Ignition device for hybrid rocket, and hybrid rocket

Abstract

[Problem] To provide an ignition device capable of re-ignition and capable of evenly burning a solid fuel. [Solution] Provided is a device for igniting a solid fuel, the device being characterized as follows. The device comprises a first member formed from an electroconductive material and having a through hole on an inner side thereof, a second member formed from an electroconductive material and having a through hole on an inner side thereof, and a third member provided between the first member and the second member, having a through hole on an inner side thereof, and formed from an insulating material for insulating the first member and the said second member. The shape of the third member is such that the thickness on an outer side is greater than the thickness on the inner side, thus making the third member have an insulation distance on the inner side that is shorter than the insulation distance on the outer side. As a result, when a voltage is applied between the first member and the second member, an electrical discharge phenomenon is created between the first member and the periphery of the through hole on the inner side of the second member.

Description

Hybrid rocket ignition device and hybrid rocket

[0001] The present invention relates to an ignition device for a hybrid rocket and a hybrid rocket using the ignition device, and in particular to an ignition device that uses arc discharge.

[0002] For example, Patent Document 1, entitled "Restartable Ignition Device, System, and Method Therefor," discloses a technology in which an insulator such as ABS resin is placed between two electrodes, and when a voltage is applied between the electrodes, a potential field is provided along the inner surface of the insulator such as ABS resin, and a local arc discharge is generated due to the effect of the electric field on the insulator such as ABS resin.

[0003] FIG. 1 illustrates the configuration of Patent Document 1. FIG. 1 shows a housing made of an insulator such as ABS resin with fine protrusions formed on it. A notch is provided in a portion of the insulator at a position approximately equidistant from two electrodes, and arc discharge occurs in the gap between the notch. Although not shown in FIG. 1 of the present application, FIG. 4 of Patent Document 1 describes that the tips of the two electrodes (reference numerals 86 and 88 in FIG. 4) extend into the combustion port (i.e., the surface of the ABS resin). Discharge occurs due to dielectric breakdown between the tips of these electrodes (reference numerals 86 and 88 in FIG. 4) and the fine protrusions formed on the resin surface of the notch (reference numeral 62 in FIG. 4). Therefore, it can be seen that the location where discharge reflection occurs is limited to the vicinity of the electrode tips (near the notch). Such notches are often referred to as voids because they are uneven areas in the insulator and lack intentionally created structures. This technology allows for Joule heating and thermal decomposition of the inner surface of an insulator such as ABS resin, enabling restartable ignition of a hybrid rocket system.

[0004] Furthermore, Patent Document 2, "Arc Igniter for Micro-Nano Satellites," discloses a technology in which an insulator such as a polymer is placed between two electrodes, and when a voltage is applied to the electrodes, an electrical breakdown occurs in a portion (conductive path) between the two electrodes when the voltage applied to the electrodes exceeds a threshold, generating a high-temperature arc discharge. Figure 2 illustrates the configuration of Patent Document 2. Figure 2 shows how a conductive path is provided in a portion of a housing made of an insulator such as a polymer at a position approximately equidistant from the two electrodes, and how discharge occurs in a gap in the insulator near the conductive path.

[0005] According to this technology, an insulator such as a polymer is exposed to high temperatures by arc discharge, generating hydrocarbon vapor, and an initial flame is formed by flowing an oxidizer, which propagates the solid fuel downstream, continuously pyrolyzing and burning the solid fuel, making re-ignition possible by turning on / off the ignition or oxidizer. Furthermore, paragraph 0008 of Patent Document 2 states, "This invention employs the ignition principle of polymer low-pressure breakdown, which minimizes instantaneous ignition power consumption to 3 W compared to other ignition methods, making it suitable for micro-nano satellite platforms with limited total power supply power."

[0006] As described above, Patent Document 1 and Patent Document 2 have in common the fact that both are configured by inserting electrodes into an insulator and generating a local arc discharge in a part of the insulator by applying a high voltage to the electrodes. Patent Document 1 and Patent Document 2 also have in common the fact that they generate a local arc discharge in a part of the insulator, rather than between the electrodes, by forming an uneven portion by providing a minute protrusion (not shown) in a part of the insulator and then providing a notch (void) (Patent Document 1) or providing a conductive path (Patent Document 2).

[0007] Therefore, the technologies of Patent Documents 1 and 2 enable discharge at a relatively low voltage of approximately several hundred volts, thereby reducing power consumption during discharge. Figures 3(a) to 3(c) are diagrams schematically illustrating the discharge phenomenon of Patent Documents 1 and 2, respectively showing a conceptual diagram, an equivalent circuit, and an image of the required voltage. Figure 3(a) shows how uneven portions such as voids are formed in a portion of an insulator such as ABS resin, causing partial discharge in those portions. Figure 3(b) shows the equivalent circuit of Figure 3(a). Figure 3(b) shows how an equivalent circuit is formed in which electrostatic capacitance is configured in parallel between electrodes.

[0008] Furthermore, when a single void or the like (uneven region) is present, the equivalent circuit is one in which the capacitance of the void or the like (uneven region) is connected in series with a portion of the capacitances connected in parallel. Figure 3(c) is a diagram showing the voltage and current of partial discharge at a void or the like and dielectric breakdown between electrodes. Figure 3(c) suggests that by utilizing partial discharge at a void or the like, ignition can be achieved with a relatively low voltage of several hundred volts, a small current, and therefore low power consumption. Patent Documents 1 and 2 are also consistent in that they provide a region corresponding to a void, such as by providing a notch in a part of an insulator, and that ignition can be achieved with relatively low power consumption, suggesting that they utilize the mechanism shown in Figure 3.

[0009] However, in the techniques described in Patent Documents 1 and 2, the location where the discharge occurs is limited to the vicinity of the void where the tip of the electrode protrudes from the surface of the resin, and the location where the discharge occurs does not recede as the solid fuel recedes due to combustion. Furthermore, when viewed in relation to the cylindrical solid fuel, the location where the discharge occurs is limited to one location away from the center, resulting in the inconvenience that the combustion and retreat of the solid fuel does not progress uniformly and results in unevenness. This is illustrated in Figure 4. Figure 4(a) shows the state immediately after the start of ignition (combustion), and Figure 4(b) shows the state after multiple ignitions (combustions) where the solid fuel has burned and retreated to a certain extent.

[0010] 4, an initial flame 720 generated by ignition by discharge and a reaction with the introduced oxidizer 710 flows into the combustion port 500, and due to the combustion promotion effect of the introduced oxidizer 710, boundary layer combustion (731, 732) occurs near the surface of the solid fuel 400. It can be seen that the boundary layer combustion (731, 732) gradually burns the solid fuel 400 while causing the solid fuel 400 to retreat.

[0011] Here, in the conventional technology, discharge point 20 of ignition device 100 is limited to one location away from the center of combustion port 500, so that the location where initial flame 720 is generated is also biased, and even if oxidizer 710 is introduced, boundary layer combustion (731, 732) is biased. More specifically, boundary layer combustion 732 on the far side is weaker than boundary layer combustion 731 on the closer side to initial flame 720 caused by ignition, and when re-ignition is repeated, there is a problem in that the combustion and retreat of solid fuel 400 is also biased (see the portion indicated in Comment 4-1).

[0012] Furthermore, unstable combustion also has the adverse effect of affecting the ability to stably generate a constant thrust. To prevent this imbalance, other measures have been required, such as generating a swirl in the flame to cause vortex-like combustion inside the combustion port 500, but these measures have often proven unsuccessful.

[0013] Therefore, a technology has been devised in which the solid fuel of a hybrid rocket engine is itself made conductive, electrodes are embedded in the conductive solid fuel, and the solid fuel is directly heated, thereby burning the solid fuel evenly, as in Patent Document 3, "Conductive solid fuel, ignition device...rocket combustion system." The technology in Patent Document 3 is shown in Figure 5.

[0014] 5 shows a structure in which electrodes are embedded in the conductive solid fuel, so that when a voltage is applied to the electrodes, a current path is generated inside the conductive solid fuel, and the heat generated in the current path is used to heat and vaporize the conductive solid fuel, thereby generating gasified fuel in the through-holes. With this structure, an oxidizer is injected onto the generated gasified fuel, generating combustion gas through a chemical reaction, thereby enabling the solid fuel to be burned stably and to be burned and retreated evenly.

[0015] US Patent Application Publication No. 2015 / 0322892 Chinese Patent Application Publication No. 114718765 International Publication No. 2023 / 074532

[0016] However, when using the technology of Patent Document 3, although it is possible to burn and retreat the solid fuel evenly, because it employs a mechanism for heating the conductive solid fuel, it consumes a lot of power and requires a relatively large battery, which makes it difficult to install on a small rocket. Also, because it is a method of embedding electrodes in the solid fuel, there is the disadvantage that, although rare, as the solid fuel burns and retreats, the electrodes may remain exposed in the through-holes (corresponding to combustion ports 500).

[0017] This situation is shown in Figure 6. Figure 6 shows that, in rare cases, problems such as impeding the smooth flow of oxidizer and flame (see the portion indicated by Comment 6-1) or the remaining electrode falling into the through-hole (see the portion indicated by Comment 6-2) can occur, damaging the nozzle.

[0018] Therefore, the present invention aims to provide an ignition device that overcomes the disadvantages of Patent Documents 1 and 2 (such as the difficulty of uniformly burning and retreating the solid fuel) and also overcomes the disadvantages of Patent Document 3 (high power consumption and adverse effects caused by remaining electrodes).

[0019] More specifically, regarding the problem of high power consumption in Patent Document 3, the present invention aims to provide an ignition device that consumes less power by utilizing a high-voltage discharge phenomenon rather than a heat generation phenomenon. Furthermore, regarding the adverse effects of the rare case of electrodes remaining in Patent Document 3 and the problems in Patent Documents 1 and 2 (such as the difficulty of uniformly burning and retreating the solid fuel), the present invention aims to provide an ignition device that enables uniform burning and retreating of the solid fuel and can stably generate a constant thrust.

[0020] In order to achieve the above object, a first invention is an apparatus for igniting solid fuel, comprising: a first member made of a conductive material and having a through hole on the inside; a second member made of a conductive material and having a through hole on the inside; a third member provided between the first member and the second member, having a through hole on the inside, and made of an insulating material for insulating the first member from the second member; and the third member is shaped so that its outer thickness is greater than its inner thickness, and the inner insulation distance of the third member is smaller than its outer insulation distance, so that when a voltage is applied between the first member and the second member, a discharge phenomenon occurs between the first member and the periphery of the through hole on the inside of the second member.

[0021] A second invention is characterized in that, in the ignition device described in the first invention, when a voltage is applied between the first member and the second member, a discharge phenomenon occurs between the first member and the peripheral edge of the through hole inside the second member, and as a result of multiple discharges, the discharge phenomenon between the first member and the peripheral edge of the through hole inside the second member occurs in a discharge area around the entire circumference of the peripheral edge of the through hole, thereby causing the second member and the third member and / or the first member to retreat evenly from the inside.

[0022] A third aspect of the present invention is the ignition device according to the second aspect, characterized in that the three-dimensional shape of the first member is a shape that increases in thickness from the inside to the outside.

[0023] A fourth invention is an ignition device according to any one of the first to third inventions, characterized in that the second member is plate-shaped and the inner shape is any one of a circle, a polygon, a star, and a fractal shape, or a combination thereof, and when a voltage is applied between the first member and the second member, a discharge phenomenon occurs between the first member and the periphery of the through hole inside the second member.

[0024] A fifth invention is an ignition device according to any one of the first to third inventions, characterized in that the shape of the second member is a lattice shape, a spider web shape, a honeycomb shape, a spiral shape, a combination of triangles, a combination of multiple small diameter holes, or any other shape in which multiple protrusions appear on the periphery of the inner through hole, and when a voltage is applied between the first member and the second member, a discharge phenomenon occurs between the first member and any of the multiple protrusions on the periphery of the inner through hole of the second member.

[0025] A sixth aspect of the present invention is an ignition device according to any one of the first to third aspects, characterized in that the conductive material used for the second member includes at least one of a conductive polymer, graphite, carbon fiber, metal powder, and metal fiber.

[0026] A seventh invention is an ignition device according to any one of the first to third inventions, characterized in that when a conductive polymer is used as the conductive material used for the second member, the physical properties of the conductive polymer are such that when formed by stacking using 3D printing, the volume resistivity is 30 to 115 Ω cm.

