer is adjacent to the impulse cartridge output and the second layer is isolated and protected from ambient moisture by the moisture insensitive first layer.
Another embodiment of the present technology provides a method of forming an igniter pellet for use with a countermeasure assembly having an igniter assembly with a pellet receptacle therein. The method comprises forming a moisture-insensitive ignition composition by dissolving a first rubber-based binder in a polar solvent to form a binder solution. The binder solution is mixed with a first fuel material that includes Boron, a first oxidizer material that includes Bismuth Oxide and/or Potassium Perchlorate and a second oxidizer material and burn rate enhancer that includes finely divided Potassium Perchlorate powder to form a mixture. A low boiling point non-polar solvent is added to the mixture and the binder is precipitated from the mixture to form a coagulation composition. The coagulation composition is converted to a moisture insensitive moldable granular composition. The moisture insensitive ignition composition is positioned into the pellet receptacle of the igniter assembly to form an igniter pellet adjacent to output of the impulse cartridge.
As seen in
In the illustrated embodiment, the ignition pellet 20 is positioned in the receptacle 22 with the outer first layer 30 fully covering the inner second layer 32. The first layer 30 engages the second layer 32 at the interface layer 28. In some embodiments, the first layer 30 is applied to the second layer 32 so that a portion of the first composition mixes with the second composition at the interface layer 28 to form an ignition pathway from the first composition to the second composition. The outer first layer 30 is positioned adjacent to the impulse cartridge 17 output so to accept ignition from the output of the expulsion or impulse cartridge. When the outer first layer 30 is ignited, it is lit and burns quickly and at high temperatures, so as to pass the ignition train across the interface area 28 to the pellet's inner second layer 32 to pass the ignition train to the flare body/material forming the payload. The composition of the first layer 30 is substantially insensitive to moisture. The first layer 30 covers the second layer 32, so the inner second layer 32 is substantially fully isolated from the ambient environment (i.e., air, moisture, particulates, potential contaminates, etc.) via the walls forming the receptacle 22 and the first layer 30. Accordingly, the moisture insensitive first layer 30 forms an exterior surface 34 of the pellet 20 facing the opening of the receptacle 22 for operative communication with the impulse cartridge's output.
The pellet's moisture insensitive first layer 30 provides superior reliability in ignition, burn rate and consistency upon activation of the impulse cartridge so as to provide the flame and thermal energy transfer across the interface area 28 to ignite the inner second layer 32. Burning of the igniter pellet 20 can also generate high temperature gases used to cause ignition of the payload of the countermeasure body upon deployment. As a result, the dual layered hybrid energetic composition igniter pellet 20 of the present technology ensures consistent ignition propagation to the payload independent of the age, storage conditions, or other environmental conditions surrounding the countermeasure assembly 10, such as while installed in an aircraft, in a storage location, or in transit to or from the storage location. The ignition pellet configuration also accommodates reliable ignition activation from a wide range of impulse cartridge outputs, therefore ensuring more reliable decoy flare ignition and function.
As indicated above, the pellet's first layer 30 is pressed onto or otherwise positioned over the second layer 32 within the igniter assembly slider receptacle 22, so entire second layer 32 is isolated from the ambient environment by the first layer 20 and the structure forming the receptacle 22. Accordingly, only the exterior surface 34 of the first layer 30 may be exposed to air, moisture, and other ambient conditions surrounding the countermeasure assembly 10. These ambient conditions may be when the countermeasure assembly 10 is in a storage location, in transit to or from the storage location, or installed in an aircraft dispensing system.
In the illustrated embodiment, the outer first layer 30 is made of a moisture insensitive ignition composition comprising a fuel material and an oxidizer that are held together by a binding material. In one embodiment the fuel material is Boron or other suitable fuel material. The Boron is combined with the oxidizer, such as Bismuth Oxide, and Potassium Perchlorate, or other suitable oxidizer material. The binding material holding fuel and oxidizer materials together is a granular matrix formed by an elastomeric rubber binding material such as Fluorel™, Kraton®, or suitable rubber material. In at least one embodiment the composition of the first layer comprises approximately 3-5% by weight of the fuel (e.g., Boron), 88-96% by weight of the oxidizer (e.g., Bismuth Oxide and/or Potassium Perchlorate), and 3-5% of the binder (e.g., Fluorel™ or other elastomeric rubber binder). In one embodiment, the composition of the first layer can comprise approximately 3-5% by weight of the fuel (e.g., Boron), 86-92% by weight of the Bismuth Oxide (oxidizer), 3-5% of the Potassium Perchlorate (oxidizer), and 3-5% of the binder (e.g., Fluorel™ or other elastomeric rubber binder).
