Boom, movement control device, and method for manufacturing boom

Abstract

The present invention provides a boom that has a high strength and can appropriately be contained.　Provided is a boom comprising: a strip-shaped first elastic member and a strip-shaped second elastic member that are disposed so as to face each other and extend to be deformable from wound states into columnar states; and a first connection member and a second connection member that connect the first elastic member and the second elastic member. The first elastic member is curved in the columnar state so as to be away from the second elastic member, while the second elastic member is curved in the columnar state so as to be away from the first elastic member. The first connection member is fixed to one side end portion of the first elastic member and to one side end portion of the second elastic member, while the second connection member is fixed to another side end portion of the first elastic member and to another side end portion of the second elastic member, and the first connection member and the second connection member are deformable so as to maintain a state in which the first elastic member and the second elastic member are connected via the first connection member and the second connection member.

Description

Boom, Movement Control Device, and Method for Manufacturing Boom

[0001] The present invention relates to a boom that can be deformed from a wound state to an extended columnar state, a movement control device on which the boom is mounted, and a method for manufacturing the boom for manufacturing the boom.

[0002] In various fields such as aircraft, ships, spacecraft, and communication equipment, columnar members called booms are used. The boom is housed and stored in a state wound around a core material, and is drawn out from the core material and extended during use to deform into a columnar shape. Thus, a boom that can be maintained in a wound state and a columnar state is called a bistable boom.

[0003] For example, a spacecraft is equipped with a movement control device (orbit detachment device) for detaching the spacecraft from an orbital path. Also, as a type of movement control device, a deployment film method in which a deployment film on which air resistance acts is supported by a boom is known. The movement control device of the deployment film method extends the boom when the spacecraft detaches from its orbit to expand the deployment film. Thereby, air resistance acts on the deployment film to decelerate the spacecraft, and the spacecraft can be detached from the orbital path. Further, the boom may be used as a support for a solar panel or a solar sail, an antenna used for information communication on the ground or in outer space, or the like.

[0004] The boom is designed to be able to take a flat belt-like form when wound around a core material and to maintain a columnar shape when extended. For example, a bistable boom having a C-shaped cross-sectional shape in an extended state (see Patent Document 1) and a bistable boom configured by connecting a pair of members having a substantially Ω-shaped cross-sectional shape (see Patent Document 2) have been proposed.

[0005] Japanese Patent Application Laid-Open No. 2018-1601 U.S. Patent Application Publication No. 2020 / 0011057

[0006] When supporting large-area deployable membranes, solar panels, solar sails, etc., with a boom, or when using a boom as an antenna that can extend to long distances, it is desirable to use a boom that is strong and resistant to bending when extended. However, in order to accommodate a high-strength boom, it is necessary to press the boom with strong force to deform it into a flat strip before winding it onto a core material, and in this process, stress acts on the boom, making it prone to distortion.

[0007] When a boom becomes distorted, gaps form between adjacent parts of the boom when it is rolled up, increasing the volume of the rolled boom. This can make it difficult to fit a boom of the desired length into a specific storage space. Furthermore, if a distorted boom is stored in a rolled-up state for a long period of time, a phenomenon called creep is likely to occur, in which the boom's shape becomes fixed as a flat strip. When creep occurs, the boom becomes difficult to extend from its rolled-up state, and it becomes difficult for the extended columnar boom to return to its intended shape. Therefore, conventional booms have had limitations in balancing boom strength with proper storage.

[0008] This invention has been made in view of the above problems, and aims to provide a boom that is strong and can be appropriately housed, a spacecraft on which the boom is mounted, and a method for manufacturing the boom.

[0009] According to one aspect of the present invention, the present invention comprises a strip-shaped first elastic member and a second elastic member arranged facing each other and deformable from a rolled-up state to a columnar state by unfolding, and a first connecting member and a second connecting member connecting the first elastic member and the second elastic member, wherein the first elastic member has one side end and the other side end, and a central portion connected to the one side end and the other side end, and in the columnar state the central portion is curved so as to be further away from the second elastic member than the one side end and the other side end, and the second elastic member has one side end and the other side end, and a central portion connected to the one side end and the other side end, and is columnar A boom is provided in which, in the state, the central portion is curved so as to be further away from the first elastic member than the one side end and the other side end, the first connecting member is fixed to the one side end of the first elastic member and the one side end of the second elastic member, and the second connecting member is fixed to the other side end of the first elastic member and the other side end of the second elastic member, and the first connecting member and the second connecting member are deformable such that, in the state in which the first elastic member and the second elastic member are wound and in the columnar state, the state in which the first elastic member and the second elastic member are connected via the first connecting member and the second connecting member is maintained.

[0010] Furthermore, when the first elastic member is in a columnar state, the distance between one side end and the other side end of the first elastic member may be smaller than the column width of the first elastic member, and when the second elastic member is in a columnar state, the distance between one side end and the other side end of the second elastic member may be smaller than the column width of the second elastic member. In addition, the first elastic member and the second elastic member may be curved in an arc shape when in a columnar state such that the central angle is greater than 180° and less than 360°.

[0011] Furthermore, the thickness of one side end and the other side end of the first elastic member may be less than the thickness of the central portion of the first elastic member, and the thickness of one side end and the other side end of the second elastic member may be less than the thickness of the central portion of the second elastic member. Also, the thickness of the first elastic member and the thickness of the second elastic member may be different.

[0012] Furthermore, the first elastic member and the second elastic member may be made of a carbon fiber composite material. The carbon fiber composite material may include carbon fibers and a resin for fixing the carbon fibers, and the first elastic member and the second elastic member and the first connecting member and the second connecting member may be fixed together by the resin. Furthermore, the first elastic member and the second elastic member and the first connecting member and the second connecting member may be fixed together via a film adhesive. Furthermore, the first connecting member and the second connecting member may be made of fiber, nonwoven fabric, or film.

[0013] Furthermore, according to another aspect of the present invention, a movement control device for controlling the movement of a spacecraft is provided, comprising: a deployable membrane that is deployed so as to act upon atmospheric resistance; and the boom that supports the deployable membrane.

[0014] Furthermore, according to another aspect of the present invention, a method for manufacturing a boom is provided, comprising: preparing a mold having a first molded part and a second molded part that are columnar with curved surfaces, with a first recess and a second recess formed at the connection between the first molded part and the second molded part; arranging the first elastic member along the surface of the first molded part; arranging the second elastic member along the surface of the second molded part; arranging the first connecting member in the first recess so as to be in contact with the first elastic member and the second elastic member; arranging the second connecting member in the second recess so as to be in contact with the first elastic member and the second elastic member; integrating the first elastic member, the second elastic member, the first connecting member and the second connecting member; and removing the mold from the inside of the first elastic member and the second elastic member while a gap is secured between the first recess and the second recess and the first elastic member and the second elastic member.

[0015] In a boom according to one aspect of the present invention, a first elastic member and a second elastic member are connected via a first connecting member and a second connecting member. The first connecting member and the second elastic member deform in a way that maintains the connection between the first elastic member and the second elastic member, whether the first elastic member and the second elastic member are rolled up or in a columnar state. By adopting such a configuration, even when a high-strength boom is folded, distortion of the boom is less likely to occur, and the boom can be properly stored.

[0016] Figure 1(A) is a perspective view showing the boom in a columnar state, and Figure 1(B) is a perspective view showing the boom being wound around a core material. Figure 2(A) is a cross-sectional view showing the boom in a columnar state, and Figure 2(B) is a cross-sectional view showing the boom in a folded state. This is a front view showing the boom unfolding from a wound state and deforming into a columnar state. This is a flowchart showing the method of manufacturing the boom. Figure 5(A) is a perspective view showing the mold used in the manufacture of the boom, Figure 5(B) is a perspective view showing the first elastic member, second elastic member, first connecting member, second elastic member and mold in the placement step, and Figure 5(C) is a perspective view showing the boom and mold in the extraction step. This is a cross-sectional view showing the boom and mold in the extraction step. This is a cross-sectional view showing the boom according to the first modified example. This is a cross-sectional view showing the boom according to the second modified example. This is a perspective view showing a spacecraft. Figure 10(A) is a front view showing the movement control device with the deployed membrane housed inside, and Figure 10(B) is a front view showing the movement control device with the deployed membrane deployed. Figure 11(A) is a perspective view showing the boom according to Comparative Example 1, and Figure 11(B) is a perspective view showing the boom according to Comparative Example 2. The graph shows the bending strength of the booms according to Comparative Examples 1 and 2 and Examples 1 to 3.

[0017] Embodiments of the present invention will be described below with reference to the attached drawings. First, an example of the configuration of a boom according to this embodiment will be described. The boom according to this embodiment is a bistable boom that can maintain both a columnar state and a coiled state.

[0018] Figure 1(A) is a perspective view showing the boom 2 in a columnar state. The boom 2 comprises a strip-shaped first elastic member 4 and a second elastic member 6 having predetermined lengths and widths. The first elastic member 4 and the second elastic member 6 are plate-shaped members that can be elastically deformed and are arranged to face each other in a curved state.

