Ignition method for multi-pulse solid rocket motors

Abstract

The rocket motor has an electrically actuated propellant initiator of a propellant grain, the electrically actuated propellant initiator including an electrode arrangement configured to concentrate an electric field at an ignition electrode for igniting the electrically actuated propellant. The rocket motor includes a combustion chamber including at least one propellant grain and an electrically actuated propellant initiator operably coupled to the propellant grain to initiate combustion of the propellant grain. The electrically actuated propellant initiator includes an electrically actuated propellant and at least one pair of electrodes configured to ignite the electrically actuated propellant. The pair of electrodes includes a ground electrode and an ignition electrode. When electrical input is applied to the electrically actuated propellant initiator, an electric field is concentrated at the ignition electrode, igniting the electrically actuated propellant at the location where the ignition electrode is disposed.

Description

[Technical field]

[0001] The present invention relates to thrust systems for flight vehicles, and more particularly to multi-pulse rocket motors. [Background technology]

[0002] Various applications require payloads to be launched from a platform appropriate for the mission, such as land, sea, air, or space vehicles. The payloads launched depend on the application. Military applications using land vehicles, aircraft, surface vessels, or underwater vehicles may use deployable munitions as the payload. The payloads may be delivered by vehicles that include rocket motors with multiple pulses that allow for non-continuous propulsion, different thrusts, and backup pulses without the need for a completely separate rocket motor stage.

[0003] The propellant grains of each pulse may be separated by an inert barrier that prevents ignition of a subsequent pulse by contact with the combustion gases formed from another burning propellant grain. When a propellant grain is ignited, the force of the resulting combustion gases breaks through the barrier, expelling thrust gases from the projectile until the propellant of the pulse burns out. At least one igniter is used to ignite each propellant pulse.

[0004] Conventional multi-pulse rocket motors can be deficient in that the rocket motors may have complex barrier and ignition systems between pulses that are difficult and costly to manufacture. One possible drawback of conventional barriers is that the barriers may be expelled or inverted, leading to nozzle clogging and combustion instability of the rocket motor. Yet another drawback of conventional multi-pulse rocket motors is that they may be limited to two pulses. Summary of the Invention

[0005] The present application provides a rocket motor having an electrically operated propellant initiator for a propellant grain, the propellant initiator including an electrode arrangement configured to focus an electric field on an ignition electrode for igniting the electrically operated propellant. According to a general embodiment, the rocket motor includes a combustion chamber including at least one propellant grain, and an electrically operated propellant initiator operatively coupled to the propellant grain for initiating combustion of the propellant grain. The electrically operated propellant initiator includes an electrically operated propellant and at least one pair of electrodes configured to ignite the electrically operated propellant. The pair of electrodes includes a ground electrode and an ignition electrode. When an electrical input is applied to the electrically operated propellant initiator, an electric field is focused on the ignition electrode, igniting the electrically operated propellant at a location where the ignition electrode is disposed.

[0006] Rocket motors including electrically actuated propellant initiators with electrode configurations are advantageous in that the electrodes can be positioned to control the location of combustion to allow for rapid and uniform propellant grain ignition, thus making the configuration less complex and more robust compared to conventional barrier and igniter systems.

[0007] The electrically actuated propellant is configured to transition from an unignited state to an ignited state when an electrical input is applied across the electrically actuated propellant initiator and to maintain the unignited state when no electrical input is applied. The ignition electrode has a greater current density than the ground plane electrode. A ratio of a surface area of ​​the propellant grains covered by the ground plane electrode to a surface area covered by the ignition electrode may be at least 2:1. At least the ignition electrode is formed of a refractory metal or refractory alloy.

[0008] The electrodes may be embedded in the electrically actuated propellant and may be located in the same plane or different planes parallel to the outer surface of the propellant grain adjacent to the electrically actuated propellant. Many different configurations of electrodes are possible. The ignition electrode may be located within a cavity formed in the propellant grain such that the electric field is directed into the cavity. In other embodiments, the ignition electrode and the ground electrode may be located in the same plane such that the electric field is directed laterally across the outer surface of the propellant grain.

[0009] In an exemplary embodiment, the electrodes are formed of wires having a serpentine, zigzag, crisscross, diagonal, parallel, non-parallel, etc. configuration. The wires may extend radially. The ignition electrode wires and the ground plane electrode wires may be formed in a non-overlapping configuration. The ignition electrode wires may cross one another and / or the ground plane electrode wires may cross one another.

[0010] The rocket motor may be a single-pulse rocket motor with a single propellant grain or a multi-pulse rocket motor with two, three or more pulses, each with a corresponding propellant grain. The electrically actuated propellant initiator may also function as a barrier separating the propellant grains from each other so that they can be initiated individually. More than one electrically actuated propellant initiator may be provided.

