Lightning resistance structure of rocket and rocket including the same

Abstract

To provide a lightning resistance structure of a rocket capable of effectively dissipating lightning current generated by lightning strike.SOLUTION: A lightning resistance structure of a rocket 1 includes: a first layer forming a rear trunk 7 of the rocket 1 and being a CFRP; a second layer 12 provided so as to cover an outer surface of the first layer and being a dielectric body; and an SDS 15 provided on an outer surface of the second layer 12. The plurality of SDSs 15 each have a linear shape extending in a longitudinal direction of the rear trunk 7 and are provided in a circumferential direction of the rear trunk part 7 at predetermined intervals.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a lightning-resistant structure for a rocket and a rocket equipped with the same. Here, a rocket refers to a flying body using a liquid or solid rocket engine as a propulsion device. [Background technology]

[0002] An aircraft may be struck by lightning. If the aircraft is made of metal, it is electrically conductive and therefore no special lightning-resistant structure is required. In contrast, if the aircraft is made of composite materials such as CFRP (Carbon Fiber Reinforced Plastics) or GFRP (Glass Fiber Reinforced Plastics), it does not have high electrical conductivity like metals and therefore requires a lightning-resistant structure. For example, in the case of an aircraft, it has been proposed to use a metal mesh or metal film (hereinafter referred to as "metal mesh, etc.") made of copper or aluminum on the outer surface of the aircraft to disperse lightning current or conduct it to metal members, etc. that are less susceptible to the current, thereby protecting the composite materials arranged under the metal mesh, etc. (e.g., Patent Documents 1 and 2).

[0003] Diverter strips are also used as lightning-resistant structures for aircraft. Diverter strips include ordinary metal rod types and segmented diverter strips (Patent Documents 3 and 4). However, diverter strips only function for structures made of electrical insulation. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2022-165281 A [Patent Document 2] JP 2009-227166 A [Patent Document 3] U.S. Pat. No. 4,506,311 [Patent Document 4] U.S. Pat. No. 4,796,153 [Non-patent literature]

[0005] [Non-Patent Document 1] Franklin A. Fisher and J. Anderson Plumer,DOT / FAA / TC-22 / 11,Published by Federal Aviation Administration,USDepartment of Transportation,Nov.2022,“Lightning Protection of Aircraft Handbook” Summary of the Invention [Problem to be solved by the invention]

[0006] However, rockets have a different airframe structure from aircraft, and lightning-resistant structures require different considerations than aircraft. For example, if CFRP, which is lighter and stronger than GFRP, is used as the main material of the airframe structure, even if a metal mesh or the like is used as a lightning-resistant structure because CFRP is conductive, the metal mesh or the like may be damaged by lightning, melted or evaporated by the lightning current, or become hot, causing damage to the CFRP due to the continued lightning current. In particular, when applied to rockets, damage to the heat-resistant paint may occur. In addition, as the rocket speed increases and the metal mesh or the like becomes hot due to aerodynamic heating, it is possible that at some point the adhesive strength of the adhesive layer will decrease or the metal mesh or the like will melt and peel off. If the material does not peel off properly, it may cause damage or melting on the outer surface of the airframe, or the peeled part may collide with the rear part of the airframe, causing unacceptable damage.

[0007] Furthermore, when using segmented diverter strips, even if they are attached to conductive CFRP, the electric field generated in the gaps of the diverter strips may be insufficient to generate plasma and to create a plasma channel for the lightning current to flow.

[0008] The present disclosure has been made in consideration of the above circumstances, and aims to provide a lightning-resistant structure for a rocket that can effectively dissipate lightning current generated by lightning strike, and a rocket equipped with the same. [Means for solving the problem]

[0009] A lightning-resistant structure for a rocket according to one embodiment of the present disclosure comprises a first layer which constitutes the body of the rocket and is made of CFRP, a second layer which is arranged to cover the outer surface of the first layer and is made of a dielectric, and a conductive layer which is arranged on the outer surface of the second layer and is made of a conductor, the conductive layer being linearly extended in the longitudinal direction of the body and provided in multiple numbers at predetermined intervals around the circumferential direction of the body.

