Laser Ignition System

Abstract

A device for firing ammunition has a chamber in which the propellant is placed, the chamber communicating with a barrel or guide through which is projectile or missile is propelled by the propellant when it is ignited, there being a window through which laser radiation can be directed onto the propellant in the chamber, the window pressure sealing the chamber when the chamber is closed.

Description

This invention relates to weapons or devices for firing ammunition and particularly to the use of laser radiation to fire the same.

A weapon, such as a gun, has a chamber connected to a barrel through which a projectile or missile, including shot or slugs, can be propelled by means of an explosive. The explosive may be in a container, such as a conventional shell, or can be unconfined, such as in bags. In prior practice, a sear mechanism has been used to control a firing pin to strike a primary explosive which in turn ignites the secondary or propellant. Other firing mechanisms also have been used including electrically heated wire means.

The invention herein is related to Applicant's copending U.S. Pat. application Ser. No. 865,770, filed Oct. 13, 1969, issued U.S. Pat. No. 3,631,623, Jan. 4, 1972, and copending U.S. Pat. application Ser. No. 125,290, filed Mar. 17, 1971.

One of the objects of the invention is to provide an improved system for firing weapons, such as guns, without mechanical contact with the explosive.

According to one aspect of the invention, a device for firing ammunition, such as a weapon, is provided with a chamber for receiving a propellant. The chamber communicates with a barrel into which or through which the projectile or missile used is projected upon firing the weapon. A laser is provided having its radiation or beam directed through a substantially pressure sustaining window to an explosive within the chamber. The window must be optically transparent to the laser radiation. The explosive may consist of only a propellant, or it may include a primary explosive which is used to ignite the secondary or main propellant. The explosive may be in a shell case, may be in bags such as in larger weapons or firearms, or may be caseless compacted pellets. The shell case may be transparent to the laser radiation or may have laser radiation transparent window means therein. The shell may have a projectile attached thereto, or the projectile can be put into the barrel of the gun. The projectile may be a single body or may be a plurality of bodies such as shot.

These and other objects, advantages and features of the invention will become apparent from the following description and drawings which are merely exemplary.

In the drawings:

FIG. 1 is a schematic sectional view of a portion of a weapon;

FIG. 2 is similar to FIG. 1 except that the laser beam is directed through the side of the shell;

FIG. 3 is similar to FIG. 1 except that it shows a weapon using separately loaded propellant which is not confined in a shell case;

FIG. 4 is similar to FIG. 3 except that ignition is through the side of the casing;

FIG. 5 is similar to FIG. 1 except it shows schematically the use of the invention with a recoilless type gun;

FIG. 6 is similar to FIG. 5 except ignition is through the side; and

FIG. 7 schematically shows an arrangement wherein a shell can be fired by a conventional firing pin or by a laser means.

When appropriate, reference numerals indicating the same parts have been used in the various views.

One form of the invention is schematically shown in FIG. 1 wherein weapon or gun 10 has a chamber 11 and barrel 12 connected to said chamber. Breech block 13 is used to close chamber 11, the breech block taking any of the usual forms for large guns or for smaller weapons such as rifles or shotguns.

Shell or casing 14 may have a primary explosive 15 in the base thereof which, when fired, will ignite the secondary or propellant explosive 16. The primer may be located in a disc 18 which has a projection 18A that fits into an aperture in the base of the shell case 14 serving as a window transparent to the laser radiation being used. Projectile 17 fits into shell case 14.

The breech block has a window means 19 for transmitting the energy from laser beam 20 to the primary explosive 15 through a suitable lens 19A. The window material, for example, can be optically transparent methyl methacrylate resin such as "Plexiglas," a trademark of Rohm & Haas Co. for its synthetic resinous sheets. Other window materials include an epoxy resin sold under the trademark "Stycast," a trademark of Emerson & Cuming for its epoxy resin. The window also could be polycarbonate sold under the trademark "Lexan," a trademark of General Electric Co. Also, glass materials of various combinations can be used. The composition of glass can be varied to suit the application. The window material must be transparent to the laser radiation being used and must be capable of withstanding the high pressures and temperatures of an explosive reaction. It must support the pressure load and should not deteriorate under the high temperatures concerned.

Laser assembly 21 can be a suitable type of laser. An example of one which has been used in neodymium glass laser made by the American Optical Company of Southbridge, Massachusetts, and sold under the trademark "Uni-Laser Mark II" operating at a wavelength of 1.06 microns. As an example, the energy delivered to the explosive surface of somewhat less than one-half joule from a 1 joule source having one-half power full angle divergence greater than 90 milliradians has been found satisfactory. The peak power and energy required to ignite both smokeless powder and primary explosives is dependent upon the coherence property of laser radiation which permits focusing of the radiation to power densities much greater than that of the source, the optical absorption coefficient of the explosive, the beam divergence of the laser, the losses in the optical path traversed by the laser radiation, and the ignition temperatures of the explosives.

Other types of lasers can be used that can be remotely located relative to the weapon. The peak power and energy required to ignite both smokeless powder and primary explosives is dependent upon the ability to focus the laser output to very small areas and high power densities. It is possible to operate the system without a focusing means, but most practicable embodiments will contain the same. Such focusing means can be a lens system or a reflector system.

