JP2016176489A - Thermal insulation material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal insulation material having a high heat resistance.SOLUTION: There is used an air-permeable structure, from which contained gases leave in the vacuum. In order that the gas contained in the air by the air-permeable structure, a foamed layer containing independent air bubbles is formed between the air-permeable structure and a thermal protection object. In order to prevent the immersion into the air-permeable structure and to reflect the sunlight or to radiate the heat input from the outside, a protective layer 233 is formed on the surface of the air-permeable structure.SELECTED DRAWING: Figure 5D

Description

  The present invention relates to a heat insulating material. The heat insulating material can be suitably used to thermally protect a liquid fuel tank such as a rocket, for example.

  A rocket that burns and propels liquid fuel such as liquid hydrogen is known. Such rockets have a liquid fuel tank that stores liquid fuel.

  In the case of liquid hydrogen, the boiling point is about minus 252.6 degrees Celsius, and vaporizes above this temperature. The vaporized gaseous hydrogen is discharged from the liquid fuel tank. In order to realize a longer cruising range of the rocket, it is conceivable to thermally protect the liquid fuel tank to prevent vaporization of the liquid fuel.

  The rocket before launch is installed on the ground. Since there is air around the rocket installed on the ground, for example, it is conceivable to thermally protect the fuel tank from heat input due to heat conduction through the air.

  In addition, the rocket that is being launched mainly compresses the air in the forward direction of the propulsion, so for example, the fuel tank is also thermally affected by heat input due to heat conduction transmitted from the air that generates heat due to adiabatic compression called aerodynamic heating. It is conceivable to protect.

  Furthermore, there is no air around the rocket that has reached the outer space, and no aerodynamic heating occurs in the rocket. On the other hand, since the rocket is exposed to direct sunlight, for example, it is conceivable to thermally protect the fuel tank from radiation heat input from the sun.

  In relation to the above, Patent Document 1 (WO 2014/087834) discloses a heat insulating material. This heat insulating material has a vacuum heat insulating material and a rigid polyurethane foam in contact with at least one surface of the vacuum heat insulating material. A vacuum heat insulating material has the outer bag which has airtightness, and the molded object by which the core material containing the fumed silica with a binder by which the binder was provided to the surface of the fumed silica was shape | molded. The molded body is sealed under reduced pressure in the outer bag. Rigid polyurethane foam has open cells.

WO2014 / 087834

  The objective of this invention is providing the heat insulating material which has high heat resistance. Other problems and novel features will become apparent from the description of the specification and the accompanying drawings.

  The means for solving the problem will be described below using the numbers used in the (DETAILED DESCRIPTION). These numbers are added to clarify the correspondence between the description of (Claims) and (Mode for Carrying Out the Invention). However, these numbers should not be used to interpret the technical scope of the invention described in (Claims).

  The heat insulating material according to some embodiments includes a first heat insulating layer (231), a second heat insulating layer (232), and a protective layer (233). Here, a 1st heat insulation layer (231) is laminated | stacked on the surface of a thermal protection target object (22). The second heat insulating layer (232) is laminated on the surface of the first heat insulating layer (231). The protective layer (233) is laminated on the surface of the second heat insulating layer (232) to prevent water from entering. A 1st heat insulation layer (231) has the 1st foam layer (231-A etc.) which includes a plurality of independent bubbles independent of each other. The second heat insulating layer (232) has a breathable structure layer (such as 232-A). At least a portion (24, 24-A to 24-C) of the breathable structure layer (such as 232-A) communicates with the external environment.

  The heat insulating material according to the present invention has high heat resistance.

FIG. 1A is a diagram illustrating a configuration example of a multistage rocket. FIG. 1B is a diagram illustrating a configuration example of a second stage rocket among the multistage rockets illustrated in FIG. 1A. FIG. 2A is a graph comparing the heat resistance performance of various heat insulating materials in an atmospheric environment and a vacuum environment. FIG. 2B is a cross-sectional view showing a configuration example of a closed cell foam heat insulating material. FIG. 2C is a cross-sectional view showing a configuration example of an open-cell foam heat insulating material. FIG. 3A is a cross-sectional view taken along the cross-sectional line AA shown in FIG. 1B, showing a configuration example of a liquid fuel tank using an open-cell foam heat insulating material. FIG. 3B is a cross-sectional view taken along a cross-sectional line BB shown in FIG. 1B, showing a configuration example of a liquid fuel tank using an open-cell foam heat insulating material. FIG. 4A is an enlarged view of a part of FIG. 3A showing an example of a phenomenon that can occur in an open-cell foam heat insulating material in air. FIG. 4B is an enlarged view of a part of FIG. 3A showing another example of a phenomenon that can occur in an open-cell foam heat insulating material in air. FIG. 5A is a cross-sectional view taken along the cross-sectional line AA shown in FIG. 1B, showing a configuration example of a liquid fuel tank using a heat insulating material according to some embodiments. FIG. 5B is a cross-sectional view taken along a cross-sectional line BB shown in FIG. 1B, showing a configuration example of a liquid fuel tank using a heat insulating material according to some embodiments. FIG. 5C is a cross-sectional view illustrating effects obtained in air with a thermal insulator according to some embodiments. FIG. 5D is a cross-sectional view illustrating effects obtained in a vacuum with a thermal insulator according to some embodiments. FIG. 6A is an enlarged view of a part of FIG. 5A showing a configuration example of the heat insulating material according to the first embodiment. FIG. 6B is an enlarged view of another part of FIG. 5A showing a configuration example of the heat insulating material according to the first embodiment. FIG. 6C is an enlarged view of still another part of FIG. 5A showing a configuration example of the heat insulating material according to the first embodiment. FIG. 7A is an enlarged view of a part of FIG. 5A showing another configuration example of the heat insulating material according to the first embodiment. FIG. 7B is an enlarged view of another part of FIG. 5A showing another configuration example of the heat insulating material according to the first embodiment. FIG. 7C is an enlarged view of still another part of FIG. 5A showing another configuration example of the heat insulating material according to the first embodiment. FIG. 8A is a cross-sectional view showing a first state in one structural example of the exhaust pipe shown in FIG. 7B. FIG. 8B is a cross-sectional view showing a second state in one structural example of the exhaust pipe shown in FIG. 7B. FIG. 9A is an enlarged view of a part of FIG. 5A showing a configuration example of a heat insulating material according to the second embodiment. FIG. 9B is an enlarged view of a part of FIG. 5A showing another configuration example of the heat insulating material according to the second embodiment. FIG. 10A is an enlarged view of a part of FIG. 5A showing a configuration example of the heat insulating material according to the third embodiment. FIG. 10B is an enlarged view of a part of FIG. 5A showing another configuration example of the heat insulating material according to the third embodiment. FIG. 10C is an enlarged view of a part of FIG. 5A showing still another configuration example of the heat insulating material according to the third embodiment. FIG. 10D is an enlarged view of a part of FIG. 5A showing still another configuration example of the heat insulating material according to the third embodiment. FIG. 11A is an enlarged view of a part of FIG. 5A showing a configuration example of a heat insulating material according to the fourth embodiment. FIG. 11B is an enlarged view of a part of FIG. 5A showing another configuration example of the heat insulating material according to the fourth embodiment.

  With reference to the attached drawings, some embodiments of the heat insulating material will be described below. In addition, below, the example which applied the heat insulating material which concerns on some embodiment to a rocket is demonstrated.

  FIG. 1A is a diagram illustrating a configuration example of a multistage rocket 1. The multistage rocket 1 shown in FIG. 1A has a first stage rocket 11 and a second stage rocket 12. The second stage rocket 12 has a fairing 13.

