Revolved body thermal protection structure of reinforced fabric with partition design

Abstract

A revolving body thermal protection structure of a partition design reinforced fabric comprises a thermal protection layer which is coaxially arranged on the outer wall of an aircraft in a sleeving mode, the inner contour of the thermal protection layer is matched with the contour of the outer wall of the aircraft, and the thermal protection layer is formed by splicing a windward side protection area arranged on the windward side of the aircraft and a leeward side protection area arranged on the leeward side of the aircraft. The windward side protection area sequentially comprises a plurality of first fiber felt layers and a first high-density fabric layer from inside to outside, the leeward side protection area sequentially comprises a plurality of second fiber felt layers and a second high-density fabric layer from inside to outside, and the first fiber felt layers and the first high-density fabric layers are sewn and fixed through normal fibers. The second fiber felt layers and the second high-density fabric layers are sewn and fixed through normal fibers, and the normal fiber sewing density of the windward side protection area is larger than that of the leeward side protection area. The manufacturing speed is increased, the weight of the structure is reduced, and the performance requirements of different strengths, temperature resistance, heat insulation and the like of the windward side and the leeward side are met.

Description

Technical Field

[0001] The utility model relates to the field of thermal protection for aviation and aerospace, in particular to a thermal protection structure of a rotating body with a partitioned design and reinforced fabric. Background Art

[0002] Spacecraft, especially hypersonic vehicles, generate a lot of aerodynamic heat due to air friction, which causes their outer surface to reach very high temperatures. Commonly used load-bearing structures such as aluminum alloys and titanium alloys cannot meet the temperature resistance requirements, so it is necessary to add a layer of thermal protection structure on its outer surface. Usually, the requirements for thermal protection structural materials are light weight, low thermal conductivity, high temperature resistance, burn resistance and high structural strength. Fiber-reinforced composite materials are the main material solution for thermal protection structures. For example, fiber-reinforced phenolic resin aerogel composite materials currently have the conditions for large-scale integral forming and application.

[0003] In actual applications, the temperature differences that different parts of the outer surface of an aircraft need to withstand are quite large, so the performance requirements for surface thermal protection materials are also very different. For example, the lower surface (windward side) and upper surface (leeward side) of an aircraft have very different scouring friction and surface temperatures due to different aerodynamic pressures during use, which places different requirements on the temperature resistance and pressure resistance of thermal protection materials. Under certain hypersonic conditions, the windward surface usually reaches a temperature of more than 800 to 1000°C, while the leeward side may only have a temperature of about 400 to 600°C.

[0004] When designing and manufacturing the overall thermal protection material structure of existing aircraft, the materials in all positions are selected and manufactured according to the highest design requirements for reinforcing fiber fabrics and matrices. This increases the overall cost of the aircraft on the one hand, and on the other hand, there are certain contradictions in the mechanical, temperature resistance (burning resistance), thermal insulation and overall density performance of the materials. For example, the increase of reinforcing fibers can usually improve the structural strength and burning resistance, but at the same time it will increase the density and thermal conductivity. Therefore, in large-area thermal protection structures, how to design and optimize the components of each structural material to meet the requirements of different use environments (windward and leeward) is the key to the overall design of the thermal protection structure. Utility Model Content

[0005] The utility model solves the shortcomings of the prior art and provides a rotor-shaped thermal protection structure of reinforced fabric with a partitioned design for enhancing different thermal environment states of the windward side and the leeward side of a rotor-shaped thermal protection material component.

[0006] To achieve the above-mentioned purpose, the utility model first proposes a rotating body thermal protection structure of a partitioned design reinforced fabric, including a thermal protection layer coaxially sleeved on the outer wall of an aircraft, and the inner contour of which matches the contour of the outer wall of the aircraft, the thermal protection layer is a fiber-reinforced phenolic resin aerogel composite material layer, and the thermal protection layer is spliced ​​by a windward surface protection zone arranged on the windward surface of the aircraft and a leeward surface protection zone arranged on the leeward surface of the aircraft, the windward surface protection zone includes multiple layers of first fiber felt layers and first high-density fabric layers from the inside to the outside, the leeward surface protection zone includes multiple layers of second fiber felt layers and second high-density fabric layers from the inside to the outside, the multiple layers of first fiber felt layers and first high-density fabric layers in the windward surface protection zone are fixed by normal fiber stitching, the multiple layers of second fiber felt layers and second high-density fabric layers in the leeward surface protection zone are also fixed by normal fiber stitching, and the normal fiber stitching density of the windward surface protection zone is greater than the normal fiber stitching density of the leeward surface protection zone.

