A micro-thruster based on annular bombardment cathode

Abstract

The present invention relates to a micro-thruster based on an annular bombardment cathode, which belongs to the field of space electric propulsion, and includes a thruster housing, insulating ceramics, a thruster anode, a plurality of annular permanent magnets, a thruster pole shoe, a cathode fixing ceramic and a cathode emitter; the thruster housing is a hollow cylinder, an insulating ceramic is arranged inside one end of the thruster housing, a thruster anode is arranged inside the insulating ceramic, the insulating ceramic and the thruster anode are arranged coaxially, the other end of the thruster housing is an open end, a cathode fixing ceramic is sleeved outside the open end, the cathode fixing ceramic is used to fix the cathode emitter, and the cathode emitter is arranged coaxially with the thruster housing; a plurality of annular permanent magnets are coaxially fixed to the inner side of the thruster housing, and fixed between the cathode fixing ceramic and the insulating ceramic, and a thruster pole shoe is arranged between each annular permanent magnet; the cathode emitter is located within the angle of the plume bombardment generated when the micro-thruster is working. The present invention improves the overall efficiency and specific impulse of the micro-thruster.

Description

Technical Field

[0001] The invention relates to the field of space electric propulsion, in particular to a micro-thruster based on an annular bombardment cathode. Background Art

[0002] Electric propulsion (or electric thruster) is a new type of propulsion device. Due to its advantages of high specific impulse and long life, it is gradually being used in new spacecraft systems. Due to the rise of micro-nano satellites and the proposal of a new generation of high-precision space measurement missions, micro-propulsion has gradually become one of the hottest research fields in the world for electric propulsion. Among the many types of micro-thrusters, HEMPT (Hall electric thruster with cusp field) is a relatively new concept of electric thruster. Due to its long service life, simple and reliable structure, and high thrust density, it has a good development prospect in micro-thrusters.

[0003] The Hall electric propulsion and ion electric propulsion, which are currently the mainstream, both need to be equipped with matching cathodes to neutralize the potential of their plasma plumes and provide the electrons required for discharge. At present, the most widely used mainstream cathode is the hollow cathode, which uses an inert gas working fluid to provide a large number of electrons by inducing a direct current hollow cathode discharge in the internal emitter. Usually, the hollow cathode consumes tens of watts of electrical power and a few sccm of inert gas flow to work, which is too large for microthrusters with very small electrical power consumption and working fluid flow consumption, and will also lead to a significant reduction in the overall efficiency and total specific impulse of the overall electric propulsion system. Summary of the invention

[0004] The purpose of the present invention is to provide a micro-thruster based on an annular bombardment cathode, so as to improve the overall efficiency and specific impulse of the micro-thruster.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A micro-thruster based on an annular bombardment cathode comprises a thruster housing, insulating ceramics, a thruster anode, a plurality of annular permanent magnets, a thruster pole shoe, a cathode fixing ceramic and a cathode emitter;

[0007] The thruster housing is a hollow cylinder, an insulating ceramic is arranged inside one end of the thruster housing, the insulating ceramic is annular, the thruster anode is arranged inside the insulating ceramic, the insulating ceramic and the thruster anode are arranged coaxially, the other end of the thruster housing is an open end, the cathode fixing ceramic is sleeved outside the open end, the cathode fixing ceramic is used to fix the cathode emitter, the cathode emitter is annular, and the cathode emitter is arranged coaxially with the thruster housing; a plurality of annular permanent magnets are coaxially fixed to the inner side of the thruster housing and fixed between the cathode fixing ceramic and the insulating ceramic, and thruster pole shoes are arranged between each annular permanent magnet; the insulating ceramic is used to achieve insulation between the thruster anode and the thruster housing and the annular permanent magnet, and the cathode fixing ceramic is used to achieve insulation between the thruster housing and the cathode emitter;

[0008] The cathode emitter is located within the bombardment angle of the plume generated when the micro-thruster is in operation.

[0009] Optionally, the material of the cathode emitter is one of barium tungsten, lanthanum hexaboride and dodecalcium heptaaluminate.

[0010] Optionally, the material of the annular permanent magnet is 2:17 type samarium cobalt permanent magnet.

[0011] Optionally, the material of the thruster pole shoe is electrical pure iron DT4C.

