Processing method of low-cost high-reliability hall electric propulsion hollow cathode for aerospace

Abstract

This invention relates to the field of aerospace technology, and particularly to a low-cost, high-reliability method for fabricating a hollow cathode for Hall thruster in aerospace applications. The method includes: fabricating a cathode tube, a cathode lead-out component, and a heating wire fixing plate using niobium metal; welding the cathode tube and the cathode lead-out component; winding a heating tungsten wire into a threaded groove in an insulating ceramic; pressing one end of the heating tungsten wire into a small hole at the top of the cathode lead-out component, and pressing the other end of the heating tungsten wire into the heating wire fixing plate; inserting an emitter into a mounting hole in the cathode tube, thus securing the emitter within the mounting hole; and non-contactly attaching a heat shield assembly to the outside of the cathode tube, with the metal support structure at the bottom of the heat shield assembly laser-welded to the base of the cathode tube, and the metal support structure at the bottom of the cathode contact assembly laser-welded to the base of the cathode tube. This invention provides a low-cost, simple-process Hall thruster hollow cathode assembly.

Description

Technical Field

[0001] This invention relates to the field of aerospace technology, and in particular to a method for processing a low-cost, high-reliability Hall electric propulsion hollow cathode for aerospace applications. Background Technology

[0002] Hollow cathodes are key components of Hall thrusters, serving to provide the initial electron source for the thruster's discharge, form the anolyte current loop, and neutralize the plume plasma. A hollow cathode typically consists of several parts: an emitter that provides electron emission, a heating element for heating the emitter, a heat shield element for thermal shielding, a contact element for plasma generation, and a base element for mounting the overall support structure. The processing and fabrication of hollow cathodes involves machining of precious metal components such as tantalum, high-temperature brazing between ceramics and metals, laser welding between metals, and special welding between dissimilar metals. Therefore, the current cathode processing is complex and costly, resulting in high component development costs.

[0003] Currently, most of the hollow cathodes used in spacecraft for Hall electric propulsion employ barium tungsten emitters or lanthanum hexaboride emitters, and use precious metals such as tantalum as high-temperature support materials. Conventional parts assembly and assembly methods are used in the cathode assembly process. High-temperature brazing is used for welding between ceramics and metals, and electron beam welding is used for welding between dissimilar metals. Summary of the Invention

[0004] To address one or more technical problems in the prior art, the present invention provides a low-cost, simple-to-process Hall electric propulsion hollow cathode assembly.

[0005] In a first aspect, the present invention provides a method for fabricating a low-cost, high-reliability Hall electric propulsion hollow cathode for aerospace applications, comprising: Using niobium metal to prepare cathode tubes, cathode leads, and heating wire fixing plates; Weld the cathode tube and the cathode lead-out component together; A heating tungsten wire is wound into a threaded groove in an insulating ceramic; wherein the insulating ceramic is sleeved outside the cathode tube; One end of the heating tungsten wire is crimped to a small hole at the top of the cathode lead-out component, and the other end of the heating tungsten wire is crimped to a heating wire fixing plate; wherein, the heating wire fixing plate is sleeved on the outside of the insulating ceramic and arc-spot welded to the cathode tube; Insert the emitter into the mounting hole of the cathode tube, so that the emitter is inserted into the mounting hole of the cathode tube; A heat shield assembly is non-contactly fitted outside the cathode tube. The metal support structure at the bottom of the heat shield assembly is laser-welded to the base of the cathode tube, and the metal support structure at the bottom of the cathode contact assembly is laser-welded to the base of the cathode tube.

[0006] Optionally, the top of the cathode contact assembly is a high-melting-point metal cylinder, and the bottom is made of stainless steel. The top and bottom of the cathode contact assembly are fixed by laser welding. The high-melting-point metal includes tungsten or niobium.

[0007] Optionally, the heat shield assembly is a tantalum sleeve that is laser-welded to the bottom of the cathode contact assembly.

[0008] Optionally, the emitter is a tungsten-based emitter impregnated with barium salt.

[0009] Optionally, the method for preparing the emitter includes: After tungsten powder is pressed and sintered to form a tungsten rod substrate, it is machined using a turning process, and then barium salt is impregnated onto the tungsten substrate to form a barium salt emitter on the tungsten substrate.

[0010] Optionally, the emitter is a perforated plate fusion emitter, which includes a columnar segment and a perforated plate segment located at one end of the columnar segment. A through hole is machined in the center of the perforated plate segment. The axial length ratio of the columnar segment and the perforated plate segment is (5~10):1, and the ratio of the inner diameter of the columnar segment to the diameter of the through hole of the perforated plate segment is (2~5):1.

[0011] Optionally, it also includes: welding the periphery of the emitter cover and the cathode tube using an arc spot welding method; wherein, the emitter cover has a through hole at its center.

