A self-neutralizing microwave ion thruster and its working method

Abstract

This invention belongs to the field of aerospace propulsion technology and relates to a self-neutralizing microwave ion thruster and its operating method. The thruster includes a discharge cavity A and a discharge cavity B connected by a cavity connection channel. Discharge cavity A, a microwave connector, and a positive charge particle extraction system form discharge chamber A. Discharge cavity B, a microwave connector, and a negative charge particle extraction system surround and form discharge chamber B. There is no permanent magnet on one side of the cavity connection channel of the discharge cavities. The magnetic fields provided by two permanent magnet arrays have opposite pole directions, creating connected magnetic field lines inside the cavity connection channel. The connected magnetic field lines between the two discharge cavities guide the movement of charged particles, connecting the plasma inside the two discharge cavities, facilitating charge exchange, maintaining quasi-electroneutrality, and providing internal conditions for plume neutralization downstream of the thruster. By applying a DC bias voltage, the positive charge particle extraction system extracts positive charge particles, and the negative charge particle extraction system extracts negative charge particles, achieving plume neutralization.

Description

Technical Field

[0001] This invention belongs to the field of aerospace propulsion technology, specifically relating to a self-neutralizing microwave ion thruster and its working method. Background Technology

[0002] Microwave ion thrusters are a type of aerospace thruster, characterized by their simple structure, high specific impulse, and high efficiency. Their working principle is as follows: permanent magnets construct magnetic mirrors to confine electrons. Through an electron cyclotron resonance mechanism, microwave energy fed into the discharge chamber by an antenna heats the electrons. The high-energy electrons ionize neutral gas to generate plasma, and the grid system accelerates and ejects the ions to produce thrust.

[0003] Currently, the self-neutralization technology of ion thrusters mainly uses grid modulation and is divided into two types: ion-to-ion thrusters and self-neutralizing radio frequency ion thrusters. The former applies a square wave voltage to the grid, allowing positive and negative ions to be extracted alternately through the same grid or through different grids; the latter applies a radio frequency voltage to the grid, extracting ions through the same grid using the DC self-bias effect, while simultaneously extracting electrons during the collapse of the electron sheath in each cycle, thus achieving self-neutralization of the ion beam.

[0004] However, both self-neutralization schemes face developmental bottlenecks. Ion-ion thrusters face application problems. On the one hand, the asymmetric magnetic field generated by the magnetic filter causes electron drift, reducing the magnetic field's confinement force on electrons and increasing thruster losses. On the other hand, to ensure equal positive and negative ion beam magnitudes, a complex gate voltage regulation system is required, reducing thruster reliability. Furthermore, the mechanism for establishing a bias voltage between the screen grid and the accelerating grid in self-neutralization radio frequency ion thrusters is complex, and currently, high voltage amplitude output and flexible control are not yet achievable, limiting thruster performance improvements and continuous thrust adjustment capabilities.

[0005] In summary, the self-neutralization technology based on gate modulation has development bottlenecks and application problems, and it is necessary to develop a new self-neutralization technology with a novel operating mode. Summary of the Invention

[0006] The purpose of this invention is to provide a self-neutralizing microwave ion thruster and its operating method, providing a novel technical solution for the self-neutralization of ion thruster plumes, and solving the problem of excessive power demand in self-neutralization and technology based on gate voltage waveform modulation.

[0007] This invention is achieved through the following technical solution:

[0008] This invention discloses a self-neutralizing microwave ion thruster, comprising a microwave plasma source A, a microwave plasma source B, and a cavity connection channel;

[0009] The microwave plasma source A includes a discharge cavity A, a permanent magnet array A, a microwave connector A, and a positively charged particle extraction system. The discharge cavity A, the microwave connector A, and the positively charged particle extraction system surround and form a discharge chamber A; the permanent magnet array A is installed on the outside of the discharge cavity A.

