OPTIMIZED SUBSONIC PROJECTILES AND RELATED METHODS

• US 20170131071A1
• Filed: 11/28/2015
• Published: 05/11/2017
• Est. Priority Date: 04/21/2015
• Status: Active Grant

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Burkart, Joseph, Taylor, IV, Lucius A.
• Granted Patent: US 10,317,178 B2
• Time in Patent Office: Days
• CPC Class Codes: F41A 1/00 Missile propulsion characterised by the use of explosive or combustible propellant charges projecting missiles without use of explosive or combustible propellant charge F41B; launching rockets or torpedoes F41F3/00; missile self-propulsion F42B15/00
• CPC Class Codes: F42B 10/00 Means for influencing, e.g. improving, the aerodynamic properties of projectiles or missiles; Arrangements on projectiles or missiles for stabilising, steering, range-reducing, range-increasing or fall-retarding F42B6/00 takes precedence
• CPC Class Codes: F42B 10/22 Projectiles of cannelured type
• CPC Class Codes: F42B 10/24 with inclined grooves
• CPC Class Codes: F42B 10/32 Range-reducing or range-increasing arrangements; Fall-retarding means
• CPC Class Codes: F42B 10/38 Range-increasing arrangements F42B10/34, F42B14/06 and F42B15/105 take precedence
• CPC Class Codes: F42B 10/44 Boat-tails specially adapted for drag reduction
• CPC Class Codes: F42B 12/74 of the core or solid body
• CPC Class Codes: F42B 33/001 Devices or processes for assembling ammunition, cartridges or cartridge elements from parts
• CPC Class Codes: F42B 5/02 Cartridges, i.e. cases with charge and missile

Abstract

Various embodiments of optimized subsonic projectiles are provided along with related methods. For example, one exemplary subsonic projectile can include an elliptical nose cone, a cylindrical body and a boattail with various design features that can be used in a subsonic ammunition cartridge where the subsonic projectile is stabile throughout at least a segment of a flight allowing for better accuracy, maintaining low drag, maximizing range and achieving desired performance while ensuring the projectile stays below the speed of sound and lowering a noise profile of projectile and a launcher firing the projectile.

Claims

1. A subsonic ammunition cartridge comprising:

a casing having a base end and an open end wherein said casing has an internal volume;

a primer inserted in said base end of said casing;

a projectile comprised of a nose cone, a body, and a boattail, wherein said body is disposed between said nose cone and said boattail, wherein a portion of the body section in proximity to said boatail of said projectile is inserted in the open end of said casing and press fitted to the portion of the body section; and

a propellant wherein said propellant is placed within said casing surrounding said boatail;

wherein said nose or body are formed with at least one turbulence generator comprising a ring or groove structure formed into said nose, body, or boattail that is perpendicular to a first axis formed by a line drawn from a center of said nose section to a center of said boattail section;

wherein said boatail is formed with a plurality of rebated or stepped structures that are formed spaced apart into said boattail;

wherein said nose cone is formed into an elliptical shape with a flattened meplat on said center of said nose cone section;

wherein said projectile is formed with a center of pressure further from said center of said nose section along said first axis than a center of gravity;

wherein said projectile is formed with a body to boattail transition having an angle of 8 degrees as defined by a first plane collinear with an external surface of said body and a second plane collinear with an external surface of said boattail;

wherein said boattail extends from a point of said body to boattail transition to said base end of said casing but not in contact with said primer, wherein said point of said body to boattail transition is further from said center of said nose cone section along said first axis than said open end of said casing when said projectile is inserted inside said casing and said casing is press fitted to said projectile;

wherein said propellant charge is selected so as to produce a force to maximize subsonic speed of said projectile as it enters an external ballistics phase to no more than a critical Mach number of less than Mach 1 at a temperature at which said projectile is functioning.

2. The subsonic ammunition cartridge of claim 1, wherein said nose cone is elliptical and wherein said nose cone minimizes a pressure coefficient, and said nose cone has a subsonic drag in the range of 0 to 0.0001.

3. The subsonic ammunition cartridge of claim 1, wherein said boattail is conical in shape.

4. The subsonic ammunition cartridge of claim 3, wherein said stepped structure of said boattail has a 90 degree step or shoulder formed into said boatail.

5. The subsonic ammunition cartridge of claim 1, wherein said projectile is selected from the group consisting of all tungsten, tungsten and aluminum, or all aluminum.

6. The subsonic ammunition cartridge of claim 1, wherein said projectile interior nose cone is comprised of tungsten and said body and said boattail are comprised of aluminum.