[0012] Optionally, the thruster casing and the thruster anode are made of 304 stainless steel or 1060 aluminum alloy.

[0013] Optionally, it further includes a first bolt and a second bolt, wherein the first bolt is used to fix the cathode fixing ceramic and the cathode emitter, and the second bolt is used to fix the cathode fixing ceramic and the thruster casing.

[0014] Optionally, the first bolt and the second bolt are made of 304 stainless steel or 1060 aluminum alloy.

[0015] Optionally, a thruster substrate is further included, wherein the thruster substrate is arranged at one end of the thruster casing, and the thruster substrate is used to fix the insulating ceramic and the thruster anode.

[0016] Optionally, the material of the thruster base plate is 304 stainless steel or 1060 aluminum alloy.

[0017] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0018] The present invention discloses a micro-thruster based on an annular bombardment cathode, wherein a cathode emitter is located within the angle of bombardment of a plume generated when the micro-thruster is in operation, and high-energy ions in a discharge channel formed by a plurality of annular permanent magnets bombard the inner surface of the cathode emitter to generate secondary electron emission, thereby achieving a higher level of electron quantity without using additional electric power, thereby improving the overall efficiency and specific impulse of the micro-thruster. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0020] Figure 1 This is a schematic diagram of the cross-sectional structure of a micro-thruster based on an annular bombardment cathode according to the present invention;

[0021] Figure 2 This is a schematic diagram of the side structure of a micro-thruster based on an annular bombardment cathode according to the present invention;

[0022] Figure 3 This is a schematic diagram of the front structure of a micro-thruster based on an annular bombardment cathode according to the present invention;

[0023] Figure 4 This is a schematic diagram of the three-dimensional appearance of a micro-thruster based on an annular bombardment cathode according to the present invention;

[0024] Figure 5 It is a schematic diagram of the overall operation principle of a micro-thruster based on an annular bombardment cathode of the present invention;

[0025] Explanation of symbols: 1-thruster housing, 2-cathode fixing ceramic, 31-first bolt, 32-second bolt, 4-cathode emitter, 5-thruster anode, 6-annular permanent magnet, 7-thruster pole shoe, 8-insulating ceramic, 9-thruster substrate, 10-discharge channel. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] The purpose of the present invention is to provide a micro-thruster based on an annular bombardment cathode, so as to improve the overall efficiency and specific impulse of the micro-thruster.

[0028] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] Figure 1 This is a schematic diagram of the cross-sectional structure of a micro-thruster based on an annular bombardment cathode according to the present invention. Figure 2 This is a schematic diagram of the side structure of a micro-thruster based on an annular bombardment cathode according to the present invention. Figure 3 This is a schematic diagram of the front structure of a micro-thruster based on an annular bombardment cathode according to the present invention. Figure 4 FIG. 1 is a schematic diagram of a three-dimensional appearance of a micro-thruster based on an annular bombardment cathode according to the present invention. Figure 1-Figure 4 As shown, a micro-thruster based on an annular bombardment cathode includes a thruster housing 1, an insulating ceramic 8, a thruster anode 5, a plurality of annular permanent magnets 6, a thruster pole shoe 7, a cathode fixing ceramic 2, a cathode emitter 4, bolts and a thruster base plate 9.

[0030] The thruster housing 1 is a hollow cylinder. An insulating ceramic 8 is arranged on the inner side of one end of the thruster housing 1. The insulating ceramic 8 is annular. A thruster anode 5 is arranged on the inner side of the insulating ceramic 8. The insulating ceramic 8 and the thruster anode 5 are arranged coaxially. The other end of the thruster housing 1 is an open end. A cathode fixing ceramic 2 is sleeved on the outer side of the open end. The cathode fixing ceramic 2 is used to fix a cathode emitter 4. The cathode emitter 4 is annular and is coaxially arranged with the thruster housing 1. A plurality of annular permanent magnets 6 are coaxially fixed to the inner side of the thruster housing 1 and fixed between the cathode fixing ceramic 2 and the insulating ceramic 8. A thruster pole shoe 7 is arranged between each annular permanent magnet 6. The insulating ceramic 8 is used to achieve insulation between the thruster anode 5 and the thruster housing 1 and the annular permanent magnet 6. The cathode fixing ceramic 2 is used to achieve insulation between the thruster housing 1 and the cathode emitter 4.

