Artificial Satellite

Abstract

Disclosed is an artificial satellite including a battery pack capable of dissipating heat, at least one radiator capable of conveying the heat dissipated by the battery pack into space, and a low-dissipation equipment item having an individual power flux density of less than 250 watts/m.sup.2. The satellite includes a thermally insulating cover delimiting, together with the radiator, an interior isothermal zone in which thermal control takes place by radiation, the battery pack and the low-dissipation equipment being arranged in thermally insulating cover. The battery pack has an operating range of between 0? C. and 50? C. and preferably of between 10? C. and 30? C.

Claims

1. An artificial satellite comprising: at least one battery pack configured to dissipate heat, at least one radiator configured to convey the heat dissipated by the battery pack into space, and at least one low-dissipation equipment item having an individual power flux density of less than 250 watts/m.sup.2, wherein the artificial satellite comprises a thermally insulating cover delimiting, together with said radiator, an interior isothermal zone in which thermal control takes place by radiation, and wherein said battery pack and said low-dissipation equipment are arranged in said thermally insulating cover, and said battery pack has an operating range of between 0? C. and 50? C.

2. The artificial satellite according to claim 1 wherein said battery pack is a Lithium battery pack.

3. The artificial satellite according to claim 1, wherein said low-dissipation equipment comprises a propellant storage and distribution system.

4. The artificial satellite according to claim 3, wherein said propellant storage and distribution system comprises at least one equipment item from among a tank, distribution pipes, valves, filters, and a portion of nozzles.

5. The artificial satellite according to claim 1, wherein said low-dissipation equipment comprises at least one reaction wheel.

6. The artificial satellite according to claim 1, wherein the thermally insulating cover is made of a flexible material.

7. The artificial satellite according to claim 1, which furthermore comprises heating equipment attached to said radiator.

8. The artificial satellite according to claim 1, which comprises: a central structure, at least one propellant tank secured to said central structure, propellant distribution pipes attached at least in part to the central structure, and valves installed on the pipes, and wherein the insulating thermal cover comprises a sheath slipped over said central structure, said sheath containing: said central structure, said tank, at least a portion of said pipes, and said valves.

9. The artificial satellite according to claim 8, wherein said sheath has a peripheral edge attached to an upper portion of the first radiator.

10. The artificial satellite according to claim 9, which comprises: an anti-Earth face supporting the central structure, wherein the thermal insulating cover comprises a substantially flat part of insulating material covering the anti-Earth face, wherein said part made of insulating material is secured to a lower portion of said at least one radiator so as to form, together with said sheath and said at least one radiator, a closed envelope.

11. The artificial satellite according to claim 1, wherein the low-dissipation equipment items of the satellite dissipate a heat flux of less than 40 watts.

12. The artificial satellite according to claim 2, wherein said low-dissipation equipment comprises a propellant storage and distribution system.

13. The artificial satellite according to claim 2, wherein said low-dissipation equipment comprises at least one reaction wheel.

14. The artificial satellite according to claim 3, wherein said low-dissipation equipment comprises at least one reaction wheel.

15. The artificial satellite according to claim 4, wherein said low-dissipation equipment comprises at least one reaction wheel.

16. The artificial satellite according to claim 2, wherein the thermally insulating cover is made of multi-layer insulation.

17. The artificial satellite according to claim 3, wherein the thermally insulating cover is made of multi-layer insulation.

18. The artificial satellite according to claim 2, which furthermore comprises heating equipment attached to said radiator.

19. The artificial satellite according to claim 1 wherein said battery pack has an operating range of between 10? C. and 30? C.

