SATELLITE WITH EXTENDABLE ANTENNA

Description

TECHNICAL FIELD

[0001] The invention relates to satellites comprising a radiating antenna and, in particular, to a radiating antenna comprising a two-phase loop. BACKGROUND

[0002] Scanning radiating antennas, often called active antennas for space applications, generally comprise a few dozen or a few hundred radiating elements associated with amplifiers and have surfaces of less than one square meter. These active radiating antennas can be easily assembled on Earth before being transported to space. These radiating antennas are also easily transportable on board rockets and / or space shuttles. In addition, during use, part of the power consumed by the amplifiers and radiating elements is dissipated in the form of heat that must be evacuated, for example, by thermal control systems based on the use of passive fluidic components (such as heat pipes or capillary pumping loops). To evacuate the heat, these antennas require proximity between the amplifiers and radiators.However, for satellites with telecommunications applications, in order to ensure high throughput and ultra-high throughput, active antennas require a large surface area and require high power consumption, thus generating high power dissipation. Thus, for applications requiring antennas with a larger surface area (for example, greater than 8 m 2 < ) and numerous radiating elements (for example, several thousand), known systems comprising radiating antennas do not guarantee a uniform temperature over their entire surface when the emitted power is high. In addition, large surface area antennas comprising numerous radiating elements are difficult to transport on board rockets and / or space shuttles, difficult to assemble and dissipate high powers (for example, greater than 10 kW) which cannot be recovered by current thermal control systems.

[0003] Finally, the concept of temperature homogeneity between the different radiating elements is a key parameter to guarantee the radiofrequency performance of systems comprising radiating antennas. A gradient of 5 to 10°C ensures this performance. US 2021 / 318074 A1 relates to a panel assembly intended for use with a spacecraft that includes a payload, a radiator panel and a heat pipe. The payload is configured to generate waste heat during operation. The radiator panel is spaced from the payload and is configured to dissipate waste heat. The heat pipe is coupled to the payload and the radiator panel. The heat pipe includes a flexible portion to allow the radiator panel to move relative to the payload.In addition, the heat pipe is configured to transfer waste heat from the payload to the radiator panel. US 6003817 A relates to deployable thermal panels that are actively controlled throughout a satellite's orbit to provide heat dissipation. By adjusting the angle of incidence of solar rays on the panel and controlling the flow of a fluid through flexible heat transport tubes, heat is charged and discharged to provide thermal stability for components that have special thermal requirements. An optional antenna panel on the nadir side of the satellite has a transmitting antenna side on one surface and a heat radiating side on the opposite surface. In addition, the movements of the thermal panels are controlled to produce torques that oppose the disturbing torques. SUMMARY

[0004] In order to overcome the drawbacks of satellites comprising radiating antennas with large surfaces (for example, greater than 8 m 2 < ) and having numerous radiating elements (for example, several thousand), the invention proposes a satellite comprising a radiating antenna comprising a fixed panel and at least one deployable panel and a two-phase loop comprising flexible connections.

[0005] To this end, the invention relates to a satellite that can be assembled and transported, even when the radiating antenna has a large surface area and high power. In addition, the two-phase loop makes it possible to recover the heat emitted by numerous radiating elements.

[0006] The invention improves the situation by proposing a satellite comprising: a chassis, a radiating antenna comprising: radiating elements; amplifiers associated with the radiating elements, a base on which the radiating elements and the amplifiers are mounted, the base being configured to carry the radiating elements and the amplifiers and to evacuate heat emitted by the radiating elements and / or the amplifiers when they are in operation, the base comprising at least one fixed panel fixed to the chassis and at least one deployable panel hinged to the first panel, each of the panels carrying at least one of the radiating elements; and a two-phase loop in which a fluid circulates and configured to recover the heat and transmitted to the base, the two-phase loop comprising: two portions, each fixed to one of the two panels of the base;and flexible connections comprising at least one flexible thermal channel and connecting the portions of the two-phase loop, the fluid circulating in the at least one flexible thermal channel.;

[0007] In one embodiment, the deployable panel is configured to have a deployed position when the satellite is in service and a stowed position when the satellite is in transport.

[0008] In one embodiment, the two-phase loop comprises a pump configured to circulate the fluid with a flow rate greater than a predetermined value and a two-phase state in each panel and at least one condenser configured to remove heat from the fluid.

[0009] In one embodiment, the radiating antenna has an area ranging from 8 m 2 < to 20 m 2 < .