[0007] By adopting the above structure, the thermal protection layer of the device is spliced ​​by the windward protection area and the leeward protection area to form an integral protection structure. The windward protection area and the leeward protection area are distinguished by the different normal fiber stitching densities according to the temperature difference that the windward side and the leeward side need to withstand. The normal fiber stitching density of the windward protection area is greater than the normal fiber stitching density of the leeward protection area. By increasing the density of the normal fiber stitching, the interlayer bonding strength between the multi-layer fiber felt layers in the anti-burning enhanced area and between the fiber felt layer and the high-density fabric layer is improved, thereby effectively reducing the risk of material delamination under high aerodynamic pressure and ablation conditions; the thermal protection layer of the present application is a fiber-reinforced phenolic resin aerogel composite material layer, and the fiber-reinforced phenolic resin aerogel composite material layer is formed by stitching the bottom multi-layer fiber felt layer and the surface high-density fabric layer through normal fibers, and then performing a phenolic resin aerogel injection composite process as a whole; the rotating body thermal protection structure formed after the injection composite can be directly installed on the aircraft for use. On the one hand, it will not damage the aerodynamic shape of the entire cabin of the aircraft over a large area, and on the other hand, it can meet the performance requirements of different temperature zones on the windward and leeward sides.

[0008] In the present embodiment, the splicing seams between the windward surface protection area and the leeward surface protection area are symmetrically arranged at the waist of the aircraft on both sides, the multiple layers of first fiber felt layers on the connecting sides at both ends of the windward surface protection area are staggered to form a first concave-convex connection structure, and the multiple layers of second fiber felt layers on the connecting sides at both ends of the leeward surface protection area are staggered to form a second concave-convex connection structure matching the first concave-convex connection structure, the windward surface protection area and the leeward surface protection area are connected to each other by the first and second concave-convex connection structures to form a splicing area, the splicing area, the first fiber felt layer and the second fiber felt layer on the same layer are connected and fixed by sewing fibers to each other, and the multiple layers of fiber felt layers and the high-density fabric layer in the splicing area are fixed by sewing normal fibers.

[0009] By adopting the above structure, the joint seams between the windward side protection zone and the leeward side protection zone are arranged at the waists on both sides of the aircraft where the ablation environment is the mildest, thereby minimizing the risk of damage and failure of the joint seams to the overall structure. In addition, the device utilizes the staggered arrangement of multiple layers of fiber felt layers on both sides to form the first and second concave-convex connection structures, so that no additional connection structure is required, and the first and second concave-convex connection structures formed constitute mortise and tenon connections, which improves the strength of the windward side protection zone and the leeward side protection zone after being connected, and the first fiber felt layer and the second fiber felt layer on the same layer are connected and fixed by sewing fibers to each other, thereby ensuring the stability of the connection between the windward side protection zone and the leeward side protection zone.

[0010] In this embodiment, the windward side protection area and the leeward side protection area each occupy 1 / 2 of the total area of ​​the heat protection layer.

[0011] In this embodiment, the first fiber felt layer is a glass fiber needle felt layer or a quartz fiber needle felt layer, and the density of the first fiber felt layer is 0.1-0.3 g / cm 3 The thickness of the single-layer first fiber felt layer is 2 to 10 mm; the first fiber felt layer is preferably a quartz fiber needle-punched felt layer, which has better heat resistance; the thickness of the single-layer first fiber felt layer is further preferably 3 to 5 mm, and the density is further preferably 0.15 to 0.2 g / cm 3 .