[0012] Optionally, the inner diameter of the cathode tube is 3~5mm.

[0013] Optionally, the top thickness of the cathode contact assembly is 1.5mm to 2.0mm, and the top of the cathode contact assembly is a countersunk hole configuration with a bevel, the bevel half-cone angle of the countersunk hole is 60°.

[0014] Secondly, embodiments of the present invention provide a Hall electric propulsion hollow cathode assembly, which is processed according to any of the processing methods described above.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: This invention innovatively proposes using low-value niobium metal as the support material for the high-melting-point metal of the hollow cathode. Based on niobium's high ductility and machinability, a corresponding oil-cooling processing technology is designed to process the cathode tube supporting the emitter, significantly reducing material costs compared to the traditional method of using tantalum as the high-temperature metal substrate for the cathode. Furthermore, leveraging niobium's high ductility and high-temperature oxidation properties, the emitter assembly employs tight-fitting mechanical connections, such as press-fitting and plug-in joints. Other connection methods, such as welding, are relatively simple, achieving the goal of low cost and simplified processes. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the Hall electric propulsion hollow cathode assembly structure of the present invention; Figure 2 This is a schematic diagram of the emitter structure of the present invention.

[0018] In the diagram: 1 is the cathode contact assembly, 2 is the thermal shield assembly, 3 is the cathode tube, 4 is the cathode lead-out component, 5 is the heating tungsten wire, 6 is the heating wire fixing plate, 7 is the insulating ceramic, 8 is the emitter, and 9 is the emitter cover. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0020] In the description of the embodiments of the present invention, unless otherwise expressly specified and limited, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance; unless otherwise specified or explained, the term "multiple sets" refers to two or more sets; the terms "connection," "fixed," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, an integral connection, or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0021] In this specification, it should be understood that the directional terms such as "upper" and "lower" used in the description of the embodiments of the present invention are used to describe the angles shown in the accompanying drawings and should not be construed as limiting the embodiments of the present invention. Furthermore, in the context, it should also be understood that when it is mentioned that one element is connected "upper" or "lower" to another element, it can be directly connected to the other element "upper" or "lower," or indirectly connected to the other element "upper" or "lower" through an intermediate element.

[0022] Please refer to Figure 1This invention provides a method for fabricating a low-cost, high-reliability Hall electric propulsion hollow cathode for aerospace applications, comprising: The cathode tube 3, the cathode lead-out component 4, and the heating wire fixing plate 6 are prepared using niobium metal; Weld the cathode tube 3 and the cathode lead-out component 4 together; The heating tungsten wire 5 is wound into the threaded groove of the insulating ceramic 7; wherein the insulating ceramic 7 is sleeved on the outside of the cathode tube 3; One end of the heating tungsten wire 5 is crimped to a small hole at the top of the cathode lead-out part 4, and the other end of the heating tungsten wire 5 is crimped to a heating wire fixing piece 6; wherein, the heating wire fixing piece 6 is sleeved on the outside of the insulating ceramic 7 and arc-spot welded to the cathode tube 3; Insert the emitter 8 into the mounting hole of the cathode tube 3, so that the emitter 8 is inserted into the mounting hole of the cathode tube 3; A heat shield assembly 2 is non-contactly sleeved on the outside of the cathode tube 3. The metal support structure at the bottom of the heat shield assembly 2 is laser-welded to the base of the cathode tube 3, and the metal support structure at the bottom of the cathode contact assembly 1 is laser-welded to the base of the cathode tube 3.

[0023] In some embodiments of the present invention, the top of the cathode contact assembly 1 is a high-melting-point metal cylinder and the bottom is made of stainless steel. The top and bottom of the cathode contact assembly 1 are fixed by laser welding. The high-melting-point metal includes tungsten or niobium.

[0024] In some embodiments of the present invention, the heat shield assembly 2 is a tantalum sleeve, which is laser-welded to the bottom of the cathode contact assembly 1.

[0025] In some embodiments of the present invention, the emitter 8 is a tungsten-based emitter 8 impregnated with barium salt.

[0026] In some embodiments of the present invention, the method for preparing the emitter 8 includes: After tungsten powder is pressed and sintered to form a tungsten rod substrate, it is machined using a turning process, and then barium salt is impregnated onto the tungsten substrate to form a barium salt emitter 8 on the tungsten substrate.

[0027] Please refer to Figure 2 In some embodiments of the present invention, the emitter 8 is a perforated plate fusion emitter, which includes a columnar segment and a perforated plate segment located at one end of the columnar segment. A through hole is machined in the center of the perforated plate segment. The axial length ratio of the columnar segment and the perforated plate segment is (5~10):1, and the ratio of the inner diameter of the columnar segment to the diameter of the through hole of the perforated plate segment is (2~5):1.

