Patent Abstract:
To provide a projectile for bird strike tests, comprising a gel-like or jelly-like material, which makes reproducible and representative results in bird strike tests possible, it is proposed that the projectile comprise a stabilizing device arranged in the projectile for stabilizing the gel-like or jelly-like material.

Full Description:
This application is a continuation of international application number PCT/EP2009/060112 filed on Aug. 4, 2009 and claims the benefit of German application number 10 2008 038 258.2 filed on Aug. 11, 2008. 
     The present disclosure relates to the subject matter disclosed in international application number PCT/EP2009/060112 of Aug. 4, 2009 and German application number 10 2008 038 258.2 of Aug. 11, 2008, which are incorporated herein by reference in their entirety and for all purposes. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a projectile, comprising a gel-like or jelly-like material. 
     Such projectiles are used, in particular, for bird strike tests as a substitute for real birds. Bird strike tests are carried out at wind power plants, for example, and, in particular, are mandatory for the certification of aircraft and trains. To that end, projectiles are fired at a high speed by a gas gun at areas of the wind power plants, the aircraft or the trains that are to be tested. Owing to the high speeds and the resulting high air resistance during a flight phase of the projectiles, deformation and/or oscillation of the projectile occurs, particularly when artificial projectiles of the above-mentioned kind are used, which leads to distortion of the test results. 
     U.S. Pat. No. 5,936,190 A, FR 2 768 504 A1, EP 0 488 911 A2, U.S. Pat. No. 3,791,303 A and WO 2007/066324 A1 disclose projectiles which are fired by hand firearms at animals and/or human beings. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, a projectile is provided, which makes reproducible and representative results in bird strike tests possible. 
     In accordance with an embodiment of the invention, a stabilizing device arranged in the projectile is provided for stabilizing the gel-like or jelly-like material. 
     A deformation of the projectile, in particular, in the flight phase is reduced, preferably completely avoided, by the stabilizing device. This leads to a reproducible shape of the projectile upon impact with a target and, therefore, to reproducible results of the bird strike tests. 
     In an embodiment of the invention it may be provided that the gel-like or jelly-like material comprises gelatin or consists of gelatin. As a result, the projectile is low-priced and easy to produce. 
     It is expedient for the gel-like or jelly-like material to be formed from a mixture of, for example, approximately four proportions of water and, for example, approximately one proportion of gelatin. 
     It is particularly expedient for the gel-like or jelly-like material to comprise ballistic gelatin or to consist of ballistic gelatin. The physical characteristics and the physical behavior of muscles can be recreated well by the use of ballistic gelatin. 
     As an alternative or supplement to this, it may be provided that the gel-like or jelly-like material comprises silicone rubber, glycerin soap, starch, polymer gel, caoutchouc, latex and/or plasticine or consists of silicone rubber, glycerin soap, starch, polymer gel, caoutchouc, latex and/or plasticine. Plasticine is a trademark registered in the name of Flair Leisure Products PLC. 
     It is expedient for the gel-like or jelly-like material to have a gel strength of from, for example, approximately 200 Bloom to, for example, approximately 300 Bloom. The physical characteristics and the physical behavior of muscles can then be recreated well. 
     Advantageously, the gelatin is a type A gelatin. 
     In an embodiment of the invention it may be provided that the projectile comprises hollow bodies, in particular, hollow balls. 
     It is expedient for at least part of the gel-like or jelly-like material to be arranged in the hollow bodies. The projectile can be stabilized in a simple way by using hollow bodies as subunits inside the projectile. Furthermore, adaptation of the density of the projectile is thereby possible. 
     It is also expedient for the hollow bodies to be surrounded at least partly by the gel-like or jelly-like material. 
     It is particularly expedient for the hollow bodies to be formed at least partly of a brittle material, in particular, from glass or polycarbonate. In this way, the shell of the hollow bodies is of stable construction, and little influence of the hollow bodies on the behavior of the projectile upon impact with a target is ensured. 
     It is particularly expedient for the stabilizing device to comprise hollow bodies that are connected to one another. An improved stabilization of the projectile is thus made possible by the hollow bodies present in the projectile. 
     In an embodiment of the invention it may be provided that the projectile has, at least in sections thereof, a substantially cylindrical shape. In this way, a bird strike can be simulated well. 
     As an alternative or supplement to this, it may be provided that the projectile is, at least on one side thereof, of substantially hemispherical configuration. 
     It is expedient for the projectile to be of substantially hemispherical configuration on either side of a middle section. As a result, the projectile has better aerodynamics and hence a reduced deformation in the flight phase. 