[0012] In this embodiment, the first high-density fabric layer is a 2.5D high-silica fiber fabric layer or a 2.5D quartz fiber fabric layer, the thickness of the first high-density fabric layer is 1-3 mm, and the fiber volume fraction of the first high-density fabric layer is 35%-48%; the first high-density fabric layer is further preferably a 2.5D quartz fiber fabric layer, and the 2.5D quartz fiber fabric layer has better structural strength and anti-burning performance; the thickness of the first high-density fabric layer is further preferably 1-2 mm, and the fiber volume fraction is further preferably 40-45%;

[0013] In this embodiment, the normal stitching fibers of the heat protection layer in the windward protection zone are made of quartz fiber yarn, the linear density of the normal stitching fibers is 100-300 TEX, and the puncture density of the normal fiber yarn is 3×3 mm-15×15 mm; the linear density of the normal stitching fibers is further preferably 150-200 TEX, and the puncture density of the normal fiber yarn is further preferably 5×5 mm-10×10 mm;

[0014] In this embodiment, the second fiber felt layer is a glass fiber needle felt layer or a quartz fiber needle felt layer, and the density of the second fiber felt layer is 0.08-0.15 g / cm 3 The thickness of the single-layer second fiber felt layer is 2 to 10 mm; the density of the second fiber felt layer is further preferably 0.08 to 0.12 g / cm3 The thickness of the single-layer second fiber felt layer is further preferably 3 to 5 mm. Since the thermal state on the leeward side is relatively mild, the second fiber felt layer with low density is selected to effectively reduce the overall density and improve the thermal insulation performance;

[0015] In this embodiment, the second high-density fabric layer is a two-dimensional quartz fiber fabric layer or a high-silica fiber fabric layer, the thickness of the second high-density fabric layer is 0.5-1 mm, and the fiber volume fraction of the second high-density fabric layer is 35%-45%; the thickness of the second high-density fabric layer is further preferably 0.5 mm, and the fiber volume fraction is further preferably 38-42%; the second high-density fabric layer in this thickness state can meet the requirements of the leeward side for mechanical and burning resistance and other properties, and minimize the amount (thickness) of high-density fabric;

[0016] In this embodiment, the normal stitching fibers of the heat protection layer in the leeward protection zone are made of quartz fiber yarn, the linear density of the normal stitching fibers is 50-200 TEX, and the puncture density of the normal fiber yarn is 5×5 mm-20×20 mm; the linear density of the normal stitching fibers is further preferably 50-100 TEX, and the puncture density of the normal fiber yarn is further preferably 10×10 mm-15×15 mm;

[0017] By adopting the above method, the fiber felt layer and high-density fabric layer constituting the windward side protection area and the leeward side protection area adopt different densities, thicknesses and fiber fabric states as needed, thereby ensuring that the windward side has good temperature resistance, excellent resistance to aerodynamic pressure and ablation performance, and the leeward side has low density and good overall thermal insulation performance.

[0018] To sum up, the thermal protection layer of the device is spliced ​​by the windward protection area and the leeward protection area to form an integral protection structure. The windward protection area and the leeward protection area are differentiated by the different normal fiber stitching densities according to the temperature difference that the windward side and the leeward side need to withstand. The normal fiber stitching density of the windward protection area is greater than that of the leeward protection area. By increasing the density of the normal fiber stitching, the interlayer bonding strength between the multi-layer fiber felt layers in the anti-burning enhanced area and between the fiber felt layer and the high-density fabric layer is improved, thereby effectively reducing the risk of material stratification under high aerodynamic pressure and ablation conditions; the device does not need to separately produce corresponding thermal protection materials for different temperature zones. The zoning design of the windward protection area and the leeward protection area of ​​the device shortens the production cycle of the thermal protection structure of the rotating body, and better realizes the optimization design of the high temperature resistance, low thermal conductivity, low density and other performances of the rotating body structure of the whole cabin in different temperature zones, which can be promoted and applied in the field of large-area thermal protection of aerospace vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The utility model is a schematic diagram of the partitioning of the reinforced fabric designed according to the windward side and the leeward side.

[0020] Figure 2 This is a schematic diagram of the staggered splicing of the layers of fabric at the two waist joints.