[0027] An eighth invention is an ignition device according to any one of the first to third inventions, characterized in that when a conductive polymer is used as the conductive material for the second member, HDPE is used as the insulating material for the third member.

[0028] A ninth invention is an ignition device according to the fourth invention, characterized in that when HDPE is used as the insulating material for the third member of the ignition device, when an oxidizer is sprayed toward the through hole inside the ignition device and a voltage is applied between the first member and the second member to ignite and burn the oxidizer by a discharge phenomenon, at least the second member of the first member and second member made of the conductive material retreats together with the third member.

[0029] A tenth invention is an ignition device according to the fifth invention, characterized in that when HDPE is used as the insulating material for the third member of the ignition device, when an oxidizer is sprayed toward the through hole inside the ignition device and a voltage is applied between the first member and the second member to ignite and burn the oxidizer by a discharge phenomenon, at least the second member of the first member and second member made of the conductive material retreats together with the third member.

[0030] An eleventh invention is a hybrid rocket equipped with an oxidizer port for injecting oxidizer and solid fuel, characterized in that it is equipped with the ignition device described in any one of the first to third inventions.

[0031] A twelfth invention is a hybrid rocket equipped with an oxidizer port for injecting oxidizer and solid fuel, comprising the ignition device according to any one of the first to third inventions, wherein when a third member of the ignition device is made of the same material as the solid fuel, when the oxidizer is injected from the oxidizer port toward a through hole inside the ignition device, and a discharge phenomenon occurs when a voltage is applied between the first and second members to ignite the oxidizer and burn the solid fuel, at least the second member of the first and second members made of the conductive material retreats together with the third member, and the retreat speed is approximately the same as the retreat speed of the solid fuel.

[0032] A thirteenth invention is a hybrid rocket equipped with an oxidizer port for injecting oxidizer and solid fuel, comprising the ignition device according to the fourth invention, wherein when a third member of the ignition device is made of the same material as the solid fuel, when the oxidizer is injected from the oxidizer port toward a through hole inside the ignition device and a discharge phenomenon occurs when a voltage is applied between the first member and the second member to ignite the oxidizer and burn the solid fuel, at least the second member of the first member and second member made of the conductive material retreats together with the third member, and the retreat speed of the second member and third member is approximately the same as the retreat speed of the solid fuel.

[0033] A fourteenth invention is a hybrid rocket equipped with an oxidizer port for injecting oxidizer and solid fuel, comprising the ignition device according to the fifth invention, wherein when a third member of the ignition device is made of the same material as the solid fuel, when the oxidizer is injected from the oxidizer port toward a through hole inside the ignition device and a voltage is applied between the first member and the second member to ignite the oxidizer by a discharge phenomenon and burn the solid fuel, at least the second member of the first member and second member made of the conductive material retreats together with the third member, and the retreat speed of the second member and third member is approximately the same as the retreat speed of the solid fuel.

[0034] A fifteenth invention is a hybrid rocket equipped with an oxidizer port for injecting oxidizer and solid fuel, comprising the ignition device according to the sixth invention, wherein when a third member of the ignition device is made of the same material as the solid fuel, when the oxidizer is injected from the oxidizer port toward a through hole inside the ignition device and a discharge phenomenon occurs when a voltage is applied between the first member and the second member to ignite the oxidizer and burn the solid fuel, at least the second member of the first member and second member made of the conductive material retreats together with the third member, and the retreat speed of the second member and the third member is approximately the same as the retreat speed of the solid fuel.

[0035] A sixteenth invention is a hybrid rocket equipped with an oxidizer port for injecting oxidizer and solid fuel, comprising the ignition device according to the seventh invention, wherein when a third member of the ignition device is made of the same material as the solid fuel, when the oxidizer is injected from the oxidizer port toward a through hole inside the ignition device and a voltage is applied between the first member and the second member to ignite the oxidizer by a discharge phenomenon and burn the solid fuel, at least the second member of the first member and second member made of the conductive material retreats together with the third member, and the retreat speed of the second member and the third member is approximately the same as the retreat speed of the solid fuel.

[0036] According to the present invention, an ignition device can be provided that uses an ignition method that utilizes the discharge phenomenon of arc discharge, thereby significantly reducing power consumption compared to heating methods. Furthermore, by using a structure that generates arc discharges successively around the entire periphery of the through-hole inside the ignition device, it is possible to evenly retract the ignition device itself from the inside and to evenly retract the solid fuel from the inside. Furthermore, stable output is possible even after multiple ignitions.

[0037] Figure 7 shows a schematic diagram of the retreating state when the ignition device of the present invention is used. Figure 7(a) shows the state immediately after the start of ignition (combustion), and Figure 7(b) shows the state after multiple ignitions (combustions) and the solid fuel has burned to a certain extent and retreated. Figure 7 shows that an initial flame 720 generated by ignition by discharge and a reaction with injected oxidizer 710 flows into combustion port 500, and boundary layer combustion (731, 732) occurs near the surface of solid fuel 400 due to the combustion promotion effect of injected oxidizer 710.

[0038] The boundary layer combustion (731, 732) gradually burns the solid fuel 400 while retreating the solid fuel 400. Here, in the conventional technology (Patent Documents 1 and 2), the discharge point 20 of the ignition device 100 is limited to one point away from the center of the combustion port 500, and therefore the initial flame 720 is generated at a biased point, and even when the oxidizer 710 is introduced, the boundary layer combustion (731, 732) is biased.

[0039] On the other hand, in the case of the ignition device of the present invention, the discharge location is throughout the entire discharge area, which is the entire periphery of the inside of the ignition device. Therefore, the initial flame 720 caused by ignition is also generated throughout the entire periphery of the inside of the combustion port 500 of the solid fuel 400, and the subsequent boundary layer combustions 731 and 732 can also be generated evenly throughout the entire periphery. Therefore, the solid fuel can be retreated evenly from the inside (see the portion indicated in Comment 7-2), enabling stable output control.

[0040] In Figure 7, only two marks (star-shaped marks) indicating the discharge points are shown on the left and right sides, but this is done only for the sake of simplicity of illustration, and discharge points can be generated one after another all around the periphery of the through-hole inside the ignition device.

[0041] Figure 8 shows a comparison table of the present invention with the above-mentioned Patent Documents 1 to 3, as well as other prior art (catalytic ignition, gas torch ignition, laser ignition, nichrome wire heating, and glow plug systems). For example, in Technology A, catalytic ignition uses polyethylene or the like as fuel and hydrogen peroxide as an oxidizer. The hydrogen peroxide is sprayed onto a catalyst, MnO2-Al2O3 (a mixture of manganese dioxide and alumina), causing the hydrogen peroxide to self-exothermally decompose and mix with the fuel, automatically igniting it. This catalytic ignition system is advantageous in terms of weight reduction because it does not require special equipment as an ignition device, but it has the disadvantage of only being applicable when the oxidizer is hydrogen peroxide. For example, while the use of nitrous oxide eliminates the need for a pressure pump due to its self-pressurization, hydrogen peroxide requires a pressure pump, which is an inconvenience.

[0042] Additionally, the gas torch ignition method of Technology D uses acrylic resin (methyl methacrylate, PMMA) as fuel and gaseous oxygen (GOX) as the oxidizer. Ignition with a gas torch using a spark plug ensures reliable ignition, but the use of methane leaves safety concerns.

[0043] In Technology E's laser ignition method, a laser is irradiated onto the ABS resin, applying high energy locally to gasify the ABS resin, which is then ignited by spraying an oxidizer onto it. While this method consumes around 10W of power, it has the drawback of requiring accessories such as a laser generator, heat sink, and lens, which makes the system more complex and increases its weight.

[0044] The heating method of Technology F uses HDPE as the fuel and nitrous oxide (NO) as the oxidizer, along with nichrome wire and gaseous oxygen (GOX). Nitrous oxide contains a high amount of nitrogen molecules, making it much more difficult to ignite than oxygen. While ignition can be ensured by heating the nichrome wire and using gaseous oxygen, the required power is around 100-200W. Furthermore, the need for oxygen to assist ignition in addition to the oxidizer has the disadvantage of complicating the system and increasing its weight.

[0045] Furthermore, Technology B (Patent Document 1), Technology C (Patent Document 2), and Technology H (Patent Document 3) also had the above-mentioned disadvantages. As described above, it can be said that there has not yet existed a small, safe, and energy-saving ignition device applicable to the propulsion systems of small spacecraft. On the other hand, the ignition device of the present invention has no particular disadvantages and has the advantages of low power consumption, being miniaturizable, and being able to burn and retreat solid fuel evenly from the inside.

[0046] FIG. 11 is a diagram showing an example of the prior art (Patent Document 1). FIG. 12 is a diagram showing an example of the prior art (Patent Document 2). FIG. 13 is a diagram showing an example of an equivalent circuit, etc., of the prior art (Patent Documents 1 and 2). FIG. 14 is a diagram showing an example of an ignition device and a combustion problem of the prior art (Patent Documents 1 and 2). FIG. 15 is a diagram showing an example of the prior art (Patent Document 3). FIG. 16 is a diagram showing an example of an ignition device and a combustion problem of the prior art (Patent Document 3). FIG. 17 is a diagram showing an example of the effect of the present invention. FIG. 18 is a comparison table between the prior art and the present invention. FIG. 19 is a diagram showing an example of the overall configuration of a hybrid rocket. FIG. 20 is a diagram showing an example of the configuration of the vicinity of the ignition device of a hybrid rocket. FIG. 21 is a diagram showing an example of a method of energizing conductive members (first member and second member). FIG. 22(a) is a diagram showing an example of a case where a cable is soldered, and FIG. 22(b) is a diagram showing an example of a case where electricity is applied using sheet metal or the like. FIG. 23 is a diagram showing an example of a typical example of an ignition device, where FIG. 23(a) is a perspective view and FIG. 23(b) is a front view. 13(a) and 13(b) are diagrams showing an example of a modified ignition device in which the shape of the device is modified to a substantially cylindrical shape, where FIG. 13(a) is a perspective view and FIG. 13(b) is a cross-sectional view taken along B-B. 14(a) and 14(b) are diagrams showing cross-sectional views of a typical example of an ignition device, where FIG. 14(a) is a perspective view taken along A-A and FIG. 14(b) is a cross-sectional view taken along B-B. 15(a) and 15(b) are diagrams showing an example of a modified ignition device in which the shape of a stepped portion is modified based on a typical example of an ignition device, where FIG. 15(a) is a perspective view taken along A-A and FIG. 15(b) is a cross-sectional view taken along B-B. 16(a) and 16(b) are diagrams showing an example of a modified ignition device in which the thickness of the first member near the peripheral edge of the through hole is modified based on a typical example of an ignition device, where FIG. 16(a) is a perspective view taken along A-A and FIG. 16(b) is a cross-sectional view taken along B-B. 17(a) and 17(b) are diagrams showing an example of a modified ignition device in which the shape of the inclined portion of the first member is modified based on a typical example of an ignition device, where FIG. 17(a) is a perspective view taken along A-A and FIG. 17(b) is a cross-sectional view taken along B-B. FIG. 16 is a cross-sectional view taken along B-B of a typical example of an ignition device (FIGS. 12 and 14), showing the dimensions of each part. FIG. 17 is a cross-sectional view taken along B-B of the ignition device of FIG. 15, showing the dimensions of each part. FIG. 18 is a cross-sectional view taken along B-B of the ignition device of FIG. 16, showing the dimensions of each part. FIG. 19 is an exploded view of a typical example of an ignition device (FIGS. 12 and 14).27 is a diagram showing that there is a degree of freedom in the combination of the first member, the second member, and the third member that constitute the ignition device, and is a diagram showing an example of several modified examples.

[0044] FIG. 28 is a diagram showing an example of the second member in the typical examples of the ignition device (FIGS. 12 and 14).

[0045] FIG. 29 is a diagram showing an example of a modified second member, showing an example of an embodiment in which the outer periphery is rectangular.

[0046] FIG. 29 is a diagram showing an example of a modified second member, showing an example of an embodiment in which the outer periphery is octagonal.

[0047] FIG. 29 is a diagram showing an example of a modified second member, showing an example of an embodiment in which the portion that burns and retreats upon discharge and ignition is made of a lattice-shaped member, has through holes that are circularly hollowed out inside the member, and protrusions appear on the periphery of the through holes.