[0011] According to one aspect of the invention, a gas generation system for a rocket motor includes an electrically actuated propellant initiator for a propellant grain.

[0012] According to one aspect of the invention, an electrically actuated propellant initiator includes an electrode arrangement in which the electrodes cover different amounts of surface area of ​​the propellant grains to focus an electric field at specific points within the electrode configuration.

[0013] According to one aspect of the invention, an electrically powered propellant initiator includes an ignition electrode and a ground plane electrode.

[0014] According to one aspect of the invention, an electrically actuated propellant initiator for a propellant grain includes an electrode arrangement embedded in the electrically actuated propellant.

[0015] According to one aspect of the invention, a multi-pulse rocket motor includes an electrically actuated propellant initiator that functions as an initiator and a barrier to operatively separate propellant grains for different pulses.

[0016] According to one aspect of the present invention, a rocket motor includes a pulse chamber including at least one propellant grain, and an electrically actuated propellant initiator operably coupled to the at least one propellant grain to initiate combustion of the at least one propellant grain, the electrically actuated propellant initiator including an electrically actuated propellant and at least one pair of electrodes arranged to ignite the electrically actuated propellant, the at least one pair of electrodes including a ground plane electrode and an ignition electrode at which an electric field is focused to ignite the electrically actuated propellant.

[0017] According to an embodiment of any paragraph(s) of this summary, the ignition electrode has a greater current density than the ground plane electrode.

[0018] According to an embodiment of any paragraph or paragraphs of this summary, the ground plane electrode extends along a first surface area of ​​the at least one propellant grain that is greater than a second surface area of ​​the at least one propellant grain along which the ignition electrode extends.

[0019] According to an embodiment of any paragraph or paragraphs of this summary, the ratio of the first surface area to the second surface area is at least 2:1.

[0020] According to an embodiment of any paragraph or paragraphs of this Summary, the ground plane electrode is formed of a wire having a first diameter that is greater than a second diameter of the wire forming the ignition electrode.

[0021] According to an embodiment of any paragraph(s) of this Summary, at least one electrode pair is formed of a plurality of wires having a zigzag, diagonal, cross, rectangular, parallel, non-parallel, or serpentine arrangement.

[0022] According to an embodiment of any paragraph(s) of this summary, at least one pair of electrodes are spaced apart without crossing each other.

[0023] According to an embodiment of any paragraph or paragraphs of this Summary, at least one propellant grain has at least one cavity in which at least one of the ignition electrode and the ground plane electrode is disposed.

[0024] According to an embodiment of any paragraph or paragraphs of this Summary, the ignition electrode and the ground plane electrode are disposed in a same plane parallel to an outer surface of the at least one propellant grain.

[0025] According to an embodiment of any paragraph(s) of this summary, the ignition electrode and the ground plane electrode are disposed in different planes.

[0026] According to an embodiment of any paragraph or paragraphs of this Summary, the ignition electrode is formed of a refractory metal or alloy.

[0027] According to an embodiment of any paragraph(s) of the present summary, the rocket motor is a multi-pulse rocket motor, and the at least one propellant grain includes a first propellant grain and a second propellant grain that is burned during a second pulse of the multi-pulse rocket motor, the second propellant grain being operatively separated from the first propellant grain via an electrically actuated propellant initiator, and the first propellant grain and the second propellant grain are individually initiated by the electrically actuated propellant initiator.

[0028] According to an embodiment of any paragraph or paragraphs of this summary, the at least one propellant grain includes a third propellant grain that is combusted during a third pulse of the multi-pulse rocket motor, the third propellant grain being operatively separated from the second propellant grain via another electrically actuated propellant initiator.

[0029] According to an embodiment of any paragraph or paragraphs of this Summary, the electrically powered propellant is configured to transition from an unignited state to an ignited state when an electrical input is applied across the electrically powered propellant initiator, and configured to maintain the unignited state when no electrical input is applied.

[0030] According to an embodiment of any paragraph or paragraphs of this Summary, a rocket motor includes a power source and a pair of leads extending from the power source to an electrically actuated propellant initiator.

[0031] According to another aspect of the present invention, a multi-pulse rocket motor includes a first pulse including a first propellant grain, a second pulse including a second propellant grain operatively separated from the first propellant grain, and at least one electrically actuated propellant initiator configured to separate the first propellant grain and the second propellant grain, the at least one electrically actuated propellant initiator configured to initiate combustion of the first propellant grain or the second propellant grain, the at least one electrically actuated propellant initiator includes at least one pair of electrodes configured to ignite the electrically actuated propellant and the electrically actuated propellant, the at least one pair of electrodes including a ground plane electrode and an ignition electrode, the ground plane electrode extending along a first surface area of ​​the second propellant grain that is greater than a second surface area of ​​the second propellant grain along which the ignition electrode extends, and the ignition electrode has a greater current density than the ground plane electrode, whereby an electric field is concentrated in the ignition electrode.

