WO2003106264A1

WO2003106264A1 - Cooling device for space craft

Info

Publication number: WO2003106264A1
Application number: PCT/FR2003/001794
Authority: WO
Inventors: Bertrand Poulain
Original assignee: Astrium Sas
Priority date: 2002-06-13
Filing date: 2003-06-13
Publication date: 2003-12-24
Also published as: FR2840881B1; FR2840881A1; AU2003255674A1

Abstract

The invention concerns a device for cooling travelling-wave tubes (26) having a collector (28) preferably operating at high temperature and thermally insulated from the rest of the tube, the device comprising a radiator (15) thermally uncoupled from the satellite body and placed in an orientation such that it disperses heat by radiation into space and a heat exchanging fluid loop (25) between hot exchangers (34, 33) thermally connected to the collectors (28) and the emitting units (30) of the tubes (26) borne by the satellite and a cold exchanger (32) belonging to the radiator (15).

Description

COOLING DEVICE FOR A SPACE VEHICLE

The present invention relates to cooling devices intended to dissipate the heat generated by charges placed on a space vehicle, in particular a geostationary satellite, and in particular the heat released by traveling wave tubes, in particular at high power at radio frequency (exceeding typically 100 watts), used to equip loads placed on telecommunications satellites. Traveling wave tubes, or TOP, now used on telecommunication satellites, have a collector which can withstand a high temperature, exceeding 90 ° C and up to 240 ° C in some cases. To dissipate the heat generated at the collector, one especially uses at present a mounting of the traveling waves tubes such as a radiator prolonging the collector is placed outside the body of the satellite and radiates towards the black space. This solution has many drawbacks. The TOPs are placed against walls of the body remote from those which carry the transmitting antennas, which imposes waveguides of appreciable length, generating a significant loss of power of the radio frequency signals. Furthermore, the coating of the connections connecting the collector to the barrel of the tube being at the end of the collector, it is subjected to extreme thermal environments and to stresses which weaken it, in particular during temperature changes.

The patents FR 93 00 729 and US Pat. satellite. However, this solution still leaves the need to place the TOP near a north or south face of the satellite.

Finally, it has been proposed to connect the TOP or each TOP to a radiator carried by a north or south face of a satellite by a heat pipe. But such a heat pipe, consisting of a rigid tube whose internal surface is provided with capillary return grooves of the condensed fluid, is necessarily short and rigid. It also requires placing the TOP near the radiator.

The present invention aims to provide a cooling device for a space vehicle, in particular for a geostationary telecommunication satellite, which meets the requirements of practice better than those previously known, in particular in that it makes it possible to place TOPs at a significant distance d '' at least one heat dissipation radiator, and therefore to leave a wide latitude for setting up the TOP in the satellite. For this, the invention uses the capacity of the materials composing the standard TOP collector (without integrated liquid heat exchanger) and / or specific current to withstand temperatures exceeding 90 ° C in operation.

The invention therefore proposes, in particular, a device for cooling at least one traveling wave tube having an emitter and a collector, the latter preferably operating at high temperature and being thermally isolated from the rest of the tube, for equipment of a load placed on a spacecraft, such as a satellite, the device comprising at least one radiator thermally decoupled from the body of the vehicle and placed in an orientation such that it dissipates heat by radiation towards space and at least a fluid heat exchange loop between at least one hot heat exchanger in thermal connection with said tube and at least one cold heat exchanger belonging to the radiator, and which is characterized in that said fluid loop is single-phase and constituted so in series cooling the emitter and then the collector of said traveling wave tube. The implementation of the invention makes it possible to place the TOPs anywhere in the satellite, because each fluid loop allows significant distances between a hot exchanger (thermally coupled to a TOP) and a cold exchanger (belonging to a radiator) . In particular, it is possible to place the TOPs near the transmitting antennas so as to eliminate the need for very long waveguides. The invention finds a particularly interesting application on satellites comprising a payload module, which can change significantly from satellite to satellite, and a service module capable of being produced in series. It is this service module which generally carries the radiators, deployable after putting into orbit, which dissipate the heat.

The TOPs are instead placed in the payload module. The invention makes it possible to ensure, with reduced thermal losses, the evacuation of the heat generated by the TOPs even if they are placed at a distance from the radiators which can reach several meters. TOP concerned by the invention requiring a hot exchanger at a temperature exceeding 90 ° C, the fluid used in the loop must be chosen accordingly. Generally, ammonia cannot be used, although it is frequently used at a lower temperature. In a single-phase loop with mechanical pumping, water, light hydrocarbons, fluorocarbons or other liquids compatible with high temperatures will often be used. Circulation will then be ensured by a pump.