[0010] A rocket according to one embodiment of the present disclosure is provided with the lightning-resistant structure of the rocket described above. Effect of the Invention

[0011] It can effectively conduct the lightning current generated by a lightning strike. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a side view showing a rocket according to a first embodiment of the present disclosure. [Diagram 2] FIG. 2 is an enlarged cross-sectional view of a portion of the rocket shown in FIG. 1. [Diagram 3] FIG. 11 is a side view showing a rocket according to a second embodiment of the present disclosure. [Figure 4] FIG. 11 is a side view showing a rocket according to a third embodiment of the present disclosure. [Diagram 5] FIG. 11 is a side view showing a rocket according to a fourth embodiment of the present disclosure. [Figure 6] FIG. 6 is a side view showing a modified example of FIG. 5. [Figure 7] FIG. 11 is a partially enlarged cross-sectional view of a rocket according to a fifth embodiment of the present disclosure. [Figure 8] FIG. 8 is a side view of the rocket of FIG. [Figure 9] FIG. 1 is a partially enlarged cross-sectional view showing the spacing of the SDS. [Figure 10] FIG. 8 is a partially enlarged cross-sectional view showing a modification of FIG. 7. [Figure 11] FIG. 13 is a side view showing a rocket according to the sixth embodiment of the present disclosure. [Figure 12] FIG. 12 is an enlarged cross-sectional view of a portion of the rocket of FIG. 11. [Figure 13] FIG. 13 is a partially enlarged cross-sectional view showing a modified example of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. [First embodiment] The first embodiment of the present disclosure will be described below. A rocket 1 equipped with a lightning-resistant structure according to this embodiment is shown in Figure 1. A body 2 of the rocket 1 is mainly made of CFRP (Carbon Fiber Reinforced Plastics).

[0014] The airframe 2 of the rocket 1 comprises, in order from the front, i.e., from the side of the traveling direction F, a tip section 3, a forward section (torso) 5, and a rear section 7. The tip section 3 has a tapered cone shape with a central axis CL. The forward section 5 has a cylindrical shape with a common central axis CL. The rear section 7 has a cylindrical shape with a common central axis CL. The dimension of the rear section 7 in the direction of the central axis CL, i.e., in the longitudinal direction, is larger than that of the forward section 5. A plurality of (e.g., four) tail fins 9 are attached to the rear end of the rear section 7. Although not shown, the forward section 5 and the rear section 7 are provided with a rocket engine (propulsion device), a release device, a communication device, a steering device, and an attitude control device.

[0015] The rear fuselage section 7 has a lightning-resistant structure. Specifically, as shown in Fig. 2, the rear fuselage section 7 has a first layer 11 made of CFRP and a second layer 12 provided so as to cover the outer surface of the first layer 11.

[0016] The first layer 11 is cylindrical and constitutes the main shape of the rear fuselage section 7. The CFRP constituting the first layer 11 provides a predetermined strength to the airframe.

[0017] The second layer 12 is formed so as to cover the entire circumference of the first layer 11 and has a cylindrical shape. The second layer 12 is made of a dielectric material, and for example, a resin-based coating (such as a heat-resistant coating) is used. Instead of coating, a porous and lightweight thermal insulator (such as cork) that contains a large amount of gas such as air can also be used. The thickness of the second layer 12 is, for example, about several mm, and is 2.5 mm or more, preferably 3 mm or more.

[0018] A segmented diverter strip (hereinafter referred to as "SDS") 15 is provided on the outer surface of the second layer 12. The SDS 15 has a structure in which a plurality of metal plates (metal pieces) 17 are fixed onto an insulating tape 16, which is an electrical insulator. The metal plate 17 is, for example, a gold-plated copper foil. The insulating tape 16 is, for example, a polyimide tape. The insulating tape 16 is fixed to the second layer 12 by an adhesive 18. For example, an adhesive having a heat resistance of about 260°C is selected as the adhesive 18.

[0019] The multiple metal plates (metal pieces) 17 of the SDS 15 are arranged linearly from the front end to the rear end in the traveling direction of the SDS 15 with a predetermined small interval (gap) between them. As shown in Fig. 1, the SDS 15 is provided linearly parallel to the longitudinal direction (direction of the central axis CL) of the rear section 7. A plurality of SDSs 15 are provided at predetermined intervals (spaces) in the circumferential direction of the rear section 7.