[0032] According to an embodiment of any paragraph or paragraphs of the present summary, the multi-pulse rocket motor includes a third pulse including a third propellant grain operatively separated from the first propellant grain and the second propellant grain, and the at least one electrically actuated propellant initiator includes a first electrically actuated propellant initiator configured to separate the first propellant grain and the second propellant grain, and a second electrically actuated propellant initiator configured to separate the second propellant grain and the third propellant grain.

[0033] According to an embodiment of any paragraph or paragraphs of this summary, the ratio of the first surface area to the second surface area is at least 2:1.

[0034] According to yet another aspect of the invention, a method of operating a rocket motor includes applying an electrical input across an electrically actuated propellant initiator operatively coupled to a propellant grain and including an electrically actuated propellant and at least one pair of electrodes, the at least one pair of electrodes including a ground plane electrode and an ignition electrode, igniting the electrically actuated propellant by an electric field focused on the ignition electrode, and initiating combustion of the propellant grain by igniting the electrically actuated propellant.

[0035] According to an embodiment of any paragraph or paragraphs of the present summary, the method includes the steps of maintaining operative separation of the propellant grain from the second propellant grain for a second propellant pulse of the rocket motor, providing a second propellant pulse to the rocket motor by applying another electrical input across a second electrically actuated propellant initiator subsequent to the electrically actuated propellant initiator operatively coupled to the propellant grain, the second electrically actuated propellant initiator being operatively coupled to the second propellant grain, igniting the second electrically actuated propellant of the second electrically actuated propellant initiator, and initiating combustion of the second propellant grain by igniting the second electrically actuated propellant.

[0036] To the accomplishment of the foregoing and related ends, the invention comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of only a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings. [Brief description of the drawings]

[0037] The accompanying drawings, which are not necessarily to scale, illustrate various aspects of the present invention.

[0038] [Figure 1] 1 illustrates a schematic of a solid rocket motor including propellant grain segments separated by an electrically actuated propellant initiator.

[0039] [Diagram 2] 1 illustrates an electrically actuated propellant initiator including an ignition electrode and a ground plane electrode.

[0040] [Diagram 3] 1 illustrates an ignition electrode and ground plane electrode configuration according to another exemplary embodiment of the present application.

[0041] [Figure 4] 1 illustrates an electrode wire configuration of an electrically powered propellant initiator according to an exemplary embodiment of the present application.

[0042] [Diagram 5] 1 illustrates an electrode wire configuration of an electrically powered propellant initiator according to another exemplary embodiment of the present application.

[0043] [Figure 6] 1 illustrates an electrode wire configuration of an electrically powered propellant initiator according to yet another exemplary embodiment of the present application.

[0044] [Figure 7] 1 illustrates an electrode wire configuration of an electrically powered propellant initiator according to yet another exemplary embodiment of the present application.

[0045] [Figure 8] 2 shows a flow chart illustrating a method of operating a rocket motor, such as the rocket motor of FIG. 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0046] The principles described herein have application in defense applications, such as hypersonic vehicles and any air vehicle where space may be constrained. The rocket motors described herein may be implemented in any suitable air vehicle or projectile. Single-pulse or multi-pulse rocket motors may be suitable. The rocket motor may be part of a missile suitable for carrying a payload. For example, the missile may include a payload module for carrying munitions for military applications. The rocket motor includes a gas generation system as described herein for generating combustion gases that propel the munitions. In other exemplary embodiments, the gas generation system may be used for other purposes, such as to drive a turbine, operate a pressure-driven machine, provide tank gas pressurization, etc.

[0047] Referring initially to FIGURE 1, a projectile 10 includes a rocket motor 12 that generates gas to drive the motion of the projectile 10. The projectile 10 includes a body having a chamber or casing 14 for the rocket motor 12. The rocket motor 12 includes a nozzle assembly 16 having a nozzle opening 18 for ejecting propellant gases generated from the rocket motor 12. The rocket motor 12 is a solid rocket motor that includes the casing 14, at least one pulse 24, 26, 28 including propellant charges or grains 24a, 26a, 28a, and at least one initiator 30, 32. The initiator 30, 32 is configured to ignite at least one of the propellant grains 24a, 26a, 28a to generate thrust during a corresponding pulse 24, 26, 28.

[0048] The rocket motor 12 may be a single pulse motor having only one pulse, or may be a multi-pulse rocket motor having two, three, or more pulses 24, 26, 28. In an exemplary embodiment, the pulses 24, 26, 28 may be formed within a single chamber or casing 14. Other configurations of the pulses 24, 26, 28 and the propellant grains 24a, 26a, 28a may be suitable as required for a particular application. In addition to initiating the propellant grains 24a, 26a, 28a, the initiators 30, 32 are also configured to act as a barrier between the propellant grains 24a, 26a, 28a. Thus, the separated initiation of the propellant grains 24a, 26a, 28a makes it possible to provide pulses that can be fired separately from one another, meaning that adjacent propellant grains 24a, 26a, 28a cannot be ignited due to gases generated from the combustion of other propellant grains 24a, 26a, 28a.