7. The subsonic ammunition cartridge of claim 1, wherein said boattail has a plurality of flat spots or grooves.

8. A method of manufacturing a subsonic ammunition cartridge comprising:

providing a casing having a base end and an open end wherein said casing has an internal volume;

providing a primer inserted in said base end of said casing;

providing a projectile comprised of a nose cone, a body, and a boattail, wherein said body is disposed between said nose cone and said boattail, wherein a portion of the body section in proximity to said boatail of said projectile is inserted in the open end of said casing and press fitted to the portion of the body section;

providing a propellant wherein said propellant is placed within said casing surrounding said boatail;

wherein said nose or body are formed with at least one turbulence generator comprising a ring or groove structure formed into said nose, body, or boattail that is perpendicular to a first axis formed by a line drawn from a center of said nose section to a center of said boattail section;

wherein said boatail is formed with a plurality of rebated or stepped structures that are formed spaced apart into said boattail;

wherein said nose cone is formed into an elliptical shape with a flattened meplat on a center of said nose cone section;

wherein said projectile is formed with a center of pressure further from said center of said nose section along said first axis than a center of gravity;

wherein said projectile is formed with a body to boattail transition having an angle of 8 degrees as defined by a first plane collinear with an external surface of said body and a second plane collinear with an external surface of said boattail;

wherein said boattail extends from a point of said body to boattail transition to said base end of said casing but not in contact with said primer, wherein said point of said body to boattail transition is further from said center of said nose cone section along said first axis than said open end of said casing when said projectile is inserted inside said casing and said casing is press fitted to said projectile; and

wherein said propellant charge is selected so as to produce a force to maximize subsonic speed of said projectile as it enters an external ballistics phase to no more than a critical Mach number of less than Mach 1 at a temperature at which said projectile is functioning.

9. The method of claim 8, wherein said nose cone is elliptical wherein said nose cone minimizes a pressure coefficient, and said nose cone has a subsonic drag in the range of 0 to 0.0001.

10. The method of claim 8, wherein said boattail is conical in shape.

11. The method of claim 10, wherein said stepped structure of said boattail has a 90 degree step or shoulder formed into said boatail.

12. The method of claim 8, wherein said projectile is selected from the group consisting of all tungsten, tungsten and aluminum, or all aluminum.

13. The method of claim 8, wherein said projectile interior nose cone is comprised of tungsten and said body and said boattail are comprised of aluminum.

14. The method of claim 8, wherein said boattail has a plurality of flat spots or grooves.

15. A method associated with a projectile system comprising the steps of:

determining a caliber of a projectile associated with a projectile launcher and casing combination that will fit within a first fit dimension determined based on a chamber length of said projectile launcher and a non-interference fit diameter of a passage through a barrel of said projectile launcher, wherein said projectile comprises a first, second, and third section, said first section is a nose cone section, said second section is a body section, and said third section is a boattail section, wherein said casing comprises a throat area configured to receive and pressfit to a section of said second section and a primer disposed on an opposing end of said casing from said throat area, said first section comprises an elliptical nose shape, said second section comprises a cylindrical shape, and third section is formed in a cone shape, wherein said third section is formed with a plurality of rebated or stepped structures, said first section is formed with a flat meplat on a top of a center section of said first section, wherein said projectile is formed with a second section to third section transition having an angle of eight degrees as defined by a first plane collinear with an external surface of said second section and a second plane collinear with an external surface of said third section, wherein said first, second, or third sections are formed with at least one turbulence generator comprising a ring or groove structure formed into said first, second, or third sections that is perpendicular to a first axis formed by a line drawn from a center of the first section to a center of an end of the third section, wherein said projectile is formed with a center of pressure that is further from a central terminal tip of said nose cone section along said first axis than a center of gravity, wherein said projectile interior first section can be comprised of tungsten and the second section and third can be comprised of aluminum;

determining a length of a said third section based on an available area within said casing defined as a length of said boattail that runs in proximity to said throat from a transition between said second and third sections to a location in proximity with but not in contact with said primer;

determining a length of said second section based on a length of said throat section that is pressfit to said second section, wherein said second section is no longer than said throat section of said casing;

determining a length of said first section based on an available length of said first fit dimension into said chamber after subtracting a casing length from said first fit dimension;

determining a critical Mach number associated with said projectile having said first, second, and third section length and said caliber and a predetermined ambient temperature associated with a propellant charge;

determining a force of said propellant charge having a first propulsive force on said projectile at said ambient temperature through said projectile launcher disposed within said casing surrounding said boatail such that said first propulsive force does not cause said projectile to exceed said critical Mach number as it enters an external ballistics phase after functioning from said projectile launcher; and

manufacturing said projectile with said casing and said propellant charge with said projectile having its third section disposed within said casing and said propellant charge disposed surrounding said third section.

16. A method as in claim 15 further comprising the steps of:

providing said projectile launcher;

loading said projectile and casing assembly into said chamber; and

operating said projectile launcher and firing said projectile.