This composition of the first layer 30 of at least one embodiment can be blended using a high-shear style mixer according to a shock-gel process that results in a granular material after mixing. For example, this first layer 30 is formed by a mixing process that comprises dissolving the binder in a low boiling point polar solvent, such as ketones or ketone mixtures, to provide a binder solution. The binder solution is then mixed with mixing the fuel material and the oxidizer material(s). A low boiling point non-polar solvent, such as saturated hydrocarbons, is added to the above mixture to precipitate the binder and form a coagulation composition. The coagulation composition is dried and converted into a granular composition using any suitable method, such as one or more conventional screening/granulating processes. The resulting granular ignition composition of the first layer has a calorific output of approximately 300 calories per gram, is stable to approximately 375° C., and has a burn rate of approximately 3.3-4.5 seconds/inch.
In another embodiment, the composition of the first layer 30 can be mixed using a static mixer process. For example, a first stream of the binder, the low boiling point polar solvent, the fuel material, and the oxidizer mixture are introduced to the static mixer. This first stream is intersected with a second stream of the low boiling non-polar solvent in the static mixer to precipitate the binder. Granules of the ignition compositions are then formed through the turbulence of the static mixer to provide the composition with the above caloric output, stability and burn rate characteristics.
The second layer 32 forming the transfer or output side of the dual layered hybrid energetic composition igniter pellet 20 comprises a second composition different than the composition of the first layer 30. In the illustrated embodiment, this second composition comprises a mixture of a second fuel material different than the fuel material of the first layer, a second oxidizer different than the oxidizer of the first layer, and a second rubber binder. In at least one embodiment, the second fuel is a finely divided Magnesium powder. The second oxidizer is a finely divided Polytetrafluoroethylene (PTFE) powder. The binder is a rubber binder, such as a rubber and fluoropolymer elastomer (e.g., Fluorel™) binder. In some embodiments, the second composition for the second layer is a combination of Magnesium, Teflon, and Viton® (MTV). The composition is blended using a high-shear style mixer according to a shock-gel process that results in a granular material after mixing. In at least one embodiment the composition of the second layer comprises approximately 74-80% by weight of the fuel (e.g., Magnesium), 16-22% by weight of the oxidizer (e.g., PTFE), and 2-6% of the binder (e.g., fluoropolymer elastomer).
A mixing method in accordance with at least one embodiment for making this second composition comprises dissolving the binder in a low boiling point polar solvent, such as such as ketones or ketone mixtures, to provide a binder solution. The binder solution is mixed with the second fuel material and the second oxidizer. A low boiling point non-polar solvent, such as such as saturated hydrocarbons, is then added to the second fuel/oxidizer/binder mixture to precipitate the binder and form the coagulation composition. The coagulation composition is converted into a granular composition. The resulting granular ignition composition has a calorific output of approximately 700 cal/g calories per gram, is stable to approximately 490° C., and has a burn time of approximately 1.25-1.75 seconds/inch.
In another embodiment, the second composition for the second later of the ignition pellet of the present technology can be formed by using a static mixer to mix the ignition composition. For example, a first stream of the binder/low boiling point polar solvent/fuel material/oxidizer mixture is introduced to the static mixer. The first stream is intersected with a second stream of the low boiling non-polar solvent in the static mixer. Granules of the ignition compositions are formed through the turbulence of the static mixer with the above caloric output, stability and burn rate characteristics.