In an advantageous embodiment, using a single-phase loop to cool several TOPs, it is proposed to cool the transmitters in series, then the collectors of said TOPs. In this case, the fluid loop is formed so that the fluid coming from at least one cold exchanger of a radiator passes successively in hot heat exchangers cooling the emitters of several traveling wave tubes, then in hot exchangers cooling the collectors of said traveling wave tubes. The fluid loop, in which the fluid is set in motion by a pump, can be regulated in various ways, for example by controlling the pump or, better, by controlling a connection between the inlet and the outlet of the minus a cold heat exchanger.

Because the single-phase fluid loops make it possible to accept large distances and tortuous paths between cold exchanger (s) and hot exchanger (s), the device according to the invention is particularly usable when at least one cold exchanger is integrated into a radiator which can pivot by at least one hinge, from a position where the radiator is pressed against the body of the satellite (during launch) to a deployed position (after coming into orbit), at least one fluid loop comprising at least one flexible section making it possible to tolerate the passage of the radiator from one position to another. Generally, at least one flexible helical pipe section or "pigtail" will be used, which can be wrapped around at least one hinge hinge of the radiator.

An additional advantage of the deformable nature of at least one section of a fluid loop is the fact that the operation can be verified under conditions simulating those encountered in space, by using a vacuum chamber whose volume does not allow not place the satellite there with the radiators deployed; by providing one or more removable hinges, the satellite can be placed in the vacuum chamber with the radiator (s) at a distance from the body of the satellite, but still connected to the loads to be cooled, and in particular to the TOP, by the loop (s) whose operation can therefore be tested.

The above characteristics as well as others will appear better on reading the following description of particular embodiments given by way of nonlimiting examples. The description refers to the accompanying drawings in which:

- Figure 1 is a diagram showing the general configuration of a geostationary telecommunications satellite provided with deployable radiators.

- Figure 2 shows a possible constitution of a single-phase fluid loop allowing several TOPs to be cooled in series

- Figure 3 shows schematically a possible constitution of heat exchangers between TOP and fluid loop.

- Figure 4 shows a possible connection mode between a radiator and the wall of the service module of a satellite, allowing to deploy the radiator once the satellite in orbit. Satellite S, the general constitution of which is shown in FIG. 1, is intended to be placed on a geostationary equatorial orbit 10. It is intended to be stabilized along three axes: X, Y and Z.

It comprises a service module 14, which carries solar panels 16 provided with motors enabling them to rotate around the pitch axis Y to keep them oriented towards the sun. The walls conventionally called “north” and “south” of the structure of the module 14 (along an axis parallel to the polar axis NS of the earth 12) are generally provided so as to have a high emissivity, but at the same time to have limited absorption of solar radiation. Most of the heat dissipation is provided by one or, preferably, by several deployable radiators 15, four for example, as shown in Figure 1, which, in operation, are deployed and oriented to the north and south. The service module 14 is fixed to a payload module 17 which contains loads which must be cooled, in particular traveling waves or TOP tubes connected to antennas 20 for transmitting to earth 12.

The cooling device shown in FIG. 2 includes a single-phase fluid loop 25, which is a closed loop through which a heat-transfer liquid passes, and this device is intended to cool several TOP 26s, the collector 28 of each of which is designed to operate at a temperature above 90 ° C and not to exceed a value of the order of 240 ° C. The collector 28 of each TOP 26 dissipates approximately 90% of the heat generated by this TOP 26. The part of each TOP 26 containing the barrel of the emitter 30 of this TOP 26 must be kept at a lower temperature, typically not exceeding not about 75 ° C.

In FIG. 2, the fluid loop 25 comprises a so-called “cold” heat exchanger 32, incorporated into a radiator 15, and two series of so-called “hot” heat exchangers 33 and 34. A pump 36 circulates the liquid which fills the loop 25. This liquid thus circulates successively in series in the first “hot” heat exchangers 33 each associated with the barrel of the emitter 30 of one of the TOP 26 respectively, then in series in the second “hot” heat exchangers 34 each ensuring the cooling of the manifold 28 of one of the TOP 26 respectively, then in the cold exchanger 32 The temperature regulation can be ensured in various ways. One can in particular use a three-way valve 38 which, in one position, allows circulation in the fluid loop 25 as it has just been defined and, in at least one other position, more or less completely opens a bypass 40 at least partially short-circuits the heat exchanger 32.

Each of the TOP 26s can be mounted on the body of the satellite S as shown in FIG. 3. Each TOP 26 is carried by the skin 41 of the satellite by means of a thermally insulating layer 42 and the exchangers 33 and 34 heat dissipation associated with this TOP 26, and one of which 33, from the first series of hot exchangers, is in heat exchange relation with the barrel of the corresponding transmitter 30, while the other 34 , of the second series of hot exchangers, is in heat exchange relationship with the corresponding collector 28. The bundle 43 of wires connecting the collector 28 to the barrel can constitute one. ply passing through the cover of the terminal connector. The collector 28 and the barrel of the emitter 30 are attached to the associated exchanger 34 or 33 can be carried out using a thermal seal capable of withstanding the temperature in operation, making it possible to minimize the temperature gradient.

