Cryogenic liquid storage system for a spacecraft

1. A cryogenic liquid storage system for a spacecraft, the system comprising:

at least one liquid tank having a diameter;

an outermost spherical casing surrounding the tank;

an evacuated space provided between the tank and the outermost casing;

a propellant management device made of material that is a good conductor of heat and that is cooled by a cryorefrigerator to localize the liquid inside the tank when in microgravity;

a filler pipe situated in the portion of the tank that is at the bottom when the tank is on the ground, and that is surrounded by an evacuated insulating double wall; and

a purge pipe connecting the tank to the outermost casing and presenting an internal length that is not less than half the diameter of the tank; and

means for holding the tank inside the outermost casing, the holding means being directly in contact with both the outermost casing and the tank and presenting a low thermal conductivity and being spaced apart angularly by 30° to 120° relative to the propellant management device that is cooled by the cryorefrigerator,

wherein said system includes super-insulating material interposed between the tank and the outermost casing,

wherein said holding means comprise a fastener frustoconical skirt of insulating material interposed in the vicinity of an equatorial plane between the tank and the outermost casing,

wherein said system includes an evaporator immersed in the liquid of the tank at the location closest to the cryorefrigerator, which the evaporator comprises a porous material and is extended by a tube of small section that is connected to the outermost casing; and

wherein a heater element is associated with the evaporator and is located at an outlet of the tube of small section and at the skirt or outermost spherical casing.

2. The system according to claim 1 , wherein the propellant management device is disposed on a polar axis of the tank.

3. The system according to claim 1 , wherein the liquid tank and the outermost casing are mounted in a central tube in the vicinity of the center of gravity of the spacecraft.

4. The system according to claim 1 , including a decoupling bellows interposed between the cryorefrigerator and the outermost casing.

5. The system according to claim 1 , including a cryorefrigerator having a cold head incorporated in the tank in the vicinity of a liquid takeoff opening, the cryorefrigerator being connected to a radiator by a cooling loop.

6. The system according to claim 5 , wherein the cryorefrigerator is of the Stirling type.

7. The system according to claim 5 , wherein the cryorefrigerator is of the pulsed gas tube type.

8. The system according to claim 1 , including a cryorefrigerator mounted directly on a radiator and connected to the tank by a cryogenic heat pipe.

9. The system according to claim 8 , wherein the cryorefrigerator is of the Stirling type.

10. The system according to claim 8 , wherein the cryorefrigerator is of the pulsed gas tube type.

11. The system according to claim 1 , including a cryorefrigerator of the Joule Thomson type.

12. The system according to claim 1 , wherein the cryogenic liquid stored in the tank is a liquefied inert gas comprising xenon, krypton, neon, or argon for feeding gridded plasma or ion electric thrusters.

13. The system according to claim 1 , wherein the cryogenic liquid stored in the tank is liquid oxygen.

14. The system according to claim 1 , wherein the spacecraft is constituted by a satellite, an automatic probe, an inhabited spacecraft.

15. The system according to claim 1 , further comprising a pressure sensor for monitoring the vapor pressure inside the tank.