[0049] The casing 14 is configured to allow for the exhaust of combustion gases from within the casing. The casing 14 may have any suitable shape, such as a cylindrical shape useful for projection applications. The casing 14 may be formed from any suitable material for containing the combustion gases burning at high pressures and temperatures. For example, the casing may be formed from an inert material that will not ignite during normal use of the rocket motor 12.

[0050] The propellant grains 24a, 26a, 28a are provided to be ignited and burned to generate high pressure gas used, for example, to propel or move an object or to pressurize a container. The propellant grains 24a, 26a, 28a may be solid, single pieces having any shape or form, such as burning cores, slotted cores, rods and tubes, pellets, grains, etc. The propellant grains 24a, 26a, 28a may be made of any suitable material or materials, such as fuels, oxidizers, binders, plasticizers, metal additives, etc. Each of the propellant grains 24a, 26a, 28a may be made of a different material, may have a different form, or may have a different shape and / or size than the other propellant grains. End burning grains and center perforated grains may be suitable. Other grooved grain configurations may also be suitable. The propellant grains 24a, 26a, 28a may be separated from each other. In other exemplary embodiments, the additional grains or pulses may or may not be separated separately.

[0051] As shown in FIG. 1, the propellant grains 24a, 26a for the first and second pulses 24, 26 are separated from each other via a first initiator 30 of two initiators 30, 32, and the propellant grains 26a, 28a for the second and third pulses 26, 28 are separated from each other via a second initiator 32. In an exemplary embodiment, only one initiator may be provided, and in yet another exemplary embodiment, more than two initiators 30, 32 may be provided. For example, initiation of an initiator may cause combustion of multiple propellant grains. The initiators 30, 32 are operatively coupled to each of the propellant grains 26a, 28a to initiate combustion in the propellant grains 26a, 28a. The coupling may include a direct coupling, such that the initiators 30, 32 are in close proximity or adjacent to the propellant grains 26a, 28a. In addition to the separation provided via the initiators 30, 32, in other embodiments, one or more propellant grains may be separated from other propellant grains via a casing wall or another inert material that does not ignite during normal use of the rocket motor 12. The propellant grains 24a of the first pulse 24 may be initiated by a separate initiator in other exemplary embodiments.

[0052] Initiation, such as ignition, of the initiators 30, 32 generates heat and / or a flame front large enough to ignite the corresponding propellant grains 26a, 28a. The initiators 30, 32 include at least one pair of electrodes 34 configured to ignite the electrically actuated propellant 36. The electrically actuated propellant 36 may be coated on the propellant grains 26a, 28a. One or more pairs of electrodes 34 may be used. In an exemplary embodiment, the pair of electrodes 34 may be embedded in the electrically actuated propellant 36. The initiators 30, 32 may extend radially outwardly from a central longitudinal axis of the casing 14 and seal against an inner surface of the casing 14. Thus, the initiators 30, 32 act as a barrier between the propellant grains 26a, 28a and the environment external to the rocket motor 12, while providing structural support to retain the propellant grains 26a, 28a within the casing 14. In other embodiments, the initiators 30, 32 may have any other suitable shape.

[0053] The initiators 30, 32 may have a circular or cylindrical shape to fit within the cylindrical casing 14. The circular shape may be provided in the form of a thin sheet of material. The thin sheet may have a thickness sufficient to allow for degradation of the surface of the initiators 30, 32 when not ignited but still exposed to the high heat and combustion environment within the casing 14. For example, the combustion of the propellant grains 26a, 28a may cause high heat within the casing 14, which may not ignite the electrically actuated propellant of the auxiliary initiator 32 when no electrical input is applied across the auxiliary initiator 32. The thin portion of the auxiliary or secondary initiator 32 exposed to the high heat and combustion environment may be configured to degrade. The initiators 30, 32 may have any suitable shape to provide operable separation of the propellant grains 26a, 28a from one another.

[0054] The electrically actuated propellants 36, and thus the initiators 30, 32, are configured to ignite in response to an electrical input and generate gas when ignited, such that the initiators 30, 32 form a gas generation system for the rocket motor 12. The electrically actuated propellants 36 are configured to transition from an unignited state to an ignited state when a respective electrical input is applied across the initiators 30, 32 between pairs of electrodes 34. The electrically actuated propellants 36 are also configured to maintain the unignited state when no electrical input is applied.