[0010] In one embodiment, the fluid is a heat transfer fluid configured for use in a liquid state and in a two-phase state.

[0011] In one embodiment, the heat transfer fluid is ammonia.

[0012] In one embodiment, the flexible connections include channels configured to transmit signals carrying an electromagnetic wave emitted and / or received by the radiating elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The invention will be better understood and other advantages will appear on reading the description which follows, given without limitation and thanks to the figures among which: There figure 1 illustrates an example of a satellite comprising a radiating antenna in the deployed position seen from the side; The figure 2 illustrates an example of a satellite comprising a radiating antenna in the folded position seen from the side; The figure 3 illustrates an example of a radiating antenna in the deployed position seen from above; and The figure 4 illustrates another example of a radiating antenna in the deployed position seen from above. DETAILED DESCRIPTION

[0014] There figure 1 illustrates an example of a satellite 100 seen in profile. The satellite comprises a chassis 102 and a radiating antenna 120. The radiating antenna comprises radiating elements 110. For example, the radiating elements 110 may be horn antennas allowing the reception of terrestrial signals or the transmission of signals to Earth. The radiating elements are associated with amplifiers 103 making it possible to amplify the signals received and / or transmitted by the radiating elements 110. For example, each of the radiating elements 110 may be associated with an amplifier 103.

[0015] In addition, the radiating antenna comprises a base 104 on which the radiating elements 110 and the amplifiers 103 are mounted. The base 104 is configured to carry the radiating elements 110 and to dissipate heat emitted by the radiating elements 110 and / or the amplifiers 103 when they are in operation. The base 104 comprises at least one fixed panel 104a fixed to the frame and at least one deployable panel 104b, 104c hinged to the fixed panel 104a, each of the panels carrying at least one of the radiating elements 110 and the associated amplifier 103. In the example illustrated in the figure 1 , the radiating antenna comprises two deployable panels 104b, 104c, each being hinged to the fixed panel 104a. In another example, the radiating antenna may comprise a single deployable panel.

[0016] In the figure 1 , the deployable panels 104b, 104c have a deployed position. The figure 2 illustrates the satellite 100 seen from the side, deployable panels 104b, 104c having a folded position. Indeed, the deployable panels 104b, 104c are configured to have a deployed position which can be used when the satellite 100 is in service and a folded position when the satellite 100 is in transport. The folded position makes it possible, in the case of large radiating antennas (for example, having a surface area greater than 8 m 2 < ) to facilitate the transport of the satellite on board rockets and / or space shuttles by optimizing the space required for transport. In one example, only one of the two deployable panels 104b, 104c can be in the deployed position when the satellite is in use. The chassis can include hinged attachment mechanisms between the deployable panels and the fixed panel, allowing the deployable panels to move from the folded to the deployed position.

[0017] In addition, the radiating antenna 120 comprises a two-phase loop 106 in which a heat transfer fluid circulates. The fluid may be, for example, ammonia, pentafluoropropane or tetrafluoroethane (“freon” type, products sold by the company DuPont de Nemours). The two-phase loop 106 is configured to recover the heat emitted by the radiating elements 110 and / or the amplifiers 103 and transmitted to the base 104. In one example, the two-phase loop 106 may be configured to recover the heat also emitted by amplifiers and transmitted to the base 104. In the example of the figure 1 , the two-phase loop 106 comprises three portions 106a, 106b, 106c, each attached to one of the three panels 104a, 104b, 104c of the base 104. In addition, the two-phase loop 106 comprises flexible connections 108 comprising at least one flexible thermal channel and connecting the three portions 106a, 106b, 106c of the two-phase loop 106, the fluid circulating in the flexible thermal channel. In particular, the flexible connections 108 connect the portion of the two-phase loop 106 attached to the first deployable panel 104b with the portion of the two-phase loop 106 attached to the fixed panel 104a. Similarly, flexible connections 108 connect the portion of the two-phase loop 106 attached to the second deployable panel 104c with the portion of the two-phase loop 106 attached to the fixed panel 104a. In another example, the radiating antenna 120 may comprise a single deployable panel.Thus, the two-phase loop 106 may comprise only two portions, each fixed to one of the two panels of the base 104 (i.e. the deployable panel and the fixed panel 104a) and the flexible connections connect the portion of the two-phase loop 106 fixed to the deployable panel with the portion of the two-phase loop 106 fixed to the fixed panel 104a. More generally, it comprises as many deployable panels as necessary for its operation. The different deployable panels may each be hinged to the fixed panel 104a or even hinged to another deployable panel. Flexible connections 108 are provided at each joint comprising at least one thermal channel. All of these channels allow, within the same two-phase loop, the circulation of the heat transfer fluid in each of the panels, fixed and deployable.

