Aerodynamic device and satellite

Abstract

Provided is an aerodynamic device that reduces the influence of atmospheric drag on a satellite. The aerodynamic device comprises an aerodynamic shaping part provided at the tip of a satellite body. The aerodynamic shaping part is configured to be deformable between a first state in which the aerodynamic shaping unit has a conical shape and a second state in which the aerodynamic shaping unit is folded from the first state.

Description

Aerodynamic device and satellite

[0001] The present disclosure relates to an aerodynamic device and a satellite.

[0002] An artificial satellite orbiting around a planet or the like in space above the Earth decelerates due to the influence of atmospheric drag. Therefore, the artificial satellite needs to increase its speed by the amount of deceleration using a propulsion device or the like to maintain its orbit. At this time, if the atmospheric drag received by the artificial satellite can be reduced, the thrust of the propulsion device or the like and the amount of propellant can be reduced, so that the costs associated with the development and operation of the artificial satellite can be reduced.

[0003] In order to reduce the atmospheric drag received by an artificial satellite, for example, Patent Document 1 discloses a configuration in which the satellite body has a shape such that the cross-sectional area in the traveling direction becomes smaller. Further, Patent Document 2 discloses a configuration in which a conical structure that tapers toward the traveling direction is provided at the tip portion.

[0004] Japanese Unexamined Patent Application Publication No. 2000-211596 Japanese Unexamined Patent Application Publication No. 2008-222102

[0005] However, in the configuration described in Patent Document 1, since the surface affected by the atmospheric drag is a flat surface, there is a possibility that the atmospheric drag cannot be effectively reduced. In addition, in the configuration described in Patent Document 2, since the dimensions of the entire satellite body are large, the volume when mounted on a rocket becomes large, so there is a possibility that the restrictions on the mounting location will increase. Therefore, there is a problem that the launch cost of the satellite increases due to a decrease in the number of satellites mounted when multiple satellites are mounted.

[0006] An object of the present disclosure is to provide an aerodynamic device and a satellite capable of reducing the launch cost of a satellite while reducing atmospheric drag.

[0007] The aerodynamic device according to the present disclosure is an aerodynamic device that reduces the influence of atmospheric drag received by a satellite, and includes an aerodynamic shaping portion provided at the tip of the satellite body, and the aerodynamic shaping portion is configured to be deformable between a first state in which it has a cone shape and a second state in which it is folded from the first state.

[0008] The satellite according to this disclosure comprises a satellite body and an aerodynamic shaping section provided at the tip of the satellite body, wherein the aerodynamic shaping section is configured to be deformable between a first state in which it is conical in shape and a second state in which it is folded from the first state.

[0009] According to this disclosure, it is possible to reduce the cost of satellite launches while reducing atmospheric drag.

[0010] This figure shows a satellite equipped with an aerodynamic device according to an embodiment of the present disclosure. This figure shows the aerodynamic device in the first state. This figure shows the aerodynamic device in the second state. This figure shows a simplified representation of the folded frame section. This figure is for explaining the inclination angle of the conical shape. This graph shows an example of analysis results showing the change in CDS for each angle. This graph shows an example of analysis results showing the change in CDS for each angle when the thermal adaptation coefficient is changed. This figure is for explaining the folds when folding the aerodynamic shaping section. This figure is for explaining the folds when folding the aerodynamic shaping section. This figure shows a simplified representation of a modified folded frame section. This figure shows a simplified representation of a modified folded frame section. This figure shows an example of a configuration without a frame section. This figure shows an example of a configuration without a frame section.

[0011] The embodiments of this disclosure will now be described in detail with reference to the drawings. Figure 1 shows a satellite 1 equipped with an aerodynamic device 100 according to an embodiment of this disclosure. In describing the structure of the aerodynamic device 100 of this embodiment, the Cartesian coordinate system shown in each figure will be used. The aerodynamic device 100 is arranged such that, for example, when the satellite 1 is flying in an attitude along the horizontal direction, the X direction is the direction of travel of the satellite 1, the Y direction is parallel to the horizontal plane and perpendicular to the direction of travel, and the Z direction is the vertical direction.