[0021] In the attached drawings, 1, windward side protection area; 2, leeward side protection area; 3, joint seam; 4, second fiber felt layer; 5, second high-density fabric layer; 6, first fiber felt layer; 7, first high-density fabric layer. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0023] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0024] A rotator heat protection structure with a partitioned design and reinforced fabric, comprising a heat protection layer coaxially sleeved on the outer wall of an aircraft, the heat protection layer being a hollow rotator with an inner cavity contour matching the outer contour of the aircraft, the heat protection layer being a fiber-reinforced phenolic resin aerogel composite material layer, the heat protection layer being spliced ​​by a windward surface protection zone 1 arranged on the windward surface of the aircraft and a leeward surface protection zone 2 arranged on the leeward surface of the aircraft, the windward surface protection zone 1 and the leeward surface protection zone 2 respectively occupying 1 / 2 of the total area of ​​the heat protection layer, the windward surface protection zone 1 from From inside to outside, it includes multiple layers of first fiber felt layer 6 and first high-density fabric layer 7 in sequence. The leeward side protection area 2 includes multiple layers of second fiber felt layer 4 and second high-density fabric layer 5 in sequence from inside to outside. The multiple layers of first fiber felt layer 6 and first high-density fabric layer 7 of the windward side protection area 1 are fixed by normal fiber stitching. The multiple layers of second fiber felt layer 4 and second high-density fabric layer 5 of the leeward side protection area 2 are also fixed by normal fiber stitching. The normal fiber stitching density of the windward side protection area 1 is greater than the normal fiber stitching density of the leeward side protection area 2.

[0025] The splicing seams 3 between the windward surface protection area 1 and the leeward surface protection area 2 are symmetrically arranged at the waist of both sides of the aircraft. The multiple layers of first fiber felt layers 6 on the connecting sides at both ends of the windward surface protection area 1 are staggered to form a first concave-convex connection structure. The multiple layers of second fiber felt layers 4 on the connecting sides at both ends of the leeward surface protection area 2 are staggered to form a second concave-convex connection structure matching the first concave-convex connection structure. The windward surface protection area 1 and the leeward surface protection area 2 are connected to each other through the first and second concave-convex connection structures to form a splicing area. The splicing area, the first fiber felt layer 6 and the second fiber felt layer 4 on the same layer are connected and fixed by sewing fibers to each other. The multiple layers of fiber felt layers and the high-density fabric layer in the splicing area are fixed by sewing normal fibers.

[0026] Specifically: the first fiber felt layer 6 is a glass fiber needle felt layer or a quartz fiber needle felt layer, the density of the first fiber felt layer 6 is 0.1-0.3g / cm3, the thickness of the single-layer first fiber felt layer 6 is 2-10mm, the first high-density fabric layer 7 is a 2.5D high-silica fiber fabric layer or a 2.5D quartz fiber fabric layer, the thickness of the first high-density fabric layer 7 is 1-3mm, the fiber volume fraction of the first high-density fabric layer 7 is 35%-48%, and the normal stitching fibers of the thermal protection layer in the windward protection area 1 are made of quartz fiber yarn, the linear density of the normal stitching fibers is 100-300TEX, and the normal fiber puncture density is 3×3mm-15×15mm.

[0027] The second fiber felt layer 4 is a glass fiber needle felt layer or a quartz fiber needle felt layer, the density of the second fiber felt layer 4 is 0.08-0.15 g / cm3, and the thickness of a single layer of the second fiber felt layer 4 is 2-10 mm. The second high-density fabric layer 5 is a two-dimensional quartz fiber cloth layer or a high-silicon fiber cloth layer, the thickness of the second high-density fabric layer 5 is 0.5-1 mm, and the fiber volume fraction of the second high-density fabric layer 5 is 35%-45%. The normal stitching fibers of the heat protection layer in the leeward protection area 2 are made of quartz fiber yarn, the linear density of the normal stitching fibers is 50-200 TEX, and the normal fiber puncture density is 5×5 mm-20×20 mm.

[0028] Example:

[0029] Next, take the preparation of a hollow cylindrical partition design reinforced fabric rotating body thermal protection structure with an inner diameter of 500mm, a thickness of 17mm, and a length of 800mm as an example.