[0055] A typical electrically actuated propellant 36 will ignite upon application of electricity and correspondingly extinguish upon cessation of electricity when exposed to elevated pressures, even below the high pressure threshold. For example, when exposed to ambient or elevated pressures within the casing 14, such as pressures greater than atmospheric pressure, 120 psi, 500 psi, 1000 psi, 1200 psi, up to 1500 psi, the electrically actuated propellant 36 will extinguish upon interruption of the electricity (e.g., voltage or current) applied across the electrically actuated propellant.

[0056] Exemplary embodiments of the electrically actuated propellant 36 include propellants having multiple components, such as an oxidizer, a fuel, and a binder. The electrically actuated propellant 36 may include approximately 50 to 90% by mass of an oxidizer, such as a perchlorate-based oxidizer. The perchlorate-based oxidizer may include perchlorate-based oxidizers, such as aluminum perchlorate, barium perchlorate, calcium perchlorate, lithium perchlorate, magnesium perchlorate, perchloric acid, strontium perchlorate, and sodium perchlorate. The electrically actuated propellant 36 may include approximately 5 to 30% by mass of a fuel, such as a metal-based fuel that aids in ignition and extinguishing of the electrically actuated propellant 36. The metal-based fuel may include tungsten, magnesium, copper oxide, copper, titanium, and aluminum. Many other configurations of the electrically actuated propellant 36 may be suitable.

[0057] The electrically actuated propellant 36 is also configured to maintain its shape when subjected to dynamic kinematic conditions within the rocket motor 12. The electrically actuated propellant 36 may be formable, for example, into any number of grain configurations, such as cast or molded. Thus, the burn rate and other performance characteristics of the electrically actuated propellant 36 are maintained throughout operation of the rocket motor 12. Exemplary performance characteristics include total impulse value, ignition rise time, peak pressure, and weight propellant density.

[0058] As shown in FIG. 1 , a power source 38 is provided to generate an electrical input to ignite the initiators 30, 32. A pair of leads 40 electrically couple each of the initiators 30, 32 to the power source 38. The leads 40 extend between the respective initiators 30, 32 and the power source 38, which may be a battery or any other suitable device capable of generating an electrical input. The leads 40 may be wires, such as insulated wires, having a material capable of withstanding the high heat generated by the rocket motor 12. In other embodiments, more than one power source 38 may be included and more than one pair of leads 40 may provide an electrical input across one or more of the initiators 30, 32.

[0059] For each electrically actuated propellant initiator 30, 32, a pair of electrodes 34 couples the respective initiator to a respective pair of leads 40. As shown in Figure 1, one of the electrodes of the pair of electrodes 34 is coupled between the lead 40 of the pair of electrodes 34 and the initiator 30, 32. The electrodes 34 are configured to allow control of the particular location or portion of the initiator 30, 32 that is ignited, the rate at which the initiator 30, 32 burns, and the intensity of the burn.

[0060] 2 and 3, one of the pair of electrodes 34 is a ground plane electrode 44, and the other of the pair of electrodes 34 is an ignition electrode 46 configured such that an electric field 48 of an electrical input is focused on the ignition electrode 46 to ignite the electrically actuated propellant 36 at the location where the ignition electrode 46 is located. The ground plane electrode 44 extends along a first surface area of ​​the propellant grains 26a, 28a that is greater than a second surface area of ​​the propellant grains 26a, 28a along which the ignition electrode 46 extends. The ignition electrode 46 has a greater current density, defined as the amount of current per unit area of ​​cross section, compared to the ground plane electrode 44. The ratio of the coverage surface area of ​​the propellant grains 26a, 28a from the ground plane electrode 44 to the ignition electrode 46 may be at least 2:1.

[0061] The ground plane electrode 44 may be formed of a wire with a diameter larger than that of the ignition electrode 46. For example, the wire diameter of the ground plane electrode 44 may be between 0.12 and 1.27 millimeters (0.005 and 0.05 inches) and the wire of the ignition electrode 48 may have a diameter between 0.002 and 0.635 millimeters (0.0001 and 0.025 inches). The wire may have any other suitable dimensions and may be sized up or down depending on the application. During ignition, electrical input flows between the electrodes 44, 46 and an electric field 48 is concentrated at the ignition electrode 46. As shown diagrammatically in FIG. 2, electrochemical reaction ignition 50 occurs at the highest current density. As a result, combustion of the electrically powered propellant 36 is initiated.

[0062] The location of the combustion can be controlled by the location of the electrodes 44, 46, for example, where the wire forming the ignition electrode 46 is located. The electrodes 44, 46 can be located adjacent to the propellant grains 26a, 28a, as shown in Figures 2 and 3. The electrodes 44, 46 can be embedded in the electrically actuated propellant 36 such that the electrodes 44, 46 are continuous with the outer surfaces 52 of the propellant grains 26a, 28a. The outer surfaces 52 of the propellant grains 26a, 28a extend along the electrically actuated propellant 36 and are flush with the electrically actuated propellant such that the outer surfaces 52 are in direct contact with the electrically actuated propellant 36. Only the ignition electrode 46 can be embedded in the electrically actuated propellant 36.