[0019] The first elastic member 4 has a first surface (front surface) 4a that constitutes the outer circumferential surface of the first elastic member 4, and a second surface (back surface) 4b that constitutes the inner circumferential surface of the first elastic member 4. The first elastic member 4 also has one side end 4c and the other side end 4d, and a central portion 4e connected to the side ends 4c and 4d. The side ends 4c and 4d correspond to both ends in a cross-section perpendicular to the length direction of the first elastic member 4. The central portion 4e corresponds to the area of ​​the first elastic member 4 other than the side ends 4c and 4d.

[0020] The second elastic member 6 has a first surface (front surface) 6a that constitutes the outer circumferential surface of the second elastic member 6, and a second surface (back surface) 6b that constitutes the inner circumferential surface of the second elastic member 6. The second elastic member 6 also has one side end 6c and the other side end 6d, and a central portion 6e connected to the side ends 6c and 6d. The side ends 6c and 6d correspond to both ends in a cross-section perpendicular to the length direction of the second elastic member 6. The central portion 6e corresponds to the area of ​​the second elastic member 6 other than the side ends 6c and 6d.

[0021] The first elastic member 4 and the second elastic member 6 are curved in opposite directions and are formed into columnar shapes with a predetermined curvature. Specifically, the first elastic member 4 is curved on the opposite side of the second elastic member 6 such that, in its columnar state, its central portion 4e is further away from the second elastic member 6 than its side ends 4c and 4d. On the other hand, the second elastic member 6 is curved on the opposite side of the first elastic member 4 such that, in its columnar state, its central portion 6e is further away from the first elastic member 4 than its side ends 6c and 6d. For example, the first elastic member 4 and the second elastic member 6 are curved in an arc shape (circular arc, elliptical arc, etc.), and the radii of curvature of the first elastic member 4 and the second elastic member 6 are approximately equal.

[0022] The materials of the first elastic member 4 and the second elastic member 6 are selected so that the first elastic member 4 and the second elastic member 6 can be elastically deformed and so that the first elastic member 4 and the second elastic member 6 can be maintained in a columnar state. For example, the first elastic member 4 and the second elastic member 6 are made of carbon fiber reinforced plastics (CFRP).

[0023] The carbon fiber composite material includes carbon fibers and a resin (plastic) that functions as a matrix for fixing the carbon fibers. The resin included in the carbon fiber composite material can be a thermosetting resin such as epoxy resin. However, the resin included in the carbon fiber composite material may also be a thermoplastic resin. Furthermore, part or all of the first elastic member 4 and the second elastic member 6 can be formed from a metal material or the like.

[0024] The dimensions of the first elastic member 4 and the second elastic member 6 are set appropriately according to the application of the boom 2. For example, when the boom 2 is used as a support for a deployable membrane mounted on a spacecraft as described later (see Figures 9 and 10(B)), the lengths of the first elastic member 4 and the second elastic member 6 can be set to 5 m or more and 20 m or less, and the thickness of the first elastic member 4 and the second elastic member 6 can be set to 0.1 mm or more and 0.5 mm or less. Also, when the first elastic member 4 and the second elastic member 6 are formed in an arc shape, the radius of curvature of the first elastic member 4 and the second elastic member 6 can be set to 30 mm or more and 300 mm or less. However, the dimensions of the first elastic member 4 and the second elastic member 6 can be changed according to the specifications of the spacecraft.

[0025] Furthermore, the boom 2 includes a first connecting member 8 and a second connecting member 10 that connect the first elastic member 4 and the second elastic member 6. The first connecting member 8 and the second connecting member 10 are flexible and deformable strip-shaped members made of fibers, nonwoven fabrics, films, etc. For example, aramid fibers, polyamide fibers, polyethylene nonwoven fabrics, resin films (polyethylene terephthalate film, polyimide film, etc.) can be used as the first connecting member 8 and the second connecting member 10. The thickness of the first connecting member 8 and the second connecting member 10 can be set to be less than the thickness of the first elastic member 4 and the second elastic member 6, for example, 0.1 mm or less.

[0026] The first connecting member 8 is fixed to the side end 4c of the first elastic member 4 and the side end 6c of the second elastic member 6. Specifically, the first connecting member 8 is bonded to the first surface 4a side (outer peripheral surface side) of the side end 4c of the first elastic member 4 and the first surface 6a side (outer peripheral surface side) of the side end 6c of the second elastic member 6 along the longitudinal direction of the first elastic member 4 and the second elastic member 6. As a result, the side end 4c of the first elastic member 4 and the side end 6c of the second elastic member 6 are connected via the first connecting member 8.

[0027] The second connecting member 10 is fixed to the side end 4d of the first elastic member 4 and the side end 6d of the second elastic member 6. Specifically, the second connecting member 10 is bonded to the first surface 4a side (outer peripheral surface side) of the side end 4d of the first elastic member 4 and the first surface 6a side (outer peripheral surface side) of the side end 6d of the second elastic member 6 along the longitudinal direction of the first elastic member 4 and the second elastic member 6. As a result, the side end 4d of the first elastic member 4 and the side end 6d of the second elastic member 6 are connected via the second connecting member 10.

[0028] The lengths of the first connecting member 8 and the second connecting member 10 are approximately equal to the lengths of the first elastic member 4 and the second elastic member 6. The first connecting member 8 and the second connecting member 10 are fixed to the region from one end to the other in the longitudinal direction of the first elastic member 4 and the second elastic member 6. The widths of the first connecting member 8 and the second connecting member 10 can be freely set within a range that allows the first connecting member 8 and the second connecting member 10 to be connected.

[0029] However, the first connecting member 8 and the second connecting member 10 may be fixed to the second surface 4b side (inner circumferential surface side) of the first elastic member 4 and the second surface 6b side (inner circumferential surface side) of the second elastic member 6. Also, the first connecting member 8 and the second connecting member 10 do not necessarily have to be fixed to the entire area of ​​the side ends 4c, 4d of the first elastic member 4 and the side ends 6c, 6d of the second elastic member 6. For example, multiple first connecting members 8 may be fixed at predetermined intervals along the side ends 4c, 6c, or multiple second connecting members 10 may be fixed at predetermined intervals along the side ends 4d, 6d.

[0030] There are no restrictions on the method of fixing the first connecting member 8 and the second connecting member 10 to the first elastic member 4 and the second elastic member 6. For example, if the first elastic member 4 and the second elastic member 6 contain a material that functions as a bonding agent, the first elastic member 4 and the second elastic member 6 can be directly joined to the first connecting member 8 and the second connecting member 10.

[0031] Specifically, if the first elastic member 4 and the second elastic member 6 are made of a carbon fiber composite material, and the carbon fiber composite material includes a thermosetting resin such as epoxy resin as a matrix, the thermosetting resin can also function as a bonding agent. In this case, by heating the thermosetting resin while the first connecting member 8 and the second connecting member 10 are in contact with the first elastic member 4 and the second elastic member 6, the first elastic member 4 and the second elastic member 6 and the first connecting member 8 and the second connecting member 10 are bonded together by the thermosetting resin.

[0032] Furthermore, if the carbon fiber composite material includes a thermoplastic resin, the thermoplastic resin may be used as a bonding agent. In this case, the first connecting member 8 and the second connecting member 10 are brought into contact with the first elastic member 4 and the second elastic member 6, and the thermoplastic resin is cooled and solidified, thereby bonding the first elastic member 4 and the second elastic member 6 to the first connecting member 8 and the second connecting member 10 by the thermoplastic resin.

[0033] However, for fixing the first connecting member 8 and the second connecting member 10, an adhesive prepared separately from the first elastic member 4 and the second elastic member 6 may also be used. In this case, the first elastic member 4 and the second elastic member 6 and the first connecting member 8 and the second connecting member 10 are bonded together via the adhesive. As the adhesive, it is preferable to use a film adhesive with a thickness of 0.1 mm or less. By using a film adhesive, it is possible to suppress the increase in the thickness of the boom 2 due to the use of adhesive.

[0034] Figure 1(B) is a perspective view showing the boom 2 wound around a core material (reel) 12. The boom 2 is stored wound around the cylindrical core material 12. Specifically, the base ends of the first elastic member 4 and the second elastic member 6 in the longitudinal direction are fixed to the core material 12. The first elastic member 4 and the second elastic member 6 are then pressed together in a direction that brings them closer to each other, and the first elastic member 4 and the second elastic member 6 are elastically deformed into a substantially flat shape and overlapped. As a result, the boom 2 is folded.

[0035] At this time, the first connecting member 8 and the second connecting member 10 are deformed and folded so as to curve outward in the width direction of the first connecting member 8 and the second connecting member 10. As a result, the first connecting member 8 and the second connecting member 10 function as hinges, and the connection between the first elastic member 4 and the second elastic member 6 is maintained by the first connecting member 8 and the second connecting member 10.

[0036] When the core material 12 is rotated with the boom 2 folded, the first elastic member 4 and the second elastic member 6 are in contact with each other and are wound onto the core material 12 together with the first connecting member 8 and the second connecting member 10. As a result, the boom 2 is wound onto the core material 12, making it possible to store the boom 2 in a reduced size.