     In an embodiment of the invention it may be provided that the projectile is configured, at least in sections thereof, substantially as an ellipsoid, in particular, as an ellipsoid of revolution. In this way, the projectile has good aerodynamics and hence reduced deformation in the flight phase. 
     In particular, for use in single-impact tests, i.e., with only one impact per target to be tested, it is provided in an embodiment of the invention that the projectile has a mass of at least approximately 1.5 kg. 
     Furthermore, it is then expedient for the projectile to have a mass of at most approximately 4 kg. 
     It is particularly preferred for the projectile to have a mass of approximately 1.814 kg (4 lb) or of approximately 3.628 kg (8 lb). 
     In particular, for use in multiple-impact tests, i.e., with several impacts per target to be tested, it is advantageously provided that the mass of the projectile is preferably at least approximately 50 g and preferably at most approximately 1 kg. For example, tests with 8 projectiles, each weighing 700 g or 16 projectiles, each weighing 85 g are representative of flocks of birds. 
     In an embodiment of the invention it may be provided that the stabilizing device is formed, at least in sections thereof, of a material having a high brittleness. In this way, upon impact of the projectile with a target, the stabilizing device is essentially immediately destroyed and, therefore, has little, in particular, no, influence on the behavior of the projectile upon target impact. 
     It is advantageous for the stabilizing device to be formed, at least in sections thereof, of a material having a high stiffness. The stability of the projectile can thereby be increased. 
     It is expedient for the stabilizing device to be formed, at least in sections thereof, of, in particular, impregnated and/or non-absorbent, paper, or, in particular, impregnated and/or non-absorbent, cardboard. As a result, the stabilizing device can be constructed in a simple way. Moreover, the stability of the projectile can be increased by using stiff paper or stiff cardboard. 
     In an embodiment of the invention it may be provided that the stabilizing device comprises at least one stabilizing element. Owing to the use of at least one stabilizing element, the stabilizing device can be arranged particularly easily and flexibly in and/or on the projectile. 
     It is advantageous for a maximum extent of the at least one stabilizing element to be at most approximately one tenth, preferably at most approximately one fiftieth, of a maximum extent of the projectile. 
     It is expedient for the at least one stabilizing element to be of substantially bar-shaped configuration. In this way, in particular, a three-dimensional structure is easy to construct by means of the stabilizing elements. 
     It is particularly expedient for the stabilizing device to be formed, at least in sections thereof, of stabilizing elements arranged in a geometrical pattern. A particularly stable three-dimensional structure of the stabilizing device is thereby ensured. 
     It is advantageous for the geometrical pattern to be based on a cubic or tetrahedral basic shape. In this way, a simple construction of a stable stabilizing device is possible. 
     As an alternative or supplement to this, it may be provided that the stabilizing device comprises at least one, for example, spinal column-like, main support. In this way, in particular, a central section of the projectile can be easily stabilized. 
     As a supplement to this, it may be provided that the stabilizing device comprises a plurality of, for example, rib-shaped, stabilizing elements which are arranged, in particular, regularly, on the main support. An additional stabilization of the projectile which is already stabilized by the main support is thus possible. 
     In an embodiment of the invention it may be provided that a material of which at least a section of the stabilizing device is formed has substantially the same density as the gel-like or jelly-like material. In this way, an influence of the stabilizing device on the behavior of the projectile upon impact with the target can be reduced, in particular, completely avoided. 
     It is advantageous for the stabilizing device to comprise a material, in particular, to consist of a material which is workable by laser sintering. In this way, a user-defined shape of the stabilizing device can be easily produced, in particular, by rapid prototyping. For this purpose, a laser for sintering thermoplastic plastic powder, for example, polypropylene or polyamide, is guided, for example, in accordance with the specifications of a CAD model. A free design of the geometry of the stabilizing device is thus possible. 
     It is advantageous for the projectile to be surrounded, at least in sections thereof, by a substantially water-impermeable material. A drying-out of the projectile and hence a change in the physical characteristics during storage of the projectile can thereby be avoided. 
     It is expedient for the projectile to be provided with a water-impermeable coating. In this way, a drying-out can be prevented particularly easily. 
     The projectile in accordance with the invention is suited, in particular, for use in a combination of a projectile and a sabot for receiving and accelerating the projectile in an acceleration device. 
     The combination of projectile and sabot may have the advantages set forth above in conjunction with the projectile in accordance with the invention. 
