Patent Publication Number: US-7213496-B2

Title: Illuminated aircraft countermeasures

Description:
FIELD OF THE INVENTION 
   This invention relates generally to selected decoys or countermeasure devices for negating or confusing tracking or guidance seeking devices of homing missiles so that they fail to lock on their intended aircraft target. 
   BACKGROUND OF THE INVENTION 
   Anti-aircraft missiles have electro-optical guidance seeking devices for tracking an infrared or other wavelength radiation emitted from a targeted aircraft (e.g., heat radiating from an aircraft engine&#39;s tailpipe). Conventional military aircraft employ hydrocarbon jells, flares or pyrotechnic compositions to produce a thermal decoy signature to attract an approaching missile away from its intended target. While the duration and intensity of such thermal decoy signatures vary, the purpose is to provide enough cover so that the approaching missile losses its ability to accurately track the intended target at least temporarily as the targeted aircraft is flown out of the line of sight of the missile. One problem with the aforementioned thermal decoys is that as components fall to earth they may still radiate enough heat to ignite material such as, for example, grass, trees and buildings, in the area of impact. 
   Increasingly, concerns have been raised throughout the world about missile attacks against commercial and other non-military aircraft. Typically, such non-military aircraft do not employ any countermeasures to secure against such attack. Additionally, few commercial, non-military airfields employ any defensive measures to provide cover for aircraft taking off or landing at their facility. 
   Accordingly, that a need exists for countermeasures that employ safer means of forming thermal decoy signatures and for safe, cost-effective countermeasures that can be employed within both military and non-military environments. The present invention provides a solution to this important need. 
   BRIEF SUMMARY OF THE PRESENT INVENTION 
   One aspect of the present invention is directed to a countermeasure device for negating a missile&#39;s guidance seeking system, comprising:
         a membrane defining an internal chamber;   a gas disposed in said chamber, said gas having a lesser density than air; and   an illuminating device including:
           a light source producing energy sufficient to provide a decoy signature detectable by said guidance seeking system; and   a power supply coupled to said light source.   
               

   Another aspect of the present invention is directed to, in the operation of an aircraft having one or more turbojet engines, a method for protecting that aircraft from infrared-seeking missiles; including:
         1) detecting the approach of such infrared-seeking missile toward said aircraft;   2) in immediate response to such detection, releasing countermeasures as described above so as to reduce the probability that the guidance system of the missile will lock on to the aircraft.       

   Another aspect of the present invention is directed, in the operation of an aircraft having one more turbojet engines, a system for protecting that aircraft from infrared-seeking missiles; including:
         (a) means for detecting the approach of said missiles toward the aircraft;   (b) one or more of the above-noted countermeasures exhaust to reduce the infrared radiation in each engine; and   (c) controller for releasing the countermeasures as described above from the aircraft; said controlling means coupled to detection means (a).       