[0063] The location and intensity of the pulse ignition is also controlled by the shape and configuration of the electrodes 44, 46. For example, the intensity and temperature of combustion will be greater adjacent the ignition electrode 46 because the ignition electrode 46 has a greater current density (defined as the amount of current per unit area of ​​cross section). If there is a large enough disparity between the current densities provided by the electrodes 44, 46, combustion, such as an initial combustion at the beginning of the electrical input, can occur only adjacent the electrode providing the highest current density, such as the ignition electrode 46 shown in FIG. 6.

[0064] The electrodes 44, 46 may be formed of wire having many different configurations. At least the ignition electrode 46 is formed of a refractory metal such as tungsten. Other suitable materials include metals and alloys with melting points above 1200°C, such as molybdenum, tantalum, niobium, chromium, and rhenium. Metals and alloys with melting points above 1850°C may be suitable, including vanadium, hafnium, titanium, zirconium, ruthenium, osmium, rhodium, and iridium. Still other materials and alloys thereof may be suitable. In an exemplary embodiment, the ground plane electrode 44 may also be formed of a refractory metal or alloy, or other metals such as copper. If both the ground plane electrode 44 and the ignition electrode 46 are formed of a refractory metal or alloy, the diameter of the electrode wire may be the same.

[0065] As shown in FIG. 2, one of the electrodes 44, 46 may be disposed in a cavity or groove 54 formed in the propellant grain 26a, 28a. For example, the ignition electrode 46 may be positioned in the groove 54 such that the electric field 48 is directed into the groove 54 for ignition within the groove 54. More than one groove 54 may be formed in the propellant grain 26a, 28a, and the groove 54 may be formed to have any suitable shape, such as tapered or triangular. In other exemplary embodiments, the groove 54 may be formed to have a planar support surface for the electrode 44, 46. More than one electrode 44, 46 may be housed within the groove 54. For example, both the ground plane electrode 44 and the ignition electrode 46 may be housed within the groove 54. In yet other embodiments, the groove 54 may have another shape, such as circular. The groove 54 may instead be formed in the propellant grain 26a, 28a.

[0066] The ground plane electrode 44 and the ignition electrode 46 may be disposed in the same plane within the groove 54 or along the outer surface 52 of the propellant grains 26a, 28a, as shown in FIG. 3. The electrodes 44, 46 may be disposed in a plane parallel to the outer surface 52 of the propellant grains 26a, 28a. As shown in FIG. 2, the electrodes 44, 46 may be disposed in different planes. For example, the ground plane electrode 44 may be disposed on the outer surface 52 of the propellant grains 26a, 28a, and the ignition electrode 46 may be disposed in the groove 54 such that the ignition electrode 46 is in a different plane. When the ground plane electrode 44 and the ignition electrode 46 are disposed in the same plane as in FIG. 3, the electric field 48 may extend laterally across the propellant grains 26a, 28a.

[0067] During operation, initial combustion may occur only adjacent the ignition electrode 46 and not at the ground plane electrode 44. Electrical input may be provided to the ground plane electrode 44. When the electrically powered propellant 36 is ignited, combustion occurs adjacent both electrodes 44, 46. Using an imbalance between the current densities provided by the electrodes 44, 46, electrical input is provided unidirectionally across the electrodes 44, 46 to vary the rate and intensity of combustion.

[0068] Returning to FIG. 1 , the electrical input to the electrodes 44, 46 may be controlled by a controller 60 that controls the timing and direction of electrical input across the electrically actuated propellant initiators 30, 32 from the power source 38. The controller 60 may be any suitable device, such as a processor having suitable algorithms for controlling the power source 38. In this manner, the timing and direction of electrical input across the electrically actuated propellant initiators may be controlled. The controller 68 may operate autonomously or may be directed, such as wirelessly, via an operator. The electrically actuated propellant initiators may be extinguished by ceasing application of current across the initiators to ignite less than 100% of the initiators to generate the desired propellant pulse.

[0069] The electrodes 44, 46 may be configured differently for each of the propellant grains 26a, 28a, depending on the desired operation of the corresponding pulses 26, 28. The first pulse 24 may occur while the propellant grain 24a is first burned without the use of an electrically actuated propellant. After the propellant grain 24a is burned or exhausted, an electrical input is applied to the electrodes 44, 46 of the initiator 30 to ignite the electrically actuated propellant 36, followed by the propellant grain 26a of the second pulse 26. After the propellant grain 26a is burned, another electrical input is applied to the electrodes 44, 46 of the initiator 32 to ignite the electrically actuated propellant 36, followed by the propellant grain 28a of the third pulse 28. In an exemplary operation, the pulse duration may be between 2 and 5 seconds, and the interpulse delay may be between 10 and 40 seconds. Both initiators 30, 32 may burn out during the corresponding pulse.