[0028] This invention innovatively proposes an integrated processing method for the emitter 8-tungsten perforated plate irregular configuration. This irregular structure transforms the tungsten top plate downstream of the emitter 8 in the traditional cathode into an electron-emitting material, significantly enhancing electron emission capability and ignition success rate. The cathode used in this invention can also be used in the electron source of other thrusters for space electric propulsion. In the actual cathode heating and ignition process, the inner wall surface of the rear cylindrical section of the fused emitter emits thermionic electrons, while the front perforated plate section acts as a cathode gas supply throttling and pressurization unit. During the cathode self-sustaining discharge process, the inner wall surface of the rear cylindrical section acts as a self-sustaining discharge electron emission unit, while the small holes in the front perforated plate section act as a cathode gas supply throttling unit and prevent plasma backflow erosion and sputtering.

[0029] In some embodiments of the present invention, the method further includes: welding the emitter cover 9 and the cathode tube 3 around the periphery using an arc spot welding method; wherein the emitter cover 9 has a through hole in the center.

[0030] In some embodiments of the present invention, the inner diameter of the cathode tube 3 is 3~5mm.

[0031] In some embodiments of the present invention, the top thickness of the cathode contact assembly 1 is 1.5mm to 2.0mm, and the top of the cathode contact assembly 1 is a countersunk hole configuration with a bevel, wherein the bevel half-cone angle of the countersunk hole is 60°.

[0032] This invention provides a Hall electric propulsion hollow cathode assembly, which is processed according to any of the above-described processing methods.

[0033] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for processing a low-cost, high-reliability Hall electric propulsion hollow cathode for aerospace applications, characterized in that, include: The cathode tube (3), cathode lead-out piece (4), and heating wire fixing piece (6) are prepared using niobium metal. Weld the cathode tube (3) and the cathode lead-out member (4); A heating tungsten wire (5) is wound around the threaded groove of an insulating ceramic (7); wherein the insulating ceramic (7) is sleeved on the outside of the cathode tube (3); One end of the heating tungsten wire (5) is crimped to the small hole at the top of the cathode lead-out part (4), and the other end of the heating tungsten wire (5) is crimped to the heating wire fixing piece (6); wherein, the heating wire fixing piece (6) is sleeved on the outside of the insulating ceramic (7) and arc-welded to the cathode tube (3); Insert the emitter (8) into the mounting hole of the cathode tube (3) so that the emitter (8) is inserted into the mounting hole of the cathode tube (3); A heat shield assembly (2) is non-contactly sleeved outside the cathode tube (3). The metal support structure at the bottom of the heat shield assembly (2) and the base of the cathode tube (3) are laser welded together. The metal support structure at the bottom of the cathode contact assembly (1) and the base of the cathode tube (3) are laser welded together.

2. The processing method according to claim 1, characterized in that, The top of the cathode contact assembly (1) is a high-melting-point metal cylinder, and the bottom is made of stainless steel. The top and bottom of the cathode contact assembly (1) are fixed by laser welding. The high-melting-point metal includes tungsten or niobium.

3. The processing method according to claim 1, characterized in that, The heat shield assembly (2) is a tantalum sleeve that is laser-welded to the bottom of the cathode contact assembly (1).

4. The processing method according to claim 1, characterized in that, The emitter (8) is a tungsten-based emitter (8) impregnated with barium salt.

5. The processing method according to claim 4, characterized in that, The method for preparing the emitter (8) includes: After tungsten powder is pressed and sintered to form a tungsten rod substrate, it is machined by turning and then impregnated with barium salts to form a barium salt emitter on the tungsten substrate (8).

6. The processing method according to claim 1, characterized in that, The emitter (8) is a perforated plate fusion type emitter (8), which includes a columnar section and a perforated plate section located at one end of the columnar section. A through hole is machined in the center of the perforated plate section. The length ratio of the columnar section and the perforated plate section in the axial direction is (5~10):1, and the ratio of the inner diameter of the columnar section to the diameter of the through hole of the perforated plate section is (2~5):

1.

7. The processing method according to claim 1, characterized in that, Also includes: The emitter cover (9) and the cathode tube (3) are welded together using an arc spot welding method; wherein, a through hole is provided in the center of the emitter cover (9).

8. The processing method according to claim 1, characterized in that, The inner diameter of the cathode tube (3) is 3~5mm.

9. The processing method according to claim 1, characterized in that, The top thickness of the cathode contact assembly (1) is 1.5mm~2.0mm. The top of the cathode contact assembly (1) is a countersunk hole configuration with a bevel, and the bevel half cone angle of the countersunk hole is 60°.

10. A Hall-effect electric propulsion hollow cathode assembly, characterized in that, It is processed according to any one of the processing methods described in claims 1-9.

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