[0012] As shown in Figure 1, satellite 1 is an artificial satellite that orbits a planet or other body of water above the Earth. Satellite 1 comprises a satellite body 11 and an aerodynamic device 100. The satellite body 11 is the main body of satellite 1 and is configured, for example, in the shape of a rectangular parallelepiped. The aerodynamic device 100 is provided at the tip of the satellite body 11 (the positive end in the X direction).

[0013] As shown in Figures 2A and 2B, the aerodynamic device 100 is a device that reduces the effect of atmospheric drag on the satellite 1, and has an aerodynamic shaping section 110 and a locking section 120.

[0014] The aerodynamic shaping section 110 is provided at the tip of the satellite body 11 (the end on the + side in the X direction) and is configured to be deformable between a first state and a second state. The first state is the state of the aerodynamic shaping section 110 shown in Figure 2A, in which the aerodynamic shaping section 110 takes on a conical shape that tapers toward the + side in the X direction. In this embodiment, the conical shape is a square pyramid. The second state is the state of the aerodynamic shaping section 110 shown in Figure 2B, in which the aerodynamic shaping section 110 is folded from the first state.

[0015] The aerodynamic shaping section 110 has a bottom section 111, a frame section 112, a linear section 113, and a surface section 114.

[0016] The base portion 111 constitutes the conical base portion described above, and is shaped to match the positive end face in the X direction of the satellite body 11. In this embodiment, the base portion 111 is made of a rectangular plate-like member. The base portion 111 is attached to the satellite body 11, for example. The base portion 111 may also be a part of the satellite body 11.

[0017] The frame portion 112 forms a part of the conical side surface (the negative side in the Z direction) and is configured to be foldable. The frame portion 112 has three frame members 112A, 112B, and 112C and three hinge members 112D, 112E, and 112F.

[0018] The three frame members 112A, 112B, and 112C are connected by their respective hinge members, so that they together form a single triangular side of a conical shape.

[0019] Frame member 112A is positioned at the very tip of the conical shape (the positive side in the X direction) of the three frame members and is configured in a triangular shape. Frame member 112A is also referred to as the first frame member.

[0020] Frame member 112B is positioned in the middle of the three frame members and is configured in a trapezoidal shape. Frame member 112B is also referred to as the second frame member 112B.

[0021] Frame member 112C is positioned at the bottommost side (the negative side in the X direction) of the conical shape among the three frame members, and is configured in a trapezoidal shape. Frame member 112C is also referred to as the third frame member 112C.

[0022] The negative end of the first frame member 112A in the X direction and the positive end of the second frame member 112B in the X direction are connected by a hinge member 112D. The hinge member 112D connects the first frame member 112A and the second frame member 112B in such a way that, for example, when the first frame member 112A and the second frame member 112B are folded, the hinge member 112D becomes convex toward the negative side in the Z direction (see also Figure 3).

[0023] The negative end of the second frame member 112B in the X direction and the positive end of the third frame member 112C in the X direction are connected by a hinge member 112E. The hinge member 112E connects the second frame member 112B and the third frame member 112C in such a way that, for example, when the second frame member 112B and the third frame member 112C are folded, it becomes convex toward the positive side in the Z direction (see also Figure 3).

[0024] The X-side end of the third frame member 112C and the bottom surface 111 are connected by a hinge member 112F. The hinge member 112F connects the third frame member 112C and the bottom surface 111 such that, for example, when the bottom surface 111 and the third frame member 112C are folded, it becomes convex toward the Z-side (see also Figure 3).

[0025] In this way, the frame portion 112 is configured to be foldable by folding it at each hinge member.

[0026] Furthermore, the inclination angle θ of the conical shape formed by the aerodynamic shaping section 110 is set to a predetermined angle. This predetermined angle is, for example, an angle at which the atmospheric resistance experienced by the aerodynamic shaping section 110 during the flight of the satellite 1 is sufficiently small, and is, for example, 80 degrees.

[0027] The inclination angle θ of the conical shape is, for example, the angle θ between the line 110A connecting the tip of the aerodynamic shaping section 110 and the Z-direction + end of the aerodynamic shaping section 110 when the satellite 1 is positioned along the horizontal direction (X direction), as shown in Figure 4, and the Z direction. Furthermore, the inclination angle θ of the conical shape may be an angle other than the angle between the line 110A and the Z direction (for example, the angle between the X direction and the line 110A), as long as it is an angle related to the inclination of the conical shape.