The same satellite S can carry several cooling loops such as 25, either to provide redundancy, or to have several groups of TOP 26 provided with independent cooling circuits. Additional loads to be cooled 44 can be interposed on at least one loop 25. In this case, as shown in FIG. 2, the additional load (s) to be cooled 44 is or are in heat exchange relation with the fluid loop 25 in one or more point (s) located between the series of first hot exchangers 33 and the series of second hot exchangers 34.

Each radiator 15 containing a cold exchanger 32 is mounted on the service module 15 of the satellite S by one or more hinges 52 making it possible to deploy the radiator 15 from a storage position, where it is pressed against the body of the satellite, for example against a so-called “east” or “west” face of the module 15, in the deployed position in which the radiator 15 is shown in FIG. 1. The connection (or connections) between the cold exchanger 32 and the rest of the loop corresponding fluid must tolerate this displacement. As shown in FIG. 4, each connection is constituted by a flexible section 50 in a helix shape of the pipe of the fluid loop 25. The use of a fluid loop with mechanical pumping 36 makes it possible to accept strong curvatures of the pipes of the loop fluid 25.

The constitution and the surface condition of the radiator 15 will be adapted to the operating temperature chosen so as to obtain a high emissivity. The coatings used to obtain high emissivities at high temperatures are for example: white paints up to 160 ° C, aluminum oxidized on the surface up to 240 ° C. At lower temperatures, up to approximately 120 ° C, a bonded coating of solar optical reflector can be used.

The cooling device with at least one single-phase fluid loop with at least one cold exchanger integrated in at least one deployable radiator according to the invention makes it possible to cool a set of standard TOPs, that is to say without an integrated liquid heat exchanger, or specific, which can be placed as required in any location in the satellite, and more specifically in its payload module, without proximity constraint vis-à-vis the deployable radiators, which can be folded down, or even removed using removable hinges, but without breaking the fluid loop (s), for testing the satellite on the ground.

Claims

1. Device for cooling at least one traveling wave tube (26) having an emitter (30) and a collector (28), the latter preferably operating at high temperature by being thermally isolated from the rest of the tube (26) for equipping a load placed on a spacecraft, such as a satellite, the device comprising at least one radiator (15) thermally decoupled from the body of the vehicle and placed in an orientation such that it dissipates heat by radiation towards the space and at least one fluid heat exchange loop between at least one hot heat exchanger in thermal connection with said tube (26) and at least one cold heat exchanger (32) belonging to the radiator (15), characterized in that said fluid loop is single-phase and constituted so as to cool in series

(33, 34) the transmitter (30) then the collector (28) of said traveling wave tube (26).

2. Device according to claim 1, characterized in that the loop is constituted so that the fluid coming from at least one cold exchanger (32) of a radiator (15) passes successively through hot heat exchangers (33) cooling the transmitters (30) of several traveling wave tubes (26), then in hot exchangers (34) cooling the collectors (28) of said traveling wave tubes (26).

3. Device according to one of claims 1 and 2, characterized in that the fluid is set in motion in the fluid loop by a pump (36).

4. Device according to one of claims 1 to 3, characterized in that the fluid loop is regulated by controlling a connection (38, 40) between the inlet and the outlet of at least one cold heat exchanger ( 32).

5. Device according to any one of the preceding claims 1 to 4, characterized in that the fluid loop comprises at least one flexible section (50).

6. Space vehicle comprising at least one fluid loop according to any one of the preceding claims 1 to 5, of which said cold exchanger (32) is integrated into a radiator (15) which can pivot by at least one hinge (52) of a position where said radiator (15) is pressed against the body of the satellite in a deployed position, said fluid loop comprising at least one flexible section (50) tolerating the passage of said radiator (15) from one position to another.

7. Space vehicle according to claim 6, characterized in that it comprises a payload module (17), which contains traveling wave tubes (26) to be cooled and connected to antennas (20) carried by said module payload (17) attached to a service module (14) carrying orientable solar panels (16) and on which is deployable at least one radiator (15) incorporating at least one cold exchanger (32) of at least one fluid loop (25) whose hot exchangers (33, 34) are in said payload module (17).

8. Space vehicle according to claim 7, characterized in that the payload module (17) contains at least one additional load (44) to be cooled, in heat exchange relationship with at least one fluid loop (25) in one point located between the first hot exchangers (33) cooling the emitters (30) and the second hot exchangers (34) cooling the collectors (28) of said fluid loop (25).

9. Space vehicle according to any one of claims 6 to 8, characterized in that at least one hinge (52) of articulation of at least one deployable radiator (15) is removable without breaking the fluid loop (25 ) connecting at least one cold exchanger (32) of said radiator (15) to hot exchangers (33, 34) of said loop (25).