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A gun barrel for firing a projectile and particularly a rail gun barrel that comprises a pair of spaced apart rails and a pair of spaced apart insulators, which separate the rails, and together define a composite bore, all disposed centrally within an outer rigid tube. A prestressed filament-wound p

A gun barrel for firing a projectile and particularly a rail gun barrel that comprises a pair of spaced apart rails and a pair of spaced apart insulators, which separate the rails, and together define a composite bore, all disposed centrally within an outer rigid tube. A prestressed filament-wound polymeric resin shell immediately surrounds and applies compressive stress to this composite, bore-defining structure. A pressure medium, positioned between the shell and the interior surface of the outer tube, is operative to apply compressive stress to the shell at least at locations generally radially outward of the rails. The compressive stresses applied by the combination of the prestressed shell and the pressure medium are additive and effectively preload the rails and the composite bore structure to resist overall forces encountered during projectile firing which, in a rail gun, include asymmetric loads upon the rails from electromagnetic repulsion forces and also axisymmetric bursting forces.

대표청구항 ▼

The invention claimed is: 1. A rail gun barrel having a bore through which a projectile may be accelerated, which barrel comprises: an outer rigid tube; a pair of spaced apart rails disposed within said tube; a pair of spaced apart insulators which separate said rails in a central region within sai

The invention claimed is: 1. A rail gun barrel having a bore through which a projectile may be accelerated, which barrel comprises: an outer rigid tube; a pair of spaced apart rails disposed within said tube; a pair of spaced apart insulators which separate said rails in a central region within said outer tube, said rails and said insulators being elongated and having side faces that are juxtaposed with one another to form a generally annular composite structure having a defined interior bore; a surrounding prestressed shell which is in contact with and applies compressive stress to said composite bore-defining structure, which shell is a filament-wound tubular structure wherein filaments having a high tensile strength and an elastic modulus of not greater than about 5 Msi are wound under tension about said composite bore-defining structure in predominately hoop orientation, with a hardened polymeric resin impregnated in said wound filaments; and a pressure medium positioned adjacent the exterior surface of said prestressed shell and within said outer rigid tube, which pressure medium is operative to apply compressive stress to the surface of said prestressed shell at least at locations generally radially outward of said rails, whereby the resultant compressive stresses applied by the combination of said prestressed shell and said pressure medium are additive and effective to preload the rails to adequately resist bursting forces that include electromagnetic repulsion forces and axisymmetric pressure if a plasma armature is employed. 2. The rail gun barrel of claim 1 wherein said pressure medium comprises a hardened polymeric resin that was injected and cured under high pressure. 3. The rail gun barrel of claim 1 wherein said pressure medium comprises an inflatable bladder into which a pressurizing fluid can be injected prior to firing a projectile. 4. The rail gun barrel of claim 1 wherein said pressure medium comprises a pair of inflatable bladders, one located radially outward of each said rail, and wherein means is provided to fill said bladders with hydraulic fluid at a pressure of at least about 5,000 psi. 5. The rail gun barrel of claim 1 wherein said outer rigid tube has a circular cross section. 6. The rail gun barrel of claim 1 wherein said prestressed shell and said outer rigid tube both have elliptical cross sections and said spaced apart rails are located on the long axis of the ellipse. 7. A method of providing a lightweight rail gun barrel having a bore through which a projectile may be accelerated, which method comprises: providing a pair of elongated rails and a pair of elongated insulators, which rails are spaced apart by said elongated insulators and together constitute a composite structure that defines the bore; radially surrounding said composite structure with a shell that prestresses said composite structure by winding filaments in predominantly hoop orientation about said composite structure under high tension up to about 85% to about 90% of their breaking point and hardening a polymeric resin which impregnates said wound filaments while said filaments remain under such tension to provide a prestressed surrounding shell which applies compressive stress upon the surface of said composite structure, providing an outer rigid tube; and positioning a pressure medium in an intermediate region between said prestressed surrounding shell and the interior surface of said outer rigid tube and causing said pressure medium to apply compressive stress to said shell, whereby compressive stresses applied by said prestressed shell and by said pressure medium to said composite structure are additive. 8. The method of claim 7 wherein said pressure medium applies at least about 5 ksi compressive stress to at least said rails, and wherein the total compressive stress applied to said rails by the combination of said prestressed shell and said pressure medium is more than 25 ksi. 9. The method of claim 7 wherein said compressive stress from said pressure medium is provided by injecting a polymeric resin under at least about 5,000 psi into said intermediate region and curing said resin to solidification while under such pressure. 10. The method of claim 7 wherein said pressure medium includes a pair of inflatable bladders, one of which is located radially outward of each said rail, and wherein said compressive stress to said shell is provided by inflating each bladder to at least about 20,000 psi. 11. The method of claim 7 wherein said shell is wound with filaments having a high tensile strength of at least about 400 ksi and an elastic modulus of not greater than about 10 Msi and wherein a wind-angle of about 70�� or greater is employed for at least the major portion of the axial length of said shell. 12. The method of claim 7 wherein said filaments are glass filaments that have an elastic modulus of not greater than about 5 Msi and said cured shell has hoop modulus of not greater than about 5 Msi. 13. A rail gun barrel having a bore through which a projectile may be accelerated, which barrel comprises: an outer rigid tube of generally elliptical cross section; a pair of spaced apart rails disposed within said tube; a pair of spaced apart insulators which separate said rails in a central region within said outer tube, said rails and said insulators being elongated and having side faces that are juxtaposed with one another to form a generally annular composite structure having a defined interior bore; an elongated integral generally elliptical tubular prestressed shell immediately surrounding said interior rigid structure which applies compressive stress to the entire periphery of said composite interior structure; and a pressure medium positioned in two recesses between said tubular prestressed shell and the interior surface of said outer rigid tube on the long axis of said generally elliptical cross section, which pressure medium is operative to apply compressive stress to said shell at least at locations generally radially outward of said rails, whereby said compressive stresses applied by the combination of said prestressed shell and said pressure medium are additive and provide overall compressive stress to adequately resist bursting force of 25,000 psi or greater in a rail gun barrel having cross sectional dimensions less than those required to construct a barrel of such strength by separately using either an integral filament-wound prestressed shell or a pressure medium within a surrounding rigid tube. 14. The gun barrel of claim 13 wherein said pressure medium comprises a hardened polymeric resin that was injected and cured under at least about 5,000 psi. 15. The gun barrel of claim 13 wherein said pressure medium comprises a pair of inflatable bladders, one located radially outward of each said rail and centered on said long axis, and wherein means is provided to fill said bladders with fluid at a pressure of at least about 20,000 psi. 16. The gun barrel of claim 13 wherein said interior rigid structure has a bore of circular cross section.