Patent Number: 
Section: claims

1. A Hall thruster with a shared magnetic structure comprising:a plurality of plasma accelerators each including an anode and a discharge zone for providing plasma discharge;an electrical circuit having one or more cathodes connected to said plurality of plasma accelerators for emitting electrons that are attracted to said anode in each of said plasma accelerators; anda shared magnetic circuit structure for establishing a transverse magnetic field in each of said plurality of plasma accelerators that creates an impedance to the flow of electrons toward said anode in each of said plurality of plasma accelerators and enables ionization of a gas moving through one or more of said plurality of plasma accelerators and which creates an axial electric field in said plurality of plasma accelerators for accelerating ionized gas through said one or more of said plurality of plasma accelerators to create thrust. 2. The Hall thruster of claim 1 in which said shared magnetic circuit structure includes at least one magnetic field source for creating said transverse magnetic field in each of said plurality of plasma accelerators. 3. The Hall thruster of claim 2 in which said at least one magnetic field source includes a magnetic field source chosen from the group consisting of: an electromagnetic coil and a permanent magnet. 4. The Hall thruster of claim 3 in which said shared magnetic circuit structure includes a selected combination of said at least one magnetic field source. 5. The Hall thruster of claim 2 in which said shared magnetic circuit structure includes an outer pole and an inner pole for each of said plurality of plasma accelerators. 6. The Hall thruster of claim 5 in which said shared magnetic circuit structure includes a magnetic material interconnecting said outer pole and said inner pole. 7. The Hall thruster of claim 6 in which said shared magnetic circuit structure includes at least one shared magnetic path for establishing said transverse magnetic field in each of said plurality of plasma accelerators. 8. The Hall thruster of claim 7 in which said shared magnetic circuit structure carries magnetic flux between said inner pole and said outer pole and through said magnetic material and said shared magnetic path. 9. The Hall thruster of claim 7 in which said shared magnetic path includes at least one magnetic field source chosen from the group consisting of: an electromagnetic coil and a permanent magnet. 10. The Hall thruster of claim 9 in which said shared magnetic path includes a selected combination of said at least one magnetic field source. 11. The Hall thruster of claim 7 further including a plurality of shared magnetic paths for establishing said transverse magnetic field in each of said plurality of plasma accelerators. 12. The Hall thruster of claim 11 in which said plurality of shared magnetic paths each include one or more magnetic field sources chosen from the group consisting of an electromagnetic coil and a permanent magnet. 13. The Hall thruster of claim 11 in which said plurality of magnetic paths include a selected combination of said one or more magnetic field sources. 14. The Hall thruster of claim 1 further including a plurality of cathodes. 15. The Hall thruster of claim 1 in which said plurality of plasma accelerators are selectively enabled for steering and attitude control of said Hall thruster. 16. The Hall thruster of claim 9 in which said shared magnetic path reduces the number of said one or more magnetic sources required to achieve a predetermined said transverse magnetic field in each of said plurality of plasma accelerators. 17. The Hall thruster of claim 16 in which the reduced number of said one or more magnetic field sources decreases the weight and volume of said Hall thruster. 18. The Hall thruster of claim 7 in which said plurality of plasma accelerators includes one or more inner plasma accelerators and one or more outer plasma accelerators arranged concentrically. 19. The Hall thruster of claim 18 in which said shared magnetic path provides an outer pole for said one or more inner plasma accelerators and an inner pole for said one or more outer plasma accelerators that establish said transverse magnetic field in each of the concentrically arranged plasma accelerators. 20. The Hall thruster of claim 7 in which said inner pole is racetrack shaped. 21. The Hall thruster of claim 20 in which said inner pole and said outer pole define a racetrack shaped plasma gap. 22. The Hall thruster of claim 7 in which said inner pole and said outer pole are linearly shaped to define at least one linearly shaped plasma gap. 23. The Hall thruster of claim 7 in which said shared magnetic path includes a plurality of branches that provide said inner pole for each of said plurality of plasma accelerators. 24. The Hall thruster of claim 23 in which said plurality of branches are arranged relative to each other in a configuration chosen from the group consisting of: an orthogonal configuration, an angle configuration, a parallel configuration, and an opposite configuration. 25. The Hall thruster of claim 24 in which said plurality of plasma accelerators are arranged relative to each other in a configuration chosen from the group consisting of: an orthogonal configuration, an angle configuration, a parallel configuration, and an opposite configuration. 26. The Hall thruster of claim 25 in which said at least one of said plurality of plasma accelerators are selectively enabled for steering and attitude control of said Hall thruster. 27. The Hall thruster of claim 1 further including one or more shared power processing units for providing power to said electrical circuit and said shared magnetic circuit structure. 28. The Hall thruster of claim 1 in which said gas is selectively provided to at least one of said plurality of plasma accelerators to create said thrust. 29. The Hall thruster of claim 28 in which selectively providing said gas to said one or more of said plurality of plasma accelerators is used for throttling, steering and attitude control of said Hall thruster.