Ion thruster having a hollow cathode assembly with an encapsulated heater, and its fabrication
First Claim
1. An ion thruster comprising a hollow cathode assembly, the hollow cathode assembly comprising:
- a heater including an inner ceramic sleeve having an outer surface, an outer ceramic sleeve having an inner surface, the outer ceramic sleeve overlying the inner ceramic sleeve with a filament volume between the outer surface of the inner ceramic sleeve and the inner surface of the outer ceramic sleeve, a wound filament having windings disposed within the filament volume, and a mass of ceramic powder filling a remaining portion of the filament volume between the windings of the filament; and
a cathode disposed within the inner ceramic sleeve of the heater.
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Abstract
An ion thruster has a hollow cathode assembly including a heater with an inner ceramic sleeve and an outer ceramic sleeve. The outer ceramic sleeve overlies the inner ceramic sleeve with a filament volume between the two sleeves. A wound filament has windings disposed within the filament volume, and a mass of ceramic powder fills the remaining portion of the filament volume between the windings of the filament. A cathode is disposed within the inner ceramic sleeve of the heater. The heater is assembled by preparing the filament and forming it into a wound cylinder, and then encapsulating it and the powder between the inner and the outer ceramic sleeves. The hollow cathode assembly may serve as a portion of a plasma source or as a portion of a charge neutralizer.
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Citations
17 Claims
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1. An ion thruster comprising a hollow cathode assembly, the hollow cathode assembly comprising:
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a heater including an inner ceramic sleeve having an outer surface, an outer ceramic sleeve having an inner surface, the outer ceramic sleeve overlying the inner ceramic sleeve with a filament volume between the outer surface of the inner ceramic sleeve and the inner surface of the outer ceramic sleeve, a wound filament having windings disposed within the filament volume, and a mass of ceramic powder filling a remaining portion of the filament volume between the windings of the filament; and
a cathode disposed within the inner ceramic sleeve of the heater. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
a heat shield overlying the outer ceramic sleeve.
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10. A method of making an ion thruster having a hollow cathode assembly, the method including the preparation of the hollow cathode assembly by the steps of:
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preparing a filament;
forming the filament into a cylindrical shape;
providing an inner ceramic sleeve, an outer ceramic sleeve, and a mass of ceramic powder;
positioning the filament and the mass of ceramic powder between the inner ceramic sleeve and the outer ceramic sleeve;
providing a cathode;
positioning the cathode within the interior of the inner ceramic sleeve;
attaching said cathode assembly to said ion thruster. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
forming a metallic piece into a wound shape. -
12. The method of claim 10, wherein the step of forming the filament includes the step of
forming the filament into a right circular cylindrical shape. -
13. The method of claim 10, wherein the step of providing an inner ceramic sleeve, an outer ceramic sleeve, and a mass of ceramic powder includes the step of
providing an inner ceramic sleeve comprising a ceramic selected from the group consisting of aluminum oxide and magnesium oxide, an outer ceramic sleeve comprising a ceramic selected from the group consisting of aluminum oxide and magnesium oxide, and ceramic powder comprising a ceramic selected from the group consisting of aluminum oxide powder and magnesium oxide powder. -
14. The method of claim 10, wherein the step of providing a cathode includes the step of
providing porous tungsten impregnated with barium carbonate, calcium carbonate, and aluminum oxide. -
15. The method of claim 10, including an additional step of
positioning a heat shield over the outer ceramic sleeve. -
16. The method of claim 10, including an additional step of
assembling the hollow cathode assembly into a plasma source. -
17. The method of claim 10, including an additional step of
assembling the hollow cathode assembly into a charge neutralizer.
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Specification