[0028] It has been analytically confirmed that the drag coefficient (CD value) of the surface portion 114 decreases as the above-mentioned inclination angle θ increases.

[0029] The atmospheric resistance of the conical aerodynamic shaping section 110 is calculated by the product of the drag coefficient CD, the surface area S, and the atmospheric dynamic pressure. Since the surface area S of the aerodynamic shaping section 110 correlates with the reciprocal of the cosine value of the inclination angle θ, CDS (the product of CD and S), which takes into account the drag coefficient CD and the surface area S, changes with respect to the change in inclination angle θ, as shown in Figure 5. In Figure 5, the product of the drag coefficient and the surface area is shown as CDS, and it has been analytically confirmed that CDS is minimized when the inclination angle θ is 80 degrees. That is, focusing only on the conical shape of the aerodynamic shaping section 110, the inclination angle θ is preferably, for example, 75 degrees to 85 degrees. Furthermore, considering the thermal adaptation coefficient α described later, the inclination angle θ is preferably in the range of 45 degrees to 80 degrees.

[0030] As shown in Figure 2A, the linear portion 113 connects the base portion 111 to the tip of the conical shape, that is, to the positive end in the X direction of the first frame member 112A. Specifically, the linear portion 113 connects the portion of the base portion 111 other than the portion to which the frame portion 112 is attached to the positive end in the X direction of the first frame member 112A. In this embodiment, the linear portion 113 has two linear members 113A and 113B.

[0031] The two linear members 113A and 113B are, for example, cables with a shape-retaining function that can be bent and deformed. The two linear members 113A and 113B are attached to each of the two vertex portions of the bottom portion 111 that do not include the edge to which the frame portion 112 is attached, and have a restoring force to maintain the aerodynamic shaping portion 110 in a first conical shape.

[0032] By providing the linear portion 113 in this manner, the aerodynamically shaped portion 110 is maintained in the first state unless any external force is applied.

[0033] The surface portion 114 constitutes the surface of the aerodynamically shaped portion 110 and is composed of a foldable thin film material such as a film, cloth, tape, or laminate. The surface portion 114 has a first portion 114A and a second portion 114B.

[0034] The first portion 114A constitutes the side surface of the aerodynamic shaping portion 110 other than the frame portion 112. The first portion 114A corresponds to the range from the positive end in the Y direction of the frame portion 112 to the negative end in the Y direction of the frame portion 112, via two linear members 113A and 113B. The two linear members 113A and 113B are attached to the back side of the first portion 114A.

[0035] The second part 114B corresponds to the frame part 112 and is attached to the surface of each of the multiple frame members 112A, 112B, and 112C. The second part 114B is connected to the first part 114A.

[0036] The surface portion 114 is made of a material that has resistance to atomic oxygen (AO). Preferably, the atomic oxygen-resistant material is an organic material or inorganic material containing silicon. Alternatively, the atomic oxygen-resistant material may be silicon dioxide, aluminum oxide, zinc oxide, titanium oxide, tin oxide, indium oxide, etc.

[0037] In this way, the surface portion 114 has atomic oxygen resistance, which helps to prevent the aerodynamic device 100 from being damaged by atomic oxygen.

[0038] Furthermore, it is preferable that the surface portion 114 is formed of a material that has specular reflectivity of gas molecules that collide with the surface during the flight of the satellite 1. The material that has specular reflectivity of gas molecules is a material that has a sufficiently smooth surface, and may be, for example, a material in which the thermal adaptation coefficient of the surface portion 114 is less than or equal to a predetermined value.

[0039] The thermal adaptation coefficient is an indicator that represents the change in energy. Specifically, the thermal adaptation coefficient is a value from 0 to 1 that indicates the degree of compatibility between gas molecules and the surface 114 when they collide with the surface 114 and are scattered. The thermal adaptation coefficient can be defined, for example, by the following equation (1).

[0040] α=(Tf-Ti) / (Ts-Ti)...(1)

[0041] In equation (1), α is the thermal adaptation coefficient. Ti is the temperature of the colliding gas molecules. Ts is the temperature of the surface 114 that is collided with by the gas molecules. Tf is the temperature of the gas molecules at temperature Ti after they have been scattered by the surface 114 at temperature Ts.

