Abstract:
A disruptive media dispersal system for aircraft which absorbs and scatters directed energy weapon beams such as tracking lasers and high energy lasers (HELs) is disclosed. The system may include laser detectors, laser beam propagation disruptive media and a dispersal system. When attacked by a directed energy weapon such as a laser, the laser detector system or vehicle operator deploys the disruptive media. The disruptive media is released by a feeder and dispersal system into the air in the path of the tracking and/or HEL weapon. For example, the dispersal system may be located onboard the aircraft near the front of the fuselage.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to the protection of aircraft from directed energy weapons, and more specifically relates to a system for dispersing from an aircraft disruptive media which absorbs and scatters laser beams and other types of directed electromagnetic radiation. 
       BACKGROUND INFORMATION 
       [0002]    The use of directed energy weapons such as laser beams and high power microwaves against aircraft represents a significant threat. It would be desirable to protect aircraft from such threats. 
       SUMMARY OF THE INVENTION 
       [0003]    The present invention provides a disruptive media dispersal system for aircraft which absorbs and scatters directed energy weapon beams such as tracking lasers and high energy lasers (HELs). The system may include laser detectors, laser beam propagation disruptive media and a dispersal system. When attacked by a directed energy weapon such as a laser, the laser detector system or vehicle operator deploys the disruptive media. The disruptive media is released by a feeder and dispersal system into the air in the path of the tracking and/or HEL laser weapon. For example, the dispersal system may be located onboard the aircraft near the front of the fuselage. 
         [0004]    An aspect of the present invention is to provide a disruptive media dispersal system for an aircraft. The system comprises a container mounted adjacent a front portion of the aircraft, disruptive media in the container capable of absorbing and/or scattering a directed energy beam, and an ejector for dispersing the disruptive media from the container to thereby protect the aircraft from the directed energy beam. 
         [0005]    Another aspect of the present invention is to provide a method of dispersing disruptive media from an aircraft. The method comprises providing disruptive media in a container adjacent a front portion of the aircraft capable of absorbing and/or scattering a directed energy beam, and dispersing the disruptive media from the container to thereby protect the aircraft from the directed energy beam. 
         [0006]    These and other aspects of the present invention will be more apparent from the following description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0007]      FIG. 1  is a partially schematic illustration of a laser beam disruption system used on an aircraft in accordance with an embodiment of the present invention. 
           [0008]      FIG. 2  is a partially schematic block diagram of a laser beam disruption test system. 
           [0009]      FIGS. 3-5  are photographs of a steel surface, showing the results of laser beam disruption tests.  FIG. 3  shows a laser-damaged surface.  FIG. 4  shows an undamaged surface resulting from the use of a disruptive medium to absorb and scatter laser beam energy in accordance with an embodiment of the present invention.  FIG. 5  shows a laser-damaged surface after the laser disruptive medium is no longer used to protect the surface. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]      FIG. 1  schematically illustrates a disruptive media dispersal system for an aircraft  10 . The aircraft  10  includes a fuselage  12  having a front end  14  from which a disruptive media  16  is dispersed. The disruptive media  16  absorbs and/or scatters directed energy beams such as tracking lasers, high energy lasers, high power microwaves and the like. For example, the disruptive media may comprise powder such as carbon black or any other material capable of absorbing or scattering directed energy beams. When carbon black or other powders are used as the disruptive media, they are typically stored on or in the aircraft in powder form, and are dispersed from the aircraft in the powder form. Alternatively, the disruptive media may be stored and deployed from another location, such as from another aircraft, unmanned aerial vehicle or missile. A gas such as air may be mixed with the powder to aid dispersion. The disruptive media is typically dispersed at a temperature approximating the ambient temperature of the aircraft, i.e., the temperature inside or outside the aircraft, rather than at significantly elevated temperatures. 
         [0011]    As shown in  FIG. 1 , a sensor  18 , such as a conventional laser sensor, may be mounted on the aircraft  10  in order to detect incoming beams such as interrogation or tracking laser beams and/or high intensity laser beams. When such an incoming directed energy beam is detected, standard control hardware and associated software may be used to initiate dispersion of the disruptive media  16  from the front  14  of the aircraft  10 , or to alert an operator to manually initiate dispersion of the media.  FIG. 1  illustrates both a tracking laser beam  22  and a high energy laser beam  24  which are directed toward the aircraft  10 . Due to the absorbing and scattering characteristics of the disruptive media  16 , both laser beams  22  and  24  do not reach the aircraft  10 , thereby preventing damage to the aircraft. 