[0031] A plurality of annular permanent magnets 6 are arranged relatively and fixed in the thruster housing 1. A discharge channel 10 is formed inside the plurality of annular permanent magnets 6. The plurality of annular permanent magnets 6 are used to form a magnetic field with a relatively high intensity (several thousand gauss) in the discharge channel 10. The magnetic field formed by the annular permanent magnets 6 in the discharge channel 10 is a multi-level cusp magnetic field. The thruster pole shoes 7 between each layer of annular permanent magnets 6 are used to enhance the local magnetic field strength.

[0032] The insulating ceramic 8 and the thruster anode 5 are coaxially mounted in the thruster housing 1 and fixed by the thruster base plate 9. The cathode emitter 4 is coaxially fixed to the open end of the thruster housing 1 by the cathode fixing ceramic 2 and bolts to receive bombardment of a part of high-energy ions when the plasma is ejected in the discharge channel 10. The axial position of the cathode emitter 4 relative to the opening of the thruster housing 1 can be adjusted by adjusting the bolts.

[0033] The cathode emitter 4 is located within the bombardment angle of the plume generated when the micro-thruster is working.

[0034] The present invention considers using an electric thruster (micro-thruster) to interact with a material with a high secondary electron emission rate. Some of the high-energy ions of the electric thruster itself are used to bombard the surface of the cathode emitter 4 material to generate secondary electrons. The secondary electrons in turn neutralize the plume of the electric thruster and provide source electrons. This solves the problem of electric power consumption and working fluid consumption of the cathode in the electric thruster without using additional power consumption, thereby achieving plume neutralization and continuous operation of the electric thruster.

[0035] The cathode emitter 4 is made of electron emitting materials with low electron overflow work function, such as barium tungsten, lanthanum hexaboride and dodecalcium heptaaluminate.

[0036] The annular permanent magnet 6 is made of a permanent magnetic material with a relatively high Curie temperature to avoid demagnetization, such as samarium cobalt 2:17.

[0037] The thruster pole shoe 7 is made of a material with a relatively high magnetic permeability, such as electrical pure iron DT4C.

[0038] The bolts are divided into first bolts 31 and second bolts 32 . The first bolts 31 are used to fix the cathode fixing ceramic 2 and the cathode emitter 4 , and the second bolts 32 are used to fix the cathode fixing ceramic 2 and the thruster casing 1 .

[0039] The thruster base plate 9 is disposed at one end of the thruster housing 1 , and is used to fix the insulating ceramic 8 and the thruster anode 5 .

[0040] The thruster housing 1, bolts, thruster anode 5, thruster base plate 9, etc. are all made of non-magnetic conductive or weakly magnetic conductive materials, such as 304 stainless steel and 1060 aluminum alloy.

[0041] Each structure in the micro-thruster of the present invention is fixedly installed by bolts.

[0042] The micro-thruster of the present invention is connected to the spacecraft through the thruster housing 1 structure and the thruster substrate 9. The thruster anode 5 is supplied with an inert gas working medium, such as xenon or krypton, through a gas supply pipeline and is connected to the positive high potential of the anode in the spacecraft system. The cathode emitter 4 is connected to the negative potential of the cathode in the spacecraft system.

[0043] When the micro-thruster of the present invention is in operation, the thruster anode 5 injects an inert gas working fluid into the discharge channel 10. The ignition process of the thruster can be achieved by applying a relatively high voltage to the thruster anode 5 to achieve gas breakdown, or by using a traditional cathode, microwave discharge, or the like to perform ignition, thereby forming a plasma in the discharge channel 10. After the plasma is formed in the channel, under the action of the high electric potential of the thruster anode 5, the ions are accelerated and ejected by the strong electric field in the axial direction, and a part of the high-energy ions bombard the inner surface of the cathode emitter 4, thereby generating secondary electron emission. A part of the emitted secondary electrons enters the thruster channel and, as source electrons, collides and ionizes with the neutral gas, forming an avalanche effect that triggers Townsend discharge, thereby maintaining the generation of plasma in the thruster; the other part enters the plume area to neutralize the potential of the plume, such as Figure 5 As shown, Figure 5 The middle emitter refers to the cathode emitter.

[0044] The micro-thruster of the present invention is a micro-thruster with watt-class HEMPT fixed thrust based on an annular bombardment cathode.

