Combustion Augmented Plasma Gun

The present invention pertains to apparatus for controlled combustion in a gun, and more particularly, to apparatus for providing a controlled increase in muzzle velocity of a projectile while reducing the peak value of pressure inside a gun barrel.

Guns traditionally include an elongated barrel having a central bore closed at a breech end and having a projectile which is moved through the bore by heated gasses from a burning powder or liquid fired by an igniter. A burning powder produces a relatively high pressure against the projectile when the powder is initially ignited, with the pressure decreasing as the projectile moves along the gun barrel. Liquid fuel can be used to provide a more even pressure as the projectile moves along the gun barrel, but requires a critical fuel chamber size, bore diameter and manner of ignition of the fuel.

The present invention includes a gun cartridge having a capillary chamber, a fuel chamber and an oxidizer chamber. The chambers are aligned with the fuel chamber between the oxidizer chamber and the capillary chamber. When the cartridge is in a gun barrel an electric power supply heats and explodes a fuse wire inside the capillary chamber to vaporize a portion of a plasma base in the capillary chamber. The vaporized plasma base provides a narrow jet of ionized gas which vaporizes and entrains a portion of the fuel and causes the fuel to combine with a portion of an oxidizer material. The power supply continues to supply energy which controls the rate of vaporization of the plasma base and thus controls the rate of combustion of the oxidizer material and the fuel. Portions of the oxidizer material and fuel are launched and travel behind the projectile. Combustion of the traveling liquid phase occurs behind the projectile during the time it takes the projectile to move a maximum of 20 bore diameters along the gun barrel. The combustion energy released by the traveling liquid causes pressure against the projectile to remain relatively constant as the projectile moves along the length of the gun barrel. This allows the breech and chamber pressures to be relatively low and still provide a high velocity projectile at the gun nuzzle.

FIG. 1 is a cross sectional view of a combustion augmented plasma gun and cartridge of the present invention.

FIGS. 2-4 disclose a sequence of operation of the apparatus of FIG. 1.

FIG. 5 discloses an electrical power pulse (in the solid line) which is needed to create a plasma in the capillary chamber and (in the dashed line) the resulting chemical pulse produced by combustion of the oxidizer material and fuel.

FIG. 6 discloses the breech pressure (in the solid line) and the projectile base pressure (in the dashed line) for a specific example of a 30 mm diameter gun having a barrel 2.67 m in length.

FIG. 7 discloses the velocity of a 50gm projectile as it travels along the barrel of a 30 mm gun.

FIG. 8 discloses another embodiment of the combustion augmented plasma gun and cartridge of the present invention.

FIG. 9 discloses still another embodiment of the combustion augmented plasma gun and cartridge of the present invention.

The combustion augmented plasma gun disclosed in FIG. 1 includes a gun 10 having a coupling block 11 with a cartridge chamber 12 extending through block 11. A gun barrel 16 is threaded into one end of block 11 and a cartridge 17 is mounted in the other end of coupling block 11. Cartridge 17 includes a metal body 18 and a plastic chamber back liner 21 with an elongated bore 22 extending lengthwise through the center of cartridge 17. A breech bolt 23 is threaded into a rear end of cartridge 17 and a projectile 27 is positioned at the other end of cartridge 17 in a bore 28 of gun barrel 16. Projectile 27 can be attached to the end of cartridge 17 or projectile 27 can be inserted separately into the position shown. A replaceable shot start bushing 29 mounted in bore 28 is adjacent to projectile 27. A pair of crush seals 33 provide sealing between coupling block 11, and barrel 16 and metal body 18. A plurality of breech ring bolts 34 secure a breech ring 35 to coupling block 11. A shoulder 39 on the breech ring 35 rests against a flange 40 on body 18 to selectively secure cartridge 17 in coupling block 11.