     It is advantageous for the sabot to comprise a receptacle for the projectile, the shape of which, at least in sections thereof, is complementary to that of at least one section of the projectile. In this way, the projectile can be easily received, in particular, loosely held, in the sabot. 
     It is advantageous for the sabot to be constructed so as to be separable along a longitudinal center plane. As a result, the projectile can be easily placed in the sabot and removed from it. 
     The combination of projectile and sabot is suited, in particular, for use in an acceleration device configured, for example, as a gas gun. 
     The acceleration device with the combination of the projectile in accordance with the invention and the sabot may have the advantages set forth above in conjunction with the projectile in accordance with the invention and the combination of projectile and sabot. 
     The projectile in accordance with the invention, the combination of projectile and sabot, and the acceleration device with the combination of projectile and sabot may also have the following advantages:
         a real bird is realistically, representatively and reproducibly simulated; and   the projectile is substantially dimensionally stable in flight.       

     Further features of the invention are presented in the following description and the drawings of embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a diagrammatic representation of a gas gun with a first embodiment of a sabot and a first embodiment of a projectile; 
         FIG. 2  shows a diagrammatic representation of the projectile from  FIG. 1 ; 
         FIG. 3  shows a diagrammatic representation of the gas gun from  FIG. 1 , in which the sabot is arranged with the projectile at the end of an acceleration section of the gas gun; 
         FIG. 4  shows a diagrammatic representation of the gas gun from  FIG. 3 , with the projectile deformed by the air resistance; 
         FIG. 5  shows a diagrammatic representation of the gas gun from  FIG. 3 , with the projectile deformed by the air resistance; 
         FIG. 6  shows a diagrammatic representation of the gas gun from  FIG. 3 , with the projectile striking a target; 
         FIG. 7  shows a diagrammatic representation of the gas gun from  FIG. 3 , with a second embodiment of a projectile; 
         FIG. 8  shows a diagrammatic representation of a third embodiment of a projectile; 
         FIG. 9  shows a diagrammatic perspective representation of a stabilizing device with a cubic basic shape of a fourth embodiment of a projectile; 
         FIG. 10  shows a diagrammatic perspective representation of a stabilizing device with a tetrahedral basic shape of a fifth embodiment of a projectile; 
         FIG. 11  shows a diagrammatic perspective representation of a stabilizing device of a sixth embodiment of a projectile; 
         FIG. 12  shows a diagrammatic perspective representation of a seventh embodiment of a projectile; 
         FIG. 13  shows a diagrammatic representation of an eighth embodiment of a projectile; and 
         FIG. 14  shows a diagrammatic representation of a ninth embodiment of a projectile. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Identical or functionally equivalent elements are given the same reference numerals in all Figures. 
     A gas gun shown in  FIGS. 1 and 3  to  6  and designated in its entirety by  100  comprises a main body  102 , a sabot  104  and a projectile  106  arranged in the sabot  104 . 
     The gas gun  100  is an acceleration device and serves to accelerate the projectile  106  by means of the sabot  104  in a direction of acceleration  108 . 
     The main body  102  is of cylindrical and hollow construction and comprises a rear end  110  in the direction of acceleration  108 , a barrel  112  and a front outlet  114  in the direction of acceleration  108 . 
     Arranged at the rear end  110  of the main body  102  is a propellant chamber  116 , which in the direction of acceleration  108  borders at the front on a rear wall  118  of the sabot  104  when the sabot  104  is arranged in an initial position (see  FIG. 1 ). 
     Stops  120  against which the sabot  104  bears in the initial position with the rear wall  118  are provided on the main body  102  to lock the sabot  104  in the direction opposite to the direction of acceleration  108 . 
     The sabot  104  is of substantially cylindrical and solid construction. 
     An outer diameter  122  of the sabot  104  is selected so that an outer lateral surface  124  of the sabot  104  can slide along an inner lateral surface  126  of the barrel  112 . 
     An inner diameter  128  of the barrel  112  of the main body  102  is, therefore, slightly larger than the outer diameter  122  of the sabot  104 . 
     Sabot stoppers  132  are provided at a front end  130  of the main body  102  in the direction of acceleration  108  for restricting movement of the sabot  104  in the direction of acceleration  108 . 
     The barrel  112  of the main body  102  of the gas gun  100  extends from the stops  120  to the sabot stoppers  132 . 
     The sabot  104  comprises a receptacle  134  for receiving the projectile  106 . 
     The receptacle  134  is of complementary construction to a section of the projectile  106  so as to be able to easily receive this section. 