  In addition, although the case where the number of stages of the multistage rocket 1 is two will be described here, this number of stages is merely an example.

  The positional relationship of the components of the multistage rocket 1 illustrated in FIG. 1A will be described. As in the coordinate system shown in FIG. 1A, the rocket traveling direction (propulsion direction) + Z direction is referred to as an upward direction, and the opposite −Z direction is referred to as a downward direction.

  The first stage rocket 11 is arranged at the lowermost part of the multistage rocket 1. The second stage rocket 12 is installed on the upper stage of the first stage rocket 11. The fairing is arranged at the top of the second stage rocket 12.

  When the multistage rocket 1 is launched, the engine of the first stage rocket 11 is first ignited. When the multistage rocket 1 reaches a predetermined altitude by the propulsive force of the first stage rocket 11, for example, the first stage rocket 11 is disconnected from the second stage rocket 12, and the second stage rocket 12 is ignited.

  The fairing 13 is provided for the purpose of protecting an artificial satellite or the like disposed therein from air resistance or aerodynamic heating. When the second stage rocket 12 reaches the outside of the atmosphere, the fairing 13 is also separated from the second stage rocket 12.

  FIG. 1B is a diagram showing a configuration example of the second stage rocket 12 in the multistage rocket 1 shown in FIG. 1A. The second stage rocket 12 illustrated in FIG. 1B includes a second stage engine 121, a liquid fuel tank 122, an artificial satellite separation device 123, and an artificial satellite 124. It should be noted that the first stage rocket 11 arranged at the first stage rocket position 110 has already been separated from the second stage rocket 12 illustrated in FIG. 1B, and the fairing provided at the fairing position 130 The ring 13 has already been cut off.

  The positional relationship of the components of the second stage rocket 12 illustrated in FIG. 1B will be described. As in the coordinate system shown in FIG. 1B, as in the case of FIG. 1A, the + Z direction is also referred to as the upward direction and the −Z direction is referred to as the downward direction.

  The second stage engine 121 is disposed at the lowermost part of the second stage rocket 12. A liquid fuel tank 122 is disposed on the second stage engine 121. An artificial satellite separator 123 is disposed on the liquid fuel tank 122. An artificial satellite 124 is arranged on the artificial satellite separator 123.

  The operation of the components of the second stage rocket 12 illustrated in FIG. 1B will be described.

  The second stage engine 121 is ignited after the first stage rocket 11 is disconnected and supplies a propulsive force. The liquid fuel tank 122 stores liquid fuel such as liquid hydrogen and supplies the liquid fuel to the second stage engine 121. For example, when the second stage rocket 12 reaches a predetermined position, the artificial satellite separation device 123 separates the artificial satellite 124 from the liquid fuel tank 122 and the second stage engine 121. The artificial satellite 124 performs a predetermined operation after being separated or before being separated.

  Here, in the multistage rocket 1 illustrated in FIGS. 1A and 1B, the liquid fuel tank 122 itself is also used as a part of the outer wall of the multistage rocket 1. In other words, outside the liquid fuel tank 122, there is no structure that supports a large load such as the weight of the rocket even though there is a surface layer material such as a heat insulating material that is thermally protected.

  At this time, the outer wall of the liquid fuel tank 122 is a part of the outer wall of the multistage rocket 1 as a structure, and is exposed to the external environment through a heat insulating material. Specifically, there is only a surface layer material such as a heat insulating material between the liquid fuel tank 122 and the surrounding air before the launch and during the launch. Therefore, the heat insulating material directly receives the heat input by heat conduction etc. which transmits the air in the outer wall of the liquid fuel tank 122. Further, after reaching the outer space, since there is no air around, the heat insulating material (surface layer material) of the liquid fuel tank 122 is exposed to direct sunlight.

  Therefore, it is desirable that the heat insulating material provided on the outer wall of the liquid fuel tank 122 has a performance of thermally protecting the liquid fuel tank 122 both in air and in vacuum, for example.

  FIG. 2A is a graph comparing the heat resistance of various heat insulating materials in an atmospheric environment and a vacuum environment. In the graph of FIG. 2A, the vertical axis represents the thermal conductivity.

  The graph of FIG. 2A includes a total of eight bar graphs. These eight bar graphs are referred to as a first bar graph a1, a second bar graph a2, a third bar graph b1, a fourth bar graph b2, a fifth bar graph c1, a sixth bar graph c2, a seventh bar graph d1, and an eighth bar graph d2, respectively. . The lengths of these eight bar graphs each represent a relative evaluation of thermal conductivity.

  The first bar graph a1 and the second bar graph a2 indicate the thermal conductivity of PIF (Polyisocyanurate Foam) in air and in vacuum, respectively.

  The third bar graph b1 and the fourth bar graph b2 indicate the thermal conductivity of the airgel heat insulating material in air and in vacuum, respectively.

  The 5th bar graph c1 and the 6th bar graph c2 have shown thermal conductivity of the airgel heat insulating material (one kind) different from the 3rd bar graph b1 and the 4th bar graph b2 in air and vacuum, respectively.

  The seventh bar graph d1 and the eighth bar graph d2 indicate the thermal conductivity of U-Vacua (registered trademark) in air and in vacuum, respectively. U-Vacua (registered trademark) is a kind of vacuum heat insulating material.

  As can be seen from the graph shown in FIG. 2A, even in the same heat insulating material, the thermal conductivity in vacuum is lower than the thermal conductivity in air. This means that the thermal conductivity of the air itself contained in the heat insulating material has an influence that cannot be ignored.

  Note that the lower thermal conductivity means that heat is more difficult to transfer, and thus means higher performance as a heat insulating material.

  As can be further read from the graph shown in FIG. 2A, the difference in thermal conductivity between air and vacuum is relatively small for PIF and U-Vacua, and relatively large for Aerogel PP and Aerogel GW. This difference is derived from the difference in the structure of each heat insulating material. That is, there is a structural difference in that PIF is a closed cell foam heat insulating material, and aerogel PP and aerogel GW are open cell foam heat insulating materials. Hereinafter, the difference between the closed cell foam heat insulating material and the open cell foam heat insulating material will be described. U-Vacua has a structure in which the surface is sealed and has different characteristics from the closed cell type foamed heat insulating material and the open cell type foamed heat insulating material.

  FIG. 2B is a cross-sectional view showing a configuration example of a closed cell foam heat insulating material. As illustrated in FIG. 2B, the closed cell foam heat insulating material has a large number of closed cells inside the resin structure. These many closed cells contain gas inside and are independent of each other. Therefore, even if the closed-cell foam heat insulating material is placed in a vacuum, the contained gas remains almost as it is. As a result, the thermal conductivity of the closed cell foam heat insulating material is relatively small in air and in vacuum.

  FIG. 2C is a cross-sectional view showing a configuration example of an open-cell foam heat insulating material. As illustrated in FIG. 2C, the open cell foam heat insulating material has a large number of open cells inside the resin structure. In the air, these many open bubbles contain air inside and communicate with each other. Therefore, when the open-cell foam heat insulating material is placed in a vacuum, the air contained inside escapes to the outside and only the resin structure remains. For this reason, the inside of an open cell also becomes a vacuum. As a result, the thermal conductivity of the open-cell foam insulation is relatively large in air and in vacuum.

  Therefore, in order to more effectively protect the liquid fuel tank 122 of the multistage rocket 1 used in a vacuum environment, it is preferable to use an open-cell foam insulation material rather than a closed-cell foam insulation material. It is considered desirable.