[0037] Figure 2(A) is a cross-sectional view showing the boom 2 in a columnar state. When the boom 2 is in a columnar state, the first elastic member 4 and the second elastic member 6 are curved in opposite directions to form a cylindrical boom 2. At this time, the side end 4c of the first elastic member 4 and the side end 6c of the second elastic member 6 do not come into contact with each other, and a gap is maintained between the side end 4c and the side end 6c. Similarly, the side end 4d of the first elastic member 4 and the side end 6d of the second elastic member 6 do not come into contact with each other, and a gap is maintained between the side end 4d and the side end 6d. Distance d between side end 4c and side end 6c １ , and the distance d between the side end 4d and the side end 6d ２ For example, it can be set to between 0.5 mm and 3 mm.

[0038] Further, in order to increase the strength of the boom 2 in the columnar state, it is preferable that each of the first elastic member 4 and the second elastic member 6 approaches a cylindrical shape within the range allowed by the specifications of the boom 2. Specifically, when the first elastic member 4 is in the columnar state, the distance d ｅ between the side end portions 4c and 4d of the first elastic member 4 is smaller than the column width Wc corresponding to the maximum value of the width in the direction perpendicular to the length direction of the first elastic member 4. For example, the distance d ｅ is set to 95% or less, preferably 90% or less, more preferably 85% or less of the column width Wc.

[0039] In particular, when the first elastic member 4 is curved in an arc shape, the central angle θ of the first elastic member 4 is larger than 180° and smaller than 360°. For example, the central angle θ of the first elastic member 4 is preferably set to 220° or more, more preferably 240° or more.

[0040] The second elastic member 6 can also be designed in the same manner as the first elastic member 4. That is, when the second elastic member 6 is in the columnar state, the distance between the side end portions 6c and 6d of the second elastic member 6 is smaller than the column width of the second elastic member 6. In particular, when the second elastic member 6 is curved in an arc shape, the central angle θ of the second elastic member 6 is larger than 180° and smaller than 360°. For example, the central angle of the second elastic member 6 is preferably set to 220° or more, preferably 240° or more.

[0041] FIG. 2(B) is a cross-sectional view showing the boom 2 in the folded state. When the boom 2 is wound around the core material 12 (see FIG. 1(B)), an external force is applied to the first elastic member 4 and the second elastic member 6, and the first elastic member 4 and the second elastic member 6 elastically deform into a flat plate shape so that the second surface 4b of the first elastic member 4 and the second surface 6b of the second elastic member 6 come into contact. As a result, the side end portion 4c of the first elastic member 4 and the side end portion 6c of the second elastic member 6 come into contact, the side end portion 4d of the first elastic member 4 and the side end portion 6d of the second elastic member 6 come into contact, and the central portion 4e of the first elastic member 4 and the central portion 6e of the second elastic member 6 come into contact. In this way, the boom 2 is in the folded state.

[0042] Further, when the boom 2 is folded, the first connecting member 8 and the second connecting member 10 also deform along with the elastic deformation of the first elastic member 4 and the second elastic member 6. As a result, the first connecting member 8 and the second connecting member 10 are folded so as to curve outward in the width direction of the first elastic member 4 and the second elastic member 6, respectively.

[0043] When the first connecting member 8 and the second connecting member 10 are folded, the side end portion 4c of the first elastic member 4 and the side end portion 6c of the second elastic member 6 are covered by the first connecting member 8, and the side end portion 4d of the first elastic member 4 and the side end portion 6d of the second elastic member 6 are covered by the second connecting member 10. As a result, at one end of the boom 2 (the left end in FIG. 2(B)), the side end portion 4c of the first elastic member 4, the side end portion 6c of the second elastic member 6, the upper and lower end portions of the first connecting member 8 overlap. Also, at the other end of the boom 2 (the right end in FIG. 2(B)), the side end portion 4d of the first elastic member 4, the side end portion 6d of the second elastic member 6, the upper and lower end portions of the second connecting member 10 overlap.

[0044] As described above, the first connecting member 8 and the second connecting member 10 are formed of flexible members. Therefore, even if the first connecting member 8 and the second connecting member 10 deform along with the elastic deformation of the first elastic member 4 and the second elastic member 6, the first connecting member 8 and the second connecting member 10 will not be damaged, and the connection between the first elastic member 4 and the second elastic member 6 is maintained.

[0045] The boom 2 is wound around the core member 12 (see FIG. 1(B)) in the folded state as described above. Ideally, the first elastic member 4 and the second elastic member 6 deform such that the entire second surface 4b and the entire second surface 6b come into contact. However, depending on the material and shape of the first elastic member 4 and the second elastic member 6, a slight gap may occur between the first elastic member 4 and the second elastic member 6. After the entire boom 2 is wound around the core member 12 (see FIG. 1(B)), the tip of the core member 12 is pressed against the core member 12 by a pressing member such as a roller and fixed. Thereby, a roll around which the boom 2 is wound is obtained. Thereafter, the boom 2 is stored in a state of being wound around the core member 12 until use.

[0046] As described above, in the columnar state (see Figure 2(A)), the boom 2 according to this embodiment forms a closed loop with the first elastic member 4 and the second elastic member 6, and the first connecting member 8 and the second connecting member 10. In this respect, booms configured in an open loop (such as booms with a C-shaped cross-section) tend to be particularly weak against bending and twisting in the open direction. In contrast, since boom 2 is configured in a closed loop, it has a certain level of resistance to bending in all directions and also has high resistance to twisting. This makes a boom 2 with high strength a reality.

[0047] Furthermore, in the boom 2 according to this embodiment, the first elastic member 4 and the second elastic member 6 are not directly fixed to each other, but are connected via flexible first connecting member 8 and second connecting member 10. Therefore, when folding the boom 2 (see Figure 2(B)), the side ends 4c, 4d of the first elastic member 4 and the side ends 6c, 6d of the second elastic member 6 can be displaced independently to some extent, improving the degree of freedom of deformation of the first elastic member 4 and the second elastic member 6. This makes it easier to stack the first elastic member 4 and the second elastic member 6 in a state where they have been elastically deformed into a flat plate shape. As a result, the boom 2 can be efficiently rolled up and stored, and the overall thickness of the rolled boom 2 can be reduced.

[0048] Furthermore, if the first elastic member 4 and the second elastic member 6 have a high degree of freedom of deformation, even if the first elastic member 4 and the second elastic member 6 are deformed into a flat plate shape, high stress concentration is less likely to occur in the first elastic member 4 and the second elastic member 6. Therefore, even if the boom 2 is stored for a long period of time in a rolled-up state, the phenomenon of the boom 2 becoming fixed in a folded state (creep phenomenon) is less likely to occur. As a result, when the boom 2 is extended from its rolled-up state, the first elastic member 4 and the second elastic member 6 are more likely to return to their original shape.

[0049] Figure 3 is a front view showing the boom 2 as it extends from a coiled state to a columnar state. When using the boom 2, the core material 12 is set to a rotatable state with the tip of the boom 2 guided to face a predetermined direction, and the fixing of the tip of the boom 2 by the pressing member is released. Then, the restoring force of the first elastic member 4 and the second elastic member 6 acts on the tip of the boom 2, causing the tip of the boom 2 to expand into a cylindrical shape. In addition, the expansion of the boom 2 puts pressure on the core material 12, causing the core material 12 to rotate in the direction that extends the boom 2. As a result, the boom 2 extends in the predetermined direction while expanding sequentially from the tip side to the base side.

[0050] As described above, the boom 2 is subjected to a self-extending force that causes it to spontaneously extend due to the restoring force of the first elastic member 4 and the second elastic member 6. This allows the boom 2 to extend without the need to apply rotational power to the core material 12 or to perform any processes to promote the extension of the boom 2 (such as supplying gas to the inside of the boom 2 or heating the boom 2). Furthermore, as mentioned above, the boom 2 is less susceptible to creep and the high restoring force of the first elastic member 4 and the second elastic member 6 is maintained, so the boom 2 has a high self-extending force.

[0051] However, the core material 12 may be connected to a rotational drive source 14, such as a motor, which controls the rotation of the core material 12. For example, if the self-extension force of the boom 2 is insufficient and the boom 2 may not extend smoothly, the extension of the boom 2 may be assisted by applying rotational power from the rotational drive source 14 to the core material 12 in the direction of extending the boom 2. On the other hand, if the self-extension force of the boom 2 is high and the extension speed of the boom 2 is too fast, the extension speed of the boom 2 may be reduced by adjusting the rotational speed of the core material 12 with the rotational drive source 14.

[0052] Next, an example of a boom manufacturing method for producing the boom 2 described above will be explained. Figure 4 is a flowchart of the boom manufacturing method. In this embodiment, the boom 2 is manufactured by integrating the first elastic member 4, the second elastic member 6, the first connecting member 8, and the second connecting member 10 using a columnar mold, and then removing the mold from the boom 2.

[0053] Specifically, first, a mold for forming boom 2 is prepared (preparation step S1). Figure 5(A) is a perspective view showing the mold 20 used in the manufacture of boom 2.

[0054] The mold 20 is made of a heat-resistant metal or the like and has a columnar first molding section 22 and a second molding section 24. The first molding section 22 is formed in a shape corresponding to the columnar first elastic member 4 and has a curved surface 22a. The second molding section 24 is formed in a shape corresponding to the columnar second elastic member 6 and has a curved surface 24a. The first molding section 22 and the second molding section 24 may be made of the same material, or they may be formed separately and then joined together.