FIG. 2 illustrates side transmittal of the beam. Wall 25 of chamber 11 has an aperture 26 closed by window 27. The side wall of casing 28 can have a window 29 therein and a primary explosive 30 into which laser beam 31 can be directed. The primer can be located in disc 30A. Laser 32 directs beam 31 to a focusing system 33. The window 27 must be arranged so as to register with window 29.

It is possible to make casing 28 of a plastic optically transparent to the laser beam in which event the window 29 is not needed. The casing also could be made of an expendable material which is consumed during the explosion used to project the projectile.

The invention further can be used in conjunction with guns employing separately loaded propellant and projectiles. An example is seen in FIG. 3 wherein chamber 11 has a plurality of bags 35 of powder or propellant therein. Projectile 17 is placed in the gun before the powder. The breech block 36 in this type of weapon usually has conventional obturator means 37 to seal the breech when the gun is fired. An igniter pad 35A can be used. In separate loading ammunition, a bag, generally made of silk filled with black powder, can be used to insure complete ignition of the smokeless powder. The separate ignition pad may not be needed if enough laser energy is available for direct ignition of the large grains of the smokeless powder.

Optically transparent and pressure sealing window means 38 is placed in the breech block through which laser beam 39 is transmitted from remotely located laser 40 through a focusing means 38A. The beam may be used to ignite directly the propellant explosive or can be used to ignite a primary explosive or igniter.

FIG. 4 shows a weapon similar to FIG. 3 except a side pressure sealing window 42 is used. Chamber 11 has propellant powder bags 35 therein, the projectile (not shown) having previously been placed in the barrel. Breech block 43, in this instance, can be the usual breech block.

Laser 44 directs beam 45 to focusing system 46 which in turn directs the laser beam to the propellant or to a primary explosive.

FIG. 5 illustrates use of the invention in conjunction with a recoilless type weapon. The previous forms usually have a recoil mechanism if needed, or the principle can be applied to other types. Chamber 47 of gun tube 48 receives shell 49 with its projectile 50. A casing is shown having a back plate with conventional apertures to provide, as is known, a path for gases which can pass to the rear so as to counteract recoil. Breech block 51 has a window assembly 52 with a focusing means which is optically aligned with the pressure-tight laser radiation transparent window 52A in the base of shell 49. The laser beam 53 can be directed from the side by laser 54. The laser also could be at the rear to direct the beam through an aperture or window in the breech block 51 to the explosive. Breech block 51 may have conventional venturi means 51A through which gases pass.

FIG. 6 is similar to FIG. 5 except a window assembly 55 is provided on the side 56 of the gun tube 48. Shell 57 has a pressure-tight optically transparent window 58 in the side thereof. Laser 59 can be arranged with suitable focusing means (not shown) to direct a laser beam 60 through assembly 55 to the primary explosive 58A held in disc 58B, said disc being transparent to laser radiation.

In some instances, a conventional shell can be used, as seen in FIG. 7, having the usual primer cup with primary explosive and adaptable to be ignited by a conventional firing pin 65 located in breech block 66. The same shell also could have a window 67 in the side thereof adapting it to be fired by the laser apparatus indicated generally at 68. With such a dual firing arrangement, both firing means could be used in a single gun so that both types of ammunition could be fired.

When the laser means is remotely located relatively to the weapon, various means can be used to direct the beam from the laser. Such can be a light guide, reflective or refractive type optical system that would be kept in alignment with the laser by a suitable servo-mechanism which would keep the optical system, laser, and explosive properly aligned. A suitable focusing means would be used.

Examples of primary explosive that can be used are lead styphnate or a lead styphnate and barium nitrate mixture. The propellant explosive can be a smokeless powder. Further, the shell or case could be reloadable with propellant. The propellant and/or primary explosive also could be solid, gaseous or liquid. The propellant also can be fired directly without a primer. It was found that only a small amount of energy, as little as 700 to 2,000 microjoules, was needed to set off primary explosives when the laser radiation was focused to spot sizes of the order of 0.0025 cm.sup.2.

It should be apparent that variations could be made in details of the invention without departing from the spirit thereof except as set forth in the appended claims.

Claims

What is claimed is:

1. A firearm having a barrel and openable breech block forming a chamber enclosing means, projectile means insertable into said barrel, a radiation ignitable charge insertable into said chamber enclosing means when said breech block is opened, said charge being adjacent to said projectile, radiation optically transparent pressure sealing means in said chamber enclosing means, said pressure sealing means being pressure sealing and heat and flame resistant, an external laser system remotely located relative to said chamber enclosing means and adjacent to said chamber enclosing means, and means optically directing and focusing said laser energy through said pressure sealing means and to said radiation ignitable charge.

2. A firearm as claimed in claim 1 wherein the charge is a primary explosive and there is a propellant in said chamber ignitable by said charge.

3. A firearm as claimed in claim 1 wherein the charge is within a casing with the projectile attached.

4. A firearm as claimed in claim 3 wherein the casing has a window therein.

5. A firearm as claimed in claim 3 wherein the casing is expendable.

6. A firearm as claimed in claim 3 wherein the casing has a transparent window and is expendable.

7. A firearm as claimed in claim 1 wherein the chamber has a breech block and the pressure sealing means is in said breech block.

8. A firearm as claimed in claim 1 wherein the sealing window is at the side of the longitudinal axis of the firearm and the laser radiation is directed therethrough.

9. A firearm as claimed in claim 1 wherein the firearm is of the recoilless type.