[0030] like Figure 1 , 2As shown, the device uses the two waists of the aircraft as the joint seams to separate the thermal protection layer into a leeward protection area in the upper half and a windward protection area in the lower half, and uses a weaving mold with an outer diameter of 500mm and a length of 850mm to lay, sew, and puncture different fiber felt bodies and surface fabrics (the weaving mold leaves a processing allowance in the length direction).

[0031] 1) Cut the first fiber felt layer and the first high-density fabric layer for the windward side: the first fiber felt layer is made of quartz fiber needle felt layer with a density of 0.18g / cm 3 , the length is 850mm (the length of the first fiber felt layer is cut according to the length of the weaving mold); the first fiber felt layer is arranged in four layers, and the thicknesses of the four first fiber felt layers from the inside to the outside are 4mm, 4mm, 4mm and 3mm respectively; the lengths of the four first fiber felt layers along the circumferential direction of the weaving mold from the inside to the outside are 791mm, 804mm, 816mm and 827mm respectively; the first high-density fabric layer adopts a 2.5D quartz fiber fabric layer with a fiber volume fraction of 42%, the thickness of the first high-density fabric layer is 2mm, the length of the first high-density fabric layer is the same as that of the first fiber felt layer, and the length of the first high-density fabric layer along the circumferential direction of the weaving mold is 835mm;

[0032] 2) Cut the second fiber felt layer and the second high-density fabric layer for the leeward side: The second fiber felt layer is a glass fiber needle-punched felt layer with a density of 0.08g / cm 3 , the length is 850mm (the length of the first fiber felt layer is cut according to the length of the weaving mold); the second fiber felt layer is arranged in four layers, and the thickness of the four second fiber felt layers is 4mm; the lengths of the four second fiber felt layers along the circumferential direction of the weaving mold from the inside to the outside are 791mm, 804mm, 816mm and 829mm respectively; the second high-density fabric layer adopts a quartz fiber plain weave layer with a fiber volume fraction of 40%, the thickness of the second high-density fabric layer is 1mm, the length is 850mm, and the length of the second high-density fabric layer along the circumferential direction of the weaving mold is 837mm;

[0033] 3) Laying the fiber felt body and the surface high-density fabric: Lay the first fiber felt layer and the second fiber felt layer on the weaving mold layer by layer, and sew the first fiber felt layer and the second fiber felt layer together after each layer is laid (quartz fiber yarn is used for sewing here), and the splicing seams of the first fiber felt layer and the second fiber felt layer of adjacent layers are staggered; after the fiber felt layer is laid, the first high-density fabric layer and the second high-density fabric layer are laid, and the splicing seams of the first high-density fabric layer and the second high-density fabric layer are placed at the middle waistline on both sides of the aircraft;

[0034] 4) The first fiber felt layer and the first high-density fabric layer of the windward protection area are sewn by normal fibers. The normal fibers are made of quartz fiber yarn. The linear density of the quartz fiber yarn is 150TEX and the puncture density is 5mm×5mm.

[0035] 5) The second fiber felt layer and the second high-density fabric layer in the leeward protection area are sewn together by normal fibers. The normal fibers are made of quartz fiber yarn. The linear density of the quartz fiber yarn is 100TEX and the puncture density is 10mm×10mm.

[0036] 6) placing the whole structure completed by normal stitching in a mold, and compounding it by a glue injection compounding process (the glue injection compounding process in this embodiment adopts the preparation method disclosed in Chinese Patent No. 202210232304.5) to obtain a thermal protection layer composed of a fiber-reinforced phenolic resin aerogel composite material;

[0037] 7) The length dimension of the heat protection layer is processed to the designed dimension to obtain the component.