[0055] When manufacturing the boom 2 as shown in Figure 2(A), the surface 22a of the first molding section 22 is formed in an arc shape with a curvature approximately equal to that of the first elastic member 4, and the surface 24a of the second molding section 24 is formed in an arc shape with a curvature approximately equal to that of the second elastic member 6. The central angles of the first molding section 22 and the second molding section 24 are set according to the central angles θ of the first elastic member 4 and the second elastic member 6 (see Figure 2(A)), and are greater than 180° and less than 360°. At the connection between the first molding section 22 and the second molding section 24, a first recess 26 and a second recess 28 are formed linearly along the length of the mold 20.

[0056] In preparation step S1, the mold 20 described above is prepared. However, the shape, dimensions, etc. of the mold 20 can be appropriately set according to the boom 2 to be manufactured. The manufacturer of the boom 2 may form the mold 20 themselves, or they may obtain a mold 20 formed by another party.

[0057] Next, the first elastic member 4, the second elastic member 6, the first connecting member 8, and the second connecting member 10 are arranged along the mold 20 (arrangement step S2). Figure 5(B) is a perspective view showing the first elastic member 4, the second elastic member 6, the first connecting member 8, the second connecting member 10, and the mold 20 in arrangement step S2.

[0058] In the placement step S2, first, the first elastic member 4 is placed along the surface 22a of the first molding section, and the second elastic member 6 is placed along the surface 24a of the second molding section 24. Specifically, the first elastic member 4 is placed while curving so that the entire second surface 4b of the first elastic member 4 is in contact with the surface 22a of the first molding section 22. Similarly, the second elastic member 6 is placed while curving so that the entire second surface 6b of the second elastic member 6 is in contact with the surface 24a of the second molding section 24. This fixes the shapes of the first elastic member 4 and the second elastic member 6 to the shape corresponding to the boom 2 to be manufactured (see Figure 2(A)).

[0059] When the first elastic member 4 and the second elastic member 6 are arranged as described above, the side end 4c of the first elastic member 4 and the side end 6c of the second elastic member 6 fit into the first recess 26, and the side end 4d of the first elastic member 4 and the side end 6d of the second elastic member 6 fit into the second recess 28. However, the side end 4c of the first elastic member 4 and the side end 6c of the second elastic member 6 do not come into contact with each other, and the side end 4d of the first elastic member 4 and the side end 6d of the second elastic member 6 do not come into contact with each other.

[0060] Next, the first connecting member 8 is placed in the first recess 26, and the second connecting member 10 is placed in the second recess 28. Specifically, the first connecting member 8 is positioned along the first recess 26 so as to contact the side end 4c of the first elastic member 4 and the side end 6c of the second elastic member 6. The second connecting member 10 is positioned along the second recess 28 so as to contact the side end 4d of the first elastic member 4 and the side end 6d of the second elastic member 6. At this time, the first connecting member 8 and the second connecting member 10 deform along the mold 20 so as to fit into the first recess 26 and the second recess 28, respectively.

[0061] Next, the first elastic member 4, the second elastic member 6, the first connecting member 8, and the second connecting member 10 are integrated (integration step S3). In integration step S3, the first connecting member 8 and the second connecting member 10 are fixed to the first elastic member 4 and the second elastic member 6, respectively. As a result, the first elastic member 4 and the second elastic member 6 are connected via the first connecting member 8 and the second connecting member 10, and the first elastic member 4, the second elastic member 6, the first connecting member 8, and the second connecting member 10 are integrated. As a result, a hollow cylindrical boom 2 is obtained.

[0062] As mentioned above, when the first elastic member 4 and the second elastic member 6 are made of carbon fiber composite material, the resin contained in the carbon fiber composite material can bond the first connecting member 8 and the second connecting member 10 to the first elastic member 4 and the second elastic member 6. For example, if the carbon fiber composite material contains a thermosetting resin, the first elastic member 4 and the second elastic member 6 are subjected to heat treatment while the first connecting member 8 and the second connecting member 10 are in contact with the first elastic member 4 and the second elastic member 6.

[0063] When the first elastic member 4 and the second elastic member 6 are heated, the thermosetting resin contained in the carbon fiber composite material hardens, and the first elastic member 4 and the second elastic member 6 are molded into a curved shape. In addition, the thermosetting resin contained in the side ends 4c, 4d of the first elastic member 4 and the side ends 6c, 6d of the second elastic member 6 hardens, and the first elastic member 4 and the second elastic member 6 are bonded to the first connecting member 8 and the second connecting member 10 by the thermosetting resin. As a result, the first elastic member 4, the second elastic member 6, the first connecting member 8 and the second connecting member 10 are integrated, and the boom 2 is formed.

[0064] However, the method for integrating the first elastic member 4 and the second elastic member 6 with the first connecting member 8 and the second connecting member 10 is not limited to the above. For example, as mentioned above, the first elastic member 4 and the second elastic member 6 with the first connecting member 8 and the second connecting member 10 may be bonded together by a thermoplastic resin contained in the carbon fiber composite material, or by an adhesive such as a film adhesive.

[0065] When using an adhesive, the first connecting member 8 and the second connecting member 10 are placed on the first elastic member 4 and the second elastic member 6 via the adhesive (placement step S2), thereby integrating the first elastic member 4 and the second elastic member 6 with the first connecting member 8 and the second connecting member 10 by the adhesive (integration step S3). In other words, the placement step S2 and the integration step S3 are performed in the same process.

[0066] Alternatively, in the placement step S2, the first connecting member 8 and the second connecting member 10 may be placed along the first recess 26 and the second recess 28, respectively, before the first elastic member 4 and the second elastic member 6 are placed. In this case, the first elastic member 4 is placed along the surface 22a of the first molded portion so as to contact the first connecting member 8 and the second connecting member 10. The second elastic member 6 is placed along the surface 24a of the second molded portion 24 so as to contact the first connecting member 8 and the second connecting member 10. As a result, the first connecting member 8 and the second connecting member 10 are fixed to the second surface 4b side of the first elastic member 4 and the second surface 6b side of the second elastic member 6.

[0067] Next, the mold 20 is removed from the inside of the first elastic member 4 and the second elastic member 6 (removal step S4). Figure 5(C) is a perspective view showing the boom 2 and the mold 20 in removal step S4.

[0068] In the removal step S4, the mold 20 is pushed out or pulled out from the inside of the first elastic member 4 and the second elastic member 6 while the first elastic member 4 and the second elastic member 6 are fixed. This yields a hollow, columnar boom 2. However, if the first elastic member 4 and the second elastic member 6 are in close contact with the mold 20, the friction acting between the first elastic member 4 and the second elastic member 6 and the mold 20 will hinder the removal of the mold 20. Therefore, when removing the mold 20, it is preferable to create a gap between the first elastic member 4 and the second elastic member 6 and the mold 20.

[0069] Figure 6 is a cross-sectional view showing the boom 2 and mold 20 in the extraction step S4. For example, in the extraction step S4, before the mold 20 is extracted from the boom 2, the side ends 4c, 4d of the first elastic member 4 and the side ends 6c, 6d of the second elastic member 6 are moved away from the mold 20. As a result, the first elastic member 4 and the second elastic member 6 are deformed into a substantially circular or substantially elliptical shape as a whole. Consequently, a gap 30 is formed between the side ends 4c of the first elastic member 4 and the side ends 6c of the second elastic member 6 and the first recess 26, and a gap 32 is formed between the side ends 4d of the first elastic member 4 and the side ends 6d of the second elastic member 6 and the second recess 28.

[0070] When gaps 30 and 32 are formed, the contact area between the first elastic member 4 and the second elastic member 6 and the mold 20 decreases, and the frictional force acting between them is reduced. Then, by removing the mold 20 from the inside of the first elastic member 4 and the second elastic member 6 while gaps 30 and 32 are maintained, the mold 20 can be removed smoothly.

[0071] There are no restrictions on the method of forming the gaps 30 and 32. For example, the gaps 30 and 32 can be formed and expanded by pulling the side ends 4c and 4d of the first elastic member 4 and the side ends 6c and 6d of the second elastic member 6 away from the mold 20. Alternatively, the gaps 30 and 32 can be formed and expanded by supplying a gas such as air into the small gaps between the first connecting member 8 and the first recess 26, and between the second connecting member 10 and the second recess 28, thereby pushing the side ends 4c and 4d of the first elastic member 4 and the side ends 6c and 6d of the second elastic member 6 away from the mold 20 by air pressure.

[0072] As described above, the boom 2 according to this embodiment has a structure in which the first elastic member 4 and the second elastic member 6 are connected via deformable first connecting member 8 and second connecting member 10. This makes it possible to ensure the strength of the boom 2 in its columnar state while also allowing the boom 2 to be efficiently wound up and stored in a state where it can be easily extended.

[0073] In the above description, a boom 2 composed of a first elastic member 4 and a second elastic member 6 having uniform thickness was described. However, the configuration of the boom according to this embodiment is not limited to the above. For example, the first elastic member and the second elastic member constituting the boom may each have regions with partially different thicknesses. Also, the thicknesses of the first elastic member and the second elastic member may be different from each other.