[0010] The microwave plasma source B includes a discharge cavity B, a permanent magnet array B, a microwave connector B, and a negative charge particle extraction system. The discharge cavity B, the microwave connector B, and the negative charge particle extraction system surround and form a discharge chamber B; the permanent magnet array B is installed on the outside of the discharge cavity B.

[0011] Discharge chambers A and B are arranged in parallel along their axes, and are connected by a cavity connection channel.

[0012] A positively charged particle extraction system is used to extract and accelerate positively charged particles to generate thrust.

[0013] The negative charge particle extraction system is used to extract negative charge particles, which then neutralize the positive charge particles extracted by the positive charge particle extraction system.

[0014] Furthermore, both discharge chamber A and discharge chamber B have a trumpet-shaped structure;

[0015] A positive charge particle extraction system is installed at the wide end of discharge chamber A, and a negative charge particle extraction system is installed at the wide end of discharge chamber B. Microwave connector A is installed at the narrow end of discharge chamber A, and microwave connector B is installed at the narrow end of discharge chamber B. Antennas are installed on both microwave connector A and microwave connector B.

[0016] The discharge cavity A has an air inlet pipe arranged perpendicular to the axis of microwave connector A on its side; the discharge cavity B has an air inlet pipe arranged perpendicular to the axis of microwave connector B on its side.

[0017] Furthermore, both discharge cavity A and discharge cavity B include a stepped shaft section, a horn section, and a cylindrical section connected in sequence;

[0018] Permanent magnet array A is disposed on the outer wall of the horn section of discharge cavity A, and permanent magnet array B is disposed on the outer wall of the horn section of discharge cavity B; microwave connector A passes through the stepped shaft section of discharge cavity A, and microwave connector B passes through the stepped shaft section of discharge cavity B; positive charge particle extraction system is bolted to the cylindrical section of discharge cavity A, and negative charge particle extraction system is bolted to the cylindrical section of discharge cavity B.

[0019] Furthermore, both discharge cavity A and discharge cavity B have pre-fabricated openings on the sides of their horn sections. The opening size is consistent with the external size of the cavity connection channel, and is used to communicate with the cavity connection channel.

[0020] Furthermore, the cavity connection channel is a trapezoidal square tube structure.

[0021] Furthermore, the length of the bottom edge of the cavity connection channel is greater than or equal to the sum of the radial widths of the cylindrical sections of discharge cavity A and discharge cavity B.

[0022] Furthermore, there is no permanent magnet on the cavity connection channel side of discharge cavity A, and there is no permanent magnet on the cavity connection channel side of discharge cavity B; the magnetic poles of the magnetic fields provided by permanent magnet array A and permanent magnet array B are opposite, so that connected magnetic field lines are formed inside the cavity connection channel.

[0023] Furthermore, permanent magnet array A and permanent magnet array B are composed of multiple tile-shaped Halbach magnets;

[0024] The magnetic field enhancement direction of each tile-shaped Halbach magnet is angular and points towards the center of the distribution circle. Multiple tile-shaped Halbach permanent magnets are evenly distributed on the outer wall of the discharge cavity in a trumpet shape.

[0025] Each Halbach tile consists of multiple magnets, with at least three magnets required.

[0026] In terms of size, in two adjacent magnets, the bottom edge of the upper magnet and the top edge of the lower magnet are the same length, and the bottom edge of the upper magnet is smaller than the bottom edge of the lower magnet.

[0027] The hypotenuses of multi-stage magnets are collinear and have the same thickness; their heights are different and increase sequentially.

[0028] In terms of coercivity distribution, the coercivity of the next-level magnet is greater than or equal to that of the next-level magnet.

[0029] Furthermore, the direction from the first-stage magnet to the third-stage magnet is defined as the positive X-axis direction, and the direction from which the first-stage magnet moves away from the discharge cavity is defined as the Z-axis direction;

[0030] In terms of magnetic pole direction, the N pole of the first-stage magnet in permanent magnet array A is magnetized along the positive Z-axis, the N pole of the second-stage magnet is magnetized along the positive X-axis, and the N pole of the third-stage magnet is magnetized along the negative Z-axis; the N pole of the first-stage magnet in permanent magnet array B is magnetized along the negative Z-axis, the N pole of the second-stage magnet is magnetized along the negative X-axis, and the N pole of the third-stage magnet is magnetized along the positive Z-axis.