[0048] FIG. 29 is a diagram showing an example of a modified second member of the embodiment of FIG. 27, showing an example of an embodiment in which the outer periphery is rectangular.

[0049] FIG. 29 is a diagram showing an example of a modified second member of the embodiment of FIG. 27, showing an example of an embodiment in which the outer periphery is octagonal.

[0023] Figure 1 shows a modified example of the second member, in which the portion that burns and retreats due to discharge and ignition is made of a radial or spider web-shaped member, has through holes that are hollowed out in a circular shape on the inside of the member, and shows an example of an embodiment in which protrusions appear around the periphery of the through holes.

[0024] Figure 1 shows a modified example of the second member, in which the portion that burns and retreats due to discharge and ignition is made of a honeycomb-shaped member, has through holes that are hollowed out in a circular shape on the inside of the member, and shows an example of an embodiment in which protrusions appear around the periphery of the through holes.

[0025] Figure 1 shows a modified example of the second member, in which the portion that burns and retreats due to discharge and ignition is made of a spiral-shaped member, has through holes that are hollowed out in a circular shape on the inside of the member, and shows an example of an embodiment in which protrusions appear around the periphery of the through holes.

[0026] Figure 1 shows a modified example of the second member, in which the portion that burns and retreats due to discharge and ignition is made of a triangular lattice-shaped member, has through holes that are hollowed out in a circular shape on the inside of the member, and shows an example of an embodiment in which protrusions appear around the periphery of the through holes. FIG. 10 is a diagram showing a modified example of the second member, in which the portion that burns and retreats due to discharge and ignition is composed of a plurality of small-diameter circular holes, and the member has a through-hole that is a circular hole cut out from the inside, with protrusions appearing on the periphery of the through-hole.24 shows a modified example of the peripheral portion of the through hole of the second member in the embodiment of FIG. 24 , illustrating that the shape and configuration of the peripheral portion of the inner through hole are flexible, and various configurations can be adopted, such as multiple small-diameter circles, polygons such as squares and octagons, star shapes, fractals, etc. 27 shows a modified example of the peripheral portion of the through hole of the second member in the embodiment of FIG. 27 , illustrating that the shape and configuration of the peripheral portion of the inner through hole are flexible, and various configurations can be adopted, such as multiple small-diameter circles, polygons such as squares, pentagons, and octagons, star shapes, etc. 28 shows a cross-sectional view along A-A illustrating that when a plate-shaped second member is used, by configuring the third member of the ignition device so that the outer thickness is thicker than the inner thickness, discharge occurs at the periphery of the inner through hole of each member. This is an A-A cross-sectional view showing that when an embodiment having protrusions on the inside of the second member is used, the outer thickness of the third member of the ignition device is configured to be thicker than the inner thickness, thereby generating a discharge at the periphery of the inner through-hole of each member. This is a plan view showing that when a plate-shaped second member is used, multiple ignitions cause discharge to progress sequentially around the entire periphery of the inner through-hole, and the retraction proceeds evenly from the inside. Note that the third member and / or the first member also retract in the same way as the second member, but this is not shown. This is a plan view showing that when a grid-shaped second member having protrusions on the inside is used, multiple ignitions cause discharge to progress sequentially around the entire periphery of the inner through-hole, and the retraction proceeds evenly from the inside. Note that the third member and / or the first member also retract in the same way as the second member, but this is not shown. 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 , 94 , 95 , 96 , 97 , 98 , 99 , 100 , 101 , 102 , 103 , 104 , 105 , 106 , 107 , 108 , 109 , 110 , 111 , 112 , 113 , 114 , 115 , 116 , 117 , 118 , 119 , 120 , 121 , 122 , 123 , 124 , 125 , 126 , 127 , 128 , 129 , 130 ,When the shape of the second member is in the form of a plate as shown in FIGS. 24 and 35, it is a diagram showing how each member retreats due to discharge. When the shape of the second member is in a form having a protrusion on the inside as shown in FIGS. 27, 30 to 34, and 36, it is a diagram showing how each member retreats due to discharge. When a mode in which the thickness inside the first member is close to the thickness of the third member is used, it is a B - B cross-sectional view showing how each member retreats due to multiple ignitions. It is a diagram showing an example of characteristics when a conductive polymer is used as the conductive material. It is a diagram showing a list of an example of the material of the third member. It is a diagram showing an example of the system configuration of the combustion experiment. It is a diagram showing an example of the ignition sequence of the combustion experiment. It is a diagram showing an example of the result of the combustion experiment, and it is a diagram showing the values of the pressure sensors before and after the Throttling Valve. It is a diagram showing an example of the transition of the chamber internal pressure in the combustion experiment. It is a diagram showing an example of the result of the combustion experiment, and it is a diagram showing the state of retreat of each part of the ignition device and the hybrid rocket.

[0047] <Explanation of Terms> ◇A hybrid rocket refers to a rocket configured with a mechanism in which an oxidizer is injected by an injector, ignited by an ignition device, the solid fuel is ignited by the high-temperature flame, and then injected from a nozzle. It is called hybrid because it combines different types of phases such as a liquid oxidizer and a solid fuel. As the oxidizer, liquid oxygen, nitrous oxide, etc. are used. Since the oxidizer is not easy to burn and the solid fuel is often made of a resin material formed and output by a 3D printer, and this is also relatively difficult to burn, it is evaluated as a safe system.

[0048] ◇Boundary layer combustion refers to the mixing and combustion of the fuel gasified from the solid fuel with the oxidizer within the turbulent boundary layer on the surface of the solid fuel. Boundary layer combustion is composed of a complex process involving various phenomena such as chemical reactions, phase changes of substances, and transport of substances and heat. However, it is difficult to sufficiently mix the oxidizer and the fuel gasified from the solid fuel. Considering that the flow of the oxidizer is turbulent, it is difficult to maintain a constant mixing ratio. Therefore, it is difficult to maintain a constant mixing ratio, and as a result, it is known that it is difficult to burn the solid fuel evenly.

[0049] ◇Reignition is the process of restarting combustion after combustion has been stopped once by reignition. The reignition configuration allows for a process of ignition - combustion - combustion interruption - reignition - combustion. For launch rockets, ignition only needs to be performed once at launch, and reignition is not necessary. However, reignition is essential for kick motors intended for orbital transfer to a non-intersecting orbit in space (such as Hohmann transfer), orbital insertion into an orbit around another celestial body, or landing on a gravitational celestial body.

[0050] Arc discharge is the most advanced form of gas discharge, sustained by the emission of thermoelectrons from a high-temperature cathode. In atmospheric arc discharges, the discharge path is arc-shaped (arc), so it is also called arc light discharge or simply arc. Most discharges with high gas pressure and currents of several amperes or more become arc discharges. Even when the gas pressure is low and the current is relatively low (several hundred milliamperes), arc discharge occurs if the cathode is prone to high temperatures or if the cathode is coated with a thermoelectron-emitting material (which makes it easy to emit thermoelectrons). The voltage is relatively low, ranging from several tens to several hundred volts, but a large current flows. The electrodes are connected by a bright, flame-like positive column, where equal numbers of electrons and positive ions form plasma. The temperature of the arc generally exceeds 1000°C and can reach 3500°C. Part of the electrode material also evaporates, becoming a spectral light source.

[0051] The term "discharge area" is a general term for the discharge location on the periphery of the through hole inside the first member and the second member. There are not just one discharge location, but multiple locations, and discharges occur one after another all around the periphery of the through hole inside the first member and the second member. Therefore, the discharge location all around the periphery of the through hole is referred to as the "discharge area." This is intended to clarify the features of the present invention and to clarify the differences from the prior art, whereas in prior art, the discharge location is often limited to a single location in a small range.

[0052] ◇The edge effect in discharge phenomena refers to the phenomenon where, when there are sharp or uneven parts, the electric field strength is greater at the convex parts, causing discharge to concentrate at these parts. ◇Anode means positive pole, and cathode means negative pole. In the combustion experiments of the present invention, the first member was the anode (positive pole) and the second member was the cathode (negative pole), but this is not limited to this and the reverse connection is also acceptable. In the case of arc discharge, the amount of heat generated on the cathode side is often greater, and when the second member is the cathode (negative pole), the second member tends to have a faster retreat speed.

[0053] ◇Recession of a component means that the periphery of the inner through-hole of the first component, second component, third component, etc. burns due to discharge (ignition), causing it to gradually spread outward (outer periphery) of the component. ◇Similarly, recession of a solid fuel means that the inner wall (combustion port) of the solid fuel burns due to discharge (ignition), causing it to gradually spread outward (outer periphery) of the solid fuel.

[0054] ◇The recession rate of a component directly refers to the speed at which the component recedes, but also includes the amount or rate at which the component recedes due to one or more discharges (ignitions). It also includes the rate at which the radius of the through-hole inside the component increases gradually from the center to the outside as the component or solid fuel burns due to multiple discharges (ignitions).

[0055] "The component retreats evenly" means that multiple ignitions cause the discharge to progress sequentially around the entire periphery of the through-hole inside the component, causing the periphery of the through-hole to retreat a predetermined distance around one circumference at approximately the same distance from the center, and then retreat a predetermined distance around the next circumference, repeating this step. In other words, it's like cutting out the periphery of the through-hole inside the component with a circle of a certain radius. This can also be explained as a method of retreat in which the step of cutting out the entire circumference, and then cutting out the periphery of the through-hole with a circle of an even larger radius, is repeated.

[0056] Furthermore, if we call the above-mentioned even retreat of the periphery of the through-hole inside the member, one circle at a time, "even retreat per circle," then "even retreat of the member" also includes a manner in which "the member retreats evenly, which can be evaluated as having retreated evenly overall as a result of multiple repeated discharges (ignitions)," as follows: In other words, although the retreat of part of the periphery of the through-hole inside the member progresses (not for each circle around the periphery of the through-hole inside the member), by repeating discharges (ignitions) multiple times, the expansion of the through-hole inside the member eventually converges into a roughly circular shape, resulting in even retreat.

[0057] The following describes embodiments of the present invention. Note that the configurations, drawings, and tables in the description are merely examples, and are applicable to other shapes and configurations.

[0058] 1. About the Hybrid Rocket 1-1. Overall Configuration First, the overall configuration of the hybrid rocket will be explained using Figure 9. As shown in Figure 9, the hybrid rocket is composed of an oxidizer tank (not shown), an oxidizer port 700, an ignition device 100, a case 200, a heat insulator 300, solid fuel 400, a combustion port 500 inside the solid fuel, and an injection nozzle 800.

[0059] 9 also shows that oxidizer discharged from an oxidizer tank (not shown) is introduced into the rocket's ignition device 100 through an oxidizer port 700. Electric power is supplied to the ignition device 100 through voltage application ports 600 and 610, and ignition by discharge is performed successively around the entire circumference of a discharge area 140 provided on the periphery of the through-hole inside the ignition device 100.

[0060] 1-2. Structure near the ignition device of a hybrid rocket Next, the structure and function near the ignition device of a hybrid rocket will be explained using Figure 10. Figure 10 is a diagram showing an example of the structure near the ignition device of a hybrid rocket. Figure 10 shows how the ignition device 100 is configured such that a first member 110 and a second member 120 made of a conductive material sandwich a third member 130 made of an insulating material from above and below. Note that the first member 110 and the second member 120 are painted gray to indicate that they are made of conductive materials (the same applies below).

[0061] Furthermore, the voltage application ports 600, 610 may have holes (holes not shown) for passing through cables, metal plates, or the like for applying voltage to the ignition device 100. Here, the two ports, the voltage application port 600 and the voltage application port 610, are provided to correspond to the anode and the cathode, respectively, and are connected to the first member 110 and the second member 120 formed of a conductive material.

[0062] In addition, in order to exhaust the exhaust gas after combustion, a ventilation port for introducing ventilation gas supplied from a purge tank (see Figure 48) may be provided as appropriate, but this is not shown in the figure. Furthermore, unlike the prior art, the present invention is characterized in that so-called electrodes themselves are not provided, and the first member 110 and the second member 120 made of a conductive material serve as electrodes and as discharge sites.