[0074] Figure 7 is a cross-sectional view showing boom 2A, which corresponds to a first modified example of boom 2. Boom 2A comprises a first elastic member 90 and a second elastic member 100, and a first connecting member 8 and a second connecting member 10 that connect the first elastic member 90 and the second elastic member 100.

[0075] The first elastic member 90 and the second elastic member 100 are plate-shaped members that can be elastically deformed and are arranged to face each other in a curved state. The overall shapes of the first elastic member 90 and the second elastic member 100 are the same as those of the first elastic member 4 and the second elastic member 6 of the boom 2 (see Figure 2(A)). The first elastic member 90 has one side end 90a and the other side end 90b, and a central part 90c connected to the side ends 90a and 90b. The second elastic member 100 has one side end 100a and the other side end 100b, and a central part 100c connected to the side ends 100a and 100b.

[0076] The first elastic member 90 and the second elastic member 100 are curved in opposite directions to each other and are formed into columnar shapes having a predetermined curvature. Specifically, the first elastic member 90 is curved on the opposite side of the second elastic member 100 such that, in its columnar state, its central portion 90c is further away from the second elastic member 100 than its side ends 90a and 90b. On the other hand, the second elastic member 100 is curved on the opposite side of the first elastic member 90 such that, in its columnar state, its central portion 100c is further away from the first elastic member 90 than its side ends 100a and 100b.

[0077] In boom 2A, the first elastic member 90 is formed such that the thickness of its side ends 90a and 90b is less than the thickness of its central portion 90c, and the second elastic member 100 is formed such that the thickness of its side ends 100a and 100b is less than the thickness of its central portion 100c. The first connecting member 8 is fixed to the side end 90a of the first elastic member 90 and the side end 100a of the second elastic member 100, and the second connecting member 10 is fixed to the side end 90b of the first elastic member 90 and the side end 100b of the second elastic member 100.

[0078] For example, the first elastic member 90 is constructed by sequentially laminating a plurality of layers 92, 94, and 96. Each of the layers 92, 94, and 96 is a plate-shaped elastic member made of carbon fiber composite material or the like, and is curved on the opposite side of the second elastic member 100. Layer 92 has side ends 92a and 92b and a central part 92c connected to the side ends 92a and 92b. Layer 94 has side ends 94a and 94b and a central part 94c connected to the side ends 94a and 94b. Layer 96 has side ends 96a and 96b and a central part 96c connected to the side ends 96a and 96b.

[0079] Layers 92 and 94 are formed in an arc shape such that their central angles are approximately equal. Therefore, the positions of the side ends 92a and 94a are approximately the same, and the positions of the side ends 92b and 94b are approximately the same. The side ends 92a and 94a constitute the side end 90a of the first elastic member 90, and the side ends 92b and 94b constitute the side end 90b of the first elastic member 90. On the other hand, the central angle of layer 96 is smaller than the central angles of layers 92 and 94. Therefore, the side end 96a of layer 96 does not reach the side ends 92a and 94a, and the side end 96b of layer 96 does not reach the side ends 92b and 94b.

[0080] As described above, when the first elastic member 90 is constructed, only layers 92 and 94 are laminated at the side ends 90a and 90b of the first elastic member 90, and layer 96 is not laminated on layers 92 and 94. On the other hand, layers 92, 94, and 96 are laminated at the central part 90c of the first elastic member 90. As a result, the thickness of the side ends 90a and 90b of the first elastic member 90 is thinner than the thickness of the central part 90c of the first elastic member 90 by the thickness of layer 96. The partially thinned areas formed at the side ends 90a and 90b of the first elastic member 90 become the fixing areas 98A and 98B to which the first connecting member 8 and the second connecting member 10 are fixed.

[0081] Similarly, the second elastic member 100 is constructed by sequentially laminating a plurality of layers 102, 104, and 106. Each of the layers 102, 104, and 106 is a plate-shaped elastic member made of carbon fiber composite material or the like, and is curved on the opposite side of the first elastic member 90. Layer 102 has side ends 102a and 102b and a central part 102c connected to the side ends 102a and 102b. Layer 104 has side ends 104a and 104b and a central part 104c connected to the side ends 104a and 104b. Layer 106 has side ends 106a and 106b and a central part 106c connected to the side ends 106a and 106b.

[0082] Layers 102 and 104 are formed in an arc shape such that their central angles are approximately equal. Therefore, the positions of the side ends 102a and 104a are approximately the same, and the positions of the side ends 102b and 104b are approximately the same. The side ends 102a and 104a constitute the side end 100a of the second elastic member 100, and the side ends 102b and 104b constitute the side end 100b of the second elastic member 100. On the other hand, the central angle of layer 106 is smaller than the central angles of layers 102 and 104. Therefore, the side end 106a of layer 106 does not reach the side ends 102a and 104a, and the side end 106b of layer 106 does not reach the side ends 102b and 104b.

[0083] As described above, when the second elastic member 100 is configured, only layers 102 and 104 are laminated at the side ends 100a and 100b of the second elastic member 100, and layer 106 is not laminated on layers 102 and 104. On the other hand, layers 102, 104, and 106 are laminated at the central part 100c of the second elastic member 100. As a result, the thickness of the side ends 100a and 100b of the second elastic member 100 is thinner than the thickness of the central part 100c of the second elastic member 100 by the thickness of layer 106. The partially thinned regions formed at the side ends 100a and 100b of the second elastic member 100 become the fixing regions 108A and 108B to which the first connecting member 8 and the second connecting member 10 are fixed.

[0084] The first connecting member 8 is fixed to a fixing region 98A formed on the side end 90a of the first elastic member 90 and to a fixing region 108A formed on the side end 100a of the second elastic member 100. The second connecting member 10 is fixed to a fixing region 98B formed on the side end 90b of the first elastic member 90 and to a fixing region 108B formed on the side end 100b of the second elastic member 100. By fixing the first connecting member 8 and the second connecting member 10 to the partially thinned fixing regions 98A, 98B, 108A, and 108B in this way, the increase in the overall thickness of the boom 2A due to the attachment of the first connecting member 8 and the second connecting member 10 can be suppressed.

[0085] In particular, it is preferable that the difference in thickness between the side ends 90a, 90b of the first elastic member 90 and the central part 90c (corresponding to the thickness of layer 96 in Figure 7), and the difference in thickness between the side ends 100a, 100b of the second elastic member 100 and the central part 100c (corresponding to the thickness of layer 106 in Figure 7), are greater than or equal to the thickness of the first connecting member 8 and the second connecting member 10, respectively. This allows the first connecting member 8 and the second connecting member 10 to be embedded in the fixed areas 98A, 98B, 108A, and 108B, making it possible to attach the first connecting member 8 and the second connecting member 10 without increasing the thickness of the boom 2A.

[0086] In the above description, an example was given in which the first elastic member 90 and the second elastic member 100 are each composed of three layers of elastic material. However, the number of layers in the first elastic member 90 and the second elastic member 100 can be changed as appropriate. Furthermore, the first elastic member 90 and the second elastic member 100 may be composed of a single layer.

[0087] Figure 8 is a cross-sectional view showing boom 2B, which corresponds to a second modified example of boom 2. The configuration of boom 2B is the same as boom 2A, except that it is equipped with a second elastic member 100A instead of the second elastic member 100 (see Figure 7).

[0088] The second elastic member 100A corresponds to the second elastic member 100 of the boom 2A (see Figure 7) with the layer 102 omitted, and has one side end 100Aa and the other side end 100Ab, and a central part 100Ac connected to the side ends 100Aa and 100Ab. The side end 104a of the layer 104 constitutes the side end 100Aa of the second elastic member 100A, and the side end 104b of the layer 104 constitutes the side end 100Ab of the second elastic member 100A.

[0089] In boom 2B, the first elastic member 90 and the second elastic member 100A have different numbers of layers, and the thickness of the first elastic member 90 and the thickness of the second elastic member 100A are different. Specifically, the second elastic member 100A is thinner than the first elastic member 90 by the thickness of layer 92. Thus, boom 2B may be equipped with a first elastic member 90 and a second elastic member 100A with different thicknesses.

[0090] For example, when the boom 2B is operated under conditions where the external force acting from the second elastic member 100A towards the first elastic member 90 is stronger than the external force acting from the first elastic member 90 towards the second elastic member 100A, it is preferable to make the first elastic member 90 thicker and the second elastic member 100A thinner. In this case, the thicker first elastic member 90 makes it easier to maintain the boom 2B in a columnar shape, and the thinner second elastic member 100A reduces the overall thickness and weight of the boom 2B.

[0091] In the above description, an example was given in which a difference in the thickness of the first elastic member 90 and the second elastic member 100A is created by a difference in the number of layers between them. However, the method for setting the relative thicknesses of the first elastic member 90 and the second elastic member 100A is not limited to the above. For example, the first elastic member 90 and the second elastic member 100A may each be composed of a single layer with a different thickness.

[0092] The booms 2, 2A, and 2B according to this embodiment can be used in various fields such as aircraft, ships, spacecraft, and communication equipment. For example, the booms 2, 2A, and 2B are mounted on a movement control device that controls the movement of a spacecraft. Below, as an example, a configuration example of a spacecraft equipped with a movement control device on which boom 2 is mounted will be described.

