Lightning-resistant structure for rocket, and rocket provided with same

Abstract

Provided is a lightning-resistant structure for a rocket, the structure being capable of effectively dissipating a lightning current generated by a lightning strike. A lightning-resistant structure for a rocket (1) comprises a first layer that constitutes a rear body part (7) of the rocket (1) and that is made of CFRP, a second layer (12) that is provided so as to cover the outer surface of the first layer and is made of a dielectric, and SDSs (15) that are provided to the outer surface of the second layer (12). The SDSs (15) each have a linear shape extending in the longitudinal direction of the rear body part (7), and a plurality of SDSs (15) are provided at prescribed intervals in the circumferential direction of the rear body part (7).

Description

Lightning-resistant structure of rocket and rocket equipped with same

[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.

[0002] An aircraft may be struck by lightning. Metallic aircraft are electrically conductive and do not require special lightning protection structures. In contrast, composite materials such as CFRP (Carbon Fiber Reinforced Plastics) or GFRP (Glass Fiber Reinforced Plastics) do not have the high electrical conductivity of metals and therefore require lightning protection structures. For example, in the case of an aircraft, it has been proposed to use a metal mesh or film (hereinafter referred to as "metal mesh, etc.") made of copper, aluminum, or the like on the outer surface of the aircraft to disperse lightning current or conduct it to metal components that are less susceptible to the current, thereby protecting the composite materials arranged underneath the metal mesh, etc. (see, for example, Patent Documents 1 and 2).

[0003] Diverter strips are also used as lightning protection structures for aircraft. Diverter strips include ordinary metal rod types and segmented diverter strips (Patent Documents 3 and 4). However, diverter strips only function on structures made of electrical insulators.

[0004] Japanese Patent Application Publication No. 2022-165281 Japanese Patent Application Publication No. 2009-227166 U.S. Patent No. 4,506,311 U.S. Patent No. 4,796,153

[0005] Franklin A. Fisher and J. Anderson Plumer, DOT / FAA / TC-22 / 11, Published by Federal Aviation Administration, U. S. Department of Transportation, Nov. 2022, “Lightning Protection of Aircraft Handbook”

[0006] However, rockets have a different airframe structure than aircraft, and lightning protection structures require different considerations than aircraft. For example, if CFRP, which is lighter and stronger than GFRP, is used as the primary material for the airframe structure, even if a metal mesh or other material is used as a lightning protection structure, the conductive properties of CFRP mean that the metal mesh or other material may be damaged by lightning strikes, melt, vaporize, or become too hot due to the lightning current, potentially damaging the CFRP due to the continued lightning current. In particular, when applied to rockets, there is a risk of damage to heat-resistant coatings. Furthermore, as the rocket's speed increases and the metal mesh or other material heats up due to aerodynamic heating, at some point the adhesive strength of the adhesive layer may weaken, or the metal mesh or other material may melt and peel off. If this occurs, the adhesive may not peel properly, causing damage or melting to the exterior of the airframe, or the peeled portion may collide with the aft portion 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 between the gaps of the diverter strips may be insufficient, preventing plasma from being generated and the generation of a plasma channel through which lightning current can 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.

[0009] A lightning-resistant structure for a rocket according to one aspect of the present disclosure comprises a first layer that constitutes the body of the rocket and is made of CFRP, a second layer that is dielectric and that is provided so as to cover the outer surface of the first layer, and a conductive layer that is conductor and that is provided on the outer surface of the second layer, wherein the conductive layer is linear and extends in the longitudinal direction of the body, and a plurality of the conductive layers are provided at predetermined intervals around the circumference of the body.

[0010] A rocket according to one aspect of the present disclosure includes the lightning-resistant structure of the rocket described above.

[0011] It can effectively conduct the lightning current generated by a lightning strike.