20. The artificial satellite according to claim 2 wherein said battery pack is a Lithium-Ion battery pack.

Description

(1) The invention will be better understood from the following description provided solely as an example and given in reference to the drawings, in which:

(2) FIG. 1A is a schematic view showing thermal zones according to the prior art;

(3) FIG. 1B is a schematic view of an artificial satellite according to the prior art

(4) FIG. 2 is a schematic view of a portion of propellant distribution pipes according to the prior art;

(5) FIG. 3A is a schematic view showing thermal zones according to a first embodiment of the invention;

(6) FIG. 3B is a schematic view of an artificial satellite according to the first embodiment of the invention; and

(7) FIG. 4A is a schematic view showing thermal zones according to a second embodiment of the invention;

(8) FIG. 4B is a schematic view of an artificial satellite according to the second embodiment of the invention.

(9) The present invention is in the field of artificial satellites and particularly in the field of geostationary satellites.

(10) In reference to FIG. 3B, artificial satellite 38 according to the first embodiment of the invention consists of a cubic or parallelepiped box 40 comprising an anti-Earth face 46, a hollow central structure 44 resting on anti-Earth face 46, an Earth face 42, East and West faces carrying equipment items (not shown), and North face 48 and South face 50 carrying radiators and equipment items.

(11) The satellite according to the invention in addition comprises a propulsion system which may be a chemical or plasma propulsion system (not shown in the figures) or consist of a combined use of these types of propulsion.

(12) The propulsion system comprises a propellant storage and distribution system 52 and two or more nozzles 54 installed on anti-Earth face 46.

(13) Propellant storage and distribution system 52 comprises two tanks 56 attached to central structure 44, propellant distribution pipes 58 which connect each tank to each nozzle, and valves 59 and filters 60 installed on pipes 58. Individually, these equipment items dissipate little heat (typically less than 3 watts) and also have a low power flux density (a value represented by the thermal power dissipated by the equipment in relation to the dissipation surface of the equipment, with this value being expressed in watt/m.sup.2), typically less than 250 watts/m.sup.2. In the present patent application, equipment items which have a thermal power flux density of less than 250 watts/m.sup.2 are referred to as low-dissipation equipment items. The equipment items of propellant storage and distribution system 52 are therefore low-dissipation equipment items in accordance with the present patent application. These equipment items do not require any conductive thermal control because the removal of their heat can be done effectively by radiative heat exchange when they are placed in a cooler environment. On the contrary, equipment items which individually have an individual power flux density greater than 250 watts/m.sup.2 require conductive thermal control and must be installed directly on a radiator or coupled to a radiator by means of conductive means, such as heat pipes or metal braids.

(14) Each of North face 48 and South face 50 is provided with a battery pack 62 capable of dissipating heat during its discharge operations, and a first radiator 64 in thermal contact with battery pack 62 for conveying the heat dissipated by the battery pack into space.

(15) According to the invention, battery pack 62 is chosen so as to be able to function at temperatures of between 0? C. and 50? C., and preferably at temperatures of between +10? C. and +30? C.

(16) Advantageously, battery pack 62 comprises a set of Lithium-Ion batteries. These batteries feature an operating temperature typically between +10? C. and +30? C.

(17) As a variant, any other battery having an operating temperature range compatible with the propulsion system, that is, between 0? C. and +50? C., could be used, such as, for instance, Lithium-Sulfur batteries.

(18) Advantageously, according to the invention, propellant storage and distribution system 52 and battery packs 62 are arranged in a thermally insulating cover or envelope 66 secured to the first two radiators 64 and defining, together with them, a first interior isothermal zone 68.

(19) This cover 66 is made of an insulating material. This material is preferably flexible. Advantageously, this cover 66 is made of a material called Multi Layer Insulation (MLI).

(20) According to the illustrated embodiment example, this thermally insulating cover 66 comprises an upper sheath 70 and a lower part 72 of insulating material. Sheath 70 is advantageously bell-shaped. The sheath is closed at its upper end and flared at its lower end. Sheath 70 has a peripheral edge 74. A portion of this peripheral edge is attached along an upper portion 75 of first radiators 64.