[0031] If there are higher-level magnets, the N pole of the fourth-level magnet in permanent magnet array A is magnetized along the negative X-axis, and the N pole of the fourth-level magnet in permanent magnet array B is magnetized along the positive X-axis. The subsequent magnets are cycled around the previous four-level magnets as a unit.

[0032] The present invention also discloses a method for operating the self-neutralizing microwave ion thruster, comprising the following steps:

[0033] The working gas enters discharge chamber A and discharge chamber B respectively. Initial electrons are generated through microwave-induced discharge or microwave local electric field breakdown discharge. The initial electrons are confined by the magnetic field and move back and forth in the magnetic mirror. Relying on the resonance between the microwave electric field and the electron cyclotron, the electrons continuously absorb microwave energy to become high-energy electrons, which further ionize the gas, generating and maintaining plasma.

[0034] After ignition, a large amount of plasma is generated inside discharge chamber A and discharge chamber B. Under the action of the magnetic field, the plasma moves into the cavity connection channel, connecting the plasma in discharge chamber A and discharge chamber B, realizing charge exchange, and keeping the plasma inside the discharge chamber quasi-neutral.

[0035] A positive voltage is applied to the positive charge particle extraction system and a negative voltage is applied to the negative charge particle extraction system. Under electrostatic action, positive charge particles are extracted from discharge chamber A and negative charge particles are extracted from discharge chamber B, and the plume self-neutralizes downstream of the thruster.

[0036] Compared with the prior art, the present invention has the following beneficial technical effects:

[0037] This invention discloses a self-neutralizing microwave ion thruster, comprising a discharge cavity, a microwave connector, an antenna, a permanent magnet array, a positive charge particle extraction system, and a negative charge particle extraction system. The discharge cavity includes discharge cavity A, discharge cavity B, and a cavity connecting channel. Discharge cavity A, the microwave connector, and the positive charge particle extraction system surround and form discharge chamber A. Discharge cavity B, the microwave connector, and the negative charge particle extraction system surround and form discharge chamber B. Discharge cavities A and B are arranged axially parallel and welded together with the cavity connecting channel, thus connecting discharge chamber A and discharge chamber B. The permanent magnet array is installed on the outside of the discharge cavity and includes permanent magnet array A and permanent magnet array B. By applying a DC bias voltage, the positive charge particle extraction system extracts positive charge particles, and the negative charge particle extraction system extracts negative charge particles, thereby achieving plume neutralization.

[0038] Furthermore, permanent magnet arrays A and B employ Halbach magnets with opposite pole directions. The N pole of permanent magnet array A points from the wide end to the narrow end of discharge chamber A, while the N pole of permanent magnet array B points from the narrow end to the wide end of discharge chamber B. The number of permanent magnet arrays is adapted to the shape of the discharge chamber. There are no permanent magnets on one side of the connecting channel section, creating a continuous magnetic field line within the connecting channel. This continuous magnetic field line between discharge chambers A and B guides the movement of charged particles, allowing the plasma in both chambers to connect, enabling charge exchange and maintaining quasi-neutrality. By applying a DC bias voltage, the positive charge particle extraction system extracts positively charged particles, and the negative charge particle extraction system extracts negatively charged particles, achieving plume neutralization. Attached Figure Description

[0039] Figure 1 This is a structural diagram of the self-neutralizing microwave ion thruster prototype of the present invention;

[0040] Figure 2 This is a cross-sectional view of the novel self-neutralizing microwave ion thruster prototype provided in the embodiments;

[0041] Figure 3 This is a schematic diagram of the principle of the novel self-neutralizing microwave ion thruster provided in the embodiments of the present invention;

[0042] Figure 4 Figure 1 shows a schematic diagram of a single tile-type Halbach magnet structure; Figure 2 shows a schematic diagram of a tile-type Halbach magnet structure in permanent magnet array A; Figure 3 shows a schematic diagram of a tile-type Halbach magnet structure in permanent magnet array B.