[0012] FIG. 1 is a side view showing a rocket according to a first embodiment of the present disclosure. FIG. 2 is a partially enlarged cross-sectional view of the rocket of FIG. 1. FIG. 3 is a side view showing a rocket according to a second embodiment of the present disclosure. FIG. 4 is a side view showing a rocket according to a third embodiment of the present disclosure. FIG. 5 is a side view showing a modified example of FIG. 5. FIG. 6 is a partially enlarged cross-sectional view of the rocket according to a fifth embodiment of the present disclosure. FIG. 7 is a side view showing the rocket of FIG. 7. FIG. 8 is a partially enlarged cross-sectional view showing the spacing of the SDS. FIG. 9 is a partially enlarged cross-sectional view showing a modified example of FIG. 7. FIG. 10 is a side view showing a rocket according to a sixth embodiment of the present disclosure. FIG. 11 is a partially enlarged cross-sectional view of the rocket of FIG. 12. FIG. 13 is a partially enlarged cross-sectional view of a modified example of FIG. 12.

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

[0014] The rocket 1 has a body 2 that, from the front, i.e., from the direction of travel F, comprises a nose section 3, a forward section (torso) 5, and aft section 7. The nose section 3 has a tapered conical shape with a central axis CL. The forward section 5 has a cylindrical shape with a common central axis CL. The aft section 7 has a cylindrical shape with a common central axis CL. The aft section 7 has a larger dimension in the direction of the central axis CL, i.e., the longitudinal direction, than the forward section 5. A plurality of (e.g., four) tail fins 9 are attached to the aft end of the aft section 7. Although not shown, the forward section 5 and aft section 7 are equipped with rocket engines (propulsion devices), release devices, communication devices, steering devices, and attitude control devices.

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

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

[0017] The second layer 12 is cylindrical and formed to cover the entire circumference of the first layer 11. The second layer 12 is made of a dielectric material, and is coated with, for example, a resin-based coating (such as a heat-resistant coating). Instead of coating, a porous, 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, several millimeters, 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 insulating tape 16, which is an electrical insulator. The metal plates 17 are, for example, thin pieces of gold-plated copper. The insulating tape 16 is, for example, polyimide tape. The insulating tape 16 is fixed to the second layer 12 using an adhesive 18. The adhesive 18 is selected to have a heat resistance of, for example, about 260°C.

[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 gap between them. As shown in Fig. 1 , the SDS 15 is provided linearly parallel to the longitudinal direction (direction of the center 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 described 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 in the above-mentioned Non-Patent Document 1, and the following description is based on that theory.

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

[0022] In either case, when the rocket 1 enters between a thundercloud and the ground, between thunderclouds, or inside a thundercloud, a strong electric field is generated around the rocket 1. A stepped leader is generated from the area 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 remains almost constant, so the position of the leader discharge generated near the tip 1a of the rocket 1 moves relatively rearward due to the movement of the rocket 1 during flight. Meanwhile, the leader discharge generated near the rear end of the rocket 1 remains connected to the same location (hangs on). When the leader discharge extending toward the cloud junctions with the leader discharge from the thundercloud, and when the leader discharge extending in the opposite direction junctions with the leader discharge from the opposite cloud or the ground, the circuit is connected, resulting in the first return lightning strike LS.

[0023] Meanwhile, simultaneously with this process, an electric field is generated on the insulating tape 16 in the minute gaps between the multiple metal plates 17 of the SDS 15, causing dielectric breakdown (creeping discharge) at some point. When dielectric breakdown occurs in all 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 the effect of the electric field intensity generated 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 section 7, either the first return lightning stroke directly strikes the conductive SDS 15 (LS), or a creeping discharge occurs on the outer surface of the SDS 15 toward the precursor discharge, connecting with the second layer 12 and 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 the metal plates 17 of the SDS 15, causing breakdown not only in the gap but also on the metal plates 17, forming a plasma channel in the atmosphere surrounding the SDS 15 and allowing the lightning current to flow. In this way, the lightning current guided by the SDS 15 is conducted to the rear side of the rocket 1 and discharged to the clouds or ground on the opposite side via the precursor discharge path on the opposite side.