         [0012]    The dispersion of the disruptive media  16  into the laser paths  22  and  24  has three primary effects. The first effect is to disrupt the tracking and aiming laser  22  for the laser system. The laser beam  22  must be precisely aimed at the surface of the aircraft  10 , and the surface heating point tracked to maintain continuous local heating. If the laser heating location is not maintained for sufficient time, such as a few seconds, the laser will not achieve damage. Disruption of the tracking laser  22  by the dispersed media  16  will disengage the tracking laser  22 , causing disruption of the heating. The second effect is on the HEL beam  24 , which is absorbed by the disruptive media  16  to prevent energy from reaching the aircraft structure surface  10  with sufficient intensity to damage the structure. Greater than 99 or even 99.9% disruption/absorption and corresponding elimination of drilling laser effects on structural surfaces may be achieved. A third effect may be the creation of a hot spot in the field of view of the tracking laser  22 , overwhelming its sensors and blinding it. 
         [0013]    A method to protect aircraft from laser DEW was demonstrated in the laboratory on a bench scale. A YAG:NDS+, 1.06-micron laser used for machining and drilling was applied for the demonstration. A test apparatus including test chamber, disruptive media feeder, and HEPA vacuum was assembled. 
         [0014]      FIG. 2  is a block diagram of the bench scale demonstration system. Air was drawn from the room through the test assembly by a vacuum (upper left side). Air is pulled into the apparatus, from the room, through the three openings to the room: top, bottom and lower right side. The test region is the vertical section between the two horizontal tubes. The drilling laser is fired through the test region. After passing through the test region the laser illuminates sample coupons mounted on a motion table.  FIG. 2  indicates the path of the drilling laser as well as a reference laser. Laser beam attenuation was determined using the reference laser. Reference beam intensity, after passing through the test section was measured using a photo detector. 
         [0015]    For the demonstration tests, the YAG laser was set for three levels of operation, which made a visible mark on a steel test sample. Each test consisted of three steps at the same laser power: (1) fire laser through test section burning a mark on the surface of a steel sample coupon before laser beam propagation disruption; (2) fire the laser through test section with the disruptive media in the test section; and (3) fire laser through test section burning a mark on the surface of a steel sample coupon after laser beam propagation disruption. Step 3 verifies that the laser had not changed. 
         [0016]    Reference beam intensity was measured for each of the three test steps. During test step 2, disruptive media was introduced into the lower right horizontal leg of the test assembly. The media was drawn upward through the test section and out into the vacuum leg. Media was fed using a feeder. There are many potential disruptive media, which could be used to absorb/scatter the laser beams. For these tests carbon black powder was used as the disruptive media. 
         [0017]    Marking a steel coupon surface is intended as an indication that the laser is at a power intensity that could damage an aircraft structure. At all three laser power levels the disruptive media prevented any mark being made on the sample surface. All three sets of before and after samples showed marks on the surface by the laser, verifying before and after performance. 
         [0018]      FIGS. 3-5  are photographs taken at the highest laser power level.  FIG. 3  is a photograph of the mark made by the laser on a steel plate before beam disruption (step 1).  FIG. 4  is a photograph of the plate when the laser was fired and the beam disrupted/absorbed (step 2). No mark was made at all. During step 2, reference laser transmission was reduced to less than 0.01% of undisrupted beam.  FIG. 5  is a photograph of the mark made by the laser on a steel plate after the beam disruption was turned off (step 3).  FIG. 5  serves to verify that the laser was still capable of making a similar mark on a plate after the beam was disrupted. 
         [0019]    This test demonstrates the disruption of a laser with sufficient power density damage steel. During disruption no damage was done to the steel test coupons. Although the absolute power of the drilling laser is low compared to an HEL weapon, the drilling laser local heat flux is sufficient to damage/remove material. When installed on an aircraft, it may be desirable to utilize a more compact dispersal system than used in the test demonstration. 
         [0020]    Whereas particular embodiments of this invention have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present invention may be made without departing from the invention as defined in the appended claims.