[0063] When a predetermined voltage is applied to the first member 110 and the second member 120, which are made of a conductive material, the presence of the third member 130, which is made of an insulating material, allows the location of discharge occurring between the first member 110 and the second member 120 to be limited to a discharge area 140 on the periphery 150 of the through-hole inside the ignition device 110. The discharge can be an arc discharge. High-temperature sparks generated by ignition through the arc discharge generate an initial flame 720 in which the third member, which is made of an insulating material such as resin, and the second member or the first member, etc., are burned.

[0064] When an oxidizer 710 is introduced simultaneously with or around the time of ignition, an initial flame 720 spreads over the surface of the solid fuel 400 while moving downstream of the combustion port, generating boundary layer combustion 731, 732 on the surface of the solid fuel 400, thereby promoting the combustion of the solid fuel 400. Here, as described above, the boundary layer combustion 731, 732 is composed of a complex process in which various phenomena, such as chemical reactions, phase changes of substances, and transport of substances and heat, are interrelated. It is known that it is difficult to burn the solid fuel evenly because it is difficult to sufficiently mix the oxidizer with the fuel gasified from the solid fuel and to maintain a uniform distribution of the burning rate.

[0065] Therefore, in the present invention, the discharge points generated inside the ignition device 100 can be generated successively around the entire inner circumference (discharge area), thereby making it possible to burn and retreat the solid fuel 400 evenly from the inside (the inner wall of the combustion port 500).

[0066] 1-3. Regarding energization of conductive materials of the ignition device Next, the configuration for applying voltage to the first member 110 and the second member 120 made of conductive materials of the ignition device 100 will be described with reference to Fig. 11. Fig. 11 is a diagram showing an example of a method for energizing the conductive members (first member and second member). Fig. 11(a) is a diagram showing an example of a case where a cable is soldered, and Fig. 11(b) is a diagram showing an example of a case where electricity is applied using sheet metal.

[0067] Voltage application cables 601, 611 are laid through two ports, voltage application port 600 and voltage application port 610, and are connected to first member 110 and second member 120, respectively, which are made of a conductive material. The connection may be by any means, such as soldering or embedding, as long as it is possible to ensure electrical continuity. Alternatively, as shown in FIG. 11(b), the cables 601, 611 may be connected via voltage application metal plates 602, 612 that come into surface contact with the first member 110. Furthermore, the cables 610, 611 themselves may also be made of metal plates.

[0068] 2. Configuration of Ignition Device 2-1. Typical Example Next, a typical example of the ignition device of the present invention will be described with reference to FIG. 12. FIG. 12 shows an example of a typical example of ignition device 100, with FIG. 12(a) being a perspective view and FIG. 12(b) being a front view. First, FIG. 12(a) shows that ignition device 100 is configured such that a third member 130 made of an insulator is sandwiched between a first member 110 and a second member 120 made of a conductive material.

[0069] Furthermore, a through hole is formed inside each member, and it is shown that through hole 112 of first member 110, through hole 122 of second member 120, and through hole 132 of third member 130 are provided with approximately the same diameter (coaxially). Here, the inner periphery of through hole 112 of first member 110 is defined as peripheral edge portion 115, the inner periphery of through hole 122 of second member 120 is defined as peripheral edge portion 125, and the inner periphery of through hole 132 of third member 130 is defined as peripheral edge portion 135.

[0070] If necessary, an inclined portion 116 may be provided on the upper surface of the first member 110, which may be shaped to generate a swirl in the flow of the oxidizer or to facilitate the efficient introduction of gas for discharging the exhaust gas after combustion. If necessary, a wiring groove 101 may be provided to pass a voltage application cable through which a voltage application cable for applying a voltage to the second member 120 is passed.

[0071] Since a high voltage is applied to the cable for applying voltage to the second member 120, care must be taken with the arrangement and configuration of the wiring groove 101 to prevent inadvertent discharge due to proximity to the first member 110. For example, it is effective to remove part of the top surface 102 of the first member 110 around the wiring groove 101 and replace it with an insulating material, thereby ensuring a sufficient insulating distance from the cable for applying voltage to the second member 120.

[0072] Fig. 12(b) is a front view of the ignition device 100. Comparing this with the thickness of the peripheral portion 135 of the through-hole 132 on the inside of the third member 130 in Fig. 12(a) shows that by ensuring that the thickness of the outside of the third member 130, which is made of an insulating material, is greater than that of the inside, the insulation distance between the first member 110 and the second member 120 is greater on the outside than on the inside. This makes it possible to prevent discharge from occurring on the outside of the ignition device, but to discharge near the peripheral portion of the through-hole on the inside.

[0073] 2-2. Cylindrical Configuration Example Next, a cylindrical modification of the first member 110 will be described using FIG. 13 . FIG. 13 shows an example of a modification in which the configuration of the ignition device 100 has been modified to be approximately cylindrical, with FIG. 13( a) being a perspective view and FIG. 13( b) being a cross-sectional view taken along the line B-B. While the typical example of FIG. 12 includes an inclined portion 116, FIG. 13 does not include an inclined portion and is modified to have a flat shape. As shown in FIG. 13( b), a stepped portion 133 is provided in the third member 130, and the thickness of the outer side of the third member 130, which is made of an insulating material, is made thicker than the thickness of the inner side. This prevents discharge from occurring outside the ignition device, and allows discharge to occur near the periphery of the inner through-hole.

[0074] 2-3. Cross-Section of a Typical Ignition Device Next, the cross-sectional configuration of a typical example of the ignition device 100 will be described using FIG. 14. FIG. 14 shows a cross-section of a typical example of the ignition device 100, with FIG. 14(a) being a perspective view of the A-A cross-section and FIG. 14(b) being a cross-sectional view of the B-B cross-section. As shown in FIGS. 14(a) and 14(b), a stepped portion 133 is provided in the third member 130, and the thickness of the outer side 139 is made thicker than the thickness of the inner through-hole periphery 135 of the third member 130, which is made of an insulating material. This prevents discharge from occurring outside the ignition device, and enables discharge and ignition to occur between the inner through-hole periphery 115 of the first member 110 and the inner through-hole periphery 125 of the second member 120.

[0075] Furthermore, the discharge does not occur in one place on the periphery of the through-hole, but can occur sequentially in discharge area 140 around the entire periphery of the through-hole. Therefore, when the ignition device of the present invention is used in a hybrid rocket, as shown in Fig. 7, boundary layer combustion 731, 732 can be generated evenly around the entire periphery of combustion port 500, and solid fuel 400 can be burned and retreated evenly.

[0076] 14, it can be seen that in a typical example of the ignition device 100, the first member 110 has a tapered structure in which the thickness gradually decreases toward the inside. This structure generates a gas flow from the outside to the inside when an oxidizer or a gas for discharging post-combustion gas is injected from above in the figure, contributing to efficient gas introduction or discharge by a swirl effect, etc. Furthermore, by making the first member 110 thicker toward the outside, it contributes to adjusting the regression speed of each of the first to third members when igniting and burning by discharge (details will be described later).

[0077] 2-4. Cross-sectional view of a modified ignition device (shape of the stepped portion) Next, an example in which the shape of the stepped portion is modified based on a typical example of ignition device 100 will be described using Fig. 15. Fig. 15 shows an example of a modified example in which the shape of the stepped portion 133 is modified based on a typical example of ignition device 100, Fig. 15(a) is a perspective view of the A-A cross section, and Fig. 15(b) is a cross-sectional view of the B-B cross section.

[0078] 15(a) and 15(b), the outer insulation distance can be increased relative to the inner distance by changing the thickness of the stepped portion 133 of the third member made of an insulating material to a tapered or curved shape instead of a stepped portion. As described above, the typical example of the ignition device 100 is just one example, and various configurations are possible as long as the outer insulation distance is ensured to be greater than the inner insulation distance.

[0079] 2-5. Cross-sectional view of a modified example of the ignition device (thickness of the peripheral portion of the through hole of the first member) Next, an example in which the thickness near the peripheral portion of the inner through hole of the first member is modified based on the typical example of ignition device 100 will be described using Fig. 16. Fig. 16 shows an example of a modified example in which the thickness of the peripheral portion of the through hole of the first member is modified based on the typical example of ignition device 100, Fig. 16(a) is a perspective view of the A-A cross section, and Fig. 16(b) is a cross-sectional view of the B-B cross section.

[0080] 16( a) and 16(b) show that the thickness of the inside of the first member 110 is thicker at the deformed portion 117. In this way, the configuration of the first member 110 can take a variety of forms, and various configurations can be adopted as long as it is possible to ensure that the insulation distance on the outside is larger than the insulation distance on the inside.

[0081] 2-6. Cross-sectional view of a modified example of the ignition device (inner thickness of the first member) Next, an example in which the shape of the inclined portion of the first member 110 is modified will be described using Fig. 17. Fig. 17 shows an example of a modified example in which the shape of the inclined portion of the first member 110 is modified based on the typical example of the ignition device 100, Fig. 17(a) is a perspective view of the A-A cross section, and Fig. 17(b) is a cross-sectional view of the B-B cross section.

[0082] 17(a) and 17(b) show that the thickness of the first member 110 is configured to be thinner at the deformed portion 117. In this way, the configuration of the first member 110 can take a variety of forms, and various configurations can be adopted as long as it is sufficient to ensure that the outer insulation distance is larger than the inner insulation distance.

[0083] As shown in FIG. 17( b), by adjusting the thickness of the first member 110 to be the same as or slightly thicker than the thickness of the second member 120, it is possible to adjust the retraction speed of the first member 110 upon discharge and ignition to be approximately equal to or slightly slower than the retraction speeds of the second member 120 to the third member 130 (details will be described later).

[0084] 2-7. Dimensions of the Ignition Device Next, the dimensions of each part of the ignition device 100 will be explained using Figures 18 to 21. Figure 18 is a diagram showing a cross-sectional view taken along line B-B of a typical example of the ignition device (Figures 12 and 14), showing the dimensions of each part. Similarly, Figures 19 to 21 are cross-sectional views taken along line B-B of the ignition devices of the embodiments shown in Figures 15 to 17, respectively, showing the dimensions of each part. All of these diagrams show the dimensions of the typical example of the ignition device 100 and modified versions of parts that are partial modifications of the typical examples, and since the dimensions are basically indicated by the same reference numerals, they will all be explained together.

[0085] First, the outer diameter of the ignition device 100 is represented by IG-L1, the inner diameter by IG-L2, and the thickness by IG-T1. Furthermore, the inner thickness of the first member 110 is represented by P1-T1, the outer thickness by P1-T2, the thickness of the second member 120 by P2-T1, and the inner thickness of the third member 130 by P3-T1 and the outer thickness by P3-T2. Furthermore, the width of the thick portion on the outer side of the third member 130 is represented by P3-L1, and the width to the periphery of the through hole of the portion where the thickness decreases toward the inside is represented by P3-L2.

[0086] Furthermore, the insulation distance between the first member 110 and the second member 120 on the inside is the same as the inner thickness P3-T1 of the third member 130, and is therefore expressed as GAPin. Similarly, the insulation distance between the first member 110 and the second member 120 on the outside is the same as the outer thickness P3-T2 of the third member 130, and is therefore expressed as GAPout.

[0087] As described above, by ensuring a sufficient outer thickness of the third member 130 made of an insulating material, it is possible to ensure that the outer insulation distance (GAPout) between the first member 110 and the second member 120 is greater than the insulation distance (GAPin) near the inner periphery of the through-hole. As a result, discharge does not occur outside the ignition device, but can occur near the inner periphery of the through-hole.

[0088] The actual dimensions of each part can be freely set depending on the size of the hybrid rocket, the burn time, the size of the solid fuel depending on the application, etc. For example, if the total length of the hybrid rocket is about 50 to 400 mm, the diameter of the hybrid rocket can be set to about 25 to 200 mm, and the diameter of the solid fuel can be set to about 20 to 180 mm.

[0089] In this case, the outer diameter IG-L1 of the ignition device 100 can be set to 20 to 180 mm, the inner diameter IG-L2 can be set to 5 to 40 mm, and the thickness IG-T1 can be set to approximately 5 to 30 mm. The inner thickness P1-T1 of the first member 110 can be set to 3 to 25 mm, the outer thickness P1-T2 can be set to 1 to 5 mm, and the thickness P2-T1 of the second member 120 can be set to approximately 0.5 to 3 mm.

