PROPELLANT CHARGE OR GRAIN

Abstract

The invention is directed to a propellant charge, to a method of preparing a propellant charge, and to uses of the propellant charge. The propellant charge or grain of the invention comprises two or more energetic materials with different linear burn rate, wherein the two or more energetic materials are distributed within the charge or grain such that two perpendicular cross-sections of said propellant charge or grain have at least two linear burn rate gradients in non-parallel directions, wherein said propellant charge or grain is layered with layers having a layer thickness in the range of 1-10 000 m, wherein, if the propellant charge or grain has a longitudinal axis, at least one of said perpendicular cross-sections is along said longitudinal axis, and wherein said propellant charge or grain further comprises one or more perforations.

Claims

1. A propellant charge or grain, comprising two or more energetic materials with different linear burn rate, wherein the two or more energetic materials are distributed within the charge or grain such that two perpendicular cross-sections of said propellant charge or grain each have at least two linear burn rate gradients in non-parallel directions, wherein said propellant charge or grain is layered with layers having a layer thickness in the range of 1-10 000 m, wherein, if the propellant charge or grain has a longitudinal axis, at least one of said perpendicular cross-sections is along said longitudinal axis, and wherein said propellant charge or grain further comprises one or more perforations.

2. The propellant charge or grain of claim 1, wherein the two or more energetic materials are present in different layers.

3. The propellant charge or grain of claim 1, wherein said propellant charge or grain further comprises two or more perforations.

4. The propellant charge or grain of claim 1, wherein the propellant charge or grain is layered with layers having a layer thickness in the range of 10-5000 m.

5. The propellant charge or grain of claim 1, wherein the propellant charge or grain is layered with layers having a layer thickness in the range of 50-2000 m.

6. The propellant charge or grain of claim 1, wherein the propellant charge or grain is layered with layers having a layer thickness in the range of 100-1000 m.

7. The propellant charge or grain of claim 1, wherein the propellant charge or grain is layered with layers having a layer thickness in the range of 200-800 m.

8. The propellant charge or grain of claim 1, wherein at least two linear burn rate gradients in each perpendicular cross-section are perpendicular to each other.

9. The propellant charge or grain of claim 1, wherein the charge or grain comprises three or more energetic materials with different linear burn rate.

10. The propellant charge of claim 1, wherein at least one of said linear burn rate gradients is such that the linear burn rate increases from the surface of the burn propellant charge or grain inwards.

11. The propellant charge of claim 1, wherein at least one of said linear burn rate gradients is such that the linear burn rate first decreases and then increases from the surface of the propellant charge or grain inwards.

12. The propellant charge or grain of claim 1, wherein said propellant charge or grain comprises 2-10 layers with different linear burn rate.

13. The propellant charge or grain of claim 1, wherein said propellant charge or grain comprises 2-8 layers with different linear burn rate.

14. The propellant charge or grain of claim 1, wherein said propellant charge or grain comprises 3-8 layers with different linear burn rate.

15. The propellant charge or grain of claim 1, wherein said propellant charge or grain comprises a binder, which binder may or may not be an energetic binder.

16. The propellant charge or grain of claim 15, wherein at least one of said energetic materials dispersed as a solid material in said binder.

17. The propellant charge or grain of claim 1 in the form of a triangular prism or rounded triangular prism, a rectangular prism or rounded rectangular prism, a pentagonal prism or rounded pentagonal prism, a hexagonal prism or rounded hexagonal prism, an octagonal prism or rounded octagonal prism, a sphere, a spheroid, an ellipsoid, a cylinder, a rosette, a cube, a cuboid, a cone, a square-based pyramid, a rectangular-based pyramid, a pentagonal-based pyramid, a hexagonal-based pyramid, or an octagonal-based pyramid.

18. The propellant charge or grain of claim 1, in the form of a rosette prism, a hexagonal prism, a sphere or a cylinder.

19. A method for the preparation of a propellant charge or grain, comprising additive manufacturing of multiple layers to produce a layered propellant charge or grain, wherein two or more of said layers each comprise at least one energetic material, wherein the linear burn rate of an energetic material in a first layer is different from the linear burn rate of an energetic material in a second layer, and wherein each of said layers has a layer thickness in the range of 1-10 000 m.

20. The method of claim 19, wherein each of said layers has a layer thickness in the range of 10-5000 m.

21. The method of claim 19, wherein each of said layers has a layer thickness in the range of 50-2000 m.

22. The method of claim 19, wherein each of said layers has a layer thickness in the range of 100-1000 m.

23. The method of claim 19, wherein each of said layers has a layer thickness in the range of 200-800 m.

24. The method of claim 19, wherein said additive manufacturing comprises layer by layer curing of a liquid curable composition, wherein said liquid curable composition comprises curable binder and energetic material, and wherein said curable binder optionally is an energetic material.

25. The method of claim 24, wherein said liquid curable binder material is cured by ultraviolet radiation or thermally.

26. The method of claim 19, wherein the two or more energetic materials are distributed within the charge or grain such that two perpendicular cross-sections of said propellant charge or grain each have at least two non-parallel linear burn rate gradients.

27. A method of preparing ballistics, pyrotechnics, fireworks or solid or hybrid propellant rockets, said method comprising using the propellant charge or grain of claim 1.

28. A layered propellant charge or grain, obtainable by the method of claim 19, wherein two or more of said layers each comprise at least one energetic material, wherein the linear burn rate of an energetic material in a first layer is different from the linear burn rate of an energetic material in a second layer, and wherein each of said layers has a layer thickness in the range of 1-10,000 m.

29. A method of preparing ballistics, pyrotechnics, fireworks or solid or hybrid propellant rockets, said method comprising using the layered propellant charge or grain of claim 27.

Description

EXAMPLES

[0064] Different pressure curves for a propellant charge or grain were simulated in order to achieve the ideal pressure curve using the following formula for dynamic vivacity, L.

[00001]$L=\frac{\mathrm{dP}.Math.\text{/}.Math.\mathrm{dt}}{P{P}_{\max }}$

[0065] There are three different curves possible, a degressive curve where the dynamic vivacity decreases with increasing relative pressure, a neutral curve where the dynamic vivacity is more or less equal with increasing relative pressure, and a progressive curve where the dynamic vivacity increases with increasing relative pressure, as shown in FIG. 4. S slow extension of the chamber volume after ignition requires a low initial combustion rate and thus points at a progressivity.

[0066] FIG. 5 shows the relationship between the relative pressure in the chamber over time and the projectile velocity over time. As shown in this figure, the broader the pressure curve is, the higher the projectile velocity will be. Hence, ideally the pressure curve is a plateau curve, meaning that the pressure remains at a constant high level over an extended period of time.

[0067] FIG. 6 shows a simulation with a medium size caliber (35 mm). Again the relationship between the relative pressure in the chamber over time and the projectile velocity over time is shown. However, FIG. 6 also shows the burn rate that is required for the plateau pressure curve. Initially, an increase in burn rate is required so as to raise the pressure to a maximum level, then a drop in burn rate results in the pressure becoming constant, after which a secondary increase in the burn rate is required for the pressure to remain constant.