[0042] According to equation (1), the smaller the temperature change of the gas molecules (Tf - Ti), the smaller the thermal adaptation coefficient α becomes. In other words, the reduction in the velocity of satellite 1 due to collisions of gas molecules is suppressed.

[0043] Figure 6 is a qualitative graph showing the change in CDS with respect to the change in the inclination angle θ of the cone shape when the thermal adaptation coefficient α is changed in three stages. E1 in Figure 6 shows the change in CDS when the thermal adaptation coefficient α is the highest of the three stages. E2 in Figure 6 shows the change in CDS when the thermal adaptation coefficient α is the second highest of the three stages. E3 in Figure 6 shows the change in CDS when the thermal adaptation coefficient α is the lowest of the three stages.

[0044] As the thermal accommodation coefficient α increases (approaches a value close to 1), the gas molecules colliding with the surface of the aerodynamic shaping portion 110 thermally adapt and are randomly scattered, making it impossible to reflect the gas molecules in an appropriate direction, and the effect of the shape for reducing CDS decreases. Therefore, the CDS of E1 with the largest thermal accommodation coefficient α in FIG. 6 hardly depends on the inclination angle θ of the cone shape. As the thermal accommodation coefficient α decreases (approaches a value close to 0), the gas molecules colliding with the surface of the aerodynamic shaping portion 110 are specularly reflected, so that the effect of the shape for reducing CDS is exerted. Therefore, the CDS of E3 with the smallest thermal accommodation coefficient α in FIG. 6 varies greatly depending on the inclination angle θ of the cone shape.

[0045] According to FIG. 6, it can be confirmed that as the inclination angle θ becomes larger than 45 degrees, the smaller the thermal accommodation coefficient α, the smaller the CDS. From this result, the inclination angle θ is preferably larger than 45 degrees.

[0046] Also, materials having specular reflectivity, that is, materials with a relatively small thermal accommodation coefficient α (materials with a thermal accommodation coefficient α of, for example, 0.5 or less) are, for example, nickel, gold, etc. The surface portion 114 is preferably made of a material having atomic oxygen resistance and reflectivity. For the surface portion 114, a material surface with a substantially smooth thermal accommodation coefficient α that does not change over time can be adopted. For example, a member coated with a metal film can be adopted. A coating film formed by a PVD method, a sputtering method, a vapor deposition method, an ion plating method, a CVD method, or an ALD method can also be adopted.

[0047] As shown in FIGS. 2A and 2B, the locking portion 120 is for locking the aerodynamic shaping portion 110 in the second state (the state folded from the cone shape), and is, for example, a pin pusher. The locking portion 120 is provided at the + side end in the Z direction of the bottom surface portion 111, and is configured to be able to lock the aerodynamic shaping portion 110 in the second state by locking the tip portion of the frame portion 112 (frame member 112A) with the pin of the pin pusher.

[0048] The operation of the aerodynamic device 100 configured as described above will be described.

[0049] Before the satellite 1 is launched, the aerodynamic device 100 is folded so that the part of the aerodynamic shaping unit 110 is in the second state.

[0050] The aerodynamic shaping unit 110 is folded so as to protrude convexly inside the cone shape at the side surface portion adjacent to the frame unit 112 in the Y direction. The folding line at the side surface portion may be at any position. For example, as shown in FIG. 7, it may be a position based on the position P corresponding to the connection portion between the frame member 112B and the frame member 112C. P is, for example, indicated by a line perpendicular to the connection portion between the frame member 112B and the frame member 112C on the side surface. For example, the lines L1, L2, and L3 connecting each vertex of the triangle constituting the side surface and an arbitrary position on the line corresponding to P may be the folding lines.

[0051] L1 corresponds to the vertex located on the tip end side of the frame unit 112 of the triangle constituting the side surface. L2 and L3 correspond to the two respectively located on the bottom surface portion 111 side of the triangle constituting the side surface.

[0052] Also, the aerodynamic shaping unit 110 is folded at the portions of L4 and L5 at the side surface portion facing the side surface corresponding to the frame unit 112 in the Z direction. L4 is a line indicating the folding line at the position corresponding to the connection portion between the frame member 112A and the frame member 112B. L5 is a line indicating the folding line at the position corresponding to the connection portion between the frame member 112B and the frame member 112C.

