Electrically powered propulsion system for use in a spacecraft

1. An electrically powered propulsion system for a spacecraft that comprises a first center of gravity at a first time of operation and a second center of gravity at a second time of operation, wherein the second center of gravity is different from the first center of gravity, wherein the electrically powered propulsion system comprises a thruster realignment mechanism and at least two thrusters coupled to the thruster realignment mechanism, each of the at least two thrusters having an individual thrust vector, wherein

the thruster realignment mechanism is adapted such that, in a first position, individual thrust vectors of the at least two thrusters pass through the first center of gravity and that, in a second position, individual thrust vectors of the at least two thrusters pass through the second center of gravity;

the thruster realignment mechanism holds the first position in the event all of the at least two thrusters are without any failure;

the thruster realignment mechanism realigns the at least two thrusters to the second position in the event of at least one of (i) a failure of one of the at least two thrusters, and (ii) a predetermined time criterion is fulfilled,

wherein the thruster realignment mechanism is adapted such that the second position once reached is reversible after actuation, and

wherein the actuation mechanism comprises a bi-stable spring arrangement for realigning the at least two thrusters.

2. The electrically powered propulsion system according to claim 1 , wherein the thruster realignment mechanism is made such that in the event of the at least one of (i) the failure of one of the at least two thrusters, and (ii) the predetermined time criterion is fulfilled, all thrusters are realigned from the first position to the second position.

3. The electrically powered propulsion system according to claim 1 , wherein the at least two thrusters are coupled to the thruster realignment mechanism such that, in the first position, resulting force generated by all thrusters having no failure passes through both the first center of gravity and the second center of gravity, while individual thrust vectors of each thruster of the at least two thrusters are inclined by a first angle with regard to a direction of the resulting force.

4. The electrically powered propulsion system according to claim 3 , wherein, after realignment to the second position, the at least two thrusters are inclined by a second angle with regard to the direction passing through both the first center of gravity and the second center of gravity wherein the second angle is different from the first angle.

5. The electrically powered propulsion system according to claim 4 , wherein an angle difference between the first and the second angle is less than 10°.

6. The electrically powered propulsion system according to claim 1 , wherein the thruster realignment mechanism is bi-stable between the first and the second position, wherein the first position and the second position are end stops.

7. An electrically powered propulsion system for a spacecraft that comprises a first center of gravity at a first time of operation and a second center of gravity at a second time of operation, wherein the second center of gravity is different from the first center of gravity, wherein the electrically powered propulsion system comprises a thruster realignment mechanism and at least two thrusters coupled to the thruster realignment mechanism, each of the at least two thrusters having an individual thrust vector, wherein

the thruster realignment mechanism is adapted such that, in a first position, individual thrust vectors of the at least two thrusters pass through the first center of gravity and that, in a second position, individual thrust vectors of the at least two thrusters pass through the second center of gravity;

the thruster realignment mechanism holds the first position in the event all of the at least two thrusters are without any failure;

the thruster realignment mechanism realigns the at least two thrusters to the second position in the event of at least one of (i) a failure of one of the at least two thrusters, and (ii) a predetermined time criterion is fulfilled,

wherein the thruster realignment mechanism is adapted such that the second position once reached is irreversible after actuation, and

wherein the actuation mechanism comprises a bi-stable spring arranqement for realigning the at least two thrusters.

8. The electrically powered propulsion system according to claim 1 , wherein the thruster realignment mechanism comprises an electric magnet or other reversible actuator arrangement for realigning the at least two thrusters.

9. The electrically powered propulsion system according to claim 1 , wherein the thruster realignment mechanism allows flipping between the first position and the second position.

10. The electrically powered propulsion system according to claim 1 , wherein the thruster realignment mechanism is made such that in the event of the at least one of (i) the failure of one of the at least two thrusters, and (ii) the predetermined time criterion is fulfilled, the thruster realignment mechanism realigns all thrusters the second position irrespective of which or how many thrusters fail.

11. An electrically powered propulsion system for a spacecraft that comprises a first center of gravity at a first time of operation and a second center of gravity at a second time of operation, wherein the second center of gravity is different from the first center of gravity, wherein the electrically powered propulsion system comprises a thruster realignment mechanism and at least two thrusters coupled to the thruster realignment mechanism, each of the at least two thrusters having an individual thrust vector, wherein

the thruster realignment mechanism is adapted such that, in a first position, the individual thrust vectors of the at least two thrusters pass through the first center of gravity and that, in a second position, the individual thrust vectors of the at least two thrusters pass through the second center of gravity;

the thruster realignment mechanism holds the first position in the event all of the at least two thrusters are without any failure;

the thruster realignment mechanism realigns the at least two thrusters to the second position in the event of at least one of (i) a failure of one of the at least two thrusters, and (ii) a predetermined time criterion is fulfilled,

wherein the thruster realignment mechanism is adapted such that the second position once reached is reversible after actuation, and

wherein the thruster realignment mechanism comprises a first plate and a second plate, which are joined by a hinge which is arranged in a center line defined by a straight line that passes through both the first center of gravity and the second center of gravity, and whose far ends are coupled to a body, wherein at least one thruster is mounted to the first plate and at least one thruster is mounted to the second plate, and wherein an inclination angle of the first plate and the second plate is changeable with regard to the center line between the first position or the second position.

12. A method for operating the electrically powered propulsion system according to one of the preceding claims, comprising the steps of:

adjusting the thruster realignment mechanism to the first position, such that individual thrust vectors of the at least two thrusters pass through the first center of gravity in case all of the at least two thrusters are without any failure while resulting force generated by all thrusters passes through both the first center of gravity and the second center of gravity; and

adjusting the thruster realignment mechanism to the second position, such that the individual thrust vectors of the at least two thrusters pass through the second center of gravity in the event of at least one of (i) the failure of one of the at least two thrusters, and (ii) the predetermined time criterion is fulfilled, to realign thrust of the electrically powered propulsion system,

wherein adjusting the thruster realignment mechanism comprises aligning all thrusters, irrespective of which or how many thrusters fail, in the event of the at least one of (i) the failure of one of the at least two thrusters, and (ii) the predetermined time criterion is fulfilled.

13. The method according to claim 12 , wherein adjusting the thruster realignment mechanism to the second position comprises deflecting an ion beam released by any non-failed thrusters.

14. The method according to claim 12 , wherein adjusting the thruster realignment mechanism to the second position comprises controlling a mechanical rotation of the thrusters.

15. The method according to claim 12 , wherein adjusting the thruster realignment mechanism comprises realigning all thrusters from the first position to the second position in the event of the at least one of (i) the failure of one of the at least two thrusters, and (ii) the predetermined time criterion is fulfilled.

16. The method according to claim 12 , further comprising coupling the at least two thrusters to the thruster realignment mechanism such that, in the first position, resulting force generated by all thrusters having no failure, passes through both the first center of gravity and the second center of gravity, while individual thrust vectors of the at least two thrusters are inclined relative to a net thrust of the at least two thrusters.