[0025] In the case of (2) above, when a swept lightning stroke reaches the aft fuselage section 7, a creeping discharge occurs from the swept lightning stroke LS toward the conductive SDS 15, causing a lightning stroke LS as in the case of (1) above, forming a lightning current LC. Further, the lightning current LC continues to be discharged using the same mechanism as in the case of (1) above. Note that in Figure 1, the line of the lightning current LC is drawn with multiple curves above the SDS 15, but in reality, it is considered to be conducted in a substantially straight path with a certain thickness above the SDS 15. This also applies to 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 section 7 of the rocket 1 using the first layer 11 made of CFRP. The CFRP of the first layer 11 is conductive, but the dielectric second layer 12 is provided to cover the outer surface of the first layer 11. Furthermore, the SDS 15 provided on the outer surface of the second layer 12 allows for the collection of lightning current generated by lightning strikes. The SDS 15 are linear and extend longitudinally of the rear section 7, and multiple SDSs 15 are provided at predetermined intervals circumferentially around the rear section 7, thereby effectively collecting and conducting lightning current. The use of the SDS 15 allows for effective conduction of lightning current. Because the dielectric second layer 12 is provided between the CFRP first layer 11 and the metal plates 17, sufficient electric field strength is generated in the gaps 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 SDS15 the path for the large lightning current LC of the lightning strike LS, the lightning strike LS can be received and the lightning current LC can be conducted without damaging the conductive layer of the first layer 11 or the dielectric of the second layer 12.

[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 components as those in the first embodiment are designated by the same reference numerals and will not be described again.

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

[0029] The effects of the present embodiment described above are as follows. The lightning strikes (LS) arrive at multiple locations on the rocket 1's body in the form of swept strokes (SS). Because the rocket 1 travels at high speed relative to the location where the lightning strikes (LS) are generated, the swept strokes (SS) are likely to arrive at multiple locations rearward of the rocket 1's direction of travel, i.e., along the longitudinal direction of the body. Therefore, the SDS 15 is arranged at a predetermined oblique angle α with respect to the longitudinal axis L1, which is parallel to the longitudinal direction of the rear section 7. This arrangement of the SDS 15 in a spiral shape increases the probability that the SDS 15 will be located at the location where the swept strokes (SS) will arrive. This allows for greater spacing between adjacent SDSs 15.

[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 components as the first and second embodiments are denoted by the same reference numerals and will not be described again.

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

[0032] The effects of the present embodiment described above are as follows. When the rocket 1 rotates around the central axis CL and moves forward, if the tilt angle of the SDS 15 coincides with the rotation angle of the rocket 1, the SDS 15 may not be positioned at the target position of the sweep lightning strike SS. Therefore, by changing the tilt angle of the SDS 15 in the longitudinal direction, the probability that the SDS 15 will be positioned at the target position of the sweep lightning strike SS can be increased. In the embodiment shown in Figure 4, the tilt angle gradually increases toward the rear of the aft section 7, but this is not limited to this. It may also be gradually decreased, or the SDS 15 may be discontinuously changed so that it forms a broken line.

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

[0034] As shown in Figure 5, an attraction SDS (lightning attraction unit) 20 is provided between the SDS 15 and the tip 1a of the rocket 1. The attraction SDS 20 attracts lightning strikes 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 also 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 Figure 2, as described in the first embodiment. The rear end of the attraction SDS 20 is connected to the forward 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 increases the probability that the subsequent swept stroke SS will reach the rear SDS 15.

[0036] As shown in Figure 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 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 differs 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 components common to the first embodiment, and descriptions thereof will be omitted.

[0038] 7, the breakdown voltage of the second layer 12A of this embodiment is higher than that 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).