[0043] Figure 5 Figure 1 shows the magnetic field distribution formed by the permanent magnet array in the embodiment, where the white solid line represents the electron cyclotron resonance region corresponding to 2.45GHz microwave; Figure 2(a) is a schematic diagram of the prototype cavity and permanent magnet model; Figure 3(b) is the XZ section; Figure 4(c) is the XY section; Figure 5(d) is the YZ section.

[0044] Figure 6 The image shown is an experimental image extracted from the Xe working fluid beam of the self-neutralizing microwave ion thruster in the embodiment.

[0045] Figure 7 This is a diagram showing the potential distribution in the downstream space of the thruster when different voltages are applied to the screen A in the embodiment.

[0046] Figure 8 To and Figure 1 The corresponding simulation diagram.

[0047] The components are: 1. Discharge cavity A; 2. Positive charge particle extraction system; 3. Cavity connection channel; 4. Negative charge particle extraction system; 5. Discharge cavity B; 6. Discharge chamber B; 7. Permanent magnet array B; 8. Antenna; 9. Microwave connector B; 10. Air inlet pipe; 11. Permanent magnet array A; 12. Discharge chamber A; 13. Magnet fixing component; 14. Microwave connector A. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of the present invention clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention; that is, the described embodiments are only a part of the embodiments of the present invention, and not all of them.

[0049] The components described and illustrated in the accompanying drawings and embodiments of this invention can be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of the invention provided in the following drawings is not intended to limit the scope of the claimed invention, but merely to illustrate one selected embodiment of the invention. All other embodiments obtained by those skilled in the art based on the accompanying drawings and embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0050] It should be noted that the terms "comprising," "including," or any other variations are intended to cover non-exclusive inclusion, such that a process, element, 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 the process, element, method, article, or apparatus. Furthermore, the terms "horizontal" and "vertical" are based on the orientation and positional relationship of the devices or components shown in the accompanying drawings and are used only for better description of the invention, not to require that the shown devices, components, or apparatus must have that specific orientation, and therefore should not be construed as limiting the invention.

[0051] To address the development bottlenecks of existing gate voltage waveform modulation-based ion thruster self-neutralization schemes, this invention proposes a self-neutralizing microwave ion thruster based on magnetic field control. The design incorporates two discharge chambers and utilizes a specific permanent magnet array structure to create a connecting magnetic field in the cavity connection channel 3 of the discharge chambers. This guides the plasma in the two discharge chambers to connect, maintaining the quasi-electrical neutrality of the internal plasma. Furthermore, a positive charge particle extraction system 2 and a negative charge particle extraction system 4 are used to extract positive and negative charge particles respectively, achieving plume neutralization.

[0052] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0053] This invention discloses a self-neutralizing microwave ion thruster based on magnetic field control, the structure of which is as follows: Figure 1 , Figure 2 , Figure 3 and Figure 8 As shown, discharge chamber A1, discharge chamber B5, and chamber connection channel 3 are welded together to form the main structure discharge chamber; discharge chamber A1, microwave connector A14, and positive charge particle extraction system 2 surround to form a horn-shaped discharge chamber A12, and discharge chamber B5, microwave connector B9, and negative charge particle extraction system 4 surround to form a horn-shaped discharge chamber B6. Discharge chamber A12 and discharge chamber B6 are connected through chamber connection channel 3.

[0054] Microwave connectors and antenna 8 are installed at the narrow end of discharge cavity A1 and the narrow end of discharge cavity B5;

[0055] The sides of the discharge chamber A1 and discharge chamber B5 have air inlet pipes 10 arranged perpendicular to the axis of the microwave connector. The two air inlet pipes 10 are arranged in parallel to facilitate connection with the gas supply device.