[0093] Figure 9 is a perspective view showing a spacecraft 40. The spacecraft 40 is a flying object that orbits a celestial body 42 such as the Earth along a ring-shaped orbit 44. For example, the spacecraft 40 may be an artificial satellite, rocket, transport vehicle, space probe, space station, etc., and may be equipped with a propulsion mechanism such as a chemical propulsion engine or an electric propulsion engine. However, there are no restrictions on the type of spacecraft 40, and the spacecraft 40 may be a flying object without a propulsion mechanism.

[0094] The orbit 44 is the path of the spacecraft 40, set outside the celestial body 42. For example, the orbit 44 is a roughly circular or elliptical path set so that the distance (altitude) from the surface (ground) of the celestial body 42 is roughly constant. The altitude of the orbit 44 is set according to the type of spacecraft 40 and its operational purpose, for example, between 200 km and 1000 km.

[0095] Figure 9 shows the three mutually perpendicular axes: the X, Y, and Z axes. The X-axis direction corresponds to the tangential direction of the orbit 44 and indicates the direction of travel of the spacecraft 40. The Z-axis direction corresponds to the normal direction of the orbit 44 and indicates the altitude direction of the spacecraft 40. The positive Z-axis direction (upward in Figure 9) corresponds to the zenith direction, which is the direction away from the celestial body 42. On the other hand, the negative Z-axis direction (downward in Figure 9) corresponds to the nadir direction, which is the direction toward the center (geocenter) of the celestial body 42.

[0096] The spacecraft 40 has three mutually perpendicular axes, namely a roll axis, a pitch axis, and a yaw axis, that pass through the center of gravity of the spacecraft 40. The spacecraft 40 is designed assuming that the roll axis, pitch axis, and yaw axis are arranged parallel to the X axis, Y axis, and Z axis, respectively. Therefore, the direction of the roll axis of the spacecraft 40 corresponds to the direction assumed to be the direction of travel of the spacecraft 40. When moving the spacecraft 40 in orbit 44, the attitude of the spacecraft 40 is controlled so that the roll axis, pitch axis, and yaw axis are parallel to the X axis, Y axis, and Z axis, respectively.

[0097] For the sake of clarity, the following explanation assumes that the roll axis, pitch axis, and yaw axis of the spacecraft 40 positioned in orbit 44 are parallel to the X axis, Y axis, and Z axis, respectively. However, when the spacecraft 40 actually moves along orbit 44, its attitude will fluctuate, and the roll axis, pitch axis, and yaw axis may not be parallel to the X axis, Y axis, and Z axis, respectively.

[0098] During the operation of spacecraft 40, spacecraft 40 orbits celestial body 42 along orbit 44 and carries out pre-specified missions (such as collecting and monitoring information on the ground and in space, conducting experiments in the space environment, communicating with the ground, and transporting goods). After the mission is completed and the operation of spacecraft 40 ends, spacecraft 40 is removed from orbit 44 to prevent it from becoming space debris and interfering with the operation of other spacecraft.

[0099] Specifically, the spacecraft 40 leaves its orbit 44 and enters a departure trajectory 46, gradually approaching the celestial body 42 while orbiting it. After that, the spacecraft 40 re-enters the atmosphere and burns up, or reaches the celestial body 42 and is recovered. The time required for the spacecraft 40 to de-orbit varies depending on the type of spacecraft 40, altitude, etc., and can range from several hours, several weeks, several months, several years, or even more than 10 years.

[0100] Attempting to remove the spacecraft 40 from orbit 44 using propulsion mechanisms such as engines would require extensive control of the spacecraft's movement, which is time-consuming and costly. Furthermore, after the end of its operational life, the spacecraft 40 may not have enough energy remaining to remove itself from orbit. Therefore, the spacecraft 40 is sometimes equipped with a movement control device (orbital de-orbit device) to remove itself from orbit. Such a movement control device is also called a PMD (Post Mission Disposal) device and operates independently of the spacecraft 40 to remove it from orbit 44.

[0101] Specifically, the spacecraft 40 comprises a main body 50 on which the spacecraft 40's main functions are installed, and a movement control device 52 that controls the movement of the main body 50. The movement control device 52 controls the direction and speed of the spacecraft 40 by utilizing the atmospheric resistance present around the celestial body 42. In particular, when the spacecraft 40 is to leave orbit 44, the movement control device 52 functions as a deorbiting device.

[0102] The movement control device 52 includes a plurality of deployable films (resistive films) 54 that are deployed so that atmospheric resistance acts upon them. The deployable films 54 are films (sheets) capable of receiving atmospheric molecules, and the surface of the deployable films 54 corresponds to the film surface that receives atmospheric resistance.

[0103] Multiple deployable membranes 54 are arranged at approximately equal angular intervals around the roll axis (X-axis). For example, as shown in Figure 9, if the movement control device 52 is equipped with two sets of deployable membranes 54, the two sets of deployable membranes 54 are installed at both ends of the main body 50 in the yaw axis direction (Z-axis direction), i.e., the upper and lower ends. As a result, the two sets of deployable membranes 54 are arranged at 180° intervals around the roll axis (X-axis) and are arranged symmetrically with respect to the roll axis (X-axis). However, there is no limit to the number of deployable membranes 54. For example, if the movement control device 52 is equipped with four sets of deployable membranes 54, the four sets of deployable membranes 54 are arranged at 90° intervals around the roll axis (X-axis).

[0104] The material, shape, dimensions, etc., of the developing film 54 are not restricted as long as the developing film 54 can withstand atmospheric resistance. For example, the developing film 54 is constructed by covering the surface of the resin film with a conductive thin film. This prevents the resin film from degrading due to exposure to atomic oxygen (AO) present on the orbital 44. Furthermore, by forming a conductive thin film on the resin film and imparting conductivity to the developing film 54, damage to the developing film 54 due to charging and discharge can be avoided.

[0105] For example, the unfolded film 54 comprises a resin film (approximately 12.5 μm thick) made of polyimide or the like, and a conductive film made of aluminum, ITO (indium tin oxide), or the like that covers the surface of the resin film, and is formed in a triangular, trapezoidal, or fan shape. The surface area of ​​the film is, for example, 100 m². ２It can be set to a certain extent. However, the material, composition, shape, size, etc. of the deployable membrane 54 can be appropriately selected according to the weight, shape, size, altitude, etc. of the spacecraft 40.

[0106] Furthermore, the movement control device 52 includes a pair of booms 2 that support the deployed membrane 54 in its stretched state. Both ends of the deployed membrane 54 are attached to the booms 2. Details of the configuration and function of the booms 2 are as described above.

[0107] During the operation of the spacecraft 40, the deployable membrane 54 is stored in the movement control device 52 in a folded state or wound around the core material. The boom 2 that supports the deployable membrane 54 is also stored in the movement control device 52 in a wound around the core material 12 (see Figure 1(B)).

[0108] When the operation of the spacecraft 40 ends, a pair of booms 2 are launched into space from the movement control device 52 (see Figure 3). As a result, the deployable membranes 54 attached to the pair of booms 2 are extended and stretched. The atmosphere surrounding the celestial body 42 then collides with the surface of the deployable membranes 54, and atmospheric resistance acts on the deployable membranes 54 in the opposite direction to the movement of the spacecraft 40. As a result, the spacecraft 40 decelerates and leaves the orbit 44, entering a departure trajectory 46.

[0109] Furthermore, boom 2 may be conductive. If boom 2 is conductive, current can be supplied to boom 2 by induced electromotive force or an external power source. This makes it possible to use the Lorentz force generated by the mutual induction between the current flowing through boom 2 and the magnetic field of celestial body 42 to control the movement of the spacecraft 40.

[0110] There are no restrictions on the method of imparting conductivity to boom 2. For example, a conductive thin film may be provided on the surface or inside boom 2, or a conductive material may be incorporated into boom 2. As the conductive thin film, for example, a thin film containing a metal such as aluminum, nickel, or chromium can be used. As the conductive material, for example, fibers containing carbon fiber can be used.

[0111] Figure 10(A) is a front view showing the movement control device 52 with the deployment membrane 54 housed inside. The movement control device 52 includes a housing section 56 for housing the deployment membrane 54 and the boom 2. For example, the housing section 56 is a box-shaped container that houses the deployment membrane 54 in a folded or rolled-up state and the boom 2 wound around the core material 12 (see Figure 1(B)). There are no restrictions on the shape and size of the housing section 56, as long as the deployment membrane 54 and the boom 2 can be housed inside it.

[0112] Figure 10(B) is a front view showing the movement control device 52 in the state where the deployable membrane 54 is deployed. When the movement control device 52 is activated, the pair of booms 2 extend in a predetermined direction from the state in which they are wound around the core material 12 (see Figure 3) and are ejected from the housing 56. For example, the pair of booms 2 extend in a direction inclined with respect to the yaw axis (Z axis) such that their tips are separated from each other in the pitch axis direction (Y axis direction). When the shape of the booms 2 is fixed in a columnar shape, the deployable membrane 54 attached to the booms 2 becomes taut and the deployable membrane 54 is deployed.