A hollow cylindrical outer insulator 41 lines a portion of bore 22 of cartridge 17. A ceramic insulator thrust collar 45 and a capillary backup insulator 46 are positioned inside insulator 41. An anode holder 47 is mounted between thrust collar 45 and insulator 46. A hollow capillary liner 51 mounted inside insulator 46 is filled with a plasma base in the form of a solid first fuel 52. A copper anode 53 extends through an anode insulator sleeve 57 and a copper anode holder. A copper/tungsten anode tip 54 threads into the anode holder 47 and extends into a rear portion of capillary liner 51. A fuse wire 58 connected to anode tip 54 extends through fuel 52 in a capillary chamber 59 to a copper/tungsten cathode 60 mounted inside cartridge body 18. A power supply 63 having a control 64 is connected between anode 53 and cathode 60 to provide electrical power to fuse wire 58 and fuel 52. Chamber back liner 21 is divided into a fuel chamber 65 and an oxidizer chamber 66 by a plurality of membranes 70-72. A second fuel 76 is stored in fuel chamber 65 and an oxidizer material 77 is stored in adjacent chamber 66. Fuel 76 is preferably a liquid hydrocarbon, such as kerosene, and oxidizer material 77 is a liquid, such as hydrogen peroxide. A number of liquid fuels and liquid oxidizer materials are suitable for use in the present invention. Criterion for choosing fuels and oxidizer material combinations include stability, toxicity, corrosion properties, energy density, chemical compatibilities, and physical properties such as mass, density, melting point, boiling point, viscosity and mistability. Other considerations are availability and cost.

To fire gun 10, control 64 (FIGS. 1-4) causes power supply 63 to provide electrical power as shown in the solid line graph of FIG. 5 which shows power vs. time. Power supply 63 causes fuse wire 58 to heat fuel 52 and produce a plasma of ionized gas containing both positive and negative ions so the gas is rendered conductive. The fuse wire quickly vaporizes to produce a plasma with gas ions which maintain an electrical current path through fuel 52 in capillary chamber 59. Current through the fuel 52 produces a narrow jet 78 (FIG. 2) of ionized gas and molten particles which punches a hole in first membrane 70, through fuel 76, second membrane 71 and oxidizer material 77. A portion of fuel 76 is quickly launched and mixed with oxidizer material 77 while additional fuel is more slowly aspirated into the fast flowing gas stream in the form of small droplets. The small droplets evaporate and decompose quickly enriching the jet with fuel. A similar process follows in the oxidizer chamber with a portion of the liquid oxidizer material and some fuel following the projectile 27 as it travels down the gun barrel as shown sequentially in FIGS. 2-4. The remainder of the oxidizer material is aspirated in the fuel rich gas where the oxidizer material reacts with the fuel, releasing combustion byproducts and heat, the released heat contributes in generating and sustaining pressure against the moving projectile. A portion of the moving fuel and oxidizer material is left as a thin film on the walls of the bore 28 of barrel 16 and droplets also fall from the rear portion of the moving fuel and oxidizer material. These droplets and film evaporate into the gas jet enriching it with reactive components. This combustion continues to provide added pressure on the rear portion of projectile 27.

The amount of film which covers the walls of the bore of the barrel and the amount of fluid which follows the projectile can be controlled by tuning the diameters of the capillary, fuel and oxidizer chambers and gun barrel. The thin film of liquid which covers the walls of bore 28 absorbs a great amount of heat to evaporate, thus protecting the walls of the bore from scorching heat and improving the life of the gun barrel. The traveling charge enhances pressure against the base of the projectile to produce more thrust and improve performance.

FIGS. 8 and 9 disclose alternate embodiments of the present invention in which a plasma base for generating a primary plasma can be either a fuel or an oxidizer material. The plasma base (FIG. 8) includes a powder 82 enclosed in a solid material 83. One plasma base combination which can be used is a powder 82 of ammonium nitrate and a solid material 83 of compression compacted ammonium nitrate. Several other combinations of fuels and combinations of oxidizer materials can also be used as a plasma base. Chamber back liner 21 is divided into a fuel chamber 65a and an oxidizer chamber 66a by a plurality of membranes 70a-72a. A liquid oxidizer material 77a is stored in oxidizer chamber 66a and a liquid fuel 76a is stored in adjacent chamber 65a.

Control 64 (FIG. 8) and power supply 63 provide electrical power which causes fuse wire 58 to vaporize and produce an ion path through the powder plasma base 82. Powder 82 and solid material produce a narrow jet of ionized gas with molten particles which punch a hole in membrane 70a, through oxidizer material 77a, membrane 71a and fuel 76a as described above.

A further embodiment of the present invention, disclosed in FIG. 9, includes the plasma base consisting of powder 82 and solid material 83 as described in FIG. 8. A liquid fuel 76b in a cylindrical plastic container 84 is surrounded by an oxidizer material 77b and enclosed in chamber back liner 21 with end membranes 70b, 72b.

Although the best mode contemplated for carrying out the present invention has been herein shown and described, it will be apparent that modification and variation may be made without departing from what is regarded to be the subject matter of the invention.