[0090] The inner thickness P3-T1 of the third member 130 can be set to about 1 to 3 mm, and the outer thickness P3-T2 can be set to about 4 to 25 mm. The width P3-L1 of the thick outer portion of the third member 130 can be set to about 3 to 10 mm, and the width P3-L2 of the portion where the thickness decreases inward to the periphery of the through hole can be set to about 5 to 50 mm.

[0091] In the combustion experiments described below, the outer diameter IG-L1 of the ignition device 100 was set to approximately 90 mm to 145 mm. The thickness P2-T1 of the second member 120 was set to approximately 1 mm, the inner thickness P1-T1 of the first member 110 was set to approximately 11 mm, and the outer thickness P1-T2 was set to approximately 2 mm. The inner thickness P3-T1 (GAPin) of the third member 130 was set to approximately 2 mm, and the outer thickness P3-T2 (GAPout) was set to approximately 11 mm.

[0092] Furthermore, if the thickness of the inside of the third member 130 is too thin, discharge will occur in undesirable locations, such as near the middle between the through hole and the outside of the third member, rather than near the periphery of the through hole, so it is preferable that the thickness be at least about 1 mm to 3 mm. Furthermore, the width P3-L1 of the thick part on the outside of the third member 130 is set to about 7 mm, and the width P3-L2 of the part where the thickness decreases toward the inside to the periphery of the through hole is set to about 20 mm.

[0093] 2-8. Exploded View of Ignition Device Next, the combination of the first member 110 to the third member 130 will be described using an exploded view ( FIG. 22 ) of the ignition device 100. FIG. 22 is an exploded view of a typical example of the ignition device 100 ( FIGS. 12 and 14 ). FIG. 22 shows that the first member 110 and the second member 120 are configured to sandwich the third member 130. Note that although modified examples of the first member 110 are shown in FIGS. 13 and 15 to 17 , modified examples of the second member 120 are shown in FIGS. 24 to 36 , and modified examples of the third member 130 are shown in FIGS. 15 to 17 , these modified examples can also be used in combination with each other, similar to FIG. 22 .

[0094] Each of the members has peripheral portions 115, 125, and 135 of the through holes formed on the inside thereof, which together form a discharge area 140. In order to generate a discharge, a voltage needs to be applied to the first member 110 and the second member 120, and a booster that boosts the voltage supplied from a power supply is connected to the first member 110 and the second member 120.

[0095] 12 to 17 and the cross-sectional views of FIGS. 18 to 22, the shape and structure of the first member 110 are not limited to these, and any shape and structure may be used for the other portions as long as the structure allows discharge to occur between the periphery 115 of the inner through-hole and the periphery 125 of the inner through-hole of the second member 120. More specifically, when viewed in plan view, a configuration similar to that of the second member 120 may be employed, for example, as shown in FIGS. 24 to 36.

[0096] 12 to 17(b) and the cross-sectional views of FIGS. 18 to 22, it is sufficient that the third member 130 has a predetermined shape and structure for ensuring insulation between the first member 110 and the second member 120, and other portions can have any shape and structure. More specifically, it is sufficient that the third member has a predetermined thickness so that discharge does not occur in portions other than the periphery of the inner through-hole, and that the thickness of the outside 139 of the third member is greater than the thickness of the periphery 135 of the inner through-hole, and other portions can have any shape.

[0097] 2-9. Examples of Combinations of the First to Third Members Constituting the Ignition Device Next, combination patterns of the first member 100, the second member 120, and the third member 130 constituting the ignition device 100 will be described using FIG. 23. FIG. 23 shows that there is a degree of freedom in the combination of the first member 110, the second member 120, and the third member 130 constituting the ignition device 100, and is a diagram showing examples of several modified examples. FIG. 23(a) shows a typical example of a combination of the first member 110, the second member 120, and the third member 130. In this case, discharge is generated at the periphery (not shown) of the through-holes provided inside the first member 110 and the second member 120.

[0098] 23(b) shows an example in which two sets of a first member 110, a second member 120, and a third member 130 are provided one above the other. In this example, the second member 120 is shared between set A and set B. In this case, a voltage is applied between the first member 110 and the second member 120 of set A and / or set B. Then, a discharge is generated at the periphery (not shown) of the through-hole provided inside the first member 110 and the second member 120 of set A and / or set B (the discharge location is not shown because it is on the inside).

[0099] 23(c) shows an example in which two sets of a first member 110, a second member 120, and a third member 130 are provided, one above the other, and the second member 120 is provided separately as set A and set B. In this case, a voltage is applied between the first member 110 and the second member 120 of set A and / or set B. Then, a discharge is generated at the periphery (not shown) of the through-hole provided inside the first member 110 and the second member 120 of set A and / or set B (the discharge location is on the inside and is therefore not shown). Although not shown, multiple sets of ignition devices, such as set C and set D, may also be provided.

[0100] 3. Configuration of the Second Member 3-1. Example of Plate-Shaped Second Member When the second member 120 is plate-shaped, its outer shape pattern will be described using Figures 24 to 26. Figure 24 is a diagram showing an example of the second member in the typical example of the ignition device 100 (Figures 12 and 14). Figure 25 is a diagram showing a modified example of the second member 120, showing an example of an embodiment in which the outer periphery has a rectangular shape.

[0101] Figure 26 is a diagram showing a modified example of the second member 120, showing an example of an embodiment in which the outer periphery has an octagonal shape. As shown in Figures 24 to 26, the outer shape of the second member 120 can have a variety of shapes. Note that although the first member 110 and the third member 130 are not shown, their outer shapes can have a variety of shapes, similar to the second member 120 in Figures 24 to 26.

[0102] 3-2. Examples of Modes in Which Multiple Protrusions Appear on the Periphery of the Through-Hole Inside the Second Member Next, examples of modes in which multiple protrusions appear on the periphery of the through-hole inside the second member 120 will be described. In order to make the protrusions appear on the inside of the member, it is preferable to provide a portion composed of multiple lines, such as a lattice shape, and hollow out the inside of that portion. In addition, shapes composed of multiple lines that can be used include a lattice shape, a spider web shape, a honeycomb shape, and a spiral shape. Several patterns will be described below using Figures 27 to 34.

[0103] (1) Example when the second member is lattice-shaped Figures 27 to 29 are diagrams showing modified examples of the second member, in which the portion that burns and retreats due to discharge and ignition is made up of a lattice-shaped member, the inside of the member has a through-hole with a circular hollowed-out shape, and protrusions appear around the periphery of the through-hole. Figure 27 shows that a certain area inward from the outside is made up of a lattice-shaped shape, and further inside is a circular hollowed-out shape. In this case, it can be seen that protrusions (protrusions 126) are formed around the periphery 125 of the inner through-hole.

[0104] As will be described in more detail later, by providing the protrusion 126, it is possible to utilize the edge effect during discharge to generate a discharge phenomenon between the peripheral edge 115 of the through hole 113 on the inside of the first member 110 and the protrusion 126 formed on the peripheral edge 125 of the through hole 122 on the inside of the second member 120, and ultimately to generate a discharge phenomenon successively around the entire circumference of the peripheral edge 125 of the through hole 122.

[0105] Fig. 28 is a diagram showing a modified example of the second member of the embodiment of Fig. 27, showing an example of an embodiment in which the outer periphery has a rectangular shape. Also, Fig. 29 is a diagram showing a modified example of the second member of the embodiment of Fig. 27, showing an example of an embodiment in which the outer periphery has an octagonal shape. In this way, various embodiments can be adopted for the outer shape.

[0106] (2) Example when the second member is spider web-shaped Figure 30 shows a modified example of the second member 120, in which the portion that burns and retreats due to discharge and ignition is composed of a radial or spider web-shaped member, has a through hole with a circular shape cut out from the inside of the member, and has a protrusion on the periphery of the through hole. In this case, too, it can be seen that a protrusion-like portion (protrusion 126) is formed on the periphery 125 of the inner through hole 122. Note that in this case as well, various external shapes can be adopted, and therefore illustrations are omitted.

[0107] (3) Modifications when configured with multiple lines In order to make the protrusions appear on the inside of the member, it is preferable to provide a section configured with multiple lines, such as a lattice or spider web, and hollow out the inside of that section, but various other modes can also be adopted. Each mode will be explained below using Figures 31 to 33.

[0108] 31 shows a modified example of the second member 120, in which the portion that burns and retreats due to discharge and ignition is made of a honeycomb-shaped member, the member has a circular through-hole cut out on the inside, and protrusions appear on the periphery of the through-hole. In this case, too, protrusions 126 are formed on the periphery 125 of the inner through-hole 122, and it can be seen that this is suitable for inducing a discharge phenomenon using the edge effect.

[0109] 32 shows a modified example of the second member 120, in which the portion that burns and retreats due to discharge and ignition is made up of a spiral member, the member has a through hole with a circular shape cut out on the inside, and a protrusion appears on the periphery of the through hole. In this case, too, a protrusion 126 is formed on the periphery 125 of the inner through hole 122, and it can be seen that this is suitable for inducing a discharge phenomenon using the edge effect.

[0110] 33 shows a modified example of the second member, in which the portion that burns and retreats due to discharge and ignition is composed of a triangular lattice-shaped member, has through-holes that are circularly hollowed out on the inside of the member, and shows an example of an embodiment in which protrusions appear on the periphery of the through-holes. In this case, too, protrusions 126 are formed on the periphery 125 of the inner through-hole 122, and it can be seen that this is suitable for inducing a discharge phenomenon using the edge effect.

[0111] (4) Other Examples Although the above describes an example in which a portion made up of a plurality of lines is provided and the inside of the portion is hollowed out to form the protrusion 126, various other embodiments can also be adopted. In addition, as a means for generating a protrusion-like shape on the periphery of the inner through-hole, for example, an embodiment such as that shown in FIG. 34 can be considered.

[0112] 34 shows a modified example of the second member, in which the portion that burns and retreats due to discharge and ignition is composed of multiple small-diameter circular holes, the member has a circular through-hole cut out from the inside, and protrusions appear around the periphery of the through-hole. In this case, too, protrusions 126 are formed around the periphery 125 of the inner through-hole 122, which is suitable for inducing a discharge phenomenon using the edge effect. Although not shown, multiple polygonal small holes, including triangular and rectangular ones, or multiple star-shaped small holes may also be provided.

[0113] 3-3. Regarding the pattern of the shape of the periphery of the inner through hole (1) Modified examples of the periphery of the through hole when the second member is plate-shaped Next, using Fig. 35, modified examples of the periphery of the through hole when the second member is plate-shaped will be described. Fig. 35 is a diagram showing modified examples of the periphery of the through hole of the second member in the embodiment of Fig. 24, and shows that there is a degree of freedom in the configuration of the periphery of the inner through hole, and various configurations can be adopted, such as multiple small-diameter circles, polygons such as squares and octagons, star shapes, fractals, etc.

[0114] In short, it is sufficient that there is at least one through hole on the inside and the thickness of the third member made of an insulating material is configured to be thicker on the outside so that a discharge phenomenon can occur around the periphery of the inner through hole. Note that, although an example of a circular outer shape is described in Figure 35, the outer shape can take various shapes as shown in Figures 24 to 26.

[0115] (2) Modified Examples of the Periphery of the Through Hole When the Second Member is Lattice-Shaped Next, using Figure 36, modified examples of the periphery of the through hole when the second member is lattice-shaped will be described. Figure 36 shows modified examples of the periphery of the through hole of the second member in the embodiment of Figure 27, and illustrates that the configuration of the periphery of the inner through hole has a degree of freedom, and various configurations can be adopted, such as multiple small-diameter circles, polygons such as squares, pentagons, and octagons, and star shapes. Note that Figure 36 shows an example of a lattice-shaped embodiment as an example of the second member, but similarly, in various embodiments (Figures 27 to 34) in which protrusions appear on the inside, the shape of the periphery of the inner through hole can take various shapes.

[0116] 4. Discharge Area 4-1. Discharge Area When the Second Member is Plate-Shaped Next, the significance of the discharge location and discharge area when the second member is plate-shaped (such as in FIG. 24) will be explained using FIG. 37. FIG. 37 is an A-A cross-sectional view showing that when a plate-shaped second member is used, the third member of the ignition device is configured so that the thickness of the outer side 139 is greater than the thickness of the inner side, thereby generating discharge at the periphery of the through-hole on the inner side of each member. Here, the up and down arrows indicate the discharge location.