[0053] As shown in FIG. 8, the aerodynamic shaping unit 110 is folded so as to protrude convexly to the - side in the Z direction at L4 and so as to protrude convexly to the + side in the Z direction at L5.

[0054] The position of the tip of the folded aerodynamic shaping section 110 corresponds to the positive Z-side end of the bottom surface section 111. A locking section 120 is provided at the positive Z-side end of the bottom surface section 111, so that the tip of the aerodynamic shaping section 110 can be locked by the pin puller's pin using the locking section 120. In this way, the aerodynamic shaping section 110 is locked to the second state (see Figure 2B).

[0055] The rocket carrying satellite 1 is launched when the aerodynamic shaping section 110 is in the second state. In other words, at the time of satellite 1's launch, the aerodynamic shaping section 110 is locked in the second state.

[0056] Thus, when satellite 1 is launched, the aerodynamic shaping section 110 is folded, which reduces the dimensions (volume) of satellite 1 when it is mounted on the rocket. As a result, the degree of freedom in mounting satellites on the rocket is increased, and various launch opportunities, such as rideshares with other satellites, can be utilized. In addition, when launching multiple satellites, more satellites can be mounted on the rocket, which contributes to reducing launch costs.

[0057] After the rocket carrying satellite 1 is launched, the lock on the locking mechanism 120 is released at an appropriate time. When the locking mechanism 120 is released, the restoring force of the hinge members 112D, 112E, and 112F causes the aerodynamic shaping mechanism 110 to unfold from the second state to the first state (see Figure 2A). In other words, the aerodynamic shaping mechanism 110 deforms from the second state to the first state when the locking mechanism 120 is released.

[0058] An appropriate timing could be, for example, after satellite 1 has separated from the rocket and its attitude has stabilized.

[0059] This allows satellite 1 to have a shape that reduces atmospheric drag, thereby reducing the atmospheric drag it experiences during flight. As a result, the thrust of the propulsion system and the amount of propellant used on satellite 1 can be reduced, thus lowering the development and operation costs of satellite 1. This effect is particularly pronounced when applied to very low-altitude satellites orbiting the Earth (below 300 km altitude) where atmospheric drag is significant, or to artificial satellites orbiting Mars in low orbit.

[0060] Based on the above, this embodiment makes it possible to reduce the cost of satellite launch while reducing atmospheric drag.

[0061] Furthermore, the provision of the frame portion 112 and the linear portion 113 makes it easier to fold the aerodynamic shaping portion 110, and also makes it easier to form the conical shape of the aerodynamic shaping portion 110.

[0062] Furthermore, since the surface portion 114 is made of a material resistant to atomic oxygen, damage to the components of the satellite 1 due to atomic oxygen can be reduced.

[0063] Furthermore, by making the surface portion 114 out of a material that has specular reflectivity of gas molecules, the effect of atmospheric resistance can be further reduced.

[0064] In the above embodiment, the aerodynamic shaping section 110 was folded so that the tip of the frame section 112 (the first frame member 112A) was located on the + side in the X direction of the satellite 1, but the disclosure is not limited thereto. For example, as shown in Figure 9, the first frame member 112A may be folded so that it is sandwiched between the second frame member 112B and the third frame member 112C. In this case, the connection portion between the first frame member 112A and the second frame member 112B may be configured to be locked by the locking section 120.

[0065] Furthermore, although the above embodiment shows that the frame portion is composed of three frame members, this disclosure is not limited thereto, and it may be composed of four or more frame members, or even just two frame members.

[0066] Furthermore, in the above embodiment, the aerodynamic shaping section was folded on the tip surface of the satellite body, but this disclosure is not limited thereto. For example, as shown in Figure 10, the aerodynamic shaping section 110 may be folded so that the frame member follows the side portion of the satellite body 11. In the example shown in Figure 10, the frame portion is composed of two frame members 112G and 112H, and the frame member 112H located at the tip of the frame portion is folded along the side portion of the satellite body 11.

[0067] Furthermore, although the above embodiment included a frame section having multiple frame members, this disclosure is not limited thereto, and a frame section may not be provided.

[0068] As an example of a configuration without a frame, as shown in Figures 11A and 11B, there is a configuration having a surface portion 114 and a spiral biasing member 115.

