billder
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Articles and methods for protection against focused beams of
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United States Patent 5,788,110
Alhamad August 4, 1998
Articles and methods for protection against focused beams of radiant energy
Abstract
A highly effective barrier for protecting objects against focused beams of radiant energy. The invention has special applicability in a combat environment for protecting military equipment against destruction by laser weapons, or for thwarting detection of such equipment by reflected radar waves. The barrier comprises a layer of slitted and expanded metal foil, made from a non-ferrous metal having an absorptivity less than 3% and a thermal conductivity above 100 W/m/K, interposed between the radiant energy beam and the object to be protected. The barrier layer may be multiple sheets of the slitted and expanded metal foil, or a contained layer of nested ellipsoids formed from the expanded metal sheets.
Inventors: Alhamad; Shaikh Ghaleb Mohammad Yassin (P.O. Box 31590, Riyadh, 11418, SA)
Appl. No.: 470254
Filed: June 6, 1995
Current U.S. Class: 342/4; 428/573; 428/577; 428/592
Intern'l Class: B65D 001/04; A02C 003/02
Field of Search: 220/450 428/573,577,592
References Cited [Referenced By]
U.S. Patent Documents
1671650 May., 1928 Newman et al.
3162231 Dec., 1964 Emerson 153/2.
3349953 Oct., 1967 Conaway et al. 220/85.
3356256 Dec., 1967 Szego 220/88.
3687329 Aug., 1972 Baum 220/26.
4149649 Apr., 1979 Szego 220/88.
4249669 Feb., 1981 Szego 220/216.
4265317 May., 1981 Knecht 169/50.
4323620 Apr., 1982 Zwabuchi et al. 220/450.
4361190 Nov., 1982 Szego 169/48.
4440076 Apr., 1984 Lines 428/92.
4444821 Apr., 1984 Young et al. 220/450.
4461054 Jul., 1984 Schrenk 220/88.
5001017 Mar., 1991 Alhamad et al. 220/450.
5500037 Mar., 1996 Alhamad 220/450.
Foreign Patent Documents
256239 Feb., 1988 EP.
601374 Nov., 1925 FR.
2440892 Feb., 1980 FR.
2602976 Feb., 1988 FR.
3435457 Feb., 1986 DE.
Other References
John Powell, "Cutting Non-Ferous Metals", CO2 Laser Cutting, pp. 71-86, Springer-Verlag (London).
Primary Examiner: Moy; Joseph M.
Attorney, Agent or Firm: Cates; Charles E., Barber; Frank T.
Parent Case Text
This application is a continuation-in-part of application Ser. No. 414,106, filed Mar. 31, 1995 (now abandoned), which is a continuation-in-part of application Ser. No. 806,901, filed Dec. 2, 1991, now U.S. Pat. No. 5,402,832, which was a division of application Ser. No. 674,277, filed Mar. 19, 1991 (now U.S. Pat. No. 5,097,907, issued Mar. 24, 1992), which was a division of application Ser. No. 417,696, filed Oct. 5, 1989 (now U.S. Pat. No. 5,001,017, issued Mar. 19, 1991), which was a division of application Ser. No. 280,317, filed Dec. 6, 1988 (now abandoned).
Claims
What is claimed is:
1. A lightweight barrier for protection of an object against a focused beam of radiant energy, comprising a layer of slitted and expanded foil, made from a non-ferrous metal having an absorptivity less than 3% and a thermal conductivity above 100 W/m/K, interposed between said object and said beam.
2. A barrier as in claim 1 wherein said beam of radiant energy is a laser beam.
3. A barrier as in claim 1 wherein said beam of radiant energy is a radar beam.
4. A barrier as in claim 1 wherein said non-ferrous metal is aluminum or an alloy thereof.
5. A barrier as in claim 1 wherein said non-ferrous metal is magnesium or an alloy thereof.
6. A barrier as in claim 1 wherein said non-ferrous metal is copper or an alloy thereof.
7. A barrier as in claim 1 wherein said interposed layer has a porosity in the range of 80 to 99% and a specific internal surface area above 250 square feet per cubic foot.
8. A barrier as in claim 1 wherein said interposed layer comprises multiple sheets of said expanded metal foil.
9. A barrier as in claim 1 wherein said interposed layer is a contained layer of nested ellipsoids formed from said expanded metal sheets.
10. A barrier as in claim 9 wherein said nested ellipsoids are contained between layers of said expanded metal sheets.
11. A barrier as in claim 9 wherein the short diameter of said ellipsoids is in the range of 20 to 40 mm and the long diameter is in the range of 30 to 60 mm.