[0056] A positive charge particle extraction system 2 is installed at the wide end of the discharge cavity A1. The positive charge particle extraction system 2 consists of two metal grids (screen grid A and acceleration grid A) and insulating fasteners. A negative charge particle extraction system 4 is installed at the wide end of the discharge cavity B5. The negative charge particle extraction system 4 consists of two metal grids (screen grid B and acceleration grid B) and insulating fasteners.

[0057] A large number of concentric holes are opened on the metal gate, and a specific electric field is formed by applying a DC voltage to accelerate the extraction of ions and electrons.

[0058] like Figure 3 As shown, the positively charged particle extraction system 2 applies a positive bias voltage to extract ions from the discharge chamber A12, and the negatively charged particle extraction system 4 applies a negative bias voltage to extract electrons from the discharge chamber B6, thereby achieving plume neutralization.

[0059] The periphery of the discharge cavity is a permanent magnet array fixed by the magnet fixing component 13 and the discharge cavity, which provides the required magnetic field conditions for ionization. The magnetic poles of the permanent magnet arrays A11 and B7 are arranged in opposite directions, and there is no permanent magnet array on the side close to the discharge cavity A1 and discharge cavity B5, so that the cavity connecting channel 3 forms a connected magnetic field line, which guides the plasma in the discharge chamber A12 and discharge chamber B6 to communicate and maintain the quasi-neutrality of the internal plasma.

[0060] Even better, such as Figure 2 As shown, the two discharge cavities have the same structure, each including a stepped shaft section, a horn section and a cylindrical section connected in sequence; the permanent magnet array is set on the outer wall of the horn section of the discharge cavity.

[0061] Specifically, the microwave connector runs through the stepped shaft section, and the positive charge particle extraction system 2 and the negative charge particle extraction system 4 are bolted to the cylindrical section.

[0062] Antenna 8 is located at the center of the narrow end of discharge chamber A1 and discharge chamber B5. It is connected to the inner conductor of the microwave connector by a thread and is used to transmit microwaves into discharge chamber A12 and discharge chamber B6 respectively.

[0063] The discharge cavity A1 and discharge cavity B5 have openings on their sides, the size of which is the same as the external size of the cavity connection channel 3, so as to fit tightly with the cavity connection channel 3 and be connected by welding.

[0064] The cavity connection channel 3 is a trapezoidal square tube structure, located outside the horn section of the discharge cavity and closely close to the cylindrical section of the discharge cavity; the length of the bottom edge of the cavity connection channel 3 is greater than or equal to the sum of the radial widths of the cylindrical sections of discharge cavity A1 and discharge cavity B5, so that discharge cavity A1 and discharge cavity B5 are in contact.

[0065] The permanent magnet array will now be described in detail.

[0066] The permanent magnet array designed in this invention is adapted to the shape of the cavity, including permanent magnet array A11 and permanent magnet array B7, which are composed of multiple tile-type Halbach magnets. The structure of a single tile-type Halbach magnet is as follows: Figure 4 As shown, this includes multi-level magnets, requiring at least three levels. Here, we take the most basic three-level magnet as an example, including a first-level magnet, a second-level magnet, and a third-level magnet. In terms of dimensions, the lower base of the first-level magnet is the same length as the upper base of the second-level magnet; the lower base of the second-level magnet and the upper base of the third-level magnet are the same length; the hypotenuses of the three magnets are collinear, the magnet thickness is the same, but the height differs, showing a progressively increasing relationship. More advanced magnets follow the same principle.

[0067] Specifically, thickness refers to the dimension in the Z-axis direction, and height refers to the dimension in the X-axis direction.