  FIG. 3A is a cross-sectional view taken along the cross-sectional line AA shown in FIG. 1B, showing a configuration example of a liquid fuel tank using an open-cell foam heat insulating material. The coordinate system shown in FIG. 3A is the same as that in FIGS. 1A and 1B, and the + Z direction indicates the propulsion direction of the multistage rocket 1. FIG. 3B is a cross-sectional view taken along a cross-sectional line BB shown in FIG. 1B, showing a configuration example of a liquid fuel tank using an open-cell foam heat insulating material.

  The liquid fuel tank 122 shown in FIGS. 3A and 3B includes a liquid fuel storage area 210, a tank outer wall 220, and a heat insulating material 230.

  The liquid fuel storage area 210 is provided inside the tank outer wall 220. Moreover, the heat insulating material 230 is laminated | stacked on the outer side of the tank outer wall 220 as a thermal protection target object.

  Here, consider a case where the heat insulating material 230 is an open cell PIF layer which is a kind of open cell foam heat insulating material. In outer space, that is, in a vacuum, the open cell PIF layer as the heat insulating material 230 protects the surface of the liquid fuel tank 122 from direct sunlight. Furthermore, the inside of the open-cell PIF layer is in a vacuum in a vacuum, that is, it does not contain a gas that can transmit the amount of heat generated by the radiant heat of sunlight to the liquid fuel tank 122. As described above, it is considered that the open cell PIF is suitable as a heat insulating material for thermally protecting the liquid fuel tank 122 in a vacuum.

  Next, it is assumed that the outer wall of the liquid fuel tank 122 is disposed in the air.

  FIG. 4A is an enlarged view of a part of FIG. 3A showing an example of a phenomenon that can occur in an open-cell foam heat insulating material in air. More specifically, in FIG. 4A, the region 30 surrounded by a broken line in the cross-sectional view shown in FIG. 3A is enlarged. In the coordinate system shown in FIG. 4A, the + Z direction indicates the propulsion direction of the multistage rocket 1 as in the case of FIG. 3A. In the region 30, the −X direction indicates the outer direction when the liquid fuel tank 122 is viewed from the inner side to the outer side.

  In the example shown in FIG. 4A, an open cell PIF layer 230 -A is laminated on the outside of the tank outer wall 220. As described above, since the outer wall of the liquid fuel tank 122 is also a part of the outer wall of the multistage rocket 1, the open cell PIF layer 230-A is in contact with the surrounding air.

  Here, in the case where it rains on the ground before the launch, intrusion 41 of moisture or the like occurs inside the open cell PIF layer 230-A. The infiltrated moisture may stay inside the open-cell PIF layer 230-A due to an effect such as surface tension. At this time, in the open cell type PIF layer 230-A, the portion where moisture or the like has permeated has deteriorated thermal conductivity due to the presence of moisture. This portion is referred to as a thermal conductivity deterioration region 230-B.

  FIG. 4B is an enlarged view of a part of FIG. 3A showing another example of a phenomenon that can occur in an open-cell foam heat insulating material in air. 4B, as in FIG. 4A, in the cross-sectional view shown in FIG. 3A, the region 30 surrounded by a broken line is enlarged, and the −X direction of the coordinate system is viewed from the inside to the outside of the liquid fuel tank 122. The outward direction is shown.

  In the example shown in FIG. 4B as well, the open cell PIF layer 230-A is laminated on the tank outer wall 220 as in the case of FIG. 4A. As described above, the liquid fuel tank 122 stores liquid fuel such as liquid hydrogen, and its temperature is very low. As a result, the cooling action 42 generated from the liquid fuel storage area 210 reaches the open cell type PIF layer 230-A, and the air contained in the open cells is liquefied. Liquid generated by liquefaction such as air may also remain inside the open-cell PIF layer 230-A due to an action such as surface tension. At this time, in the open cell type PIF230-A, the portion where the liquid remains is deteriorated in thermal conductivity due to the presence of the liquid. This portion is referred to as a thermal conductivity deterioration region 230-C. In addition, when the tank outer wall 220 is at a low temperature (for example, 10 degrees Celsius or less, or 0 degrees Celsius or less), water vapor in the air around the tank outer wall 220 is solidified to become water. Also in this case, the thermal conductivity deteriorates due to the presence of moisture.

  In some embodiments, a configuration is proposed in which the generation of the thermal conductivity deterioration regions 230-B and 230-C is prevented while the liquid fuel tank 122 is thermally protected using an open-cell foam insulation.

  FIG. 5A is a cross-sectional view taken along the cross-sectional line AA shown in FIG. 1B, showing a configuration example of a liquid fuel tank using a heat insulating material according to some embodiments. The coordinate system shown in FIG. 5A is the same as in FIG. 3A and the like, and the + Z direction indicates the propulsion direction of the multistage rocket 1. FIG. 5B is a cross-sectional view taken along a cross-sectional line BB shown in FIG. 1B, showing a configuration example of a liquid fuel tank using a heat insulating material according to some embodiments.

  The liquid fuel tank 122 shown in FIGS. 5A and 5B has a liquid fuel storage area 21, a tank outer wall 22, and a heat insulating material 23. The heat insulating material 23 includes a first heat insulating layer 231, a second heat insulating layer 232, and a protective layer 233.

  The liquid fuel storage area 21 is provided inside the tank outer wall 22. The heat insulating material 23 is laminated | stacked on the outer side of a side wall part among the tank outer walls 22 as a thermal protection target object, for example.

  Of the heat insulating material 23, the first heat insulating layer 231 is laminated on the surface of the tank outer wall 22. The second heat insulation layer 232 is laminated on the outer surface of the first heat insulation layer 231. The protective layer 233 is laminated on the outer surface of the second heat insulating layer 232. Thus, the tank outer wall 22, the first heat insulating layer 231, the second heat insulating layer 232, and the protective layer 233 are laminated in this order.

  In some embodiments, a breathable structure layer is used as the second thermal insulation layer 232. The breathable structure layer is at least partially communicated with the external environment, and has a space that encloses a gas such as ambient air in the air, like the open cell foam heat insulating material described above. In addition, the structure layer has air permeability such that the gas contained in the vacuum is discharged and the space is vacuumed. As the second heat insulating layer 232, as will be described later, an open cell PIF layer, an open cell PI (Polyimide) foam layer, or a fiber structure layer can be used.

  In some embodiments, the protective layer 233 is used to respond to the event described with reference to FIG. 4A. As described later, as the protective layer 233, an open-cell-type heat insulating material, a laminated structure of a radiation film made of a reflective film and a coating agent made of paint, metal, or the like, or an F-OSR (Flexible-Optical Solar Reflector: It is desirable to use an airtight structure layer that suppresses intrusion of gas or liquid into the second heat insulating layer 232, such as a flexible optical solar reflector.

  Further, in some embodiments, the first thermal insulation layer 231 is used to respond to the event described with reference to FIG. 4B. As the first heat insulating layer 231, as described later, it is desirable to use a foam layer containing closed cells, such as a closed cell type PIF layer.

  FIG. 5C is a cross-sectional view showing effects obtained in the air by the heat insulating material 23. FIG. 5D is a cross-sectional view showing effects obtained in a vacuum by a heat insulating material.

  5C and 5D both show an enlarged region 31 surrounded by a broken line in the cross-sectional view shown in FIG. 5A. As indicated by the coordinate systems shown in FIGS. 5A to 5D, the + Z direction indicates the propulsion direction of the multistage rocket 1. Further, the −X direction indicates an outward direction when the liquid fuel tank 122 is viewed from the inside to the outside in the region 31 illustrated in FIGS. 5A, 5C, and 5D.