The first and second compositions can be pressed together in the layered arrangement to provide the hybrid layered pellet 20 with the interface area 28 between the two layers 30 and 32. For example, in one embodiment the second composition can be mechanically pressed into the receptacle 22 of the slider of the igniter assembly to form the second layer 32. Then the first composition can be mechanically pressed into the receptacle 22 atop the second layer 32 to form the first layer 30 that fully covers the second layer and insolates the second layer from moisture and other ambient conditions. When the first layer 30 is pressed onto the second layer 32, a portion of the first composition forming the first layer 30 mixes with the second composition forming the second layer 32 at the interface area 28 to provide full and consistent ignition propagation between the layers upon activation of the countermeasure assembly 10. In other embodiments, the hybrid dual layered ignition pellet 20 can be formed in a mold by pressing the first and second compositions into the mold to form the first and second layers 30 and 32. The pellet 20 can then be removed from the mold and inserted into the impulse cartridge 16, such as during assembly of the countermeasure assembly 10. In yet another embodiment, the first composition can be applied to the second layer 32 in a slurry application to cover selected portions of the exterior surface of the second layer 30, as shown in
The above description are examples of some embodiments of the present technology. In other embodiment, the composition weights can be varied within allowable tolerances while still achieving the identified performance characteristics. The fuels, oxidizers, mixture ratios, and particle sizes can be adjusted according to the desired output performance of the moisture insensitive ignition composition, i.e., by varying the ratios of Boron, Bismuth Oxide, Potassium Perchlorate, binder, as well as the Magnesium/Teflon (PTFE)/Fluorel (MTV), etc.
Another embodiment of the present technology provides a moisture insensitive ignition composition for an igniter pellet that can quickly and reliably ignite the pyrotechnic or propellant materials in the countermeasure assembly without ignition delay or propagation failures. The ignition material can be molded or otherwise formed into a pellet format for use in the igniter assembly 16 in the base of the countermeasure assembly 10. This composition comprises a first fuel, such as a Boron powder, a first oxidizer, such as finely divided Bismuth Oxide powder, and a binder, such as a Fluorel™ rubber binder. This composition also includes a second oxidizer and burn rate enhancer, such as a finely divided Potassium Perchlorate powder.
This ignition composition can be blended using a high-shear style mixer according to a shock-gel process that results in a granular material after mixing. For example, the mixing method for making the moisture insensitive ignition composition can comprise dissolving the binder in a low boiling point polar solvent, such as acetone or other ketones or ketone mixtures to provide a binder solution. The binder solution is mixed with the fuel material and the first and second oxidizers. A low boiling point non-polar solvent, such as hexane or other saturated hydrocarbons, is added to the mixture to precipitate the binder and form the coagulation composition. The coagulation composition is converted into granular composition using one or more conventional screening/granulating processes. The resulting granular ignition composition has a calorific output of approximately 300 calories per gram, is stable to approximately 375° C., and has a burn time of approximately 3.3-4.5 seconds/inch.
In another embodiment, the ignition composition can be mixed using a static mixer process. For example, a first stream of the mixture of the binder, the low boiling point polar solvent, the fuel material, and the first and second oxidizers is introduced to the static mixer. The first stream is intersected with a second stream of the low boiling non-polar solvent in the static mixer. Granules of the ignition compositions are formed through the turbulence of the static mixer with the above caloric output, stability and burn rate characteristics. The fuels, oxidizers, mixture ratios, and particle sizes for these alternative compositions can be adjusted according to the desired output performance of the moisture insensitive ignition composition, i.e., by varying the ratios of Boron, Bismuth Oxide, Potassium Perchlorate, and binder materials.
The above description and drawings are illustrative and are not to be construed as limiting. Numerous specific details are described to provide a thorough understanding of the disclosure. However, in some instances, well-known details are not described in order to avoid obscuring the description. Further, various modifications may be made without deviating from the scope of the embodiments.
Reference in this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Moreover, various features are described which may be exhibited by some embodiments and not by others. Similarly, various requirements are described which may be requirements for some embodiments but not for other embodiments.
The terms used in this specification generally have their ordinary meanings in the art, within the context of the disclosure, and in the specific context where each term is used. It will be appreciated that the same thing can be said in more than one way. Consequently, alternative language and synonyms may be used for any one or more of the terms discussed herein, and any special significance is not to be placed upon whether or not a term is elaborated or discussed herein. Synonyms for some terms are provided. A recital of one or more synonyms does not exclude the use of other synonyms. The use of examples anywhere in this specification, including examples of any term discussed herein, is illustrative only and is not intended to further limit the scope and meaning of the disclosure or of any exemplified term. Likewise, the disclosure is not limited to various embodiments given in this specification. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. In the case of conflict, the present document, including definitions, will control.