[0117] According to Figure 37, since the insulation distance (GAPout) on the outside 139 of the third member is larger than the insulation distance (GAPin) on the inside, discharge does not occur on the outside (see the indicated portion of Comment 37-1), but occurs between the peripheral portion 115 of the through hole 112 on the inside of the first member 110 and the peripheral portion 125 of the through hole 122 on the inside of the second member 120.

[0118] Furthermore, the discharge location (up and down arrows) is not one location, but indicates that discharges occur one after another in discharge area 140 around the entire periphery of the through-hole due to repeated charging and discharging of electric charge by the igniter during the energization time. Note that the order in which discharges occur is random, and as a result, discharges occur one after another in discharge area 140 around the entire periphery of the through-hole.

[0119] 4-2. Cases where a protrusion is provided on the inside of the second member Next, the significance of the discharge location and discharge area in cases where the second member has a protrusion on its inside (such as in FIG. 27) will be explained using Figure 38. Figure 38 is an A-A cross-sectional view showing that when a protrusion is provided on the inside of the second member, a discharge occurs at the periphery of the through-hole on the inside of each member by configuring the outside 139 of the third member of the ignition device to be thicker than the inside.

[0120] 38, similar to FIG. 37, shows that the insulation distance (GAPout) on the outside 139 of the third member is greater than the insulation distance (GAPin) on the inside, causing discharge to occur inside the members. It also shows that, due to the edge effect in the discharge phenomenon, discharge occurs between the protrusion 126 on the inside of the second member and the edge of the peripheral portion 115 of the through hole 113 in the first member. It also shows that the discharge location (up and down arrows) does not occur in one place, but occurs successively in a discharge area 140 around the entire peripheral portion of the through hole.

[0121] 5. How Discharge (Ignition) and Combustion Proceed in the Discharge Area Around the Entire Circumference Inside the Member 5-1. When the Second Member is Plate-Shaped Next, the way discharge (ignition) and combustion proceed in the discharge area around the entire circumferential circumference inside the member will be explained using Figure 39. Figure 39 is a plan view showing that when a plate-shaped second member is used, multiple ignitions cause discharges to occur one after another around the entire periphery of the inner through-hole, and the retraction proceeds evenly from the inside. Note that the first member or third member also retracts in the same way as the second member, but is not shown in the figure.

[0122] 39 shows that the discharge (ignition) and combustion progress in the discharge area around the entire periphery inside the member for the first (t1), second (t2), ... discharge (ignition), and as the discharge (ignition) and combustion progress, by the nth (tn) discharge, the peripheral edge 125 of the through hole 122 inside the second member 120 retreats evenly. In this way, the location of the discharge (ignition) moves one after another, and the discharge (ignition) can be generated all around the inside of the member, so that boundary layer combustion can also occur evenly all around, and the solid fuel can be burned and retreated evenly.

[0123] Depending on conditions such as the thickness of each component and the flow of the oxidizer, some parts may retreat earlier than other parts, but even in this case, by performing multiple discharges (ignitions), it is possible to eventually cause the solid fuel to retreat evenly around the entire circumference of the through hole inside the component. Therefore, even if the solid fuel retreats partially, it is possible to burn and retreat the solid fuel evenly.

[0124] 5-2. In the case of an embodiment in which a protrusion is provided on the inside of the second member When an embodiment in which a protrusion is provided on the inside of the second member is used, the manner in which discharge (ignition) and combustion progress in the discharge area (Discharge Area) around the entire periphery of the inside of the member will be described using Figures 40 and 41. Figure 40 is a plan view showing that when a grid-shaped protrusion is used as an example of an embodiment in which a protrusion is provided on the inside of the second member, multiple ignitions cause discharges to occur one after another around the entire periphery of the inner through-hole, and the retraction progresses evenly from the inside. Note that the first member or third member also retracts in the same way, but is not shown in the figure. The first member or third member also retracts in the same way, but is not shown in the figure.

[0125] 41 is a plan view showing that when a spider web-shaped projection is used among the projections provided on the inside of the second member, multiple ignitions cause discharges to progress sequentially around the entire periphery of the inner through-hole, causing the second member to retreat evenly from the inside. Note that the first member or third member also retreats in the same way as the second member, but this is not shown in the figure.

[0126] As described above, according to the present invention, it can be seen that discharge (ignition) and combustion progress successively in the discharge area (Discharge Area) around the entire periphery of the inner member, with the first discharge (ignition) (t1), the second discharge (t2), and so on. Furthermore, it can be seen that once discharge (ignition) and combustion have progressed to a certain extent, by the nth discharge (tn), the periphery 125 of the through hole 122 inside the second member 120 can be made to retreat evenly. In this way, since the location of discharge (ignition) moves successively and discharge (ignition) can be generated around the entire periphery, boundary layer combustion can also occur evenly around the entire periphery, and the solid fuel can be burned and retreated evenly.

[0127] 6. Regarding discharge in the discharge area when the first member is in the form of FIG. 14 and the second member is in the form of FIG. 24 (the form in which the inside is formed of a continuous line or surface)

[0128] 6-1. How each part recedes due to discharge (ignition) as seen from a B-B cross section In Chapter 5, we used a plan view from above to show how parts recede evenly from the inside due to discharge (ignition), but in this section we will use a B-B cross section as seen from the side to show how parts recede evenly from the inside due to discharge (ignition).

[0129] Figure 42 is a B-B cross-sectional view showing how each member retreats due to multiple ignitions when the ignition device has an outer shape like those in Figures 14 to 16, when the second member has a plate-like shape like those in Figures 24 and 35, or when it has a protrusion on the inside like those in Figures 27, 30 to 34, and 36. Figure 42 shows how discharge (ignition) and combustion occur one after another in the discharge area (Discharge Area) around the inside of the member (after t1, t2, ...) with the first discharge (ignition) (t1), second discharge (ignition) (t2), ..., and the discharge (ignition) and combustion progress as each member retreats (after t1, t2, ...).

[0130] Here, for example, at t1, because the third member 130 is made of an insulating material, even if a voltage is applied to the first member 110 and the second member 120, no discharge occurs inside the third member (see the indicated portion of Comment 42-1), but instead, a discharge occurs near the edge portions of the peripheries of the through holes inside the first member 110 and the second member 120 (in a gas or in a vacuum in the case of outer space). Then, a spark is generated by the discharge (ignition), and in combination with the oxidizer 710, the first member 110, the second member 120, and the third member 130 are combusted, generating an initial flame (not shown).

[0131] Because the initial flame has more momentum downstream due to the direction of oxidizer flow, the third member 130 and the second member 120 tend to retreat slightly more than the first member 110. The reason we say "tend to" is that the retreat speed of each member varies depending on the thickness and material of the first member 110, the third member 130, and the second member 120, and also varies depending on the flow rate and flow velocity of the oxidizer.

[0132] Furthermore, in the case of arc discharge, the cathode side tends to have a higher temperature than the anode side (the cathode side retreats faster), so the retreat speed can also be adjusted by determining whether the first member 110 or the second member 120 is the cathode. In Figure 42, an example is shown in which the first member 110 is configured to be thicker than the other members, so the retreat speeds of the third member 130 and the second member 120 are slightly faster.

[0133] 6-2. Mechanism for Generating Discharges Around the Entire Periphery of the Through-Hole Next, the mechanism for generating discharges around the entire periphery of the through-hole and uniformly retracting the members will be described using Figures 43 and 44. 6-2-1. Discharge Phenomenon in the Discharge Area When the Second Member is Plate-Shaped as in Figures 24 and 35. For example, if the thickness of the second member 120 is thinner than that of the first member 110, the second member tends to retract more easily, resulting in a tendency for the retraction speed of the second member 120 to be slightly faster. This is shown in Figure 43. Figure 43(a) is a diagram showing the state of each part before discharge (t0), with the left side being a cross-sectional view taken along A-A and the right side being a cross-sectional view taken along B-B. Figure 43(b) is a diagram showing the state of each part after the first discharge (after t1), with the left side being a cross-sectional view taken along A-A and the right side being a cross-sectional view taken along B-B.

[0134] The term "first discharge" refers to the occurrence of one or more arc discharges, including multiple single discharges. This occurs when an igniter ON / OFF switch (described later) is turned ON, causing a single discharge, and multiple cycles of charging, discharging, charging, discharging, etc. are repeated during the specified time that the igniter is turned ON.

[0135] Figure 43 (c) is a diagram showing that when the discharge has progressed to a certain extent (nth discharge), if the retraction speed of the second member 120 is faster than the retraction speed of the first member 110, the shortest distance (GAPtn-vertical) between the second member 120 and the first member 110 is shorter than the distance (GAPtn-edge) between the edge of the peripheral portion 115 of the through hole 112 in the first member 110 and the edge of the peripheral portion 125 of the through hole 122 in the second member 120.

[0136] As shown in Figures 43(a) and (b), if we define the insulation distance between the first member 110 and the second member 120 on the inside before discharge (ignition) (t0) as GAPt0 and the insulation distance after the first discharge (ignition) (after t1) as GAPt1, we can see that GAPt1 > GAPt0. In such a case, the location where discharge has occurred will remain less likely to cause discharge than the location where discharge has not yet occurred (while suspending the discharge's progression from the location where discharge has already occurred to the outer side 119, 129), and discharge will continue around the entire circumference in the more inner location where discharge has not yet occurred, allowing for uniform retreat. See Figures 39 to 41.

[0137] This is an effect not found in the prior art, and the discharge area around the entire periphery of the inner through-hole is called the "discharge area 140" to express the difference from the prior art. As a result, the ignition device of the present invention enables ignition around the entire periphery of the through-hole, generating an initial flame around the entire periphery, and ultimately generating boundary layer combustion around the entire periphery of the solid fuel, making it possible to uniformly retreat the solid fuel from the inside (see FIG. 7). At the same time, there is also the advantage of being able to achieve uniform output.

[0138] Next, we will use Figure 43(c) to provide a supplementary explanation of the mechanism by which discharge due to the edge effect occurs in preference to discharge at locations with a shorter insulation distance. Here, the edge effect in discharge phenomena refers to the phenomenon in which, when there are sharp or uneven parts, the electric field strength is greater at the convex parts, causing discharge to concentrate at these parts.

[0139] The peripheries (edge ​​portions) of the through holes on the inside of the first member 110 and the second member 120 are each sharp or convex, and therefore susceptible to the edge effect caused by the discharge phenomenon. As shown in Figure 43 (c), if the retraction speed of the first member 110 is slower than the retraction speed of the second member 120, the shortest gap (GAPtn-vertical) between the first member 110 and the second member 120 will be a distance equal to the thickness of the third member 130.

[0140] On the other hand, the gap (GAPtn-edge) between the edge portion of the periphery of the innermost through hole of the first member 120 and the edge portion of the innermost protrusion of the second member has the relationship (GAPtn-vertical) < (GAPtn-edge), and (GAPtn-edge) tends to be slightly larger.

[0141] In this case, when a voltage is applied between the first member 110 and the second member 120, it appears at first glance that a discharge occurs in the area of ​​the shortest distance (GAPtn-vertical) (between Inside1 and Edge2). However, as described above, due to the edge effect of the discharge phenomenon, the electric field strength is greater in the area of ​​(GAPtn-edge) than in the area of ​​the shortest distance (GAPtn-vertical). Therefore, despite the relatively large insulation distance, a discharge occurs in the area of ​​(GAPtn-edge) (between Edge1 and Edge2). As a result, the location where the discharge occurs is uneven, and some parts do not retreat toward the outside 119, 129. Instead, after a discharge occurs around the entire periphery of the inner through-hole, the members can be uniformly retreated outward in sequence.

[0142] Depending on conditions such as the thickness of each component and the flow of the oxidizer, some parts may retreat earlier than other parts, but even in this case, by performing multiple discharges (ignitions), it is possible to eventually cause the solid fuel to retreat evenly around the entire periphery of the through-hole. Therefore, even in such cases, it is possible to burn and retreat the solid fuel evenly.

[0143] Furthermore, depending on conditions such as the thickness of each component and the flow of the oxidizer, it is possible that the first component does not retreat and only the second component 120 and the third component 130 retreat. In this case, the relationship GAPtn-edge >> GAPtn-vertical holds in Figure 43(c), and discharge occurs mainly between the edge portion (Edge2) of the periphery of the through-hole inside the second component and the plane (Inside1) of the first component directly above, i.e., GAPtn-vertical.