  First, FIG. 5C shows a configuration example in which the tank outer wall 22, the first heat insulating layer 231, the second heat insulating layer 232, and the protective layer 233 are laminated in this order. FIG. 5C shows a state in which the liquid fuel tank (tank outer wall 22) is in an air environment. There is air outside the protective layer 233, and the second heat insulating layer 232 contains air inside the open cell.

  In the state shown in FIG. 5C, as an example of the operational effect obtained by providing the protective layer 233 on the surface of the second heat insulating layer 232, there is a suppression 51 of wind and rain intrusion into the second heat insulating layer 232. That is, as described with reference to FIG. 4A, it is possible to suppress a situation in which the heat conduction efficiency deteriorates at a portion where moisture enters the continuous bubbles of the second heat insulating layer 232 from the outside. Further, if the protective layer 233 has a reflection performance for reflecting light, a radiation performance for radiating heat to the outside, and other heat insulation performance, the heat insulation material 23 as a whole from the outside to the liquid fuel tank The heat input suppression 52 is improved.

  In the state shown in FIG. 5C, as an effect obtained by providing the first heat insulating layer 231 between the tank outer wall 22 and the second heat insulating layer 232, there is a cooling suppression 53 by liquid fuel. That is, as described with reference to FIG. 4B, it is possible to suppress a situation in which the heat conduction efficiency deteriorates in a portion where air, water vapor, or the like included in the second heat insulating layer 232 is cooled and liquefied. Moreover, the 1st heat insulation layer 231 contributes also to the suppression 52 of the heat input from the outside naturally.

  Next, FIG. 5D shows a configuration example in which the tank outer wall 22, the first heat insulating layer 231, the second heat insulating layer 232, and the protective layer 233 are laminated in this order, similarly to FIG. 5C. Yes. However, FIG. 5D shows a state in which the liquid fuel tank (tank outer wall 22) is in a vacuum environment, unlike FIG. 5C, and the outside of the protective layer 233 is a vacuum such as outer space. Further, in this environment, the second heat insulating layer 232 having air permeability is in a state where the gas contained therein has escaped to the outside.

  In the state shown in FIG. 5D, as an example of the effect obtained by providing the protective layer 233 on the surface of the second heat insulating layer 232, when the protective layer 233 has reflection performance, the sunlight reflection 54 There is. At this time, it is desirable that the reflection performance of the protective layer 233 be exhibited with respect to visible light, which is a band that particularly affects radiation heat input, among sunlight. Moreover, if the protective layer 233 has the reflective performance which reflects light, and other heat insulation performance, the suppression 52 of the heat input to the liquid fuel tank from the outside as the whole heat insulating material 23 will improve. Furthermore, when the protective layer 233 has radiation performance, radiation 56 of heat quantity is obtained.

  In addition, the heat insulation performance is improving the 2nd heat insulation layer 232 in the state which air has escaped in the vacuum compared with the state which encloses air in the air. For heat input exceeding the second heat insulating layer 232 with improved heat insulating performance, the first heat insulating layer 231 suppresses heat input to the liquid fuel tank 122.

  Hereinafter, more specific embodiments will be described.

(First embodiment, configuration example 1)
FIG. 6A is an enlarged view of a part of FIG. 5A showing a configuration example of the heat insulating material 23 according to the first embodiment. More specifically, FIG. 6A shows an enlarged region 31 surrounded by a broken line in the cross-sectional view shown in FIG. 5A. However, as indicated by the coordinate system shown in each of FIGS. 5A and 6A, the + Z direction indicates the propulsion direction of the rocket, and the −X direction indicates the outside from the inside of the liquid fuel tank 122 in the region 31. The outer direction is shown.

  In the embodiment shown in FIG. 6A, the closed cell PIF layer 231-A is used as the first heat insulating layer 231 shown in FIGS. 5A to 5D. Similarly, an open cell PIF layer 232 -A is used as the second heat insulating layer 232, and a closed cell PIF layer 233 -A is used as the protective layer 233.

  In other words, in the embodiment shown in FIG. 6A, the tank outer wall 22, the closed cell PIF layer 231-A, the open cell PIF layer 232-A, and the closed cell PIF layer 233-A are arranged in this order. Are stacked.

  Here, the air inside the open cell PIF layer 232 -A cooled by the liquid fuel tank (tank outer wall 22) is desired to be kept in a gaseous state. On the other hand, it is desirable to keep the total weight of the multistage rocket 1 as small as possible. At this time, as an example, it is desirable that the thickness of the closed cell PIF layer 231 -A is 10 millimeters or more and 40 millimeters or more, particularly 20 millimeters or more and 30 millimeters or less.

  FIG. 6B is an enlarged view of another part of FIG. 5A showing a configuration example of the heat insulating material 23 according to the first embodiment. More specifically, FIG. 6B shows an enlarged region 32 surrounded by a broken line in the cross-sectional view shown in FIG. 5A. The coordinate system is the same as in FIG. 6A.

  FIG. 6B shows an end face of the heat insulating material 23 according to the present embodiment on the lower side of the liquid fuel tank 122. In order to ensure that the gas contained in the open-cell PIF layer 232 -A as the air-permeable structure escapes to the outside in a vacuum, that is, to ensure communication with the external environment, this end surface has the air-permeable portion 24. It is desirable to provide

  The ventilation part 24 shown in FIG. 6B faces the direction of gravity before launching the multistage rocket 1 in the −Z direction. Therefore, there is little possibility that rainwater or the like enters the open cell of the open cell type PIF layer 232 -A from the ventilation part 24 before the launch.

  In the heat insulating material 23 according to the embodiment shown in FIG. 6B, the features other than the above description are the same as those in the region 31 described with reference to FIG. 6A.

  FIG. 6C is an enlarged view of still another part of FIG. 5A showing a configuration example of the heat insulating material 23 according to the first embodiment. More specifically, FIG. 6C shows an enlarged region 33 surrounded by a broken line in the cross-sectional view shown in FIG. 5A. The coordinate system is the same as in FIG. 6A.

  FIG. 6C shows an end face on the upper side of the liquid fuel tank 122 in the heat insulating material 23 according to the present embodiment. This end face faces the + Z direction, that is, the direction opposite to the gravity until the multistage rocket 1 is launched. Therefore, in order to protect the open-cell type PIF layer 232 -A from the intrusion of rainwater or the like, it is desirable to provide the sealing portion 25 having an airtightness (sealability). As this sealing part 25, you may use a closed cell type PIF, for example.

  Other configurations and operations of the heat insulating material 23 according to the embodiment shown in FIG. 6C are the same as those in the region 31 described with reference to FIG. 6A.

  In the heat insulating material 23 according to the present embodiment described with reference to FIGS. 6A to 6C, all of the first heat insulating layer 231, the second heat insulating layer 232, and the protective layer 233 are formed with the same PIF, although the expansion ratios are different. ing. PIF can be switched between the formation of a closed cell type PIF layer and the formation of an open cell type PIF layer by appropriately adjusting the expansion ratio at the time of formation. Therefore, the heat insulating material 23 according to the present embodiment can form all of the first heat insulating layer 231, the second heat insulating layer 232, and the protective layer 233 with the same apparatus relatively easily and at a relatively low cost. Note that the first heat insulating layer 231 (closed cell layer), the second heat insulating layer 232 (open cell layer), and the protective layer 233 (closed cell layer) can be formed using the same material other than PIF. It is.

(First embodiment, configuration example 2)
Here, the example of a change of the ventilation part 24 shown to FIG. 6B is demonstrated. When the second stage rocket 12 including the liquid fuel tank 122 reaches the outer space which is a vacuum environment, the air contained in the second heat insulating layer 232 which is a breathable structure is quickly discharged to the outside. It is desirable. In addition, the air discharged from the second heat insulating layer 232 may be cooled and liquefied in outer space, and may adhere to an undesired location of the second stage rocket 12. Therefore, a method for changing the arrangement, discharge direction, total area, and the like of the ventilation portion 24 shown in FIG. 6B is proposed.