(21) Sheath 70 can be easily slipped over or removed from central structure 44. Once installed, it surrounds the upper portion of central structure 44, tanks 56, pipes 58, valves 59, and filters 60. Sheath 70 may consist of one or a plurality of insulating pieces arranged together so as to form a sealed enclosure.

(22) Part 72 made of insulating material is substantially flat. This part comprises opening through which the nozzles pass. Peripheral edge 76 of this part 72 is attached along a lower portion 77 of the first radiators and to the peripheral edge 74 of the sheath. Consequently, sheath 70, first radiators 64, and part 72 made of insulating material form a closed enclosure defining a three-dimensional space referred to as first isothermal zone 68 in the present patent application. The removal of the heat generated in this cover 66 is done by means of first radiators 64.

(23) In order to keep the temperature in first isothermal zone 68 at the minimum temperature that can be withstood by battery packs 62, heating equipment 78, of the small heater type, are arranged in said cover 66. As described earlier, this minimum temperature is +10? C. when Lithium-Ion battery packs are used.

(24) According to the embodiment example shown in the figures, North face 48 and South face 50 are also provided with a second radiator 80, a third radiator 82, and a fourth radiator 84, to which are connected on-board computer 86, electrical power supply unit 88, payload 90 operating at low power, and payload 92 operating at high power. Layers 94 of multi-layer insulation are attached between each radiator and to Earth face 42 so as to create, together with sheath 70, a second isothermal zone 96.

(25) This second isothermal zone 96 also comprises reaction wheels 97, each of which is connected to a radiator by a thermal link 98 of the heat pipe or metal braid type.

(26) Lastly, this second isothermal zone 96 comprises heating equipment 99 of the small heater type to keep this zone at a temperature of between ?10? C. and +50? C.

(27) According to a variant not illustrated, the satellite comprises more than two isothermal zones, each of which being delimited by a layer of multi-layer insulation and a radiator. For example, the satellite may comprise: a first isothermal zone identical to the thermal zone illustrated in FIG. 3B, a second isothermal zone kept at a temperature of between +50? C. and ?20? C.; this second isothermal zone comprises second radiator 80, reaction wheels 97, on-board computer 86, electrical power supply unit 88, and heating equipment 99, a third isothermal zone kept at a temperature of between ?10? C. and +50? C., the third isothermal zone comprising third radiator 82, the payload operating at low power 90, and heating equipment 99, a fourth isothermal zone kept at a temperature of between ?20? C. and +70? C., the fourth isothermal zone comprising fourth radiator 84, the payload operating at low power 92, and heating equipment 99.

(28) According to another less advantageous variant, not shown, a single battery assembly and a single first radiator 64 are included in the first isothermal zone, with the battery assembly located on the other side of the satellite being wrapped in its own multi-layer insulation.

(29) As a variant, the low-dissipation equipment items comprise a gyroscope.

(30) FIG. 4B shows an artificial satellite 100 according to a second embodiment of the invention. Artificial satellite 100 according to the second embodiment is identical to satellite 38 according to the first embodiment of the invention, except for the fact that reaction wheel or wheels 97 are placed in first isothermal zone 68 instead of in second isothermal zone 96.

(31) Each reaction wheel 97 has a thermal power flux density of less than 250 watts/m.sup.2. The reaction wheel or wheels are therefore part of the low-dissipation equipment items in accordance with the present patent application.

(32) This second embodiment will not be described in detail. The components of satellite 100 according to the second embodiment, which are identical or similar to the components of satellite 38 according to the first embodiment, include the same reference numbers and will not be described a second time.

(33) As in the case of the first embodiment, the satellite according to the second embodiment may include several isothermal zones. For example, the satellite may include four isothermal zones as described above. Still, in this case reaction wheels 97 are placed in the first isothermal zone.

(34) As a variant, nozzles 54 or additional nozzles are installed on a lower portion of North face 48, South face 50, the East face, or the West face. In this case, nozzles 54 and/or the additional nozzles are placed below sheath 70 and are contained in first isothermal zone 68.