[0113] When the movement control device 52 deploys the deployable membrane 54, gravity gradient stabilization guides the attitude (angle) of the spacecraft 40 so that the yaw axis, which is the deployment direction of the deployable membrane 54, is aligned with the Z-axis direction. Specifically, as shown in Figure 9, when the pair of deployable membranes 54 are deployed, a gravity gradient is generated on the spacecraft 40, and the moment of inertia of the deployment direction (yaw axis) of the deployable membrane 54 becomes smaller than the moment of inertia of the roll axis and pitch axis. As a result, a torque acts on the spacecraft 40 so that the deployment direction (yaw axis) of the deployable membrane 54 is aligned with the Z-axis. Consequently, the attitude of the spacecraft 40 is controlled and maintained so that one deployable membrane 54 points towards the zenith (positive Z-axis direction) and the other deployable membrane 54 points towards the base of the point (negative Z-axis direction).

[0114] The timing for removing the spacecraft 40 from orbit 44 is set appropriately according to the content of the mission performed by the spacecraft 40 and the lifespan of the spacecraft 40. For example, the deployable membrane 54 is deployed when a command to deploy the deployable membrane 54 is input to the mobile control device 52 from the main body 50 of the spacecraft 40 or from the ground. The mobile control device 52 may also deploy the deployable membrane 54 when the operating time or flight time of the spacecraft 40 reaches a predetermined time limit. Furthermore, the mobile control device 52 may also deploy the deployable membrane 54 when it receives a signal indicating that the operation of the main body 50 of the spacecraft 40 has stopped.

[0115] Furthermore, the movement control device 52 may also include a rotating unit 58 for rotating the deployable membrane 54. For example, the rotating unit 58 is connected to the housing unit 56, and the rotating unit 58 is connected to the deployable membrane 54 via the housing unit 56. The rotating unit 58 may be a rotating mechanism that passively changes the rotation angle of the deployable membrane 54 in accordance with the atmospheric resistance acting on the deployable membrane 54, or it may be a rotational drive source such as a motor that can actively adjust the rotation angle of the deployable membrane 54.

[0116] As shown in Figure 10(B), the rotating part 58 rotates the deployable membrane 54 together with the housing part 56 around the rotation axis 60. This adjusts the rotation angle of the deployable membrane 54. The rotation axis 60 corresponds to the rotation axis (center of rotation) of the deployable membrane 54, boom 2, and housing part 56, and is set along a direction that intersects with the direction of travel of the spacecraft 40 (X-axis direction, roll axis direction). For example, the rotation axis 60 is set parallel to the deployment direction of the deployable membrane 54 (yaw axis direction).

[0117] By controlling the rotation angle of the deployable film 54 with the rotating unit 58, the magnitude of atmospheric resistance acting on the deployable film 54 can be adjusted. For example, by maintaining the deployable film 54 in a position perpendicular to the direction of travel of the spacecraft 40 (X-axis direction) (YZ plane) using the rotating unit 58, the atmospheric resistance acting on the deployable film 54 can be maximized, allowing the spacecraft 40 to decelerate efficiently. Furthermore, by controlling the rotation angle of the deployable film 54, the direction of travel and attitude of the spacecraft 40 can also be adjusted.

[0118] Furthermore, the movement control device 52 may include a torque detection unit (not shown) for detecting the torque acting on the unfolding membrane 54. For example, the torque detection unit is composed of a torque sensor such as a two-axis force gauge. By equipping the movement control device 52 with a torque detection unit, it becomes possible to adjust the rotation angle of the unfolding membrane 54 in accordance with the torque acting on the unfolding membrane 54.

[0119] Furthermore, the movement control device 52 includes a controller (control unit, control unit, and control device) that controls the movement control device 52. The controller is connected to the components that make up the movement control device 52 and controls the operation of the movement control device 52 by outputting control signals to each component.

[0120] For example, the controller is comprised of a computer. In this case, the controller includes a processor such as a CPU (Central Processing Unit) that performs calculations and other processing necessary for controlling the movement control device 52, and a memory such as a ROM (Read Only Memory) or RAM (Random Access Memory) that stores various information (data, programs, etc.) used for controlling the movement control device 52. The controller controls the extension of the boom 2, the deployment of the deployment membrane 54, the rotation of the deployment membrane 54, etc., by executing the program stored in the memory.

[0121] However, the movement control device 52 can also be controlled by a controller mounted on the main body 50 of the spacecraft 40 (see Figure 9). In this case, each component of the movement control device 52 is connected to the controller provided on the main body 50. Control signals are then output from the controller on the main body 50 to each component of the main body 50 and the movement control device 52, thereby controlling the operation of the main body 50 and the movement control device 52.

[0122] As described above, the boom 2 according to this embodiment has high strength in its columnar state and can reduce its overall thickness when rolled up. Therefore, by using the boom 2 as a support column for the unfolding membrane 54, it is possible to reliably support the unfolding membrane 54 while reducing the storage space required for the boom 2.

[0123] Although the above description explains how the spacecraft 40 is deorbited from orbit 44 by the movement control device 52, the use of the movement control device 52 is not limited to deorbiting the spacecraft 40. For example, even during the operation of the spacecraft 40, it may be necessary to temporarily change the direction and speed of the spacecraft 40, such as when the spacecraft 40 is about to collide with a space debris or other flying object. In this case, the movement of the spacecraft 40 can be controlled by the movement control device 52 to avoid a collision between the spacecraft 40 and the flying object.

[0124] Furthermore, the use of boom 2 is not limited to the mobile control device 52 mounted on the spacecraft 40. For example, boom 2 can also be used as a support for solar panels or solar sails, or as an antenna used for information communication on the ground or in space.

[0125] Furthermore, the configurations, methods, etc., according to this embodiment can be modified as appropriate without departing from the scope of the object of the present invention.

[0126] (Example) Next, the results of evaluating the characteristics of the boom according to this embodiment will be described. In this embodiment, the mechanical strength of the boom according to this embodiment was evaluated.

[0127] Figure 11(A) is a perspective view showing a boom 70 according to Comparative Example 1. The boom 70 is a columnar member formed by curving a strip-shaped elastic member 72 into an arc shape in the width direction. One end 72a and the other end 72b of the elastic member 72 in the width direction are not in contact, and the boom 70 has a C-shaped cross-section. In Comparative Example 1, the elastic member 72 was made of a carbon fiber composite material. The length of the elastic member 72 was 10 m, the thickness was 0.4 mm, the radius of curvature was 20 mm, and the central angle was 218°.

[0128] Figure 11(B) is a perspective view showing a boom 80 according to Comparative Example 2. The boom 80 comprises a strip-shaped first elastic member 82 and a second elastic member 84. The first elastic member 82 has one end 82a and the other end 82b in the width direction, and a central portion 82c connected to the ends 82a and 82b. The second elastic member 84 has one end 84a and the other end 84b in the width direction, and a central portion 84c connected to the ends 84a and 84b.

[0129] The central portion 82c of the first elastic member 82 and the central portion 82c of the second elastic member 84 are spaced apart from each other, and the boom 80 is formed into a cylindrical shape. Furthermore, the end portion 82a of the first elastic member 82 and the end portion 84a of the second elastic member 84 are fixed in a state where they overlap each other in a generally parallel manner. Similarly, the end portion 82b of the first elastic member 82 and the end portion 84b of the second elastic member 84 are fixed in a state where they overlap each other in a generally parallel manner.

[0130] The first elastic member 82 has curved portions 82d to 82f in order from end 82a to end 82b, and the second elastic member 84 has curved portions 84d to 84f in order from end 84a to end 84b. The curved portions 82d, 82f, 84d, and 84f curve inward from the boom 80, and the curved portions 82e and 84e curve outward from the boom 80. Therefore, the first elastic member 82 and the second elastic member 84 each have a roughly Ω-shaped cross-section and have two inflection points in cross-sectional view.

[0131] In Comparative Example 2, the first elastic member 82 and the second elastic member 84 were made of carbon fiber composite material. The length of the first elastic member 82 and the second elastic member 84 was 10 m, and the thickness was 0.2 mm. The radius of curvature in the curved portions 82d to 82f of the first elastic member 82 and 84d to 84f of the second elastic member 84 was 11 mm.

[0132] In this embodiment, the boom 2 shown in Figure 1(A) was used. The first elastic member 4 and the second elastic member 6 of boom 2 were formed in an arc shape, and the first elastic member 4 and the second elastic member 6 were connected by a first connecting member 8 and a second connecting member 10.

[0133] The first elastic member 4 and the second elastic member 6 were made of carbon fiber composite material. The length of the first elastic member 4 and the second elastic member 6 was 10 m and the thickness was 0.2 mm. In addition, sheet-like aramid fibers were used for the first connecting member 8 and the second connecting member 10. The length of the first connecting member 8 and the second connecting member 10 was 10 m, the width was 15 mm and the thickness was 0.08 mm. Also, the distance d １ d ２ (See Figure 2(A)) was set to 1 mm.

[0134] In this embodiment, in order to evaluate the effect of the central angle θ of the first elastic member 4 and the second elastic member 6 (see Figure 2(A)) on the strength of the boom 2, three types of booms 2 were prepared in which the central angle θ of the first elastic member 4 and the second elastic member 6 differed within the range of 180° < θ < 360°. Specifically, the central angle θ of the boom 2 in Embodiment 1 was set to 220° and the radius of curvature to 20 mm. The central angle θ of the boom 2 in Embodiment 2 was set to 240° and the radius of curvature to 18 mm. The central angle θ of the boom 2 in Embodiment 3 was set to 320° and the radius of curvature to 13 mm.