[0070] Advantageously, the gas generation system using the electrode configuration described herein may be used in a multi-pulse rocket motor in which propellant grains are operatively separated and ignited by an initiator 30, 32. In contrast, conventional multi-pulse rocket motors may use complex and expensive barrier / ignition systems. The system and method described herein is further advantageous in that the electrode configuration allows for rapid and uniform grain ignition by directing an electric field at the location where the ignition electrode is located.

[0071] 4-7, exemplary configurations of the electrodes 44, 46 are shown. Many other configurations are possible. Each of the electrodes 44, 46 may be formed of multiple wires arranged in a particular pattern. The pattern may be an ordered and / or symmetrical pattern, or in other exemplary embodiments, the pattern may not be symmetrical. The pattern may be selected to achieve a particular combustion profile. As shown in FIGS. 4 and 5, the ignition electrode 46 may include multiple wires that cross and are spaced apart from the wires of the ground plane electrode 44 such that the wires are spaced apart. The wires may extend radially along the electrically actuated propellant 36. The surface area of ​​the propellant grains 26a, 28a covered by the ground plane electrode 44 may be at least twice the surface area covered by the ignition electrode 46.

[0072] As shown in Figures 4 and 5, the wires of the ignition electrode 46 and the ground plane electrode 44 do not intersect. The wires may be arranged in a zigzag, diagonal, cross, rectangular, parallel, non-parallel, and / or serpentine shape. The wires may be formed to run in a direction transverse to one another, as shown in Figures 5 and 6, or in a direction parallel to one another, as shown in Figure 7. The wires may be arranged to run along the entire surface of the propellant grains 26a, 28a so that the current may travel throughout the propellant grains 26a, 28a. In other exemplary embodiments, the wires may run along portions of the propellant grains 26a, 28a that are less than the entire length. Many different configurations and patterns of wires may be possible, and the configuration of the wires may depend on the application.

[0073] 8, a method 70 of operating a rocket motor, such as the rocket motor 12 of FIG. 1, is illustrated in a flow chart. Step 72 of the method 70 includes applying an electrical input across an electrically actuated propellant initiator 30 operatively coupled to the propellant grain 26a and including an electrically actuated propellant 36 and at least one pair of electrodes 34 (shown in FIG. 1). The at least one pair of electrodes 34 includes a ground plane electrode 44 and an ignition electrode 46 (shown in FIG. 2) at which an electric field 48 is focused to ignite the electrically actuated propellant 36 at a location where the ignition electrode 46 is located. In an exemplary embodiment, the ground plane electrode 44 extends along a first surface area of ​​the propellant grain 26a, 28a that is greater than a second surface area along which the ignition electrode 46 extends. The ignition electrode 46 has a greater current density than the ground plane electrode 44.

[0074] Step 74 of the method 70 includes igniting the electrically actuated propellant 36 with an electric field 48 focused on the ignition electrode 46 (shown in FIG. 2). Step 76 of the method 70 includes initiating combustion of the propellant grains 26a by igniting the electrically actuated propellant 36. Step 78 of the method 70 includes maintaining operative separation of the propellant grains 26a from the second propellant grains 28a of the auxiliary or second propellant pulse 26, 28 of the rocket motor 12. The electrically actuated propellant initiator 30 may be completely combusted during the pulse.

[0075] A step 80 of the method 70 includes providing a second propellant pulse to the rocket motor 12 by applying another electrical input across a second electrically actuated propellant initiator 32 subsequent to the electrically actuated propellant initiator 30 operatively coupled to the propellant grain 26a. The second electrically actuated propellant initiator 32 is operatively coupled to the second propellant grain 28a. A step 82 of the method 70 includes igniting the second electrically actuated propellant 36 of the second electrically actuated propellant initiator 32. A step 84 of the method 70 includes initiating combustion of the second propellant grain 28a by igniting the second electrically actuated propellant 36. The steps of the method may be repeated for additional pulses.

[0076] Although the present invention has been shown and described with respect to one or more specific preferred embodiments, it will be apparent to those skilled in the art upon reading and understanding this specification and the accompanying drawings that equivalent changes and modifications will occur to those skilled in the art. In particular, with respect to the various functions performed by the above elements (external components, assemblies, devices, configurations, etc.), the terms used to describe such elements (including references to "means") are intended to correspond to any element that performs the specified function of the described element (i.e., that is functionally equivalent), even if it is not structurally equivalent to the disclosed structure that performs the function in the exemplary embodiment or embodiments described herein. Moreover, although a particular feature of the present invention may be described above only with respect to one or more of some illustrated embodiments, such feature can be combined with one or more other features of other embodiments as desired and advantageous for any given or specific application.