12. A fuel tank which is protected against the destructive rays of a laser beam weapon, said fuel tank comprising a container for said fuel and a jacket enveloping said container, said jacket comprising a layer of slitted and expanded foil made from a non-ferrous metal having an absorptivity less than 3% and a thermal conductivity above 100 W/m/K.
13. A fuel tank as in claim 12 wherein said non-ferrous metal is aluminum or an alloy thereof.
14. A fuel tank as in claim 12 wherein said non-ferrous metal is magnesium or an alloy thereof.
15. A fuel tank as in claim 12 wherein said non-ferrous metal is copper or an alloy thereof.
16. A fuel tank as in claim 12 wherein said jacket layer has a porosity in the range of 80 to 99% and a specific internal surface area above 250 square feet per cubic foot.
17. A fuel tank as in claim 12 wherein said jacket layer comprises multiple sheets of said expanded metal foil.
18. A fuel tank as in claim 12 wherein said jacket layer comprises a contained layer of nested ellipsoids formed from said expanded metal sheets.
19. A fuel tank as in claim 12 wherein said jacketed container is filled with multiple pieces of said expanded metal net formed in the shape of ellipsoids, for protection against explosion and for scattering focused beams of radiant energy.
20. A fuel tank as in claim 12, said fuel tank being located in an aircraft.
21. A fuel tank as in claim 12, said fuel tank being located in a guided missile.
22. A fuel tank as in claim 12, said fuel tank being located in a ground vehicle.
23. An article which is protected against detection by reflected radar waves, said article being covered by a layer of slitted and expanded metal foil for scattering said radar waves and preventing the return of true echoes, in which said metal is a non-ferrous metal having an absorptivity less than 3% and a thermal conductivity above 100 W/m/K.3.
24. An article as in claim 23 wherein said non-ferrous metal is aluminum or an alloy thereof.
25. An article as in claim 23 wherein said non-ferrous metal is magnesium or an alloy thereof.
26. An article as in claim 23 wherein said non-ferrous metal is copper or an alloy thereof.
27. The invention of claim 23 in which said article is a vehicle.
28. The invention of claim 23 in which said article is an air vehicle.
29. The invention of claim 23 in which said article is a land vehicle.
30. A method for protection of an article against a focused beam of radiant energy, comprising interposing between said article and said beam a layer of slitted and expanded foil made from a non-ferrous metal having an absorptivity less than 3% and a thermal conductivity above 100 W/m/K.
31. A method as in claim 30 wherein said non-ferrous metal is aluminum or an alloy thereof.
32. A method as in claim 30 wherein said non-ferrous metal is magnesium or an alloy thereof.
33. A method as in claim 30 wherein said non-ferrous metal is copper or an alloy thereof.
34. A method as in claim 30 wherein said beam of radiant energy is a laser beam.
35. A method as in claim 30 wherein said beam of radiant energy is a radar beam.
36. A method as in claim 30 wherein said interposed layer has a porosity in the range of 80 to 99% and a specific internal surface area above 250 square feet per cubic foot.
37. A method as in claim 30 wherein said interposed layer comprises multiple sheets of said expanded metal foil.
38. A method as in claim 30 wherein said interposed layer is a contained layer of nested ellipsoids formed from said expanded metal sheets.
39. A method as in claim 38 wherein said nested ellipsoids are contained between layers of said expanded metal sheets.
40. A method as in claim 38 wherein the short diameter of said ellipsoids is in the range of 20 to 40 mm and the long diameter is in the range of 30 to 60 mm.
Description
FIELD OF THE INVENTION
This invention relates generally to barriers or shields for the protection of objects against focused beams of radiant energy. The invention has special applicability in a combat environment for protecting military equipment against destruction by laser weapons, or for thwarting detection of such equipment by reflected radar waves.
All radiant energy exists in the form of electromagnetic waves. The various forms of radiant energy are categorized according to their characteristic wave lengths. Thus, the most important kinds of electromagnetic energy in terms of increasing wave lengths are: cosmic rays, gamma rays given off by radium, X rays, ultraviolet rays, visible light, infrared or heat waves, radio waves, and electric waves. All of these forms of radiant energy have been harnessed for use in industry, medicine, communications, warfare, and the like.
Although natural sources of radiant energy send out their electromagnetic waves in all directions, great strides have been made in refining and enhancing the power and usefulness of these energy sources by focusing the waves into unidirectional beams and concentrating the energy on a single small area to be treated. Thus, in laser technology, light waves are amplified and focused into a beam which can be brought to bear on a point which may be only one ten-thousandths of an inch wide. When the energy of the beam is concentrated on such a small area, it may produce temperatures higher than 10,000 degrees F. In this way, the laser is used to melt and vaporize many hard materials and to carry out many precision operations involving the treatment of tiny areas. The unusual characteristics of laser light make the laser a useful tool in industry, medicine, navigation and communications.