[0020] The lightning-resistant structure of the rocket 1 configured as above functions as follows. The principle of how a flying object is struck by lightning is described in detail in 3.4 Aircraft Lightning Strike Mechanisms of the above-mentioned Non-Patent Document 1, and the following description is based on that theory.

[0021] There are two possible lightning scenarios for the CFRP-based main structure of the rear fuselage 7 of the rocket 1: (1) the first return stroke and (2) the swept stroke.

[0022] In either case, when the rocket 1 enters between the thundercloud and the ground, between the thundercloud and the thundercloud, or inside the thundercloud and a strong electric field is generated around the rocket 1, a stepped leader is generated from the part where the electric field is concentrated at the tip or rear end of the rocket, and progresses along the direction of the electric field. At this time, the position of the leader discharge in the atmosphere hardly moves, so the position of the leader discharge generated near the tip 1a of the rocket 1 moves relatively to the rear of the rocket 1 due to the movement of the aircraft during the flight of the rocket 1. On the other hand, the leader discharge generated near the rear end of the rocket 1 continues to connect to the same part (hang on). When the leader discharge extending in the direction of the cloud joins with the leader discharge from the thundercloud (Junction), and the leader discharge extending in the opposite direction joins with the leader discharge from the opposite cloud or the ground surface, the circuit is connected and the first return lightning stroke LS occurs.

[0023] Meanwhile, simultaneously with this process, an electric field is generated on the insulating tape 16 in the minute gaps provided between the multiple metal plates 17 of the SDS 15, and at some point, a dielectric breakdown (creeping discharge) occurs. When dielectric breakdown occurs in all the gaps of the SDS 15, the SDS 15 becomes conductive. At this time, the conductive first layer 11 is separated from the SDS 15 by the second layer 12, so that the effect on the generation of the electric field intensity in the gaps between the metal plates 17 can be suppressed.

[0024] In the case of (1) above, when the precursor discharge reaches the rear fuselage 7, the first return lightning stroke directly causes a lightning stroke LS on the conductive SDS 15, or a creeping discharge occurs on the outer surface toward the precursor discharge from the conductive SDS 15 to the second layer 12 and couples with it, causing a lightning stroke LS, thereby forming a path for the lightning current LC on the SDS 15. Specifically, a sufficient voltage is generated between each metal plate 17 of the SDS 15, causing a dielectric breakdown not only in the gap but also on the metal plate 17, forming a plasma channel in the atmosphere around the SDS 15, through which the lightning current flows. The lightning current guided by the SDS 15 in this way is conducted to the rear side of the rocket 1 and discharged to the clouds or ground on the opposite side through the path of the precursor discharge on the opposite side.

[0025] In the case of (2) above, when the swept stroke reaches the aft fuselage section 7, a creeping discharge occurs from the lightning stroke LS caused by the sweep stroke toward the conductive SDS15, causing a lightning stroke LS as in the case of (1) above, forming a lightning current LC. Thereafter, the lightning current LC is discharged by a mechanism similar to that of (1) above. Note that in FIG. 1, the line of the lightning current LC is drawn with multiple curved parts on the top of the SDS15, but in reality it is considered to be conducted in a nearly straight path with a certain thickness on the top of the SDS15. This is also true in the following embodiments.

[0026] The effects of the present embodiment described above are as follows. The weight of the rocket 1 can be reduced by constructing the rear body 7 with the first layer 11 using CFRP. The CFRP of the first layer 11 is conductive, but a second layer 12 made of a dielectric material is provided to cover the outer surface of the first layer 11. The lightning current generated by lightning strike can be collected by providing SDS 15 on the outer surface of the second layer 12. The SDS 15 is linear and extends in the longitudinal direction of the rear body 7, and multiple SDS 15 are provided at predetermined intervals around the circumference of the rear body 7, so that the lightning current can be effectively collected and conducted. The use of SDS 15 allows lightning current to be conducted effectively. Since the second layer 12 made of a dielectric is provided between the first layer 11 made of CFRP, sufficient electric field strength is generated in the gap between the metal plates 17, causing dielectric breakdown, and effectively demonstrating the function of the SDS. By making the dielectric breakdown path generated in the atmosphere by SDS 15 the path for the large lightning current LC of the lightning stroke LS, the lightning stroke LS can be received without damaging the conductive layer of the first layer 11 or the dielectric of the second layer 12, and the lightning current LC can be conducted.