[0045] When designing the overall structure of the micro-thruster of the present invention, the electron emission level of the cathode emitter is changed by adjusting the relative position of the cathode emitter and other thruster structures, the shape, material, and roughness of the inner surface of the cathode emitter, so as to match electric thrusters of different levels. Since the electron providing capacity of the cathode emitter is limited, the overall electric thruster should be considered to work under fixed working conditions. The method of maintaining discharge and plume neutralization of the present invention is not only applicable to HEMPT (Hall thruster with cusped field), but can also be used for matching design work for traditional Hall electric thrusters, ion electric thrusters, etc. For electric thrusters with different levels of electronic demand, it is necessary to change the bombardment surface area of ​​the cathode emitter to make a relatively large adjustment to its electron emission capacity. The specific implementation method shall be subject to the actual operation.

[0046] The present invention utilizes the secondary electron emission effect of high secondary electron emission materials under ion bombardment to provide a higher level of electrons without using additional electric power, so as to meet the plume neutralization requirements and discharge source electron requirements of a specific type of electric thruster. The scheme of the present invention can greatly reduce the electric power and working fluid flow consumption of the overall electric propulsion system, especially the micro-propulsion system, thereby improving the overall efficiency and specific impulse and other performance parameters. At the same time, since the cathode emitter adopts a ring-shaped axisymmetric design, compared with the cathode working in a traditional fixed point source mode, the spatial asymmetry caused by the cathode to the plume is greatly reduced, and the thrust vector accuracy index of the electric thruster is improved.

[0047] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0048] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A micro-thruster based on annular bombardment cathode, characterized in that: It includes a thruster casing, insulating ceramics, a thruster anode, a plurality of annular permanent magnets, a thruster pole shoe, a cathode fixing ceramic and a cathode emitter; The thruster housing is a hollow cylinder, an insulating ceramic is arranged inside one end of the thruster housing, the insulating ceramic is annular, the thruster anode is arranged inside the insulating ceramic, the insulating ceramic and the thruster anode are arranged coaxially, the other end of the thruster housing is an open end, the cathode fixing ceramic is sleeved outside the open end, the cathode fixing ceramic is used to fix the cathode emitter, the cathode emitter is annular, and the cathode emitter is arranged coaxially with the thruster housing; a plurality of annular permanent magnets are coaxially fixed to the inner side of the thruster housing and fixed between the cathode fixing ceramic and the insulating ceramic, and thruster pole shoes are arranged between each annular permanent magnet; the insulating ceramic is used to achieve insulation between the thruster anode and the thruster housing and the annular permanent magnet, and the cathode fixing ceramic is used to achieve insulation between the thruster housing and the cathode emitter; The cathode emitter is located within the angle of bombardment of the plume generated when the micro-thruster is working; the material of the cathode emitter is one of barium tungsten, lanthanum hexaboride and dodecalcium heptaaluminate; The micro-thruster based on annular bombardment cathode further includes a first bolt and a second bolt, wherein the first bolt is used to fix the cathode fixing ceramic and the cathode emitter, and the second bolt is used to fix the cathode fixing ceramic and the thruster casing; The axial position of the cathode emitter relative to the thruster housing opening is adjusted by adjusting the bolt; The thruster anode is supplied with inert gas through a gas supply pipeline.

2. The micro-thruster based on annular bombardment cathode according to claim 1, characterized in that: The material of the annular permanent magnet is 2:17 type samarium cobalt permanent magnet.

3. The micro-thruster based on annular bombardment cathode according to claim 1, characterized in that: The material of the thruster pole shoe is electrical pure iron DT4C.

4. The micro-thruster based on annular bombardment cathode according to claim 1, characterized in that: The thruster housing and the thruster anode are made of 304 stainless steel or 1060 aluminum alloy.

5. The micro-thruster based on annular bombardment cathode according to claim 1, characterized in that: The first bolt and the second bolt are made of 304 stainless steel or 1060 aluminum alloy.

6. The micro-thruster based on annular bombardment cathode according to claim 1, characterized in that: It also includes a thruster base plate, which is arranged at one end of the thruster shell and is used to fix the insulating ceramic and the thruster anode.

7. The micro-thruster based on annular bombardment cathode according to claim 6, characterized in that: The material of the thruster base plate is 304 stainless steel or 1060 aluminum alloy.

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