     The projectile  106  is of rotationally symmetrical construction with respect to an axis of rotation  137  and comprises a front hemispherical section  136 , a cylindrical section  138  located centrally and a rear hemispherical section  140 , the hemispherical sections  136  and  140  having, for example, a substantially identical radius  142  (see  FIG. 2 ). 
     The radius  142  of the front hemispherical section  136  and of the rear hemispherical section  140  corresponds, for example, approximately to a radius  144  of the cylindrical section  138  of the projectile  106  and, for example, approximately to half of a length  146  of the cylindrical section  138 . 
     A length  148  of the projectile  106  therefore corresponds, for example, approximately to four times the radius  142  of the front hemispherical section  136  and of the rear hemispherical section  140 . 
     In the initial position, the projectile  106  is arranged in the receptacle  134  of the sabot  104  so that the receptacle  134  surrounds the rear hemispherical section  140  and, for example, approximately half of the cylindrical section  138  of the projectile  106  (see  FIG. 1 ). 
     In an embodiment (not shown) of the sabot  104 , the projectile  106  is substantially completely received in the sabot  104 . 
     The gas gun  100  described above with the sabot  104  and the projectile  106  operates in the following way: 
     A compressed gas or gas mixture is introduced into the propellant chamber  116  of the main body  102  of the gas gun  100 . 
     The resulting rise in pressure in the propellant chamber  116  causes a force to be applied to the rear wall  118  of the sabot  104  and hence the sabot  104  including the projectile  106  to be accelerated in the direction of acceleration  108  to, for example, approximately 70 m/s to simulate an impact on rotor blades (not shown) of a wind power plant. 
     The sabot  104  of the projectile  106  is thus brought in the direction of acceleration  108  from the initial position to an end position at the front end  130  of the main body  102  (see  FIG. 3 ). 
     The sabot  104  is braked by the sabot stoppers  132 . 
     The projectile  106  held loosely in the sabot  104  separates from the sabot  104  on account of its inertia and flies in the direction of acceleration  108  towards a target  150 . 
     During the flight phase the projectile  106  is deformed by the air resistance (see  FIGS. 4 and 5 ). 
     The deformations shown in  FIGS. 4 and 5  result in an inaccuracy in the reproducibility of the impact of the projectile  106  on the target  150  shown in  FIG. 6 . 
     A second embodiment of the projectile  106  shown in  FIG. 7  comprises, in particular, for stabilization of the projectile  106  in the flight phase a stabilizing device  152 . 
     The deformations of the projectile  106  caused by the air resistance can be reduced, in particular, avoided altogether by means of the stabilizing device  152 . 
     The stabilizing device  152  is formed by square honeycombs and extends in both the radial and the axial direction over the entire extent of the projectile  106 . 
     To produce the projectile  106 , the stabilizing device  152  is placed in a mold into which, for example, a mixture of gelatin and water is subsequently introduced. 
     Apart from that, the embodiment of the gas gun  100  shown in  FIG. 7  with the sabot  104  and the projectile  106  corresponds with respect to construction and operation to the embodiment of the gas gun  100  shown in  FIGS. 1 and 3  to  6  with the sabot  104  and the projectile  106 , to the above description of which reference is made in this respect. 
     The third embodiment of the projectile  106  shown in  FIG. 8  differs from the embodiment shown in  FIG. 7  in that instead of a square honeycomb pattern, the stabilizing device  152  has a triangular honeycomb pattern. 
     Apart from that, the third embodiment of the projectile  106  shown in  FIG. 8  corresponds with respect to construction and operation to the second embodiment shown in  FIG. 7 , to the above description of which reference is made in this respect. 
     In an embodiment (not shown) of the projectile  106  corresponding substantially to the third embodiment shown in  FIG. 8 , the honeycomb pattern is a hexagonal honeycomb pattern. 
     A fourth embodiment of the projectile  106  shown in  FIG. 9  differs from the second embodiment shown in  FIG. 7  in that the stabilizing device  152  comprises a cubic lattice formed by stabilizing elements  156 . 
     The stabilizing elements  156  are connected to one another by connecting elements  158 . 
     Lamellae  160  which are, for example, rectangular, are provided on the stabilizing elements  156  for further stabilization of the projectile  106 . Such lamellae  160  can be provided on individual stabilizing elements  156  or also on all stabilizing elements  156 . 
     Apart from that, the fourth embodiment of the projectile  106  shown in  FIG. 9  corresponds with respect to construction and operation to the second embodiment shown in  FIG. 7 , to the above description of which reference is made in this respect. 