The laser also has applications in the military arena, where the intense heat of the laser beam can be used from a long distance to create holes in vehicle fuel tank walls or other vehicle components or to otherwise disable operating systems. The fuel tanks on aircraft are one of the most vulnerable areas to attack. Because of the nature of aircraft fuel, an explosive or combustible fuel-air mixture normally exists in the ullage of an aircraft fuel tank, and when the integrity of the fuel tank walls is pierced by a laser beam, the resulting fire and explosion can cause significant and often fatal structural damage not only to the fuel tank but also to the aircraft itself.
Guided missiles are a form of military weaponry which are particularly subject to interception and destruction because of the supplies of liquid or solid fuel which they carry on board for propulsion. Guided missiles of all types, including surface-to-surface, surface-to-air, air-to-air, and air-to-surface, are vulnerable to this type of laser attack. When an anti-missile device in the form of a laser beam is directed at a guided missile, particularly one with outboard fuel tanks, the piercing of the fuel tank by the laser beam causes explosion and destruction of the missile in its course, and a resultant failure of the expensive weapon.
The destructive effect of a laser beam attack on the fuel tank of a ground combat vehicle is of a different nature, but equally destructive. Although the danger of explosion on the inside of the fuel tank of a ground vehicle is lessened because of the lesser tendency of diesel fuel to produce an explosive fuel-air mixture, nevertheless many flammable materials are carried aboard ground combat vehicles, including fuel, hydraulic fluid, and ammunition. The serious damage in a ruptured land vehicle tank is the burning of pooled fuel outside the tank. When a fuel tank is ruptured by a laser beam, the contained fuel is spilled on surrounding surfaces and is then ignited by the energy of the laser beam or the surrounding hot surfaces (engine, gun breech, etc.). The burning fuel ignites surrounding displaced and stored fuel, rapidly engulfing the vehicle and its personnel in flames.
Radar technology is another area in which the usefulness of radiant energy has been enhanced by focusing electromagnetic waves into unidirectional beams. A radar device produces pulses of radio waves which are focused into a unidirectional beam, and the echo from the focused beam against a distant object is used to calculate the distance and direction of the object. Radar is thus a useful tool in many applications. It is used for traffic control and navigation in the aviation and shipping industries; for law enforcement; for weather forecasting; and for many scientific purposes, such as astronomy, oceanography, and the like.
Radar has also become a military tool of many uses. For defensive purposes, early warning radar systems help prevent surprise attacks by detecting approaching enemy aircraft or ballistic missiles. However, it is used for important offensive purposes as well. Fire control radar aims and fires guns and missiles such as rockets. Bombers with radar bombsights drop bombs on targets at night or in bad weather. Especially damaging shells or bombs are equipped with radar proximity fuses, which explode the bombs in the air near a designated target.
Concurrently with the development of military uses of focused radiant energy beams, such as laser and radar, there has been a need and an effort to develop effective defensive countermeasures.
It is an object of the present invention to provide a barrier or shield against focused beams of radiant energy.
It is another object of the invention to provide jacketed articles which are protected against the destructive forces of focused beams of radiant energy such as laser or radar.
It is a further object of the invention to provide articles, such as fuel tanks, which are protected not only against radiant beam weaponry but also against internal explosion of the fuel contained therein.
It is a further object to provide methods for use of the new barrier in the protection of structures which are otherwise subject to destruction from the destructive forces of focused beams of radiant energy.
It is another object of the invention to provide a barrier which is extremely light, durable, simple and inexpensive to manufacture, easy to assemble, and relatively maintenance-free.
Other objects and advantages of the invention will become apparent as the specification proceeds.
SUMMARY OF THE INVENTION
This invention is based on the discovery that focused beams of radiant energy, such as laser or radar, can be effectively unfocused, or scattered, when they strike a barrier comprising a layer of slitted and expanded metal foil, such as aluminum, copper or magnesium or alloys thereof. It has been found that the barrier is effective in scrambling the focused rays in such manner that the intended purpose of such rays is successfully thwarted.
The barrier of the present invention is useful in many applications for protecting against focused radiant energy beams which are used for military or other unfriendly destructive purposes. Thus, it is effective in neutralizing or counteracting the effectiveness of laser beams designed to penetrate and explode fuel tanks in various types of aircraft, guided missiles, land vehicles, and the like. It is also effective for inactivating radar beams which are used in defensive warning systems for detecting the presence of objects and personnel, and it is also effective against military offensive systems in which the radar is used in radar bombsights or radar proximity fuses, or to aim or guide missiles.