[0144] Even in such a case, as shown in Fig. 7, the location where discharge (ignition) occurs and initial flame 720 is generated remains directly above the solid fuel, and there is no effect on the subsequent occurrence of boundary layer combustion of the solid fuel. Furthermore, by repeating discharge (ignition), the discharge eventually progresses around the entire circumference of the second member, allowing the solid fuel to burn and retreat evenly.

[0145] Regarding discharge in the discharge area when the second member has a structure with gaps, such as a grid or line combination shape, or a combination of many small circles, triangles, or diamonds, as shown in Figures 27, 30 to 34, and 36, and has protrusions on the inside

[0146] For example, if the thickness of the second member 120 is thinner than the thickness of the first member 110, or if the shape of the second member 120 is a structure with gaps rather than a surface, such as a lattice shape or a shape made up of a combination of lines, for example, as shown in Figures 27 to 34 and 36, the second member tends to retract more easily, and the retraction speed of the second member 120 tends to be slightly faster. This state is shown in Figure 44.

[0147] Figures 44(a) and (b) show that if a discharge occurs at protrusion 1 (126-1), the insulation distance (GAPt1) between the edge of the periphery of the through hole in the first member 110 and protrusion 1 (126-1) on the periphery of the through hole in the second member will be greater than the insulation distance (GAPt0) between protrusions 2 to n (126-2 to 126-n) in which no discharge has yet occurred and the edge of the periphery of the through hole in the first member 110.

[0148] As a result, discharges occur randomly one after another between protrusions 2 to n (126-2 to 126-n) where discharge has not yet occurred and the edge of the periphery of the through-hole of the first member 110, causing the second member 120 to retreat evenly from the inside to the outside 129. In other words, the retreat does not progress outward in some parts, but discharges occur one after another until discharge is completed around the entire periphery of the inner through-hole, and when one circumference of discharge is completed, discharge starts on the outer circumference, causing the second member 120 to retreat evenly from the inside to the outside.

[0149] As shown in Figures 44(a) and (b), if the insulation distance inside the first member 110 and the second member 120 before discharge (ignition) (t0) is defined as GAPt0 and the insulation distance after the first discharge (ignition) (after t1) is defined as GAPt1, it can be seen that GAPt1 > GAPt0.

[0150] In such a case, the discharge will remain difficult to occur at the location where the discharge has occurred compared to the location where the discharge has not yet occurred, and the discharge will continue all around the inner location where the discharge has not yet occurred. This makes it possible to ignite all around the periphery of the through hole, and an initial flame will be generated all around, which in turn makes it possible to generate boundary layer combustion all around the solid fuel, making it possible to retreat the solid fuel evenly (see Figures 40 and 41).

[0151] Figure 44 (c) shows that when the discharge has progressed to a certain extent (nth discharge), if the retreat speed of the second member 120 is slightly faster than the retreat speed of the first member 110, the shortest distance (GAPtn-vertical) between the second member 120 and the first member 110 becomes slightly shorter than the distance (GAPtn-edge) between the edge of the peripheral portion 115 of the through hole 113 of the first member 110 and the edge of the "protrusion portion 126-1 to n" of the peripheral portion 125 of the through hole 122 of the second member 120.

[0152] In this case, when a voltage is applied between the first member 110 and the second member 120, it appears at first glance that a discharge occurs in the area of ​​the shortest distance (GAPtn-vertical) (between Inside1 and Edge2). However, as described above, due to the edge effect of the discharge phenomenon, the electric field strength is greater in the area of ​​(GAPtn-edge) than in the area of ​​the shortest distance (GAPtn-vertical), so a discharge occurs in the area of ​​(GAPtn-edge) (between Edge1 and Edge2) despite the large insulation distance.

[0153] In particular, since a protrusion is formed on the periphery of the inner through-hole of the second member 120, the edge effect is enhanced compared to the case of a plate-like member, and therefore discharge can be reliably generated between the protrusion 126 (Edge 2) of the inner through-hole of the second member 120 and the periphery (Edge 1) of the inner through-hole of the first member 110. Therefore, there is no bias in the location where discharge occurs, and partial retraction outward in some locations, and after discharge occurs around the entire periphery of the inner through-hole, it is possible to uniformly retract (the member) outward in sequence.

[0154] 6-2-3. When the inner thickness of the first member is close to the thickness of the second member or the third member, how each member recedes due to discharge (ignition) as seen from the B-B cross section

[0155] Next, the manner in which each member retracts when a first member 110 having an inner thickness close to that of the third member 130 as shown in Figures 17 and 21 is used and a second member 120 such as that shown in Figures 24 to 36 is used will be described using Figure 45. Figure 45 is a cross-sectional view taken along line B-B showing the manner in which each member retracts due to multiple ignitions when a first member having an inner thickness close to that of the third member is used.

[0156] FIG. 45 shows the first (t1), second (t2), ... discharge (ignition) and combustion in the discharge area around the inside of the components, with each component retreating (after t1, t2, ...). Furthermore, FIG. 45 shows that the difference in the retreat speed between the first component 110 and the second component 120 to the third component 130 is smaller than in the case of FIG. 42. This is because, as shown in FIG. 45, when the thickness of the first component 110 is close to the thickness of the second component 120 or the third component 130, the first component 110 can be burned in the same way as the other components, and the difference in the retreat speed between the first component 110 and the other components can be reduced.

[0157] In this case, too, the relationship GAPt1>GAPt0 holds (not shown), as in the explanations of Figures 43 and 44. That is, in the area where discharge has occurred, it will remain difficult for discharge to occur compared to areas where discharge has not yet occurred (discharge will continue to advance further outward from the area where discharge has already occurred, with the progression of discharge remaining suspended). Therefore, discharge will continue all around the inner area where discharge has not yet occurred, and will retreat evenly. See Figures 39 to 41.

[0158] 7. Physical Properties of the Conductive Material of the First and Second Members Next, the physical properties of the first and second members 110 and 120, which are made of conductive materials, will be described. The conductive material used for the first and second members 110 and 120 is preferably a material that burns and retreats upon discharge (ignition) (see FIG. 7). On the other hand, in order to function as a substitute for an electrode, it is required that the material have conductivity within a moderate range of resistance. Furthermore, since the material will be placed in a high-temperature environment, it is desirable that the material have a certain degree of heat resistance.

[0159] Conductive materials generally refer to materials with a surface electrical resistance of 10^3 to 10^5 Ωm or less, expressed as a volume resistivity. In the case of plastics or resins, the electrical resistance can be reduced by incorporating a powdered conductive material such as carbon or coating the surface with a material that allows electricity to pass through easily, allowing them to be used as conductive materials. In the present invention, in addition to materials in which a powdered conductive material such as carbon is incorporated into plastics or resins, conductive polymers (intrinsically conducting polymers, ICPs) and the like can also be used. Conductive polymers or conductive polymers are polymeric compounds with high electrical conductivity. Representative materials include polyacetylene and polythiophenes.

[0160] The physical properties of the conductive polymer used in the experiment are listed in Figure 46. Figure 46 shows an example of the characteristics when a conductive polymer is used as the conductive material. In Figure 46, PLA is an abbreviation for Poly-Lactic Acid, which refers to a resin material called polylactic acid. It can be based on plastic materials derived from plants such as starch found in corn and potatoes.

[0161] Here, the conductive material used for the first member 110 and the second member 120 is preferably a material that burns and retreats upon discharge (ignition). Therefore, PLA was used as the base material, but this is not limited to this, and other flammable resin materials may be used as the base material. Furthermore, it is desirable to incorporate a conductive carbon (carbon-based material) material and achieve an electrical characteristic of a volume resistivity of 30 to 115 (Ω·cm) to provide conductivity. Furthermore, it has been confirmed that the melting point is approximately 155°C, allowing it to be used in high-temperature environments. Other physical properties are as shown in Figure 46, so a description thereof will be omitted.

[0162] The first member 110 and the second member 120 may be formed by layering using a 3D printer, or by creating a mold and pouring raw materials into it. The volume resistivity when 3D printed using a 3D printer differs when viewed in the XY layer direction (horizontal direction) and when viewed in the Z layer direction (vertical direction), and the numerical values ​​are as shown in FIG.

[0163] 8. Physical Properties of the Insulating Material of the Third Member The third member 130, formed from an insulating material, is a member for insulating the first member 110 and the second member 120. By adjusting the thickness and material of the third member 130, it is possible to cause discharge at a desired location (such as the periphery of the inner through-hole) while preventing discharge from occurring at locations other than the desired location (such as locations closer to the outer side 129 than the periphery of the through-hole) (see the indicated portion of Comment 42-1 in Figure 42).

[0164] Here, "a portion in a direction approaching the outside of the periphery of the through hole" means a portion in a direction away from the center of the member and approaching the outside of the member (e.g., 129). Furthermore, when a voltage is applied between the first member 110 and the second member 120 and the first member 110 and / or the second member 120 combusts due to discharge (ignition), it is desirable that the third member 130 also combusts and retreats together (see the description of FIG. 7, FIG. 10, etc.).

[0165] Furthermore, it is desirable for the third member 130 to retreat together with the solid fuel 400 as it retreats (see the description of FIG. 7 , FIG. 10 , etc.). To achieve this effect, the third member 130 can be made of a material such as that shown in FIG. 47 . As shown in FIG. 47 , examples of materials that can be used include HDPE (high-density polyethylene), ABS (ABS resin), TPU (thermoplastic polyurethane elastomer), POM (polyacetal resin), PMMA (acrylic resin), and PC (polycarbonate). All of these materials have a volume resistivity exceeding 10 to the power of 14 (Ω·cm) and a dielectric breakdown strength exceeding 14 (KV / mm), providing sufficient insulating performance. Other physical properties are as shown in FIG. 47 , and therefore will not be described here.

[0166] However, since the third member 130 is used in the ignition device of a hybrid rocket, it will be exposed to a high-temperature environment due to discharge (ignition) and combustion, so it is desirable to determine the material of the third member 130 from the standpoint of a certain degree of heat resistance and appropriate arc resistance.

[0167] Here, arc resistance refers to the time from when tracking occurs until the arc is extinguished. More specifically, when an arc is generated on the surface of a resin, the resin decomposes and carbonizes due to the high temperature. This phenomenon first occurs near the electrodes, and when the carbide eventually becomes a conductive path between the electrodes (called arc tracking), the arc discharge is extinguished. Arc resistance refers to the time from when tracking occurs until the arc is extinguished.

[0168] In the present invention, when the first member 110 and / or the second member 120 burns due to discharge (ignition), it is desirable that the third member 130 also burns and retreats together, so materials such as HDPE (high density polyethylene) and ABS (ABS resin), which have a good balance between a moderate range of melting point and a moderate range of arc resistance, are suitable.

[0169] 9. Combustion Experiment 9-1. System Configuration Next, the configuration of a combustion experiment system for measuring the performance of the ignition device of the present invention will be described with reference to FIG. 48. FIG. 48 is a diagram showing an example of the system configuration for a combustion experiment. A booster is connected to the ignition device 100, allowing a predetermined voltage to be applied. The power supply is provided with an ON / OFF switch, allowing the voltage application to the ignition device 100 to be turned ON / OFF manually or by a sequencer or the like.

[0170] The oxidizer tank stores oxidizers such as nitrous oxide and liquid oxygen. Nitrous oxide can be self-pressurized, eliminating the need for a pressure pump. By controlling each valve with a control device, the oxidizer pressure can be controlled with the main valve, and the oxidizer can be precisely switched on and off with the throttling valve. The purge tank is a tank for storing gas used to discharge exhaust gases after combustion.

[0171] 9-2. Ignition Sequence in Combustion Experiment Next, the ignition sequence in the combustion experiment of the ignition device of the present invention will be explained using Figure 49. In Figure 49, the igniter (Arc Ignitor) refers to the entire combination of the power supply (Power Supply), booster (Booster), and ON / OFF SW in Figure 48, and means a device that controls the ON / OFF of discharge (ignition) by applying voltage to the ignition device.

[0172] In Figure 49(a), the main valve is left open from 0 seconds on the time axis. Also, the oxidizer throttling valve is opened by only one rotation between 0 and 10 seconds. This mode is called "Throttling Slow mode" because the throttling valve opens slowly, and is indicated by "*1" in Figure 49.