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows one embodiment of a countermeasure of the present invention. 
       FIGS. 2A and 2B  illustrate how this countermeasure is inflated. 
       FIG. 3  shows the use of tethered countermeasures of the present invention at the end of an airport summary. 
       FIG. 4  shows the use the countermeasures of the present invention relieved from an aircraft. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The terms “aircraft” and “aircraft having one or more turbojet engines” as used in the present specification and claims refer to any type of aircraft (including both commercial and military aircraft) that has an engine that has an exhaust of sufficient infrared radiation to be tracked by a heat-seeking missile. While turbojet engines are a common type of engine on both commercial and military aircraft, the present invention does not exclude other types of engines that have this same characteristic. 
   In the operation of a turbojet engine, the exhaust of the turbine in such engines is a source of heat (and thus infrared radiation). The exhaust also emits heated carbonaceous materials, which also carry heat in the infrared signature. Together, the pure heat of the exhaust, these heated carbonaceous materials, and the infrared radiation emitting from the heated engine material itself create an infrared signature of the aircraft. It is this signature that heat-seeking surface-to-air (and also heat-seeking air-to-air) missiles are able to detect and target. 
   With reference to  FIG. 4 , the present invention allows for the immediate release and activation of the countermeasure  10  by controller  64  when an incoming missile  70  has been detected by detector means  62 . Preferably, these countermeasures  10  of the present invention provide an intense light source  30  that is either constant for a short period of time (e.g. up to several minutes or more) or will flash on and off in a regular manner (e.g. flashes about every second or so). 
   When a threat is detected, this system allows for these countermeasures to be released manually by the pilots or automatically by threat sensors coupled to the electronic controllers or other conventional electronic release means. Also, this system may be used in combination with other defense measures, such as flares or chaf. Moreover, the system can be activated during every take-off and landing automatically as the cost of these countermeasures is minimal. This automatic use of this system may eliminate the need for the extra (and very expensive electronics) to detect threatening missiles. 
     FIG. 1  illustrates one preferred embodiment of a countermeasure of the present invention, shown generally at  10 , for preventing or impeding a guidance seeking device of a missile from tracking a target of interest. The countermeasure  10  includes a membrane  12  defining a pressurized gas-filled chamber  14  and an illuminating device  30 . In one embodiment, the membrane  12  is formed from a polymeric material such as, for example, polyethylene terephthalate (commonly known as PET), or other polymeric materials such as, for example, materials sold under the brand names MYLAR® and KEVLAR® (registered trademarks of E.I. DuPont De Nemours and Company, Wilmington, Del. USA). The membrane  12  is at least partially transparent or translucent so that light illuminated from the illuminating device  30  (as described below) can be seen through the membrane  12 . 
   In one embodiment, the countermeasure  10  includes a tether  16  such as for example, a rope, cable or the like, for holding the countermeasure  10  in a position about an area of interest  40  such as, for example, a runway, flight deck or platform, or the like ( FIG. 3 ). It should be appreciated that a number of such countermeasures  10  may be deployed about the area of interest  40  at various altitudes. When activated, the countermeasures  10  provide a number of decoy signals to substantially prevent a missile from targeting an aircraft, shown generally at  50 , taking off from or landing at the area of interest  40 . In another embodiment, the countermeasures of the present invention may be used to protect ground, amphibious and ocean-going vehicles from infra-red seeking missiles. In such cases, they may be released from the vehicles themselves or placed in intermittent locations like street lamps. Alternatively, they may be placed on tethers above such vehicles as well as placed around such vehicles in defensive positions, (either on tethers or on the ground.) 
   The chamber  14  is filled with a buoyant, “lighter-than-air” gas (e.g., a gas having a lesser density than air) such as, for example, helium, so that the countermeasure “floats” in air. In one embodiment, illustrated in  FIGS. 2A and 2B , the countermeasure  10  is filled as it is being deployed. For example, a container  20  holding the buoyant gas is coupled to an opening  18  of the membrane (in a deflated state  12 ′). Upon deployment, the container  20  releases the buoyant gas through the opening  18  to fill the chamber  14  of the membrane  12 ″. In one embodiment ( FIG. 4 ), the container  20  is activated to release the gas as the countermeasure  10  is launched from an aircraft  60  into the path of an approaching missile  70 . 
   In accordance with the present invention, the illuminating device  30  is sufficiently lightweight so as not to impact the ability of the countermeasure  10  from floating. In one embodiment, the illuminating device  30  includes a light source  32  such as, for example, a light emitting diode, electrically coupled to a power source  34  such as, for example, a battery. The light source  32  produces energy sufficient to provide a decoy signature detectable by the guidance seeking device of an air-to-air or surface-to-air missile. The illuminating device may be located inside the chamber or outside the chamber (e.g. either attached to chamber by a short tether or attached to the outer surface of the chamber). The overall countermeasure device is thus buoyant and will remain in position behind the aircraft for a reasonable time. 
   A control circuit  36  is employed to selectively activate the light source  32 . In one embodiment, the control circuit  36  includes a switch that, when closed, couples the light source  32  to the power source  34 . The switch may be closed as the countermeasure  10  is deployed, e.g., released from the aircraft  60  as illustrated in  FIG. 4 . In another embodiment, the control circuit  36  includes a timer for activating the countermeasure  10  (coupling the light source  32  and power source  34 ) at a predetermined time or in predetermined time intervals (e.g., a predetermined number of minutes). In yet another embodiment, the control circuit  36  includes a receiver for receiving activation signals provided by a transmitter, as is generally known in the art, located within, for example, a targeted aircraft deploying the countermeasure  10  while evading an approaching missile or located in, for example, an airport control tower activating a number of such countermeasures  10  as aircraft are taking off or landing. 
   While the aforementioned light source  32  is described above as including a light emitting diode, it should be appreciated that other light emitting material may equally be implemented. For example, the light source  32  may include a semiconductor device generally referred to as a laser diode, injection laser or diode laser. The semiconductor device produces coherent radiation (e.g., waves that all are of a same frequency and phase) in the visible or infrared (IR) spectrum. Further, the light source  32  could be a standard electronic flash apparatus similar to those used in photography. The light source  32  may be any suitable wavelength of light and, for some uses, may be a variable wavelength to cover a large section or the complete portion of the operating wavelength spectrum of missile guidance systems. 
   Although described in the context of preferred embodiments, it should be realized that a number of modifications to these teachings may occur to one skilled in the art. Accordingly, it will be understood by those skilled in the art that changes in form and details may be made therein without departing from the scope and spirit of the invention.