Ammunition and explosives – Pyrotechnics – Flare
Reexamination Certificate
1997-08-29
2002-08-06
Nelson, Peter A. (Department: 3641)
Ammunition and explosives
Pyrotechnics
Flare
Reexamination Certificate
active
06427599
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to pyrotechnic compositions and, more specifically, to pyrotechnic compositions having combustion reaction products that include a high percentage of carbon dioxide at high temperatures. In particular, this invention relates to pyrotechnic compositions which include a fuel-component that is a compound having a relatively high carbon content and a relatively low hydrogen content. Examples of such compounds include, but are not limited to, aromatic polycarboxylic anhydrides, aliphatic polycarboxylic acid anhydrides, quinones, acetylenics, acid salts, polycyano compounds, substituted polynuclear compounds, polyanhydrides, polymeric anhydrides or polylactone compounds having combustion products having a relatively high long to short wavelength infrared output color ratio and/or a relatively high percentage of CO
2
and a relatively low percentage of H
2
O.
2. Description of the Related Art
Infrared decoy flares are used by aircraft as protection against attack by heat seeking missiles. These flares are typically ejected from an aircraft and ignited to produce infrared (“IR”) radiation that simulates the infrared emissions of aircraft engines of the targeted aircraft. The IR emissions of the decoy flare are intended to confuse a heat seeking anti-aircraft missile, thereby causing the missile to turn away from the target aircraft toward the decoy flare.
Modern heat seeking anti-aircraft missiles typically employ seeker heads capable of distinguishing between short and long wavelength IR emissions. Long wavelength IR emissions are typically produced by aircraft components, such as hot jet engines. Short wavelength IR emissions are characteristic of gray-body materials having higher temperatures and/or heated water vapor. In this respect, missile seeker heads may be configured to compare particular IR output color ratios. As used herein, “color ratio” is defined as the ratio of long wavelength IR output (“LW”) to short wavelength IR output (“SW”).
Because seeker heads of anti-aircraft missiles are designed to identify IR characteristics of aircraft engine emissions, flare decoy burn requirements are dictated by the characteristics of aircraft engine IR emissions. Aircraft engines typically produce a spectrum of IR radiation characteristic of a gray-body radiator in the 600-900 degree Centigrade range. In this regard, a flare decoy should burn to produce IR emissions having a large percentage of long IR wavelengths, similar to aircraft engine emissions.
In the past, flares have been configured to include combustible flare pellets, which are ignited when a decoy flare is deployed. Flare pellets have typically included a shaped quantity of flare material coated with an ignition composition. For example, a typical flare pellet is made of a solid pyrotechnic composition that includes magnesium, “TEFLON”, and “VITON” (this composition is commonly known as “MTV”), the latter two components being commercially available from DuPont. Such conventional flare compositions suffer from several disadvantages. For example, they may emit IR radiation which does not correspond with IR emissions of the missile target, especially when used against missiles which measure or detect the IR color ratio of targets.
In order to address these and other problems, certain “two color” decoy flare compositions have been developed which will generate IR color ratios more similar to that of targeted aircraft. For example, “two color” boron-based and red phosphorous-based compositions that produce flare emissions with higher LW/SW color ratios than MTV have been developed. However, the IR output of such two color compositions typically degrades in a windstream, exhibiting increased short wavelength IR energy when a decoy flare is ejected from an aircraft. Generally, the output color ratio of such a flare changes with increases in wind speed until it no longer matches the signature of a jet engine exhaust at operating temperatures, thus allowing a heat seeking anti-aircraft missile to distinguish the decoy flare from the aircraft.
In order to address windstream IR emission degradation, several measures have been taken. For example, protective shields have been added to keep the wind stream from directly impinging on the flare plume. These devices tend to be cumbersome and relatively inefficient. In other cases, decoy flare devices which control mixing of air with the output of flare compositions have also been developed. These devices tend to be costly and/or mechanically complex.
SUMMARY OF THE INVENTION
In one respect this invention is a pyrotechnic composition having the property that combustion of the pyrotechnic composition produces a combustion product with a molecular ratio of CO
2
to H
2
O of greater than about 1.0. In other embodiments this molecular ration may be greater than about 2.0 or 4.0, respectively. This composition may also have the property that combustion of the pyrotechnic composition produces infrared emissions having an output infrared color ratio of greater than about 1.0 or, in another embodiment, greater than about 3.0. In one typical embodiment, the pyrotechnic composition includes a fuel component including at least one aromatic polycarboxylic acid anhydride. In this embodiment, the aromatic polycarboxylic acid anhydride may be, among other things, any one of benzene tetracarboxylic acid dianhydride, benzophenone tetracarboxylic dianhydride, benzene hexacarboxylic acid trianhydride, or a mixture thereof. In another embodiment, the pyrotechnic composition may include a fuel component including anthraquinone. In another embodiment, the pyrotechnic composition may have an oxidizing agent and an afterburning stoichiometry, in which the pyrotechnic composition includes an amount of oxidizing agent sufficient to supply between about 40% and about 95% of the stoichiometric amount of oxidizing agent required for complete combustion of the fuel component. In another embodiment, the pyrotechnic composition may have a fuel component, further include an oxidizing agent, and have an afterburning stoichiometry, in which the pyrotechnic composition includes between about 28% and about 40% by weight of the fuel component, and between about 45% and about 69% by weight of the oxidizing agent.
In another respect, this invention is a pyrotechnic composition having the property that combustion of the pyrotechnic composition produces infrared emissions having an output infrared color ratio of greater than about 3:1. In one embodiment of this composition, the pyrotechnic composition may have the property that combustion of the pyrotechnic composition produces infrared emissions having an output infrared color ratio of greater than about 3:1 under windstream conditions of about Mach 0.2. In another embodiment of this composition, the pyrotechnic composition may have the property that combustion of the pyrotechnic composition produces a combustion product having a molecular ratio of CO
2
to H
2
O of greater than about 1.0. In still another embodiment of this composition, the pyrotechnic composition may have the property that combustion of the pyrotechnic composition produces infrared emissions having an output infrared color ratio of greater than about 1:1 under windstream conditions of about Mach 0.2. In yet still another embodiment of this composition, the pyrotechnic composition may have the property that combustion of the pyrotechnic composition produces infrared emissions having an output infrared color ratio of greater than about 1:1 under windstream conditions of up to at least about Mach 0.75. In still yet another embodiment of this composition, the pyrotechnic composition may have the property that combustion of the pyrotechnic composition produces infrared emissions having an output infrared color ratio of greater than or equal to about 1.5:1 under windstream conditions of up to at least about Mach 0.7. In yet still another embodiment of this composition, the pyrotechnic composition may have the property that combust
Baggett, Jr. Albert J.
Posson Philip L.
BAE Systems Integrated Defense Solutions Inc.
Fulbright & Jaworski LLP
Nelson Peter A.
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