[0018] There figure 3 illustrates the radiating antenna 120 seen from above and with the deployable panels 104b, 104c in the deployed position. In this example, the two-phase loop 106 comprises channels shown in dotted lines allowing the fluid to circulate and recover the heat from each of the radiating elements 110 and the associated amplifier 103. In this example, the channels are arranged on the lower face of the radiating antenna 120 (i.e. on the face of the base 104 in contact with the chassis 102). It is also possible to arrange the channels on the opposite face of the base, face on which the radiating elements 110 and the amplifiers 103 are arranged. It is also possible to embed the channels in the base 104. The channels can run along the edges of the base 104 and advantageously opposite each of the radiating elements 110 and amplifiers 103 in order to best ensure temperature homogeneity over the entire surface of the base 104.As illustrated in the . figure 3 , the fluid circulates in the radiating antenna 120 between a fluid inlet 112 and a fluid outlet 114.

[0019] The two-phase loop 106 comprises a pump 114 configured to circulate the fluid with a flow rate greater than a predetermined value and a two-phase state in each panel 104a, 104b, 104c. The predetermined value may depend for example on the pump, the fluid, a dimension of the two-phase loop. In particular, any type of pump 114 may be used to circulate the fluid in the two-phase loop 106, and the fluid circulating in the pump is in the liquid state. However, a two-phase state of the fluid (which may be, for example, ammonia) makes it possible to guarantee a high heat exchange coefficient between the fluid and the radiating elements 110 and / or amplifiers 103. On the contrary, when the fluid is in the liquid state, the heat exchange coefficient is low and the temperature of the fluid increases when it recovers heat from the radiating elements 110 and amplifiers 103.Thus, the two-phase loop 106 of the present invention is configured so that, when the fluid circulates in the two-phase loop 106 close to the radiating elements 110 and recovers the heat from the radiating elements 110, the temperature of the fluid increases until it reaches its saturation temperature. To have a two-phase state under each panel 104a, 104b, 104c, several solutions can be proposed such as the use of heaters, the regulation of the flow rate in the panels or the use of a heat exchanger between an inlet and an outlet of the panels. Thus, by having a fluid in the two-phase state making it possible to recover the heat emitted by the radiating elements and the amplifiers 103, it is possible to recover high dissipation powers (for example, greater than 10 kW) with a fluid temperature which remains constant as long as the fluid is in the two-phase state.The two-phase loop therefore makes it possible to recover the heat emitted by the radiating elements and the amplifiers 103, even for a very large number of radiating elements (for example, thousands) with constant exchange conditions and, therefore, temperature homogeneity of the radiating elements (with a difference of less than 10°C between the radiating elements), which is necessary to guarantee the radiofrequency performance of the radiating antenna.

[0020] In one example, the two-phase loop 106 may include a heat exchanger (not shown) between an outlet of the pump 114 and the inlet 112 in order to increase the temperature of the fluid to its saturation temperature before reaching the radiating elements 110.

[0021] In another example, the two-phase loop 106 may include one or more temperature sensors for measuring the temperature of the fluid at one or more locations and thus verifying whether the temperature of the fluid is indeed above the saturation temperature at the radiating antenna 120. Similarly, one or more temperature sensors may ensure that the temperature of the fluid is below the saturation temperature before circulating in the pump (the pump operating with a fluid in the liquid state.

[0022] In addition, the two-phase loop 106 comprises at least one condenser 116 configured to remove heat from the fluid. In the figure 3 , a condenser 116 is shown. However, in another example, two or more condensers may be used. For example, the condenser 116 may be thermally linked to one or more radiators for removing heat from the radiating elements 110 and associated amplifiers recovered by the fluid to the outside of the satellite 100. Thus, the condenser 116 allows the heat transfer fluid to be condensed and then the temperature of the fluid to be reduced below its saturation temperature in order to return to the liquid state. The fluid may therefore be in the liquid state at an outlet of the condenser 116 in order to be in the liquid state while circulating in the pump 114.

[0023] As illustrated in the figure 3 , in this example, the radiating antenna 120 comprises two deployable panels 104b, 104c which are in the deployed position. The flexible connections 108 make it possible to connect the portion 106a of the two-phase loop 106 which is placed on the fixed panel 104a with the portion 106b of the two-phase loop 106 which is placed on the deployable panel 104b. Similarly, the flexible connections 108 make it possible to connect the portion 106a of the two-phase loop 106 which is placed on the fixed panel 104a with the portion 106b of the two-phase loop 106 which is placed on the deployable panel 104c.