[0027] [Second embodiment] Next, a second embodiment of the present disclosure will be described. This embodiment is similar to the first embodiment except for the arrangement of the SDS 15. Therefore, the same reference numerals are used for the configurations common to the first embodiment, and the description thereof will be omitted.

[0028] As shown in Fig. 3, the SDS 15 is provided to have a spiral shape. Specifically, the SDS 15 is disposed at a predetermined oblique angle α with respect to the longitudinal axis L1 that is parallel to the longitudinal direction of the rear fuselage section 7. This oblique angle α is constant along the longitudinal direction of the rear fuselage section 7.

[0029] The effects of the present embodiment described above are as follows. The lightning strikes LS reach multiple locations on the rocket 1's body in the form of a swept stroke SS. Since the rocket 1 moves at high speed toward the location where the lightning strikes LS are generated, it is considered that the arrival location of the swept stroke SS is rearward of the direction in which the rocket 1 moves, that is, along the longitudinal direction of the body, and reaches multiple locations. Therefore, the SDS15 is arranged at a predetermined oblique angle α with respect to the longitudinal axis L1 parallel to the longitudinal direction of the rear fuselage 7. This allows the SDS15 to be arranged in a spiral shape, increasing the probability that the SDS15 will be located at the arrival location of the swept stroke SS. This makes it possible to widen the interval between adjacent SDS15.

[0030] [Third embodiment] Next, a third embodiment of the present disclosure will be described. This embodiment is similar to the second embodiment except for the arrangement of the SDS 15. Therefore, the same reference numerals are used for the configurations common to the first and second embodiments, and the description thereof will be omitted.

[0031] In the second embodiment, the oblique angle α of the SDS 15 is constant in the longitudinal direction of the rear torso section 7, but in this embodiment, the oblique angle is made to change in the longitudinal direction of the rear torso section 7. As shown in Fig. 4, the oblique angle α2 on the rear side (the right side in the figure) of the rear torso section 7 is made larger than the oblique angle α1 on the front side (α1<α2). In other words, the oblique angle is made to gradually increase toward the rear side of the rear torso section 7.

[0032] The effects of the present embodiment described above are as follows. When the rocket 1 rotates around the central axis CL, if the oblique angle of the SDS 15 coincides with the rotation angle of the rocket 1, the SDS 15 may not be located at the target position of the sweep torpedo strike SS. Therefore, by changing the oblique angle of the SDS 15 in the longitudinal direction, the probability that the SDS 15 will be located at the target position of the sweep torpedo strike SS can be increased. In the embodiment shown in FIG. 4, the oblique angle gradually increases toward the rear of the rear section 7, but the present invention is not limited to this. The oblique angle may gradually decrease, or may change discontinuously so that the SDS 15 forms a broken line.

[0033] [Fourth embodiment] Next, a fourth embodiment of the present disclosure will be described. This embodiment is different from the first embodiment in that a configuration has been added, but is otherwise similar. Therefore, the same reference numerals are used for the configurations common to the first embodiment, and the description thereof will be omitted.

[0034] As shown in Fig. 5, an attraction SDS (lightning attraction section) 20 is provided between the SDS 15 and the tip 1a of the rocket 1. The attraction SDS 20 attracts lightning to the SDS 15. The attraction SDS 20 is provided in the forward section 5 in correspondence with each SDS 15. The attraction SDS 20 may be provided up to the tip 3. In this case, the cross-sectional shape of the forward section 5 (and tip 3) is configured as shown in Fig. 2 as described in the first embodiment. The rear end of the attraction SDS 20 is connected to the front end of the SDS 15, and the front end of the attraction SDS 20 faces the tip 1a of the rocket 1.

[0035] The effects of the present embodiment described above are as follows. The stepped leader is likely to occur near the tip 1a of the rocket 1. The first return stroke and the swept stroke that follow the stepped leader are attracted by the attractor SDS 20. This allows the subsequent swept stroke SS to reach the rear SDS 15 with a high probability.