Although the invention is applicable to protection against many forms of radiant energy, the discussion herein will be directed, by way of example, to the deflection and scrambling of laser beams. The invention with respect to lasers is based in part on the determination that the expanded metal foil must be made from a non-ferrous metal having an absorptivity less than 3% and a thermal conductivity above about 100 W/m/K, such as aluminum, magnesium and copper. Although slit and expanded sheets may be made from a number of ferrous metals, such as steel, and other materials, such as acrylic plastics, and the like, such materials offer no resistance or retardation to the intense heat of a laser beam. Accordingly, a candidate deflection barrier made of such materials would be instantaneously melted and pierced before there was any opportunity to deflect or scatter the laser beam. It has been found that, in order to accomplish the deflection, the barrier material must be capable of causing the laser beam to dwell for a minimum period of time on the surface of the material before melting and piercing takes place.
The focused beam of a laser is capable of locally boiling and thereby piercing most metals if they are exposed to the laser beam for a sufficient length of time. As the metals are heated they become better absorbers and are thus more effectively heated to become even more absorptive and so on. This heating/increased absorption/ heating cycle causes immediate melting and piercing of the metal. However, the heating/increased absorption/heating cycle is difficult to set up in materials, such as aluminum, magnesium and copper, which are very highly reflective (i.e., possess very low absorptivity). These non-ferrous metals combine a high reflectivity (which inhibits laser input to the piercing zone) with a high thermal conductivity (which effectively cools the piercing zone). Although they could eventually be pierced by the laser, the piercing process is substantially slower in any practical range of laser power. Consequently, a dwell time is established by these materials, allowing them to survive for a period of time long enough to permit the angled surfaces of the expanded metal net to effectively deflect or scatter the focused laser beam.
It has been determined that, in order to provide the resistance to the laser beam necessary to be an effective deflecting agent, the non-ferrous metals should have an absorptivity of less than about 3% and a thermal conductivity above about 100 W/m/K. Absorptivity (%)=100 minus Reflectivity (%).
The product of the present invention therefore is a lightweight barrier for protection of an object against a focused beam of radiant energy, comprising a layer of slitted and expanded metal foil, made from a nonferrous metal having an absorptivity less than about 3% and a thermal conductivity above about 100 W/m/K, interposed between said object and said beam.
In one embodiment hereinafter described the barrier is placed in the form of a jacket or covering around the object to be protected. The barrier may be one or more sheets of slitted and expanded metal foil, or it may be a contained layer of nested ellipsoids formed from expanded metal sheets. For example, the layer of nested ellipsoids may be contained between two sheets of slitted and expanded metal foil.
In another embodiment, the invention is a fuel container which is jacketed with said layer of slitted and expanded metal foil, for protection against destruction from laser beams, and which is also filled with multiple pieces of expanded metal net formed in the shape of ellipsoids, for protection against internal explosion.
In another embodiment, a barrier layer of the type described above is incorporated in the outer shell or skin of an aircraft, missile, ground vehicle, and the like, to produce scrambling of radar beams and thus avoid radar detection or avoid destruction by weapons which are guided by radar beams.
In the preferred form of the invention, the barrier layer has a porosity in the range of 80 to 99% and a specific internal surface area above 250 square feet per cubic foot. This open-structured configuration not only produces a highly effective scattering of the focused laser or radar beams but it also provides significant flame arresting properties for additional protection of the shielded object.
The invention also comprises a method for protection of an article against a focused beam of radiant energy, comprising interposing between said article and said beam a layer of slitted and expanded foil, made from a non-ferrous metal having an absorptivity less than 3% and a thermal conductivity above 100 W/m/K.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view of a section of the barrier of the present invention, showing use of two sheets of expanded metal net.
FIG. 1-A is a cross-sectional view of a section of the barrier, showing a layer of ellipsoids contained between two sheets of expanded metal net.
FIG. 2 is a top view of a slitted metal foil sheet, which can be expanded by stretching to provide the expanded metal net usable in the present invention.
FIGS. 3 through 6 are top views of the expanded metal net, showing changes in configuration as the slitted sheet is pulled to open up the expanded metal net.
FIG. 7 is a perspective view showing the ellipsoid form made from the expanded metal net, for use in the present invention.
FIG. 8 is a side view of an aircraft external pylon fuel tank, with the barrier jacket of the present invention installed.
FIG. 9 is a cross-sectional end view of the pylon fuel tank, with the barrier jacket installed.
FIG. 10 is a cross-sectional end view of the pylon fuel tank, with the barrier jacket installed externally and with the inside of the tank filled with anti-explosion ellipsoids.
FIG. 11 is a perspective view showing a rectangular fuel tank from a ground combat vehicle, with the barrier jacket of the present invention in place.
FIG. 12 is a cross-sectional side view of the fuel tank of FIG. 11. [/b] |
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