  FIG. 7A is an enlarged view of a part of FIG. 5A showing another configuration example of the heat insulating material 23 according to the first embodiment. More specifically, FIG. 7A is a modified example corresponding to FIG. 6A, and shows an enlarged region 31 surrounded by a broken line in the cross-sectional view shown in FIG. 5A. The coordinate system is the same as in FIG. 6A.

  The configuration example shown in FIG. 7A is obtained by adding an exhaust pipe 26-A and a plug 25-A to the configuration example shown in FIG. 6A. Here, the component called the plug 25-A may actually be a sealing material that fills the gap between the exhaust pipe 26-A and the surrounding heat insulating material 23, or the exhaust pipe 26-A is fixed. It may be a supporting part. Such components are collectively referred to as a stopper hereinafter. Other components shown in FIG. 7A are the same as those in FIG. 6A.

  The exhaust pipe 26 -A passes through the closed cell PIF layer 233 -A as the protective layer 233. One end of the exhaust pipe 26-A protrudes outside the heat insulating material 23 and has an opening 24-A. The other end of the exhaust pipe 26 -A reaches the open cell PIF layer 232 -A as the second heat insulating layer 232. The plug 25-A closes the gap between the exhaust pipe 26-A and the closed cell PIF layer 233-A.

  Both ends of the exhaust pipe 26-A communicate with each other, and the air contained in the open cell PIF layer 232-A, which is a breathable structure, passes through the inside of the exhaust pipe 26-A in a vacuum. It is discharged outside. In order to prevent rain or the like from entering the open cell PIF layer 232-A through the inside of the exhaust pipe 26-A in the air, the opening 24-A is in the −Z direction, that is, in the direction of gravity (vertically below Direction). However, from the viewpoint of suppressing undesirable adhesion of discharged air or the like to the second stage rocket 12, the direction of the opening 24-A is more outward than the −Z direction as viewed from the second stage rocket 12. For example, it may be directed in a diagonally downward direction, which is a combined direction of the gravity direction and the outer direction.

  FIG. 7B is an enlarged view of another part of FIG. 5A showing another configuration example of the heat insulating material 23 according to the first embodiment. More specifically, FIG. 7B is a modified example corresponding to FIG. 6B, and shows an enlarged region 32 surrounded by a broken line in the cross-sectional view shown in FIG. 5A. The coordinate system is the same as in FIG. 6A.

  The configuration example shown in FIG. 7B is obtained by adding an exhaust pipe 26-B and a plug 25-B to the configuration example shown in FIG. 6B. The other components shown in FIG. 7B are the same as in FIG. 6B.

  The exhaust pipe 26-B and the plug 25-B shown in FIG. 7B have the same configuration as the exhaust pipe 26-A and the plug 25-A shown in FIG. 7A, respectively, but the place and the shape are changed. Yes. That is, the exhaust pipe 26 -B and the plug 25 -B are provided on the end surface of the open cell PIF layer 232 -A on the lower side of the liquid fuel tank 122. Further, since the exhaust pipe 26-B itself is provided in the -Z direction, that is, in the direction of gravity, the opening 24-B of the exhaust pipe 26-B is also oriented in the -Z direction. In other words, the exhaust pipe 26-B shown in FIG. 7B does not need to be bent like the exhaust pipe 26-A shown in FIG. 7A.

  Other configurations and operations of the exhaust pipe 26-B and the plug 25-B are the same as those of the exhaust pipe 26-A and the plug 25-A shown in FIG. 7A, respectively.

  FIG. 7C is an enlarged view of another part of FIG. 5A, showing another configuration example of the heat insulating material 23 according to the first embodiment. More specifically, FIG. 7C is a modified example corresponding to FIG. 6C, and shows an enlarged region 33 surrounded by a broken line in the cross-sectional view shown in FIG. 5C. The coordinate system is the same as in FIG. 6A.

  The configuration example shown in FIG. 7C is obtained by adding an exhaust pipe 26-C and a plug 25-C to the configuration example shown in FIG. 6C. The other components shown in FIG. 7C are the same as in FIG. 6C.

  The exhaust pipe 26-C and the plug 25-C shown in FIG. 7C have the same configuration as the exhaust pipe 26-A and the plug 25-A shown in FIG. 7A, respectively, but the location and shape are changed. Yes. That is, the exhaust pipe 26 -C and the plug 25 -C are provided on the end surface of the open cell PIF layer 232 -A on the upper side of the liquid fuel tank 122. Therefore, the exhaust pipe 26-C shown in FIG. 7C is further bent than the exhaust pipe 26-A shown in FIG. 7A because the opening 24-C faces the −Z direction. As a result, the direction of the opening 24-C is directed to the direction of gravity. Alternatively, the direction of the opening 24-C may be directed obliquely downward, which is a combined direction of the direction of gravity and the outer side direction of the side wall that is the outer wall 22.

  Other configurations and operations related to the exhaust pipe 26-C and the plug 25-C are the same as those of the exhaust pipe 26-A and the plug 25-A shown in FIG. 7A, respectively.

  In the configuration using the exhaust pipes 26-A to 26-C and the plugs 25-A to 25-C described with reference to FIGS. 7A to 7C, in order to suppress the intrusion of rain or the like into the second heat insulating layer 232 In addition, the openings 24-A to 24-C are directed, for example, in the direction of gravity. As a modification of this configuration, check valves may be provided inside the exhaust pipes 26-A to 26-C. This modification will be described.

  FIG. 8A is a cross-sectional view showing a first state in one configuration example of the exhaust pipe 26-B shown in FIG. 7B. FIG. 8B is a cross-sectional view showing a second state in one configuration example of the exhaust pipe 26-B shown in FIG. 7B. 8A and 8B show a first state in which the intrusion of wind and rain 57 from the atmospheric environment to the second heat insulation layer 232 is performed in the case where the check valve 27 is provided in the exhaust pipe 26-B shown in FIG. A second state in which air outflow 58 from the second heat insulating layer 232 to the vacuum environment is shown. A similar check valve 27 can be provided in the exhaust pipe 26-A shown in FIG. 7A and the exhaust pipe 26-C shown in FIG. 7C.

  The exhaust pipe 26 -B according to the configuration example shown in FIGS. 8A and 8B includes, for example, a check valve 27, a hinge 28, and a spring 29. The hinge 28 is provided on the inner wall of the exhaust pipe 26-B. The check valve 27 is provided so as to block or communicate the inside of the exhaust pipe 26 -B, and one end thereof is connected to the hinge 28. One end of the spring 29 is connected to the inner wall of the exhaust pipe 26 -B, and the other end is connected to the check valve 27.

  In the atmospheric state of the first state shown in FIG. 8A, the check valve 27 shuts off the exhaust pipe 26-B when wind and rain try to enter from the opening 24-B into the exhaust pipe 26-B. It is desirable to be placed in position.

  In the vacuum environment of the 2nd state shown to FIG. 8B, the non-return valve 27 is arrange | positioned in the position which releases the exhaust pipe 26-B so that the air which flows out from the 2nd heat insulation layer 232 outside may not be blocked. Is desirable.

  The arrangement of the check valve 27 may be realized by appropriately adjusting the force of the spring 29, or another control device may be used.