[0036] As shown in Fig. 6, a metal fin 22 may be provided as a lightning attraction part instead of the SDS 20 for attraction. In this case, the forward body section 5 and the tip section 3 may be made of metal. Also, a wing shape may be used instead of a fin shape.

[0037] [Fifth embodiment] Next, a fifth embodiment of the present disclosure will be described. This embodiment is different from the first embodiment in that the second layer has a different configuration, but is otherwise similar. Therefore, the same reference numerals are used for the configurations common to the first embodiment, and the description thereof will be omitted.

[0038] 7, the breakdown voltage of the second layer 12A of the present embodiment is higher than the breakdown voltage of the first layer 11. Specific examples of materials having a high breakdown voltage include Teflon (registered trademark), polyimide, meta-aramid fiber, and GFRP (Glass Fiber Reinforced Plastic).

[0039] The effects of the present embodiment described above are as follows. 8, even if lightning strikes the second layer 12A between the SDSs 15 instead of striking the SDSs 15, the breakdown voltage of the second layer 12A is high, so that the second layer 12A does not break down, and a creeping discharge occurs toward the SDSs 15, leading to the lightning current being conducted to the SDSs 15. At this time, no significant damage occurs to the portion of the second layer 12A where the creeping discharge occurs, or to the lightning current conducting portion of the SDSs 15.

[0040] As shown in Fig. 9, the circumferential interval S of the SDS 15 is determined based on the relationship between the dielectric breakdown voltage and the creeping discharge voltage of the second layer 12A, which is an electrical insulator. Specifically, it is determined so that the creeping discharge voltage is less than the dielectric breakdown voltage. In this case, the interval S is set so that the creeping discharge distance is 1 / 2.

[0041] As shown in FIG. 10, a second layer 12A having a high dielectric breakdown voltage of this embodiment may be provided below the second layer 12 described in the first embodiment.

[0042] [Sixth embodiment] Next, a sixth embodiment of the present disclosure will be described. This embodiment is different from the first embodiment in that SDS15 is not used and the second layer has a different configuration, but the rest is the same. Therefore, the same symbols are used for the configurations common to the first embodiment, and the description thereof will be omitted.

[0043] 11, the breakdown voltage of the second layer 12A of this embodiment is higher than the breakdown voltage of the first layer 11. Specific examples of materials with a high breakdown voltage include Teflon (registered trademark), polyimide, meta-aramid fiber, and GFRP (Glass Fiber Reinforced Plastic). Instead of the SDS 15 and the metal plate 17 of the first embodiment, a metal mesh 24 is provided on the insulating tape 16. Note that instead of the metal mesh, a metal film or a metal rod may be used.

[0044] The effects of the present embodiment described above are as follows. By using the metal mesh 24 as the conductive layer, a lightning-resistant structure can be easily constructed. In addition, by using these conductive layers, it is possible to reduce the penetration of the electromagnetic field into the rocket interior and reduce the lightning indirect effect on the internal electric circuits. 11, even if lightning strikes the second layer 12A between the metal meshes 24 instead of striking the metal meshes 24, the breakdown voltage of the second layer 12A is high, so that the second layer 12A does not break down, and a creeping discharge occurs toward the metal mesh 24, leading to the lightning current being conducted to the metal mesh 24. At this time, no significant damage is caused to the portion of the second layer 12A where the creeping discharge occurs.

[0045] As shown in Fig. 12, the circumferential interval S of the metal mesh 24 is determined based on the relationship between the dielectric breakdown voltage and the creeping discharge voltage of the second layer 12A, which is an electrical insulator. Specifically, it is determined so that the creeping discharge voltage is smaller than the dielectric breakdown voltage. At this time, the interval S is set so that the creeping discharge distance is 1 / 2.

[0046] As shown in FIG. 13, a second layer 12A having a high dielectric breakdown voltage of this embodiment may be provided below the second layer 12 described in the first embodiment.

[0047] The lightning-resistant structure of a rocket and a rocket equipped with the same described in each of the embodiments described above can be understood, for example, as follows.