[0069] The biasing member 115 is a spring member that biases the surface portion 114 toward the positive side in the X direction, and constitutes the framework of the surface portion 114. The surface portion 114 is the same member as in the above embodiment, and is configured to be conical in shape by the biasing member 115 unless any external force is applied (see Figure 11A).

[0070] For example, by compressing the biasing member 115 and locking the end of the biasing member 115 located at the tip of the surface portion 114 with a locking part (not shown), the surface portion 114 and the biasing member 115 become folded (see Figure 11B). Then, when the locking by the locking part is released, the biasing member 115 deforms the surface portion 114 into a conical shape (see Figure 11A).

[0071] Another configuration that does not have a frame is one in which the surface portion 114 is inflated with air.

[0072] In this configuration, for example, when the surface portion 114 is folded, air is injected from the inside of the surface portion 114 to deform it into a cone shape.

[0073] Furthermore, although the cone shape in the above embodiment was a square pyramid, this disclosure is not limited to this, and the cone shape does not have to be a square pyramid as long as it matches the shape of the satellite body. For example, if the satellite body is constructed as a cylinder, the cone shape may be a cone. Also, if the satellite body is constructed as a triangular prism, the cone shape may be a triangular pyramid.

[0074] Furthermore, in the above embodiment, the material having specular reflectivity was defined as a material with a small thermal adaptation coefficient α, but this disclosure is not limited to this. For example, a material determined based on an index other than the thermal adaptation coefficient may be determined as a material having specular reflectivity.

[0075] Furthermore, the embodiments described above are merely examples of how this disclosure may be implemented, and the technical scope of this disclosure should not be limited by them. In other words, this disclosure can be implemented in various ways without departing from its essence or its main features.

[0076] All disclosures in the specification, drawings, and abstract contained in the Japanese application 2024-162025, filed on September 19, 2024, are incorporated herein by reference.

[0077] The aerodynamic device of this disclosure is useful as an aerodynamic device and satellite capable of reducing launch costs while reducing atmospheric drag.

[0078] 1 Satellite 11 Satellite body 100 Aerodynamic device 110 Aerodynamic shaping section 111 Bottom section 112 Frame section 112A First frame member 112B Second frame member 112C Third frame member 112D Hinge member 112E Hinge member 112F Hinge member 113 Linear section 114 Surface section 120 Locking section

Claims

1. An aerodynamic device for reducing the effects of atmospheric drag on a satellite, comprising an aerodynamic shaping section provided at the tip of the satellite body, wherein the aerodynamic shaping section is configured to be deformable between a first state in which it is conical in shape and a second state in which it is folded from the first state.

2. The aerodynamic device according to claim 1, further comprising a locking mechanism for locking the aerodynamic shaping section into the second state, wherein the aerodynamic shaping section deforms from the second state to the first state when the locking mechanism is released.

3. The aerodynamic device according to claim 2, wherein the locking part locks the aerodynamic shaping part when the satellite is launched and unlocks the aerodynamic shaping part after the satellite is launched.

4. The aerodynamic device according to claim 1, wherein the aerodynamic shaping portion comprises a base portion that constitutes the bottom surface of the conical shape, a surface portion that constitutes the surface of the side portion of the conical shape, and a linear portion that connects the base portion and the tip of the conical shape and has a restoring force for maintaining the aerodynamic shaping portion in the first state.

5. The aerodynamic device according to claim 4, wherein the aerodynamic shaping portion further comprises a plurality of frame members that constitute a part of the side surface of the conical shape and are foldably attached to the bottom surface, and the linear portion is provided on the bottom surface at locations other than where the plurality of frame members are attached.

6. The aerodynamic device according to claim 5, wherein the surface portion comprises: a first portion which is made of a foldable member and which constitutes the sides of the conical shape other than the plurality of frame members; and a second portion which is attached to the surface of the plurality of frame members.

7. The aerodynamic device according to claim 4, wherein the surface portion is made of a material resistant to atomic oxygen.

8. The aerodynamic device according to claim 4, wherein the surface portion is made of a material having specular reflectivity of gas molecules that collide with the surface during the flight of the satellite.

9. A satellite comprising a satellite body and an aerodynamic shaping section provided at the tip of the satellite body, wherein the aerodynamic shaping section is configured to be deformable between a first state in which it is conical in shape and a second state in which it is folded from the first state.

Images