(Second Embodiment)
Here, the second embodiment will be described. Hereinafter, with reference to FIG. 9A and FIG. 9B, two types of configuration examples will be described as the heat insulating material 23 according to the present embodiment. These two types of configuration examples have common features. That is, as in the first embodiment shown in FIG. 6A, a closed cell PIF layer is used as the first heat insulation layer 231 and an open cell PIF layer is used as the second heat insulation layer 232. In other words, in each of these two types of configuration examples, the configuration of the protective layer 233 is different from the first embodiment shown in FIG. 6A.

  Therefore, among the effects obtained by the heat insulating material 23 according to the present embodiment, the portions related to the first heat insulating layer 231 and the second heat insulating layer 232 are the same as in the case of the first embodiment.

(Second embodiment, part 1)
FIG. 9A is an enlarged view of a part of FIG. 5A showing a configuration example of the heat insulating material 23 according to the second embodiment. More specifically, FIG. 9A is a modified example corresponding to FIG. 6A, and shows an enlarged region 31 surrounded by a broken line in the cross-sectional view shown in FIG. 5A.

  The heat insulating material 23 shown in FIG. 9A is obtained by replacing the closed cell PIF layer 233-A as the protective layer 233 with the coating film 233-B in the heat insulating material 23 according to the first embodiment shown in FIG. 6A. be equivalent to. Other components shown in FIG. 9A are the same as those in FIG. 6A. That is, the open cell type PIF layer 232-B and the closed cell type PIF layer 231-B shown in FIG. 9A are the same as the open cell type PIF layer 232-A and the closed cell type PIF layer 231-A shown in FIG. 6A, respectively. Corresponding to

  The coating film 233-B is obtained by applying a paint on the surface of the open-cell PIF layer 232-B, and evaporating and drying the solvent contained in the paint. The main component of the coating film 233-B is a base material contained in the paint.

The pigment 61 contained in the paint is distributed at a predetermined density inside the coating film 233-B. It is desirable that the pigment 61 has a reflection performance for sunlight, particularly in the visible light band. Specific examples of the pigment 61 having such characteristics include titanium oxide (TiO ₂ ). Titanium oxide is also used in general white paints and is relatively easy to obtain and handle.

(Second embodiment, part 2)
FIG. 9B is an enlarged view of a part of FIG. 5A showing another configuration example of the heat insulating material 23 according to the second embodiment. More specifically, FIG. 9B is a modified example corresponding to FIG. 9A and shows an enlarged region 31 surrounded by a broken line in the cross-sectional view shown in FIG. 5A.

  The heat insulating material 23 shown in FIG. 9B is equivalent to the protective layer 233 in which the coating film 233-B shown in FIG. 9A is replaced with F-OSR 233-C. Other components shown in FIG. 9B are the same as those in FIG. 9A. That is, the open cell type PIF layer 232-C and the closed cell type PIF layer 231-C shown in FIG. 9B are respectively the open cell type PIF layer 232-B and the closed cell type PIF layer 231-B shown in FIG. 9A. Corresponding to

  F-OSR233-C is a solar reflector having a low solar absorptance and a high total hemispherical infrared emissivity, and adheres to the surface of the open-cell PIF layer 232-C (for example, It is possible to wrap and adhere to the surface). Note that the surface shape of the open-cell PIF layer 232-C is desirably designed within a range suitable for the deformation characteristics of the F-OSR.

  As described above, in the heat insulating material 23 according to the present embodiment, the protective layer 233 has reflection performance. The reflection performance of the protective layer 233 provides an effect of thermally protecting the liquid fuel tank 122 from radiant heat generated by sunlight, particularly components in the visible light band, in outer space.

  In addition, both the coating film 233-B shown in FIG. 9A and the F-OSR 233-C shown in FIG. 9B can prevent intrusion of wind and rain into the open cell PIF layers 232-B and 233-C.

(Third embodiment)
Here, the third embodiment will be described. Hereinafter, with reference to FIG. 10A to FIG. 10D, four types of configuration examples will be described as the heat insulating material 23 according to the present embodiment. These four types of configuration examples have common features. That is, as in the first embodiment shown in FIG. 6A and the second embodiment shown in FIGS. 9A and 9B, the present embodiment uses a closed cell PIF layer as the first heat insulating layer 231. As the second heat insulating layer 232, in this embodiment, an open cell type PI foam layer is used instead of the open cell type PIF layer. Further, in each of these four types of configuration examples, the configuration of the protective layer 233 is different.

  Therefore, the part which concerns on the 1st heat insulation layer 231 among the effects acquired by the heat insulating material 23 by this embodiment is the same as that of the case of 1st Embodiment and 2nd Embodiment. Note that the open-cell PI foam layer used for the second heat insulating layer 232 of the present embodiment is formed of a PI foam obtained by foaming a PI material. Since the heat resistance performance of the PI foam is superior to that of PIF, the heat insulating material 23 according to the present embodiment is expected to have a heat resistance performance superior to that of the heat insulating material 23 according to the first embodiment or the second embodiment. Is done.

(Third embodiment, part 1)
FIG. 10A is an enlarged view of a part of FIG. 5A showing a configuration example of the heat insulating material 23 according to the third embodiment. More specifically, FIG. 10A is a modified example corresponding to FIG. 9A, and shows an enlarged region 31 surrounded by a broken line in the cross-sectional view shown in FIG. 5A.

  The heat insulating material 23 shown in FIG. 10A is equivalent to the second heat insulating layer 232 in which the open cell type PIF layer 232 -B shown in FIG. 9A is replaced with an open cell type PI foam layer 232 -D. The other components shown in FIG. 10A are the same as those in FIG. 9A. That is, the closed cell PIF layer 231-D, the coating film 233-D and the pigment 61 shown in FIG. 10A are the closed cell PIF layer 231-B, the coating film 233-B and the pigment 61 shown in FIG. 9A, respectively. Corresponding to

  The reflection performance of the coating film 233-D and the pigment 61 as the heat insulating material 23 according to the present embodiment and the operational effects brought about by this reflection performance are the same as in the case of FIG. 9A.

  On the other hand, as described above, the PI resin constituting the open-cell PI foam layer 232 -D has better heat resistance than the PIF resin. That is, the PI foam has a heat resistance of about 300 degrees Celsius or higher, while the PIF has a heat resistance of about 120 degrees Celsius or less. Here, it is considered that the temperature of the closed-cell PIF layer 231 -D heated by external heat input is kept at, for example, about 100 degrees Celsius or less. On the other hand, consider keeping the total weight of the multistage rocket 1 as small as possible. At this time, as an example, the thickness of the open-cell PI foam layer 232 -D is desirably 10 mm or more and 50 mm or less.

  In addition, the air inside the open-cell PI foam layer 232-D cooled by the liquid fuel tank 122 is desired to be kept in a gaseous state. On the other hand, it is desirable to keep the total weight of the multistage rocket 1 as small as possible. At this time, as an example, the thickness of the closed-cell PIF layer 231 -D is desirably 10 mm or more and 40 mm or less.

(Third embodiment, part 2)
FIG. 10B is an enlarged view of a part of FIG. 5A showing another configuration example of the heat insulating material 23 according to the third embodiment. More specifically, FIG. 10B is a modified example corresponding to FIG. 10A, and shows an enlarged region 31 surrounded by a broken line in the cross-sectional view shown in FIG. 5A.

  The heat insulating material 23 shown in FIG. 10B is equivalent to a protective layer 233 in which the coating film 233-D shown in FIG. 10A is replaced with a laminated structure of a reflective film 233-E and a radiation film 234-E. The other components shown in FIG. 10B are the same as in FIG. 10A. That is, the open cell type PI foam layer 232-E and the closed cell type PIF layer 231-E shown in FIG. 10B are the same as the open cell type PI foam layer 232-D and the closed cell type PIF shown in FIG. 10A, respectively. Corresponds to layer 231-D.