[0173] After that, it is opened nine times between 10 and 20 seconds. This mode is called "Throttling Fast mode" because it opens the throttle valve quickly, and is indicated by "*2" in Figure 49. For this reason, it is fully open from 20 seconds onwards. The igniter is only turned on between 0 and 10 seconds. While the voltage application is on, multiple discharges (ignitions) occur as appropriate.

[0174] Figure 49(b) also shows that the oxidizer throttle valve is opened one rotation between 0 and 10 seconds (Throttling Slow mode), then nine rotations between 10 and 20 seconds (Throttling Fast mode), and then fully open from 20 seconds onwards (this is the same as Figure 49(a)).

[0175] On the other hand, the igniter is only turned on for 0 to 5 seconds. In this way, if the solid fuel is already burning with a flame, the burning state can be maintained even if the igniter is turned off. If the igniter is turned on for a certain period of time, one discharge (ignition) occurs when the charge is sufficiently charged, and once the first discharge (ignition) is completed, the next charge begins, causing a second discharge (ignition). Thereafter, multiple discharges (ignitions) and charges are repeated while the igniter is turned on.

[0176] As described above, the ON / OFF of solid fuel combustion can be controlled by turning the throttle valve and / or igniter ON / OFF. Note that in the following explanation, the experimental results of the ignition device of the present invention will be shown as data obtained when ignition and combustion were performed according to the sequence shown in Figure 49(a).

[0177] 9-3. Combustion Experiment Data Next, the pressure data before and after the throttle valve when ignition and combustion were performed using the sequence in Figure 49(a) will be explained using Figure 50. Figure 50 shows an example of the results of a combustion experiment, and is a diagram showing the values ​​of the pressure sensor P (pressure sensor) before and after the throttle valve. Nitrous oxide (liquid) was used as the oxidizer.

[0178] "Throttling long slow" corresponds to a state in which the throttle valve is slowly opened one full rotation between 0 and 10 seconds, with an oxidizer pressure of approximately 2.8 MPa and a flow rate of approximately 24 g / s. "Throttling fast" corresponds to a state in which the throttle valve is quickly opened nine full rotations between 10 and 20 seconds, with an oxidizer pressure of approximately 4.5 MPa and a flow rate of approximately 40 g / s. "Full open" corresponds to a state in which the throttle valve is fully open, with the difference in pressure before and after the throttle valve indicating pressure loss due to the throttle valve.

[0179] 9-4. Changes in Chamber Pressure Next, the changes in chamber pressure will be explained using Figure 51. Figure 51 shows an example of changes in chamber pressure during a combustion experiment. Here, chamber 90 refers to the space immediately after passing through the oxidizer inlet of the hybrid rocket, as shown in Figure 48, and the chamber pressure can be measured using the value of pressure sensor P (pressure sensor) immediately after the throttling valve. Figure 51 shows that in throttle long slow (when the throttling valve is opened by only one rotation), the pressure in the chamber is in a negative pressure state.

[0180] Furthermore, in throttling fast (throttling valve opened 9 times), the pressure inside the chamber gradually increased and continued to increase until the main valve was closed, reaching approximately 0.15 MPa. According to Figure 51, in this experiment, the main valve was closed and nitrogen purging started when a flame was seen from the combustor nozzle, so the measurement ended while the pressure inside the chamber was still rising (Main Valve shutdown). When the pressure inside the chamber was measured until it was saturated, the pressure was approximately 0.3 MPa.

[0181] 9-5. Combustion Experiment Results Finally, the results of the combustion experiment of the present invention, showing how the second member 120 and the solid fuel 400 retreated, will be explained using Figure 52. Figure 52 shows an example of the results of the combustion experiment, showing the retreat of each part of the ignition device and hybrid rocket after multiple discharges (ignitions). Note that the third member 130 retreats in almost the same way as the second member 120, so it is not shown in the illustration.

[0182] Fig. 52(a) is a diagram showing the state of the second member before combustion. Fig. 52(b) is a diagram showing the state of retreat of the second member 120 and the solid fuel 400 after multiple ignitions. Fig. 52(c) is a diagram showing the state of retreat of the solid fuel after multiple ignitions. Fig. 52(d) is a diagram showing the state of retreat of the solid fuel after multiple ignitions, viewed from a slightly oblique direction.

[0183] 52(a) and 52(b) show that the second member 120 is uniformly recessed from the inside all around. Also, according to FIGS. 52(c) and 52(d), it can be seen that the solid fuel 400 or the combustion port 500 is uniformly recessed from the inside, similar to the second member 120.

[0184] 10. Summary As described above, the present invention provides an ignition device that significantly reduces power consumption compared to heating methods by adopting an ignition method that utilizes the discharge phenomenon caused by arc discharge. Furthermore, by using a structure that generates arc discharges successively around the entire periphery of the through-hole inside the ignition device, it is possible to evenly retract the ignition device itself from the inside and to evenly retract the solid fuel from the inside. Furthermore, stable output is possible even after multiple ignitions.

[0185] The ignition device of the present invention is suitable for hybrid rockets, but can also be used for other types of rockets. Furthermore, it can be used in a variety of applications, including those that require solid fuel to be burned multiple times, and is not limited to rockets.

[0186] 1 Hybrid rocket 20 Discharge point 90 Chamber 100 Ignition device 101 Wiring groove 110 First member 112 Through hole of first member 115 Peripheral portion of through hole of first member 116 Sloped portion of first member (optional) 117 Deformed portion of first member 119 Outside (outer periphery) of first member 120 Second member 122 Through hole of second member 125 Peripheral portion of through hole of second member 126 Protrusions (multiple) 129 Outside (outer periphery) of second member 130 Third member 132 Through hole of third member 133 Step portion 135 Peripheral portion of through hole of third member 139 Outside (outer periphery) of third member 140 Discharge area 200 Case 300 Heat insulating material 400 Solid fuel 500 Combustion port 600 Voltage application port 601 Voltage application cable 602 Voltage application plate 610 Voltage application port 611 Voltage application cable 612 Voltage application plate 700 Oxidizer port 710 Oxidizer 720 Initial flame (pilot flame) by ignition 731 Boundary layer combustion 732 Boundary layer combustion 800 Nozzle 810 Nozzle heat insulating material

Claims

1. An apparatus for igniting solid fuel, comprising: a first member made of a conductive material and having an internal through-hole; a second member made of a conductive material and having an internal through-hole; a third member provided between the first and second members, having an internal through-hole and made of an insulating material to insulate the first and second members; and the third member is shaped so that its outer thickness is greater than its inner thickness, and the internal insulation distance of the third member is smaller than its outer insulation distance, so that when a voltage is applied between the first and second members, a discharge phenomenon occurs between the first member and the periphery of the internal through-hole of the second member.

2. An ignition device as claimed in claim 1, wherein when a voltage is applied between the first member and the second member, a discharge phenomenon occurs between the first member and the periphery of the through hole inside the second member, and as a result of multiple discharges, the discharge phenomenon between the first member and the periphery of the through hole inside the second member occurs in a discharge area over the entire circumference of the periphery of the through hole, thereby causing the second member and third member and / or the first member to retreat evenly from the inside.

3. An ignition device according to claim 2, wherein the three-dimensional shape of the first member is a shape that increases in thickness from the inside to the outside.

4. An ignition device according to any one of claims 1 to 3, wherein the second member is plate-shaped, and the peripheral shape of the inner through-hole is any one of or a combination of a circle, a polygon, a star, and a fractal shape, and wherein when a voltage is applied between the first member and the second member, a discharge phenomenon occurs between the first member and the peripheral edge of the inner through-hole of the second member.

5. An ignition device according to any one of claims 1 to 3, wherein the shape of the second member is a lattice shape, a spider web shape, a honeycomb shape, a spiral shape, a combination of triangles, a combination of multiple small diameter holes, or any other shape in which multiple protrusions appear on the periphery of the inner through-hole, and wherein when a voltage is applied between the first member and the second member, a discharge phenomenon occurs between the first member and any of the multiple protrusions on the periphery of the inner through-hole of the second member.

6. An ignition device according to any one of claims 1 to 3, characterized in that the conductive material used for the second member includes at least one of conductive polymer, graphite, carbon fiber, metal powder, and metal fiber.

7. An ignition device according to any one of claims 1 to 3, wherein, when a conductive polymer is used as the conductive material used for the second member, the physical properties of the conductive polymer are such that, when formed by laminating layers using 3D printing, the volume resistivity is 30 to 115 Ω·cm.

8. An ignition device according to any one of claims 1 to 3, characterized in that, when a conductive polymer is used as the conductive material used for the second member, HDPE is used as the insulating material for the third member.

9. An ignition device as claimed in claim 4, wherein, when HDPE is used as the insulating material for the third member of the ignition device, when an oxidizer is sprayed toward the through-hole inside the ignition device and a voltage is applied between the first member and the second member to cause a discharge phenomenon that ignites and burns the oxidizer, at least the second member of the first member and second member made of the conductive material recedes together with the third member.

10. An ignition device as claimed in claim 5, wherein, when HDPE is used as the insulating material for the third member of the ignition device, when an oxidizer is sprayed toward the through-hole inside the ignition device and a voltage is applied between the first member and the second member to cause a discharge phenomenon that ignites and burns the oxidizer, at least the second member of the first member and second member made of the conductive material recedes together with the third member.

11. A hybrid rocket equipped with an oxidizer port for injecting oxidizer and solid fuel, characterized in that it is equipped with the ignition device according to any one of claims 1 to 3.

12. A hybrid rocket equipped with an oxidizer port for injecting oxidizer and solid fuel, comprising the ignition device according to any one of claims 1 to 3, wherein when a third member of the ignition device is made of the same material as the solid fuel, the hybrid rocket is characterized in that, when the oxidizer is injected from the oxidizer port toward the through-hole inside the ignition device, and a discharge phenomenon occurs when a voltage is applied between the first member and the second member to ignite the oxidizer and burn the solid fuel, at least the second member of the first and second members made of the conductive material retreats together with the third member, and the retreat speed is approximately the same as the retreat speed of the solid fuel.

13. A hybrid rocket equipped with an oxidizer port for injecting oxidizer and solid fuel, comprising the ignition device of claim 4, wherein when the third member of the ignition device is made of the same material as the solid fuel, when the oxidizer is injected from the oxidizer port toward the through-hole inside the ignition device and a voltage is applied between the first member and the second member to ignite the oxidizer by a discharge phenomenon and burn the solid fuel, at least the second member of the first member and second member made of the conductive material retreats together with the third member, and the retreat speed of the second member and third member is approximately the same as the retreat speed of the solid fuel.

14. A hybrid rocket equipped with an oxidizer port for injecting oxidizer and solid fuel, comprising the ignition device of claim 5, wherein when the third member of the ignition device is made of the same material as the solid fuel, the oxidizer is injected from the oxidizer port toward the through-hole inside the ignition device, and when a voltage is applied between the first member and the second member, the oxidizer is ignited by a discharge phenomenon and the solid fuel is burned, at least the second member of the first member and second member made of the conductive material retreats together with the third member, and the retreat speed of the second member and third member is approximately the same as the retreat speed of the solid fuel.

15. A hybrid rocket equipped with an oxidizer port for injecting oxidizer and solid fuel, comprising the ignition device of claim 6, wherein when the third member of the ignition device is made of the same material as the solid fuel, when the oxidizer is injected from the oxidizer port toward the through-hole inside the ignition device and a voltage is applied between the first member and the second member to ignite the oxidizer by a discharge phenomenon and burn the solid fuel, at least the second member of the first member and second member made of the conductive material retreats together with the third member, and the retreat speed of the second member and third member is approximately the same as the retreat speed of the solid fuel.

16. A hybrid rocket equipped with an oxidizer port for injecting oxidizer and solid fuel, comprising the ignition device of claim 7, wherein when the third member of the ignition device is made of the same material as the solid fuel, the oxidizer is injected from the oxidizer port toward the through-hole inside the ignition device, and when a voltage is applied between the first member and the second member, the oxidizer is ignited by a discharge phenomenon when the voltage is applied between the first member and the second member, and the solid fuel is burned, at least the second member of the first member and second member made of the conductive material retreats together with the third member, and the retreat speed of the second member and the third member is approximately the same as the retreat speed of the solid fuel.

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