Abstract:
The invention is an apparatus for producing an IR (infra-red) signature. In the method, the apparatus is mounted on a target to give the target an infra-red signature whereby the target can be acquired by an appropriate weapon sensor.

Description:
CROSS-REFERENCE TO OTHER APPLICATIONS 
   This application is a divisional application of Ser. No. 09/738,823 filed Dec. 15, 2000 now U.S. Pat. No. 6,521,904, entitled “IR Source, Method and Apparatus” the entire disclosure of which is incorporated herein by reference. 

   This invention relates to an IR (infra-red) source, and more particularly to a structure of an IR source to be used on targets to allow the siting of weapons having appropriate sensors on the target. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     In the accompanying drawings: 
       FIG. 1  shows an exploded view of the apparatus. 
       FIG. 2  shows a side view of a target, in this case a drone aircraft, with the apparatus mounted thereon. 
       FIG. 3  shows a top view of the target depicted in FIG.  2 . 
       FIG. 4  shows a view of what an observer perceives from the IR source. 
   

   BRIEF SUMMARY OF THE INVENTION 
   An overview of the apparatus of the present invention is depicted in FIG.  1 . The IR source  1  is comprised of a catalytic assembly  10 , which radiates when contacted by a first fluid  15 , positioned within an exit  17  of a housing  5 . Housing  5  is depicted in two parts to more clearly show that catalytic assembly  10  is positioned within exit  17  of housing  5 . It should further be understood that there can be multiple exits  17  each with a catalytic assembly  10  positioned therein. 
   The catalytic assembly  10  is comprised an element  50  with a catalyst  51  positioned thereon. The catalytic assembly  10  can be made from a single element or a plurality of elements. 
   The entrance  16  of housing  5  is adapted to be connected to the source of first fluid  15 , in this case the exhaust port of an internal combustion engine. The first fluid  15  enters the housing through entrance  16  and is directed through catalyst assembly  10  then out exit  17 . 
   The housing  5  comprises an exterior surface  19  with a partition  35  extending outwardly therefrom. The partition  35  is positioned such that a second fluid  8  flowing toward the downstream face  11  of catalytic assembly  10  will be deflected away from the downstream face  11 . 
   Within housing  5 , baffle  21  is positioned outwardly from the interior surface  18  to direct the first fluid  15  flow toward catalytic assembly  10 . 
     FIG. 2  shows the apparatus of  FIG. 1  mounted on a target  60 , in this case an aerial drone. The apparatus is connected to an engine  61  such that the first fluid  15 , in this case the exhaust from the engine, causes the catalytic assembly to radiate. Catalytic assembly  10  is positioned in the exit  17  such that the generated radiation  75  is visible to a distant observer  70 .  FIG. 2  also shows that the engine  61  is integrated into the propulsion system, attached to a propeller  62 , of the target  60 . 
     FIG. 3  shows another view of target  60  to illustrate that multiple catalytic assemblies  10  can be employed. 
     FIG. 4  shows a schematic representation from the distant observer&#39;s perspective. The device is intended as an IR source that can be acquired by a sensor that is part of a weapon (not shown). The sensor is manipulated by the distant observer  70 . Thus an irradiance  71  at the location of the sensor, assumed to the distant observer  70 , must be sufficient for the sensor to detect. 
   DETAILED DESCRIPTION 
   The catalytic assembly  10  is comprised of at least one element  50  with a catalyst  51  positioned thereon. As those skilled in the art will recognize, there are numerous structures for element  50  as well as numerous catalyst for catalyst  51  and still further numerous ways of positioning the catalyst on the element. Element  50  must be capable of radiating, elements providing greater emissivity are preferred. In the case of the present invention, a metallic, short channel element, woven metal 10×10 mesh constructed of Haynes  230 , was used. Other element structures such as expanded metal, gauze, foam, or monolith constructed of almost any material including metals or ceramics could be used. 
   It is preferred that the shape of the material chosen for element  50 , or most downstream element  50  in the case where multiple elements  50  are employed, provide a radiation pattern off the downstream face  11  in more than a single direction. An element  50  is comprised of members  52 , in this case wire woven into a mesh. Wire has a round cross-section that generates a hemispherical radiating pattern off the downstream face  11 . If the shape of the members at the downstream face were planar, a typical monolith, the members  52  would generate a radiation pattern in a single direction. It would be possible, however, to use members  52  with cooperating planer surfaces to generate a multi-directional radiation pattern. For example, two planar surfaces oriented at an acute angle to one another. 