  The reflective film 233-E is a deposited layer formed by, for example, depositing a metal containing silver (Ag), gold (Au), or aluminum (Al) on the surface of the open-cell PI foam layer 232-E. . Here, the three kinds of metals are materials that can obtain a particularly high reflectance in the visible light band of sunlight, but the reflective film 233 -E according to the present embodiment is limited to a vapor deposition layer using these metals. It is not a thing.

  The radiation film 234-E is a film made of a transparent coating agent using a material such as silicone. Here, the silicone has a high total hemispherical infrared emissivity and a high vertical emissivity, and the radiation film 234 -E radiates the amount of heat input from the outside to the liquid fuel tank 122. The effect of reducing the total amount of heat to be heated is obtained. Furthermore, it is desirable that the transparent coating agent such as silicone has excellent transparency to visible light and does not hinder the reflective performance of the reflective film 233-E.

(Third embodiment, part 3)
FIG. 10C is an enlarged view of a part of FIG. 5A showing still another configuration example of the heat insulating material 23 according to the third embodiment. More specifically, FIG. 10C is a modified example corresponding to FIG. 10A and shows an enlarged region 31 surrounded by a broken line in the cross-sectional view shown in FIG. 5A.

  The heat insulating material 23 shown in FIG. 10C is on the surface of the open-cell PI foam layer 232 -D as the second heat insulating layer 232 as the protective layer 233 instead of the coating film 233 -D shown in FIG. 10A. This is equivalent to holding the pigment 61 using the PI skin film 233-F. Other configurations shown in FIG. 10C are the same as those in FIG. 10A. That is, the closed cell type PIF layer 231 -F and the open cell type PI foam layer 232 -F shown in FIG. 10C are the closed cell type PIF layer 231 -D and the open cell type PI foam shown in FIG. 10A, respectively. Corresponds to layer 232-D.

  As a method for producing a PI foam, a method using a mold is known. That is, a PI foam having a desired shape is obtained by preparing a mold having a desired shape and foaming the PI material inside the mold. At this time, on the surface of the PI foam that has been in contact with the inner wall of the mold, a film-like portion having an airtightness that has a lower expansion ratio than other portions or is not foamed is formed. Such a portion is called a PI skin film. The PI skin film can prevent wind and rain from entering the PI foam.

  In the present embodiment, the PI skin film 233-is formed on the outer surface of the open cell type PI foam layer 232 -F as the second heat insulating layer 232 as viewed from the liquid fuel tank 122 using the manufacturing method described above. F is formed. However, as a previous step, the pigment 61 is spread in advance on the surface of the inner wall of the formwork where the PI skin film 233-F is to be formed. In this state, when the PI material flows into the mold and the PI material is foamed to form the open-cell PI foam layer 232-F, the pigment 61 is taken into the PI skin film 233-F. , Adhere to its surface or disperse within it.

  As a result, the PI skin film 233-F encapsulating the pigment 61 is not limited to sunlight, particularly in the case of the coating film 233-B shown in FIG. 9A, the coating film 233-D shown in FIG. It functions as a protective film having reflection performance for the visible broadband.

(Third embodiment, part 4)
FIG. 10D is an enlarged view of a part of FIG. 5A showing still another configuration example of the heat insulating material 23 according to the third embodiment. More specifically, FIG. 10D is a modified example corresponding to FIG. 9B or FIG. 10A, and shows an enlarged region 31 surrounded by a broken line in the cross-sectional view shown in FIG. 5A.

  When attention is paid to the protective layer 233, the heat insulating material 23 shown in FIG. 10D is equivalent to a film obtained by replacing the coating film 233-D shown in FIG. 10A with F-OSR 233-G. The other components shown in FIG. 10D are the same as in FIG. 10A. That is, the open cell type PI foam layer 232-G and the closed cell type PIF layer 231-G shown in FIG. 10D are the same as the open cell type PI foam layer 232-D and the closed cell type PIF shown in FIG. 10A, respectively. Corresponds to layer 231-D.

  When attention is paid to the second heat insulating layer 232, the heat insulating material 23 shown in FIG. 10D is obtained by replacing the open cell type PIF layer 232-C shown in FIG. 9B with an open cell type PI foam layer 232-G. equal. Other components shown in FIG. 10D are the same as those in FIG. 9B. That is, the F-OSR 233-G and the closed cell type PIF layer 231-G shown in FIG. 10D correspond to the F-OSR 233-C and the closed cell type PIF layer 231-C shown in FIG. 9B, respectively.

  With respect to F-OSR233-G shown in FIG. 10D, its characteristics, obtained effects, precautions for formation, and the like are the same as in FIG. 9B.

(Fourth embodiment)
Here, the fourth embodiment will be described. Hereinafter, with reference to FIG. 11A and FIG. 11B, two types of configuration examples will be described as the heat insulating material 23 according to the present embodiment. These two types of configuration examples have common features. That is, as in the first to third embodiments shown in FIGS. 6A, 9A, 9B and 10A to 10D, the present embodiment also uses a closed cell PIF layer as the first heat insulating layer 231. Yes. On the other hand, unlike the first to third embodiments, the second heat insulating layer 232 is not an open-cell type PIF layer or an open-cell type PI foam layer, but is breathable. A fiber structure layer which is a structure layer is used. Further, in the two types of configuration examples according to the present embodiment, the configuration of the protective layer 233 is different.

  The fiber structure layer used in the present embodiment is composed of a fiber structure. The fiber structure desirably has high flame retardancy and high heat resistance and low thermal conductivity. Moreover, it is desirable that the fiber structure layer has air permeability that allows the contained air to escape in vacuum, like the open-cell PIF layer and open-cell PI foam.

  As an example, the fiber structure layer used in the present embodiment is configured by laminating a flame retardant sheet material made of needle-fired acrylic fire-resistant flame fibers or a three-dimensional woven fabric so as to have a hollow structure. I can do it. It is desirable that the flame retardant sheet material configured as described above has a high interlayer strength so that the laminated fibers are not separated from each other.

  As a specific example of such an acrylic fire-resistant fiber, there is a polyacrylonitrile-based flameproofing fiber which is a fiber obtained by firing and carbonizing a polyacrylonitrile precursor at about 300 to 500 degrees Celsius.

  Other alternative fibers include meta-aramid fiber, PTFE (PolyTetraFluoroethylene: polytetrafluoroethylene), PEEK (PolyEtherEtherKetone: polyetheretherketone), PPS (PolyPhenylene Sulfide: polyphenylene sulfide), and the like. All of these substitute fibers are organic fibers having high heat resistance and high flame retardancy.

  Moreover, it is desirable to provide a skin material on the surface of the fiber structure layer configured as described above. This skin material can be bonded with a resin binder or the like, and it is desirable that a protective layer 233 can be laminated on the surface thereof.

  The adhesive used in this embodiment (adhesive that bonds the skin material and the protective layer 233) desirably has high heat resistance. Specific examples of such an adhesive include thermosetting adhesives such as epoxy, epoxy / bismaleimide, and polyimide / silicone. These thermosetting adhesives can be applied up to a high temperature of about 350 degrees Celsius. In addition, there are also one-component curable epoxy and two-component curable epoxy. These adhesives can be applied up to a high temperature of about 200 degrees Celsius at the maximum.

(Fourth embodiment, configuration example 1)
FIG. 11A is an enlarged view of a part of FIG. 5A showing a configuration example of the heat insulating material 23 according to the fourth embodiment. More specifically, FIG. 11A is a modified example corresponding to FIG. 9A and shows an enlarged region 31 surrounded by a broken line in the cross-sectional view shown in FIG. 5A.