[0068] In terms of coercivity distribution, the coercivity of the first-stage magnet is greater than or equal to that of the second-stage magnet, which is greater than or equal to that of the third-stage magnet, with all coercivity values ​​falling within the range of 600–700 kA / m. The direction from the first-stage magnet to the third-stage magnet is defined as the positive X-axis, and the direction from the first-stage magnet away from discharge chamber 2 is defined as the Z-axis. Therefore, in the magnetic pole directions, in permanent magnet array A11, the N-pole of the first-stage magnet is magnetized along the positive Z-axis, the N-pole of the second-stage magnet is magnetized along the positive X-axis, and the N-pole of the third-stage magnet is magnetized along the negative Z-axis; in permanent magnet array B7, the N-pole of the first-stage magnet is magnetized along the negative Z-axis, the N-pole of the second-stage magnet is magnetized along the negative X-axis, and the N-pole of the third-stage magnet is magnetized along the positive Z-axis.

[0069] If there are more advanced magnets, their magnetization direction continues according to the traditional Halbach magnetic array arrangement. Specifically, in permanent magnet array A11, the N pole of the fourth-stage magnet is magnetized along the negative X-axis, forming one cycle. The magnetization direction of the fifth-stage magnet is the same as that of the first-stage magnet, the magnetization direction of the sixth-stage magnet is the same as that of the second-stage magnet, and so on. In permanent magnet array B7, the N pole of the fourth-stage magnet is magnetized along the positive X-axis, forming one cycle. The magnetization direction of the fifth-stage magnet is the same as that of the first-stage magnet, the magnetization direction of the sixth-stage magnet is the same as that of the second-stage magnet, and so on.

[0070] like Figure 5As shown in Figure (a), in this embodiment, permanent magnet array A11 and permanent magnet array B7 each contain 7 Halbach magnets. The 7 magnets are only one type in this embodiment, and other numbers can be flexibly designed according to requirements.

[0071] The seven Halbach magnets in permanent magnet array A11 are arranged in an octagonal array along the discharge cavity A1, with the direction of the magnetic field strengthening the magnets pointing towards the axis of discharge cavity A1. Similarly, the seven Halbach magnets in permanent magnet array B7 are arranged in an octagonal array along the discharge cavity B5, with the direction of the magnetic field strengthening the magnets pointing towards the axis of discharge cavity B5. There are no permanent magnets at the cavity connection channel 3, thus the permanent magnet arrays can form continuous magnetic field lines within the cavity connection channel 3.

[0072] The magnetic field distribution formed by the permanent magnet array is as follows: Figure 5 As shown, where Figure 5 Figure (b) shows the XZ section. Figure 5 Figure (c) shows the XY section. Figure 5 Figure (d) shows the YZ section. It can be seen that the magnetic field provided by the permanent magnet array not only provides the magnetic field conditions required for ionization, but also forms a connected magnetic field between discharge chambers A1 and B5. Furthermore, there are connected magnetic field lines in the cavity connection channel 3, which can guide the movement of charged particles, connect the plasma in discharge chambers A12 and B6, enable charge exchange, maintain quasi-neutrality, and provide conditions for external plume neutralization.

[0073] The complete working process of the self-neutralizing microwave ion thruster described in this invention is as follows:

[0074] The working gas enters discharge chambers A12 and B6 through inlet pipe 10. Microwaves are output from two microwave power supplies, transmitted via two coaxial transmission lines to microwave connectors, and fed into discharge chambers A12 and B6 through antenna 8. Initial electrons are generated through microwave-induced discharge or microwave local electric field breakdown discharge. These initial electrons are confined by a magnetic field and reciprocate within a magnetic mirror. Relying on the resonance between the microwave electric field and the electron cyclotron, the electrons continuously absorb microwave energy to become high-energy electrons, further ionizing the gas and generating and maintaining plasma. After ignition, a large amount of plasma is generated inside discharge chambers A12 and B6. Under the influence of the magnetic field, the plasma moves into the cavity connecting channel 3, connecting the plasma in discharge chambers A12 and B6, realizing charge exchange, and maintaining the quasi-neutrality of the plasma inside the discharge cavity.