[0038] The above are only preferred embodiments of the present invention, and do not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A thermal protection structure of a rotating body with a partitioned design and reinforced fabric, characterized in that: The invention comprises a heat protection layer which is coaxially sleeved on the outer wall of an aircraft and whose inner contour matches the contour of the outer wall of the aircraft. The heat protection layer is formed by splicing a windward surface protection zone arranged on the windward surface of the aircraft and a leeward surface protection zone arranged on the leeward surface of the aircraft. The windward surface protection zone comprises, from the inside to the outside, a plurality of first fiber felt layers and a first high-density fabric layer in sequence, and the leeward surface protection zone comprises, from the inside to the outside, a plurality of second fiber felt layers and a second high-density fabric layer in sequence. The plurality of first fiber felt layers and the first high-density fabric layers in the windward surface protection zone are fixed by normal fiber stitching, and the plurality of second fiber felt layers and the second high-density fabric layers in the leeward surface protection zone are also fixed by normal fiber stitching, and the normal fiber stitching density of the windward surface protection zone is greater than the normal fiber stitching density of the leeward surface protection zone.

2. The thermal protection structure of a rotating body with a partitioned design reinforced fabric according to claim 1, characterized in that: The heat protection layer is a fiber-reinforced phenolic resin aerogel composite material layer.

3. The thermal protection structure of a rotating body with a partitioned design reinforced fabric according to claim 1, characterized in that: The splicing seams between the windward surface protection area and the leeward surface protection area are symmetrically arranged at the waist of both sides of the aircraft, the multiple layers of first fiber felt layers on the connecting sides at both ends of the windward surface protection area are staggered to form a first concave-convex connection structure, the multiple layers of second fiber felt layers on the connecting sides at both ends of the leeward surface protection area are staggered to form a second concave-convex connection structure matching the first concave-convex connection structure, the windward surface protection area and the leeward surface protection area are plug-connected to each other through the first and second concave-convex connection structures to form a splicing area, the splicing area, the first fiber felt layer and the second fiber felt layer on the same layer are sewn and fixed to each other, and the multiple layers of fiber felt layers and the high-density fabric layer in the splicing area are fixed by normal fiber sewing.

4. The thermal protection structure of a rotating body with a partitioned design reinforced fabric according to claim 1, characterized in that: The windward side protection area and the leeward side protection area respectively occupy 1 / 2 of the total area of ​​the heat protection layer.

5. The thermal protection structure of a rotating body with a partitioned design reinforced fabric according to claim 1, characterized in that: The first fiber felt layer is a glass fiber needle felt layer or a quartz fiber needle felt layer, and the density of the first fiber felt layer is 0.1-0.3 g / cm 3 The thickness of the single-layer first fiber felt layer is 2~10mm.

6. The thermal protection structure of a rotating body with a partitioned design reinforced fabric according to claim 1, characterized in that: The first high-density fabric layer is a 2.5D high-silica fiber fabric layer or a 2.5D quartz fiber fabric layer, the thickness of the first high-density fabric layer is 1-3 mm, and the fiber volume fraction of the first high-density fabric layer is 35%-48%.

7. The thermal protection structure of a rotating body with a partitioned design reinforced fabric according to claim 1, characterized in that: The normal stitching fibers of the heat protection layer in the windward protection zone are made of quartz fiber yarn, the linear density of the normal stitching fibers is 100-300 TEX, and the normal fiber puncture density is 3×3mm-15×15mm.

8. The thermal protection structure of a rotating body with a partitioned design reinforced fabric according to claim 1, characterized in that: The second fiber felt layer is a glass fiber needle felt layer or a quartz fiber needle felt layer, and the density of the second fiber felt layer is 0.08-0.15 g / cm 3 The thickness of the single-layer second fiber felt layer is 2~10mm.

9. The thermal protection structure of a rotating body with a partitioned design reinforced fabric according to claim 1, characterized in that: The second high-density fabric layer is a two-dimensional quartz fiber fabric layer or a high-silica fiber fabric layer, the thickness of the second high-density fabric layer is 0.5-1 mm, and the fiber volume fraction of the second high-density fabric layer is 35%-45%.

10. The thermal protection structure of a rotating body with a partitioned design reinforced fabric according to claim 1, characterized in that: The normal stitching fibers of the heat protection layer in the leeward protection zone are made of quartz fiber yarn, the linear density of the normal stitching fibers is 50-200 TEX, and the normal fiber puncture density is 5×5 mm-20×20 mm.

11. The thermal protection structure of a rotating body with a partitioned design reinforced fabric according to claim 1, characterized in that: The heat protection layer is a hollow rotating body whose inner cavity contour matches the outer contour of the aircraft.

Images