[0135] Then, the bending strength was measured for booms 70 and 80 in Comparative Examples 1 and 2 and boom 2 in Examples 1 to 3. The method for measuring the bending strength of each boom is as follows. First, the boom was positioned horizontally while maintaining its columnar shape. At this time, the base end (one end) of the boom was fixed to the wall as a fixed end, and the tip end (the other end) of the boom was left unfixed as a free end. Next, a vertical external force was applied to the tip of the boom to deform it so that it bent. The external force was then increased until the boom bent, and the maximum value of the external force was recorded as the bending strength.

[0136] Figure 12 is a graph showing the bending strength of the booms according to Comparative Examples 1 and 2 and Examples 1 to 3. As shown in Figure 12, the bending strength of boom 2 (central angle θ = 220°) according to Example 1 was significantly higher than that of booms 70 and 80 according to Comparative Examples 1 and 2. Furthermore, booms 2 (central angle θ = 240° and 320°) according to Examples 2 and 3 achieved bending strengths that were more than four times that of boom 70 according to Comparative Example 1 and more than twice that of boom 70 according to Comparative Example 1.

[0137] From the evaluation results above, it was confirmed that by setting the central angle θ to a value greater than 180° and making the cross-sectional shape of the first elastic member 4 and the second elastic member 6 closer to a circle than a semicircle, the mechanical strength in the columnar state becomes extremely high. In particular, it was found that setting the central angle θ to preferably 220° or more, and more preferably 240° or more, is particularly effective in improving the strength of the boom 2.

[0138] The boom 70 according to Comparative Example 1 is configured in an open loop shape with a C-shaped cross-section, as shown in Figure 11(A). This boom 70 tends to be particularly weak against bending and twisting in the open direction. In contrast, the boom 2 according to this embodiment is configured in a closed loop by the first elastic member 4 and the second elastic member 6 and the first connecting member 8 and the second connecting member 10 (see Figure 1(A), etc.), and therefore has a certain level of resistance to bending in all directions and also has high resistance to twisting. Therefore, the boom 2 according to this embodiment is advantageous over the boom 70 from the viewpoint of resistance to bending and twisting in all directions.

[0139] The boom 80 according to Comparative Example 2 has higher bending strength than the boom 70 according to Comparative Example 1, and can be said to have a more advantageous configuration than the boom 70 in terms of strength in a columnar state. However, the boom 80 is curved in a complex manner so that multiple inflection points are formed, and the shapes of the first elastic member 82 and the second elastic member 84 are easily distorted when the boom 80 is deformed into a folded state. As a result, when the boom 80 is rolled up, a gap is created between the first elastic member 82 and the second elastic member 84, and the overall thickness of the boom 80 tends to increase.

[0140] Furthermore, when the boom 80, which has a complex structure as described above, is folded, stress concentrations occur at various points on the first elastic member 82 and the second elastic member 84. If the boom 80 is stored for a long time in this state, a creep phenomenon is likely to occur, in which the shapes of the first elastic member 82 and the second elastic member 84 become fixed. As a result, the restoring force of the first elastic member 82 and the second elastic member 84 decreases, making it difficult for the boom 80 to return to a columnar shape when extending it from its rolled-up state. Moreover, the self-extending force of the boom 80 also decreases along with the decrease in the restoring force.

[0141] On the other hand, the boom 2 according to this embodiment is composed of an arc-shaped first elastic member 4 and a second elastic member 6 that do not have inflection points, and does not have a complex structure with many inflection points like the boom 80. Furthermore, since the first elastic member 4 and the second elastic member 6 are connected via flexible first connecting member 8 and second connecting member 10, the side ends 4c, 4d of the first elastic member 4 and the side ends 6c, 6d of the second elastic member 6 can be displaced independently to a certain extent, and the first elastic member 4 and the second elastic member 6 have a high degree of freedom in deformation.

[0142] Therefore, when the boom 2 is folded and retracted, the first elastic member 4 and the second elastic member 6 are easily deformed to be in close contact with each other. This makes it possible to efficiently retract and store the boom 2, and reduces the overall thickness of the retracted boom 2. In addition, even when the boom 2 is folded, stress concentration is less likely to occur in the first elastic member 4 and the second elastic member 6, and creep is less likely to occur. Therefore, when the boom 80 is extended from its retracted state, the boom 80 is more likely to return to its columnar shape, and a high self-extending force is maintained. Thus, the boom 2 according to this embodiment is advantageous compared to the boom 80 in terms of storage efficiency and self-extending force.

[0143] 2, 2A, 2B Boom 4 First elastic member 4a First surface (front) 4b Second surface (back) 4c, 4d Side ends 4e Central part 6 Second elastic member 6a First surface (front) 6b ​​Second surface (back) 6c, 6d Side ends 6e Central part 8 First connecting member 10 Second connecting member 12 Core material (reel) 14 Rotation drive source 20 Type 22 First molding part 22a Surface 24 Second molding part 24a Surface 26 First recess 28 Second recess 30, 32 Gap 40 Spacecraft 42 Celestial body 44 Orbit 46 Detachment orbit 50 Main body 52 Movement control device 54 Deployable film (resistive film) 56 Housing part 58 Rotating part 60 Rotating shaft 70 Boom 72 Elastic member 72a, 72b Ends 80 Boom 82 First elastic member 82a, 82b Ends 82c Central section 82d-82f Curved section 84 Second elastic member 84a, 84b Ends 84c Central section 84d-84f Curved section 90 First elastic member 90a, 90b Side ends 90c Central section 92, 94, 96 Layers 92a, 92b, 94a, 94b, 96a, 96b Side ends 92c, 94c, 96c Central section 98A, 98B Fixed area 100 Second elastic member 100a, 100b Side ends 100c Central section 102, 104, 106 Layers 102a, 102b, 104a, 104b, 106a, 106b Side end portion 102c, 104c, 106c Center portion 108A, 108B Fixed area

Claims

1. A first elastic member and a second elastic member are arranged facing each other and are deformable from a rolled-up state to a columnar state by unfolding; a first connecting member and a second connecting member connect the first elastic member and the second elastic member, wherein the first elastic member has one side end and the other side end, and a central portion connected to the one side end and the other side end, and in the columnar state the central portion is curved so as to be further away from the second elastic member than the one side end and the other side end; the second elastic member has one side end and the other side end, and a central portion connected to the one side end and the other side end, and in the columnar state the central portion is curved so as to be further away from the first elastic member than the one side end and the other side end; the first connecting member is fixed to the one side end of the first elastic member and the one side end of the second elastic member. The second connecting member is fixed to the other side end of the first elastic member and the other side end of the second elastic member, and the first connecting member and the second connecting member are deformable such that the first elastic member and the second elastic member are connected via the first connecting member and the second connecting member in both the coiled state and the columnar state of the boom.

2. The boom according to claim 1, wherein, when the first elastic member is in a columnar state, the distance between one side end and the other side end of the first elastic member is smaller than the column width of the first elastic member, and when the second elastic member is in a columnar state, the distance between one side end and the other side end of the second elastic member is smaller than the column width of the second elastic member.

3. The boom according to claim 2, wherein the first elastic member and the second elastic member are curved in an arc shape such that, in a columnar state, the central angle is greater than 180° and less than 360°.

4. The boom according to claim 1, wherein the thickness of one side end and the other side end of the first elastic member is less than the thickness of the central portion of the first elastic member, and the thickness of one side end and the other side end of the second elastic member is less than the thickness of the central portion of the second elastic member.

5. The boom according to claim 1, wherein the thickness of the first elastic member and the thickness of the second elastic member are different.

6. The boom according to claim 1, wherein the first elastic member and the second elastic member are made of a carbon fiber composite material.

7. The boom according to claim 6, wherein the carbon fiber composite material comprises carbon fibers and a resin for fixing the carbon fibers, and the first elastic member and the second elastic member and the first connecting member and the second connecting member are fixed by the resin.

8. The boom according to claim 1, wherein the first elastic member and the second elastic member and the first connecting member and the second connecting member are fixed together via a film adhesive.

9. The boom according to claim 1, wherein the first connecting member and the second connecting member are fibers, nonwoven fabrics, or films.

10. A movement control device for controlling the movement of a spacecraft, comprising: a deployable membrane that is deployed so as to act upon atmospheric resistance; and a boom according to any one of claims 1 to 9 that supports the deployable membrane.

11. A method for manufacturing a boom according to any one of claims 1 to 9, comprising: preparing a mold having a first molded part and a second molded part that are columnar and have curved surfaces, with a first recess and a second recess formed at the connection between the first molded part and the second molded part; arranging the first elastic member along the surface of the first molded part; arranging the second elastic member along the surface of the second molded part; arranging the first connecting member in the first recess so as to be in contact with the first elastic member and the second elastic member; arranging the second connecting member in the second recess so as to be in contact with the first elastic member and the second elastic member; integrating the first elastic member, the second elastic member, the first connecting member and the second connecting member; and removing the mold from the inside of the first elastic member and the second elastic member while a gap is secured between the first recess and the second recess and the first elastic member and the second elastic member.

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