Ion thruster having a hollow cathode assembly with an encapsulated heater, and its fabrication

• US 6,336,318 B1
• Filed: 02/02/2000
• Issued: 01/08/2002
• Est. Priority Date: 02/02/2000
• Status: Expired due to Fees

• Current Assignee: L-3 Communications Electron Technologies, Inc. (L3Harris Technologies, Inc.)
• Original Assignee: Hughes Electronics Corporation (AT&T, Inc.)
• Inventors: Falce, Louis Raymond, Beattie, John R.
• Primary Examiner(s): Thorpe, Timothy S.
• Assistant Examiner(s): Gartenberg, Ehud
• Application Number:
  US09/496,889
• Time in Patent Office: 706 Days
• Field of Search: 602/02, 315/111.81, 313/231.31, 313/362.1, 445/23, 445/29
• US Class Current: 60/202
• CPC Class Codes: B64G 1/405 Ion or plasma engines per se F03H1/00
• CPC Class Codes: B64G 1/413 Ion or plasma engines
• CPC Class Codes: F03H 1/0031 Thermal management, heating or cooling parts of the thruster temperature control for cosmonautic vehicles B64G1/50

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.

Claims

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.

2. The ion thruster of claim 1, wherein the inner ceramic sleeve and the outer ceramic sleeve are made of a ceramic selected from the group consisting of aluminum oxide and magnesium oxide.

3. The ion thruster of claim 1, wherein the ceramic powder is selected from the group consisting of aluminum oxide powder and magnesium oxide powder.

4. The ion thruster of claim 1, wherein the filament is made of a material comprising tungsten-3 weight percent rhenium.

5. The ion thruster of claim 1, wherein the filament is in the form of a flat ribbon.

6. The ion thruster of claim 1, wherein the cathode is made of a material comprising porous tungsten impregnated with barium carbonate, calcium carbonate, and aluminum oxide.

7. The ion thruster of claim 1, wherein the hollow cathode assembly comprises a portion of a charge neutralizer.

8. The ion thruster of claim 1, wherein the hollow cathode assembly comprises a portion of a plasma source.

9. The ion thruster of claim 1, further including

a heat shield overlying the outer ceramic sleeve.

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:

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.

11. The method of claim 10, wherein the step of preparing the filament includes the step of

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.