  The heat insulating material 23 shown in FIG. 11A is equivalent to the second heat insulating layer 232 in which the open-cell PIF layer 232-B shown in FIG. 9A is replaced with a flame retardant sheet 232-H as a fiber structure layer. . Other components shown in FIG. 11A are the same as those in FIG. 9A. That is, the closed cell PIF layer 231-H, the coating film 233-H, and the pigment 61 shown in FIG. 11A are the closed cell PIF layer 231-B, the coating film 233-B, and the pigment 61 shown in FIG. 9A, respectively. Corresponding to

  The reflection performance of the coating film 233-H and the pigment 61 as the heat insulating material 23 according to this configuration example, and the effect that brings about this reflection performance are the same as those in FIG. 9A.

(Fourth embodiment, configuration example 2)
FIG. 11B is an enlarged view of a part of FIG. 5A showing another configuration example of the heat insulating material 23 according to the fourth embodiment. More specifically, FIG. 11B is a modified example corresponding to FIG. 9B, and shows an enlarged region 31 surrounded by a broken line in the cross-sectional view shown in FIG. 5A.

  The heat insulating material 23 shown in FIG. 11B is equivalent to the second heat insulating layer 232 in which the open cell PIF layer 232 -B shown in FIG. 9B is replaced with a flame retardant sheet 232 -I as a fiber structure. Other components shown in FIG. 11B are the same as those in FIG. 9B. That is, the closed cell PIF layers 231 -I and F-OSR 233 -I shown in FIG. 11B correspond to the closed cell PIF layers 231 -C and F-OSR 233 -C shown in FIG. 9B, respectively.

  About the reflective performance which F-OSR233-I as the heat insulating material 23 by this structural example has, and the effect which this reflective performance brings, it is the same as that of the case of FIG. 9B.

  When the heat insulating material 23 according to the embodiment described above is applied to a rocket, a rocket having a heat insulating material having high heat resistance is provided in both an air environment on the ground and a vacuum environment in space. Is done.

  The invention made by the inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say. In addition, the features described in the embodiments can be freely combined within a technically consistent range.

DESCRIPTION OF SYMBOLS 1 Multistage rocket 11 First stage rocket 110 First stage rocket position 12 Second stage rocket 121 Second stage engine 122 Liquid fuel tank 123 Artificial satellite separation device 124 Artificial satellite 13 Fairing 130 Fairing position 21 Liquid fuel storage area 210 Liquid fuel storage area 22 Tank outer wall 220 Tank outer wall 23 Heat insulating material 230 Heat insulating material 230-A Open-cell PIF layer 230-B Thermal conductivity deteriorated area 230-C Thermal conductivity deteriorated area 231 First heat insulating layer 231-A Closed cell Type PIF layer 231 -B closed cell type PIF layer 231 -C closed cell type PIF layer 231 -D closed cell type PIF layer 231 -E closed cell type PIF layer 231 -F closed cell type PIF layer 231 -G closed cell type PIF Layer 231-H Closed cell type PIF layer 231-I Closed cell type PI Layer 232 Second heat insulation layer 232-A Open cell PIF layer 232-B Open cell PIF layer 232-C Open cell PIF layer 232-D Open cell PI foam layer 232-E Open cell PI foam layer 232-F Open-cell PI foam layer 232-G Open-cell PI foam layer 232-H Flame retardant sheet 232-I Flame retardant sheet 233 Protective layer 233-A Closed cell PIF layer 233-B Coating film 233 C F-OSR
233-D coating film 233-E reflective film 233-F PI skin film 233-G F-OSR
233-H coating film 233-I F-OSR
234-E Radiation membrane 24 Ventilation part 24-A Opening part 24-B Opening part 24-C Opening part 25 Sealing part 25-A Plug 25-B Plug 25-C Plug 26-A Exhaust pipe 26-B Exhaust pipe 26- C Exhaust pipe 27 Check valve 28 Hinge 29 Spring 30 Region 31 Region 32 Region 33 Region 41 Intrusion of moisture 42 Cooling action 51 Suppression of intrusion of wind and rain 52 Suppression of heat input 53 Suppression of cooling 54 Reflection of sunlight 55 Heat input Suppression 56 Radiation of heat 57 Suppression of wind and rain intrusion 58 Air outflow 61 Pigment

Claims (19)

A first heat insulating layer laminated on the surface of the thermal protection object;
A second heat insulating layer laminated on the surface of the first heat insulating layer;
A protective layer which is laminated on the surface of the second heat insulating layer and prevents water from entering,
The first heat insulating layer is
Comprising a first foam layer enclosing a plurality of independent cells independent of each other;
The second heat insulating layer is
Comprising a breathable structure layer;
At least a part of the breathable structure layer communicates with an external environment. The heat insulating material according to claim 1,
The breathable structure layer is a second foam layer having open cells. The heat insulating material according to claim 2,
The first foam layer is
Comprising a closed cell PIF (polyisocyanurate foam) layer;
The second foam layer is
A heat insulating material comprising an open cell PIF layer. The heat insulating material according to claim 2,
The first foam layer is
A closed cell PIF layer,
The second foam layer is
A heat insulating material comprising an open-cell type PI (polyimide) foam layer. The heat insulating material according to claim 1,
The first foam layer is
A closed cell PIF layer,
The breathable structure layer is
A heat insulating material comprising a fibrous structure layer. In the heat insulating material according to claim 3,
The protective layer is
A heat insulating material comprising a closed cell PIF layer. In the heat insulating material according to any one of claims 2 to 5,
The protective layer is
A heat insulating material comprising a coating film containing a white pigment having a reflective property to visible light. In the heat insulating material according to any one of claims 2 to 5,
The protective layer is
F-OSR (flexible optical solar reflector) with reflective performance for visible light
A heat insulating material comprising: In the heat insulating material according to claim 4,
The protective layer is
A reflective film that is laminated on the surface of the second heat-insulating layer and has a reflective performance with respect to visible light;
A heat insulating material comprising a radiation film laminated on the surface of the reflective film and having a transmission performance for visible light and a radiation performance related to the amount of heat. In the heat insulating material according to claim 9,
The reflective film is
A heat insulating material containing at least one of silver, gold, and aluminum. In the heat insulating material according to claim 4,
The protective layer is
A PI skin layer formed on the surface of the open-cell PI foam layer;
A heat insulating material comprising: a white pigment dispersed or adhered to the surface of the PI skin layer and having a reflective property with respect to visible light. In the heat insulating material according to claim 5,
The fiber structure layer is
A heat insulating material comprising at least one of calcined carbonized fiber, meta-aramid fiber, PTFE (polytetrafluoroethylene), PEEK (polyetheretherketone) or PPS (polyphenylene sulfide). In the heat insulating material according to any one of claims 1 to 12,
At least a part of the breathable structure layer and the external environment communicate with each other through an exhaust pipe. The heat insulating material according to claim 13,
The exhaust pipe is
A heat insulating material comprising a check valve capable of closing the exhaust pipe in an atmospheric environment. In the heat insulating material according to any one of claims 1 to 14,
A heat insulating material further comprising a water intrusion preventing member disposed on at least one end face of the second heat insulating layer. In the heat insulating material according to any one of claims 1 to 15,
The thickness of the first heat insulation layer is greater than 10 millimeters and less than 40 millimeters. In the heat insulating material according to any one of claims 1 to 16,
The thickness of the second heat insulation layer is greater than 10 millimeters and less than 50 millimeters. The liquid fuel tank which provided the heat insulating material as described in any one of Claims 1-17 in the outer surface of the outer wall. A rocket comprising the liquid fuel tank according to claim 18.

Images