[0039] The effects of the present embodiment described above are as follows: As shown in Figure 8, even if lightning strikes the second layer 12A between the SDSs 15 without striking the SDSs 15, the breakdown voltage of the second layer 12A is high, so the second layer 12A does not break down, and a creeping discharge occurs toward the SDSs 15, conducting the lightning current to the SDSs 15. In this case, 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 spacing S of the SDS 15 is determined based on the relationship between the breakdown voltage and the creeping discharge voltage of the second layer 12A, which is an electrical insulator. Specifically, the spacing S is determined so that the creeping discharge voltage is less than the breakdown voltage. In this case, the spacing 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 breakdown voltage according to 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 differs from the first embodiment in that the SDS 15 is not used and the second layer has a different configuration, but is otherwise similar. Therefore, the same reference numerals are used for components common to the first embodiment, and their description will be omitted.

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

[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. Furthermore, using these conductive layers reduces the penetration of electromagnetic fields into the rocket's interior and reduces lightning noise (lightning indirect effect) on the internal electrical circuits. As shown in FIG. 11 , even if lightning strikes the second layer 12A between the metal meshes 24 rather than the metal meshes 24, the high breakdown voltage of the second layer 12A prevents the second layer 12A from breaking down, resulting in a creeping discharge toward the metal mesh 24 and conducting the lightning current to the metal mesh 24. In this case, no significant damage occurs to the portion of the second layer 12A where the creeping discharge occurs.

[0045] As shown in Fig. 12, the circumferential spacing S of the metal mesh 24 is determined based on the relationship between the breakdown voltage and the creeping discharge voltage of the second layer 12A, which is an electrical insulator. Specifically, the spacing S is determined so that the creeping discharge voltage is less than the breakdown voltage. In this case, the spacing 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 breakdown voltage according to this embodiment may be provided below the second layer 12 described in the first embodiment.

[0047] The lightning-resistant structures for rockets and rockets equipped with the same described in each of the embodiments 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) that constitutes the body (7) of the rocket and is made of CFRP, a second layer (12) that is provided so as to cover the outer surface of the first layer and is made of a dielectric, and a conductive layer (15) that is provided on the outer surface of the second layer and is made of a conductor, the conductive layer being linear and extending in the longitudinal direction of the body, and a plurality of the conductive layers are provided at predetermined intervals around the circumferential direction of the body.

[0049] The rocket's barrel is constructed with a first layer made of CFRP (Carbon Fiber Reinforced Plastics), achieving weight reduction. The first layer of CFRP is electrically conductive, but a second layer made of a dielectric is provided to cover the outer surface of the first layer. This provides electrical insulation and protection for the first layer. Furthermore, providing a conductive layer on the outer surface of the second layer allows lightning current generated by lightning strikes to be collected by the conductive layer. The conductive layers are linear and extend longitudinally along the barrel, with multiple layers spaced circumferentially at predetermined intervals. This effectively collects and conducts lightning current. Note that "linear" refers to the conductive layers arranged along an imaginary line, and includes not only a continuous linear structure but also multiple conductive layers (metal pieces) arranged linearly with small gaps between them, such as segmented diverter strips. Furthermore, a rocket refers to a flying vehicle propelled by a liquid or solid rocket engine.

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

[0051] The use of a segmented diverter strip (SDS), a conductive layer consisting of metal pieces arranged linearly at predetermined intervals, effectively conducts lightning current. The dielectric second layer is located between the CFRP first layer, generating sufficient electric field strength in the gap between the metal pieces, causing dielectric breakdown and enabling the SDS to function effectively. When the SDS functions, lightning current conducts through the atmospheric plasma path and is discharged through the pre-discharge path on the opposite side, preventing damage to the CFRP first layer and the dielectric second layer. The dielectric second layer can be, for example, a resin-based paint or a porous, lightweight thermal insulator (e.g., cork) that contains a large amount of gas, such as air. Furthermore, it can also serve two purposes by using heat-resistant paint or materials, which are required for aerodynamic heating in rockets. The thickness of the dielectric second layer is, for example, several millimeters, at least 2.5 mm, and preferably at least 3 mm.