[0075] A DC voltage is applied to the positively charged particle extraction system 2, with the screen grid A carrying a positive voltage and the accelerating grid A grounded. The voltage of the screen grid A is greater than that of the accelerating grid A, forming a positive high-voltage sheath that accelerates and extracts ions from the discharge chamber A12, generating an ion beam. A DC voltage is applied to the negatively charged particle extraction system 4 and the discharge chamber, with a negative voltage applied to the discharge chamber and the screen grid B. The accelerating grid B is grounded, with the voltage of the screen grid B being less than that of the accelerating grid B, forming a negative high-voltage sheath that extracts electrons from the discharge chamber B6, generating an electron beam. The ion beam generated by the positively charged particle extraction system 2 and the electron beam generated by the negatively charged particle extraction system 4 neutralize each other, achieving self-neutralization of the plume.

[0076] A prototype of this embodiment has been produced and relevant tests have been conducted, such as... Figure 6 The image shown is a beam extraction image of the device in Xe working fluid. The thruster can generate both ion beams and electron beams simultaneously.

[0077] like Figure 7 The potential distribution in the space downstream of the thruster when different voltages are applied to the screen A shows that the potential in the space downstream of the thruster is significantly lower than that applied to the screen A, which can achieve plume neutralization.

[0078] The present invention is designed to create a discharge cavity with two cavity structures connected by a cavity connection channel 3. Through the permanent magnet array A11 and permanent magnet array B7 forming connecting magnetic field lines in the cavity connection channel 3, the plasma in discharge chamber A12 and the plasma in discharge chamber B6 are connected and charge exchange occurs, so that the plasma inside the discharge cavity is kept electrically neutral. At the same time, the positive charge particle extraction system 2 extracts ions and the negative charge particle extraction system 4 extracts electrons, thereby achieving plume neutralization.

[0079] 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 it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A self-neutralizing microwave ion thruster, characterized in that, Includes microwave plasma source A, microwave plasma source B and cavity connection channel (3); The microwave plasma source A includes a discharge cavity A (1), a permanent magnet array A (11), a microwave connector A (14), and a positive charge particle extraction system (2). The discharge cavity A (1), the microwave connector A (14), and the positive charge particle extraction system (2) surround and form a discharge chamber A (12); the permanent magnet array A (11) is installed outside the discharge cavity A (1); The microwave plasma source B includes a discharge cavity B (5), a permanent magnet array B (7), a microwave connector B (9), and a negative charge particle extraction system (4). The discharge cavity B (5), the microwave connector B (9), and the negative charge particle extraction system (4) surround and form a discharge chamber B (6); the permanent magnet array B (7) is installed outside the discharge cavity B (5). Discharge chambers A (1) and B (5) are arranged in parallel along the axis, and discharge chambers A (12) and B (6) are connected through the chamber connection channel (3). Positively charged particle extraction system (2) is used to extract positively charged particles and accelerate them out to generate thrust; The negative charge particle extraction system (4) is used to extract negative charge particles, which neutralize the positive charge particles extracted by the positive charge particle extraction system (2).

2. The self-neutralizing microwave ion thruster according to claim 1, characterized in that, Both discharge chamber A (12) and discharge chamber B (6) are horn-shaped structures; A positive charge particle extraction system (2) is installed at the wide end of discharge chamber A (12), a negative charge particle extraction system (4) is installed at the wide end of discharge chamber B (6), a microwave connector A (14) is installed at the narrow end of discharge chamber A (12), and a microwave connector B (9) is installed at the narrow end of discharge chamber B (6); an antenna (8) is installed on both microwave connector A (14) and microwave connector B (9); The side of the discharge cavity A (1) is provided with an air inlet pipe (10) arranged perpendicular to the axis of the microwave connector A (14); the side of the discharge cavity B (5) is provided with an air inlet pipe (10) arranged perpendicular to the axis of the microwave connector B (9).