   Depending upon the element chosen and the application, a single or multiple element catalytic assembly might be devised. The most downstream surface of the most downstream element  50 , based on the flow of the first fluid through the catalyst assembly, is defined as the downstream face  11 . In the case of a multiple element  50  catalytic assembly, it is preferred that the members  52  of respective elements  50  be offset to one another relative to the flow of the first fluid  15  through the catalytic assembly. 
   The catalyst  51  is application dependent, depending upon the composition and operating conditions of the first fluid  15  in combination with the weapon sensor and the range on which the target will be used. The catalyst must be positioned on the element, or elements, such that the catalytic assembly  10  when contacted with the first fluid  15  radiates. Positioning could be accomplished through any number of commonly used deposition techniques or integrated into the composition of the element. In the case of the present embodiment wherein the first fluid  15  is the exhaust gas of an internal combustion engine, any precious metal catalyst, such as platinum or palladium, could be used. 
   While this embodiment depicts the first fluid  15  as an exhaust gas of an internal combustion engine, this should not be considered a limitation of the invention. It is preferred that the invention utilizes a first fluid  15  that is presently available onboard the target, the exhaust gas or a fuel. The present invention, however, will function as intended if the first fluid is ancillary to the target, for example a bottled fuel. In addition, it is anticipated that other engines, other than internal combustion, may be used to generate the second fuel  15 . 
   The housing  5  is the structure that holds the catalytic assembly  10  in the housing&#39;s exit  17 . The design of exit  17  is application dependent, but it is preferred that the opening be sized to permit the maximum exposure of the catalytic assembly  10  downstream face  11  to a distant observer. It should be realized, that the housing can be adapted to the first fluid source with multiple entrances  16 . The material selected for the housing is application dependent. 
   A partition  35  extends outwardly from the housing  5  exterior surface  19 . Where the target is moving, such as in the depicted aerial drone, the catalyst assembly  10  could be cooled by a second fluid  8  passing over the surface. It is preferred that the partition  35  be located upstream of the downstream face  11 , relevant to the flow of fluid  8 , to prevent as much as possible this cooling effect, in the presented embodiment thereby defining a partition angle  36  that is acute. The partition  35  also has an overhang  9  that extends beyond the width of the downstream face  11  to account for non-parallel second fluid  8  flow patterns. 
   When the housing  5  is adapted to be in fluid communication with the source of the first fluid, the passage created by the housing may have turns. In order to assure maximum utilization of the catalyst  51 , it is preferred that the first fluid be distributed equally throughout the catalyst assembly  10 . In the present embodiment, baffle  21  extends outwardly from the interior surface  18  of housing  5  to accomplish this objective. When baffle  21  is performing this function, as depicted in this embodiment, it is preferred that the baffle in cooperation with the downstream face define a baffle angle  22  that is acute. Baffle  21 , however, might be employed to simply reduce the pressure drop between entrance  16  and exit  17 . The shape and positioning of the baffle is based on the application, but in the preferred embodiment that baffle was given a fair surface and the surface was given a parabolic shape. 
   In the method of the present invention, the catalytic assembly  10  is engineered such that the catalyst  51  cooperates with the first fluid  15  to create a radiation  75 . The amount of radiation  75  required is dependent upon the sensor being used and the parameters of the range such as distance from sensor, which is illustrated herein as the distance from observer  70  to the target. The first fluid can either by a fluid onboard the target, exhaust gas or fuel, or from an ancillary source added to the target. To provide additional benefit to the observer by illuminating the target from multiple perspectives, multiple exits  17  each with a catalyst assembly  10  can be positioned at different locations on the target.