[0048] The lightning-resistant structure of the rocket (1) according to the first aspect of the present disclosure comprises a first layer (11) constituting the body (7) of the rocket and made of CFRP, a second layer (12) which is a dielectric and is arranged to cover the outer surface of the first layer, and a conductive layer (15) which is a conductor and is arranged on the outer surface of the second layer, the conductive layer being linearly extended in the longitudinal direction of the body and provided at a predetermined interval in a circumferential direction of the body.

[0049] The rocket's body can be made lighter by using a first layer made of CFRP (Carbon Fiber Reinforced Plastics). The first layer of CFRP is conductive, but a second layer made of a dielectric is provided to cover the outer surface of the first layer. This allows the first layer to be electrically insulated and protected by the second layer. Furthermore, by providing a conductive layer on the outer surface of the second layer, the lightning current generated by lightning strike can be collected in the conductive layer. The conductive layer is linear and extends in the longitudinal direction of the body, and multiple conductive layers are provided at predetermined intervals around the circumference of the body, so that the lightning current can be effectively collected and conducted. Here, "linear" means that the conductive layers are arranged along an imaginary line, and includes not only a continuous line, but also multiple conductive layers (metal pieces) arranged linearly with tiny gaps between them, such as in a segmented diverter strip. Also, a rocket refers to a flying vehicle that uses a liquid or solid rocket engine as a propulsion device.

[0050] In the lightning-resistant structure of a rocket according to the second aspect of the present disclosure, in the first aspect, the conductive layer is a segmented diverter strip (15) in which metal pieces are arranged linearly at predetermined intervals.

[0051] By using a segmented diverter strip (SDS), a conductive layer in which metal pieces are arranged in a line at regular intervals, lightning current can be effectively conducted. Since the second layer, which is made of a dielectric, is placed between the first layer, which is made of CFRP, sufficient electric field strength is generated in the gap between each metal piece, causing dielectric breakdown, and the SDS function can be effectively demonstrated. When the SDS functions, the lightning current is conducted through the plasma path in the atmosphere and discharged from the precursor discharge path on the opposite side, so there is no damage to the first layer of CFRP or the second layer of dielectric. The second layer, which is made of a dielectric, can be made of, for example, a resin-based paint, or a porous, lightweight thermal insulator that contains a lot of gas such as air (such as cork).Furthermore, it can have two functions by using heat-resistant paint or materials that are necessary for aerodynamic heating in rockets. The thickness of the second layer made of a dielectric material is, for example, about several mm, and is 2.5 mm or more, and preferably 3 mm or more.

[0052] A lightning-resistant structure for a rocket according to a third aspect of the present disclosure is the same as that of the second aspect, wherein the segmented diverter strips are arranged at a predetermined oblique angle with respect to a longitudinal axis parallel to the longitudinal direction of the body.

[0053] The lightning strikes reach multiple locations on the rocket's body in the form of a swept stroke. Since the rocket travels at high speed relative to the sweep stroke, it is believed that the location of the sweep stroke will be along the direction of the rocket's travel, i.e., the longitudinal direction of the body. Therefore, the SDS is arranged at a specified oblique angle to the longitudinal axis parallel to the longitudinal direction of the body. This allows the SDS to be arranged in a spiral shape, increasing the probability that the SDS will be located at the location where the sweep stroke will reach. This allows the spacing between adjacent SDS to be increased.

[0054] A lightning-resistant structure for a rocket according to a fourth aspect of the present disclosure is the lightning-resistant structure for a rocket according to the third aspect, wherein the oblique angle changes in the longitudinal direction of the body.

[0055] The SDS's inclination angle is changed along the length of the fuselage. In other words, instead of making the SDS a spiral shape with a constant inclination angle, the SDS is made to have a spiral shape with a varying inclination angle along the length. For example, when a rocket rotates around its central axis, if the SDS's inclination angle and the rocket's rotation angle match, the SDS may not be positioned at the target of the sweep torpedo. Therefore, by changing the SDS's inclination angle along the length, the probability that the SDS will be positioned at the target of the sweep torpedo can be increased.

[0056] The lightning-resistant structure of a rocket according to a fifth aspect of the present disclosure is any one of the second to fourth aspects, and includes a lightning attraction section (20) provided between the segmented diverter strip and the tip of the rocket, which attracts lightning strikes to the segmented diverter strip.