Claims

1. a combustion chamber containing at least one propellant grain; an electrically actuated propellant initiator operably coupled to the at least one propellant grain for initiating combustion of the at least one propellant grain, the electrically actuated propellant initiator including an electrically actuated propellant and at least one pair of electrodes arranged to ignite the electrically actuated propellant, the at least one pair of electrodes including a ground plane electrode and an ignition electrode having an electric field focused thereon to ignite the electrically actuated propellant; the ground plane electrode extends along a surface of the at least one propellant grain having a first surface area, and the ignition electrode extends along a surface of the at least one propellant grain having a second surface area, the first surface area being greater than the second surface area; Rocket motor.

2. the ignition electrode has a greater current density than the ground plane electrode; 2. The rocket motor of claim 1.

3. a ratio of said first surface area to said second surface area is at least 2:1; A rocket motor according to claim 1 or 2.

4. the ground plane electrode being formed of a wire having a first diameter greater than a second diameter of a wire forming the ignition electrode; A rocket motor according to any one of claims 1 to 3.

5. the at least one electrode pair is formed of a plurality of wires having a zigzag, diagonal, cross, rectangular, parallel, non-parallel, or serpentine configuration; A rocket motor according to any one of claims 1 to 4.

6. The at least one pair of electrodes are spaced apart without crossing each other. A rocket motor according to any one of claims 1 to 5.

7. the at least one propellant grain has at least one cavity in which at least one of the ignition electrode and the ground plane electrode is disposed; A rocket motor according to any one of claims 1 to 6.

8. the ignition electrode and the ground electrode are disposed in the same plane that is parallel to an outer surface of the at least one propellant grain. A rocket motor according to any one of claims 1 to 7.

9. the ignition electrode and the ground electrode are disposed in different planes; A rocket motor according to any one of claims 1 to 7.

10. The ignition electrode is formed of a refractory metal or a refractory alloy. A rocket motor according to any one of claims 1 to 9.

11. The rocket motor is a multi-pulse rocket motor, and the at least one propellant grain includes a first propellant grain and a second propellant grain that is burned during a second pulse of the multi-pulse rocket motor, the second propellant grain is operatively separated from the first propellant grain via the electrically actuated propellant initiator, and the first propellant grain and the second propellant grain are independently initiated. A rocket motor according to any one of claims 1 to 10.

12. The at least one propellant grain includes a third propellant grain combusted during a third pulse of the multi-pulse rocket motor, the third propellant grain being operatively separated from the second propellant grain via another electrically actuated propellant initiator.

12. The rocket motor of claim 11.

13. the electrically powered propellant is configured to transition from an unignited state to an ignited state when an electrical input is applied across the electrically powered propellant initiator, and configured to maintain the unignited state when the electrical input is not applied. A rocket motor according to any one of claims 1 to 12.

14. a power source and a pair of leads extending from the power source to the electrically powered propellant initiator; A rocket motor according to any one of claims 1 to 13.

15. The at least one propellant grain comprising: a first pulse including a first propellant grain; and a second pulse including a second propellant grain operatively separated from the first propellant grain; The electrically actuated propellant initiator includes at least one electrically actuated propellant initiator configured to separate the first propellant grain and the second propellant grain, the at least one electrically actuated propellant initiator configured to initiate combustion of the first propellant grain or the second propellant grain; the first surface area and the second surface area of ​​the second propellant grain are surface areas of the second propellant grain; 2. The rocket motor of claim 1.

16. and a third pulse including a third propellant grain operatively separated from the first propellant grain and the second propellant grain, the at least one electrically actuated propellant initiator including a first electrically actuated propellant initiator configured to separate the first propellant grain and the second propellant grain, and a second electrically actuated propellant initiator configured to separate the second propellant grain and the third propellant grain.

16. The rocket motor of claim 15.

17. A method of operating a rocket motor as claimed in any one of claims 1 to 10, comprising: applying an electrical input to the electrically actuated propellant initiator operably coupled to the at least one propellant grain and including the electrically actuated propellant and the at least one pair of electrodes, the at least one pair of electrodes including the ground plane electrode and the ignition electrode; igniting the electrically actuated propellant with an electric field focused on the ignition electrode; and initiating combustion of the propellant grains by igniting the electrically actuated propellant. method.

18. maintaining an operable separation of the propellant grains from a second propellant grain of a second propellant pulse for the rocket motor; providing a second propellant pulse for the rocket motor by applying another electrical input across a second electrically actuated propellant initiator subsequent to the electrically actuated propellant initiator operably coupled to the propellant grain, the second electrically actuated propellant initiator being operably coupled to the second propellant grain; igniting a second electrically powered propellant in the second electrically powered propellant initiator; and initiating combustion of the second propellant grains by igniting the second electrically actuated propellant.

20. The method of claim 17.

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