[0024] In one example, the flexible connections 108 comprise channels configured to transmit signals carrying an electromagnetic wave emitted and / or received by the radiating elements 110. For example, the flexible connections 108, in addition to transmitting the fluid through the two-phase loop 106, can transmit optical, electrical, etc. signals allowing the operation of the radiating antenna 120.

[0025] It is noted that in the example illustrated in the figure 3 , the pump is used to circulate the fluid with a two-phase state in each panel 104a, 104b, 104c. However, in another example, other systems may be used to circulate the fluid with a two-phase state in each panel, such as a compressor.

[0026] There figure 4 illustrates another example of a radiating antenna 220 seen from above and with the deployable panels 104b, 104c in the deployed position. In this example, the two-phase loop 106 is not shown. However, the two-phase loop 106 described above with regard to the figure 3can be used with the radiating antenna 220. The radiating antenna 220 comprises tiles 202 fixed on the base 104. Each tile 202 comprises radiating elements 110. Each tile 202 is connected to the adjacent tile(s) so as to form a radiating antenna 220 having the functionalities of a formed radiating antenna not being divided into different tiles. The tiles 202 make it easier to manufacture and assemble large radiating antennas. For example, the radiating antenna 220 can have a surface area ranging from 8 m 2 < to 20 m 2 < . Thus, by using tiles 202 allowing the radiating antenna 220 to be divided, for example, from 1 m 2 < to 2.5 m 2 < , the manufacture and assembly of the radiating antenna 220 can be facilitated.

[0027] Although the invention has been illustrated and described in detail using a preferred embodiment, the invention is not limited to the disclosed examples. Other variations may be deduced by those skilled in the art without departing from the scope of protection of the claimed invention. For example, in the examples described above, between 13 and 36 radiating elements have been shown. However, in other examples, the radiating antenna 120, 220 may comprise several hundred to several thousand radiating elements 110. In addition, the invention has been illustrated with two deployable panels. In another example, the satellite may comprise only one deployable panel. Furthermore, in the examples shown above, an amplifier is associated with a radiating element. However, in another example, an amplifier may be associated with several radiating elements.Furthermore, in the examples illustrated above, the radiating and amplifier elements are mounted on the upper face of the panels and the two-phase loop is on the lower face of the panels. However, in another example, the radiating elements may be fixed on the upper face of the panels, the amplifiers placed on trays placed inside the panels, and whose planes are orthogonal to the upper and lower faces of the panels.

Claims

1. A satellite comprising: a chassis (102); a radiating antenna (120) comprising: radiating elements (110); amplifiers (103) associated with the radiating elements; a base (104), on which the radiating elements and the amplifiers are mounted, the base being configured to support the radiating elements and the amplifiers and to discharge heat emitted by the radiating elements and / or the amplifiers (103) while they are operating, the base comprising at least one fixed panel (104a) fixed to the chassis and at least one deployable panel (104b, 104c) hinged to the first panel, each of the panels supporting at least one of the radiating elements and an amplifier; and a two-phase loop (106), in which a fluid circulates and which is configured to recover the heat and transferred to the base, the two-phase loop comprising: two portions (106a, 106b, 106c), each fixed to one of the two panels of the base; and flexible connections (108) comprising at least one flexible thermal channel and connecting the portions of the two-phase loop, with the fluid circulating in the at least one flexible thermal channel.

2. The satellite according to claim 1, wherein the deployable panel is configured to assume a deployed position when the satellite is in service and a stowed position when the satellite is transported.

3. The satellite according to any of the preceding claims, wherein the two-phase loop comprises a pump configured to circulate the fluid with a flow rate that is greater than a predetermined value and a two-phase state in each panel and at least one condenser configured to discharge heat from the fluid.

4. The satellite according to any of the preceding claims, wherein the radiating antenna has a surface area ranging from 8 m2 to 20 m2.

5. The satellite according to any of the preceding claims, wherein the fluid is a heat transfer fluid configured to be used in the liquid state and in the two-phase state.

6. The satellite according to claim 5, wherein the heat transfer fluid is ammonia.

7. The satellite according to any of the preceding claims, wherein the flexible connections comprise channels configured to transmit signals conveying an electromagnetic wave emitted and / or received by the radiating elements.