[0057] A lightning attraction section was installed between the segmented diverter strip and the tip of the rocket, which can attract the first return stroke and the swept stroke that occur following the stepped leader, so that the subsequent swept stroke can be made to reach the rear SDS with a high probability. The lightning attractor may be a segmented diverter strip or a metallic fin or wing.

[0058] A lightning-resistant structure for a rocket according to a sixth aspect of the present disclosure is, in any one of the first to fifth aspects, such that the breakdown voltage of the second layer is higher than the breakdown voltage of the first layer.

[0059] Even if lightning strikes the second layer between the SDSs instead of the SDSs, the breakdown voltage of the second layer is higher than that of the first layer, so the second layer does not break down and a creeping discharge occurs toward the SDS, leading to the lightning current being conducted to the SDS. At this time, no significant damage occurs to the part of the second layer where the creeping discharge occurs, or to the lightning current conducting part of the SDS. Examples of materials with a high breakdown voltage include Teflon (registered trademark), polyimide, meta-aramid fiber, GFRP (Glass Fiber Reinforced Plastic), etc. The second layer may be made of a material with a high breakdown voltage, or a material with a high breakdown voltage may be used as a part of the second layer.

[0060] A seventh aspect of the present disclosure relates to a lightning-resistant structure for a rocket, wherein in the first aspect, the conductive layer is a metal mesh, a metal film, or a metal rod, and the breakdown voltage of the second layer is higher than the breakdown voltage of the first layer.

[0061] The conductive layer can be easily constructed by using a metal mesh, metal film, or metal rod. Also, using these conductive layers can reduce the penetration of the electromagnetic field into the rocket interior and reduce the lightning indirect effect on the internal electrical circuits. Even if lightning strikes the second layer between the conductive layers instead of the SDS, the breakdown voltage of the second layer is higher than that of the first layer, so the second layer does not break down and a creeping discharge occurs toward the conductive layer, leading to the lightning current being conducted to the conductive layer. At this time, no significant damage occurs to the part of the second layer where the creeping discharge occurs.

[0062] A rocket according to the first aspect of the present disclosure has the lightning-resistant structure of any one of the rockets according to the first to seventh aspects. [Explanation of symbols]

[0063] 1. Rocket 1a Tip 2. Aircraft 3 Tip 5 Front torso 7 Rear fuselage (fuselage) 9 tail fin 11 1st layer 12 2nd layer 15 SDS (conductive layer) 16 Electrical tape 17 Metal plate (metal piece) 18 Adhesive 20 SDS for attraction 22 Finn 24 Metal mesh (conductive layer)

Claims

1. A first layer that constitutes the rocket's body and is made of CFRP; a second layer that is provided so as to cover an outer surface of the first layer and is made of a dielectric material; a conductive layer provided on an outer surface of the second layer and made of a conductor; Equipped with A lightning-resistant structure for a rocket, wherein the conductive layer is linearly extending in the longitudinal direction of the body and is provided in a plurality of layers at predetermined intervals around the circumferential direction of the body.

2. 2. The lightning-resistant structure of a rocket according to claim 1, wherein the conductive layer is a segmented diverter strip in which metal pieces are arranged linearly at predetermined intervals.

3. 3. The lightning-resistant structure of a rocket according to claim 2, wherein the segmented diverter strips are arranged at a predetermined oblique angle with respect to a longitudinal axis parallel to the longitudinal direction of the body.

4. 4. A lightning-resistant structure for a rocket according to claim 3, wherein the inclination angle changes in the longitudinal direction of the body.

5. 4. A lightning-resistant structure for a rocket as described in claim 2 or 3, further comprising a lightning attraction portion provided between the segmented diverter strip and the tip of the rocket, which attracts lightning strikes to the segmented diverter strip.

6. 4. The lightning-resistant structure for a rocket according to claim 2 or 3, wherein the second layer has a higher dielectric breakdown voltage than the first layer.

7. The conductive layer is a metal mesh, a metal film, or a metal rod; 2. The lightning-resistant structure for a rocket according to claim 1, wherein the second layer has a higher dielectric breakdown voltage than the first layer.

8. A rocket equipped with the lightning-resistant structure of claim 1 or 7.

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