[0052] A lightning-resistant structure for a rocket according to a third aspect of the present disclosure is 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] Lightning strikes reach multiple locations on the rocket's body in the form of swept strokes. Because the rocket travels at high speed relative to the sweep strokes, the strikes are expected to reach locations along the rocket's direction of travel, i.e., the longitudinal direction of the body. Therefore, the SDSs are arranged at a predetermined oblique angle to the longitudinal axis of the body, which is parallel to the longitudinal direction of the body. This arrangement allows the SDSs to be arranged in a spiral shape, increasing the probability that the SDSs will be located at the strike locations of the sweep strokes. This also allows for a wider spacing between adjacent SDSs.

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

[0055] The SDS's oblique angle is varied along the length of the fuselage. This means that the SDS is not spirally shaped with a constant oblique angle, but rather has a spiral shape with varying oblique angles along the length. For example, when a rocket rotates around its central axis, if the SDS's oblique angle and the rocket's rotation angle coincide, the SDS may not be positioned where the sweep strike will land. Therefore, by varying the SDS's oblique angle along the length, the probability that the SDS will land where the sweep strike will land 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 attracting 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 element is installed between the segmented diverter strip and the rocket's nose. This attracts the first return stroke and swept stroke that follow the stepped leader, increasing the probability that the subsequent swept stroke will reach the SDS at the rear. The lightning attraction element may be a segmented diverter strip, or a metal fin or wing.

[0058] The lightning-resistant structure of 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 without striking 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, conducting the lightning current to the SDS. In this case, no significant damage occurs to the creeping discharge portion of the second layer or the lightning current-conducting portion of the SDS. Materials with a high breakdown voltage include Teflon (registered trademark), polyimide, meta-aramid fiber, and GFRP (glass fiber reinforced plastic). 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 part of the second layer.

[0060] The lightning-resistant structure for a rocket according to a seventh aspect of the present disclosure is such that, 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. Furthermore, using these conductive layers can reduce the penetration of electromagnetic fields into the rocket's interior and reduce lightning noise (lightning indirect effect) on the internal electrical circuits. Even if lightning strikes the second layer between the conductive layers without striking 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, conducting the lightning current to the conductive layer. In this case, no significant damage occurs to the portion of the second layer where the creeping discharge occurs.

[0062] The rocket according to the first aspect of the present disclosure is equipped with the lightning-resistant structure of any one of the rockets according to the first to seventh aspects.

[0063] 1 Rocket 1a Tip 2 Airframe 3 Tip 5 Forward body 7 Rear body (body) 9 Tail 11 First layer 12 Second layer 15 SDS (conductive layer) 16 Insulating tape 17 Metal plate (metal piece) 18 Adhesive 20 Guidance SDS 22 Fin 24 Metal mesh (conductive layer)

Claims

1. A lightning-resistant structure for a rocket comprising: a first layer which constitutes the body of the rocket and is made of CFRP; a second layer which is dielectric and covers the outer surface of the first layer; and a conductive layer which is an electrical conductor and is provided on the outer surface of the second layer, wherein the conductive layer is linear and extends in the longitudinal direction of the body, and a plurality of conductive layers are provided at predetermined intervals around the circumference of the body.

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

3. A lightning-resistant structure for a rocket as described in claim 2, wherein the segmented diverter strips are arranged at a predetermined oblique angle to a longitudinal axis parallel to the longitudinal direction of the body.

4. A lightning-resistant structure for a rocket as described in claim 3, in which the oblique angle changes in the longitudinal direction of the body.

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

6. A lightning-resistant structure for a rocket as described in claim 2 or 3, wherein the dielectric breakdown voltage of the second layer is higher than the dielectric breakdown voltage of the first layer.

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

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

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