     A fifth embodiment of the projectile  106  shown in  FIG. 10  differs from the fourth embodiment shown in  FIG. 9  in that instead of a cubic lattice, a tetrahedral lattice is provided, which is formed by a plurality of stabilizing elements  156 . 
     Apart from that, the fifth embodiment of the projectile  106  shown in  FIG. 10  corresponds with respect to construction and operation to the fourth embodiment shown in  FIG. 9 , to the above description of which reference is made in this respect. 
     A stabilizing device  152  of a sixth embodiment of the projectile  106  shown in  FIG. 11  differs from the second embodiment shown in  FIG. 7  in that the stabilizing device  152  is formed by four substantially identical plate-shaped stabilizing elements  156 . 
     Two of the plate-shaped stabilizing elements  156  are arranged parallel to each other, parallel to the axis of rotation  137  of the projectile  106  and at a distance from each other which corresponds, for example, approximately to the radius  142  of the hemispherical sections  136  and  140  of the projectile  106 . 
     The two stabilizing elements  156  are arranged in mirror-symmetrical relation to each other with respect to the axis of rotation  137  of the projectile  106  and extend along the largest extent of the projectile  106  and in a direction transverse thereto as far as a surface  161  of the projectile  106  in each case. 
     The two further plate-shaped stabilizing elements  156  correspond in their extent, their position relative to each other and their arrangement on the projectile  106  to the previously described plate-shaped stabilizing elements  156 , but are arranged at, for example, approximately 90° to the previously described two plate-shaped stabilizing elements  156  with respect to the axis of rotation  137  of the projectile  106 . 
     In a viewing direction along the axis of rotation  137  of the projectile  106 , an arrangement of the plate-shaped stabilizing elements  156  thus corresponds substantially to a hash sign. 
     One or more stabilizing plates (not shown) aligned substantially perpendicularly to the axis of rotation  137  may also be provided for further reinforcement of the stabilizing device  152 . 
     Apart from that, the sixth embodiment of the projectile  106  shown in  FIG. 11  corresponds with respect to construction and operation to the second embodiment shown in  FIG. 7 , to the above description of which reference is made in this respect. 
     A seventh embodiment of the projectile  106  shown in  FIG. 12  differs from the second embodiment shown in  FIG. 7  in that the stabilizing device  152  is formed by a plurality of hollow bodies in the form of hollow balls  162 . 
     The hollow balls  162  are filled with the gel-like or jelly-like material and are arranged on one another and connected to one another in such a way that the projectile  106  has substantially the same outer contour as the second embodiment of the projectile  106  shown in  FIG. 7 . 
     Apart from that, the seventh embodiment of the projectile  106  shown in  FIG. 12  corresponds with respect to construction and operation to the second embodiment shown in  FIG. 7 , to the above description of which reference is made in this respect. 
     An eighth embodiment of the projectile  106  shown in  FIG. 13  differs from the first embodiment shown in  FIGS. 1 to 6  in that the projectile  106  is of cylindrical configuration and has no hemispherical sections. 
     The length  146  of the cylindrical section  138  in this embodiment is, for example, approximately four times the radius  144  of the cylindrical section  138 . 
     One, or a combination of several, of the stabilizing devices  152  shown in  FIGS. 7 to 12  may be provided in the eighth embodiment of the projectile  106 . 
     Apart from that, the eighth embodiment of the projectile  106  shown in  FIG. 13  corresponds with respect to construction and operation to the first embodiment shown in  FIGS. 1 to 6 , to the above description of which reference is made in this respect. 
     A ninth embodiment of the projectile  106  shown in  FIG. 14  differs from the first embodiment shown in  FIGS. 1 to 6  in that the shape of the projectile  106  is an ellipsoid. 
     A length  164  of the first semiaxis of the ellipsoid in this embodiment is, for example, approximately half of a length  166  of the second semiaxis of the ellipsoid. 
     The length of the third semiaxis is identical to the length of the first semiaxis, so that the projectile  106  has the shape of an ellipsoid of revolution. 
     In the ninth embodiment of the projectile  106 , one, or a combination of several, of the stabilizing devices  152  shown in  FIGS. 7 to 12  may be provided. 
     Apart from that, the ninth embodiment of the projectile  106  shown in  FIG. 14  corresponds with respect to construction and operation to the first embodiment shown in  FIGS. 1 to 6 , to the above description of which reference is made in this respect. 
     In principle, each of the projectiles described above may be provided with one of the stabilizing devices described above or with a combination of several of the stabilizing devices described above. 
     Bird strike tests can be carried out with reproducible and representative results by using projectiles with a stabilizing device.

Technology Classification (CPC): 5