3. The self-neutralizing microwave ion thruster according to claim 1, characterized in that, Both discharge cavity A(1) and discharge cavity B(5) include a stepped shaft section, a horn section and a cylindrical section connected in sequence; The permanent magnet array A (11) is set on the outer wall of the horn section of the discharge cavity A (1), and the permanent magnet array B (7) is set on the outer wall of the horn section of the discharge cavity B (5); the microwave connector A (14) passes through the stepped shaft section of the discharge cavity A (1), and the microwave connector B (9) passes through the stepped shaft section of the discharge cavity B (5); the positive charge particle extraction system (2) is bolted to the cylindrical section of the discharge cavity A (1), and the negative charge particle extraction system (4) is bolted to the cylindrical section of the discharge cavity B (5).

4. The self-neutralizing microwave ion thruster according to claim 3, characterized in that, Both the horn section of the discharge cavity A (1) and the discharge cavity B (5) have pre-made openings on their sides. The opening size is consistent with the external size of the cavity connection channel (3) and is used to connect with the cavity connection channel (3).

5. The self-neutralizing microwave ion thruster according to claim 1, characterized in that, The cavity connection channel (3) is a trapezoidal square tube structure.

6. The self-neutralizing microwave ion thruster according to claim 5, characterized in that, The length of the bottom edge of the cavity connecting channel (3) is greater than or equal to the sum of the radial widths of the cylindrical sections of discharge cavity A (1) and discharge cavity B (5).

7. The self-neutralizing microwave ion thruster according to claim 1, characterized in that, There is no permanent magnet on the cavity connection channel (3) side of the discharge cavity A (1), and there is no permanent magnet on the cavity connection channel (3) side of the discharge cavity B (5); The magnetic field poles provided by permanent magnet array A (11) and permanent magnet array B (7) are opposite, so that the cavity connecting channel (3) forms a connected magnetic field line.

8. The self-neutralizing microwave ion thruster according to claim 1, characterized in that, The permanent magnet arrays A (11) and B (7) are composed of multiple tile-type Halbach magnets; The magnetic field enhancement direction of each tile-shaped Halbach magnet is angular and points towards the center of the distribution circle. Multiple tile-shaped Halbach permanent magnets are evenly distributed on the outer wall of the discharge cavity in a trumpet shape. Each Halbach tile consists of multiple magnets, with at least three magnets required. In terms of size, in two adjacent magnets, the bottom edge of the upper magnet and the top edge of the lower magnet are the same length, and the bottom edge of the upper magnet is smaller than the bottom edge of the lower magnet. The hypotenuses of multi-stage magnets are collinear and have the same thickness; their heights are different and increase sequentially. In terms of coercivity distribution, the coercivity of the next-level magnet is greater than or equal to that of the next-level magnet.

9. The self-neutralizing microwave ion thruster according to claim 1, characterized in that, The direction from the first-stage magnet to the third-stage magnet is defined as the positive X-axis, and the direction from which the first-stage magnet moves away from the discharge cavity is defined as the Z-axis. In the magnetic pole direction, the first-stage magnet N pole of permanent magnet array A(11) is magnetized along the positive Z-axis, the second-stage magnet N pole is magnetized along the positive X-axis, and the third-stage magnet N pole is magnetized along the negative Z-axis; the first-stage magnet N pole of permanent magnet array B(7) is magnetized along the negative Z-axis, the second-stage magnet N pole is magnetized along the negative X-axis, and the third-stage magnet N pole is magnetized along the positive Z-axis. If there are higher-level magnets, the N pole of the fourth-level magnet in permanent magnet array A(11) is magnetized in the negative direction of the X-axis, and the N pole of the fourth-level magnet in permanent magnet array B(7) is magnetized in the positive direction of the X-axis. The subsequent magnets are cycled with the previous four-level magnets as a unit.

10. The method of operating the self-neutralizing microwave ion thruster according to any one of claims 1-9, characterized in that, The process includes the following: The working gas enters the discharge chamber A (12) and the discharge chamber B (6) respectively. Initial electrons are generated by microwave-induced discharge or microwave local electric field breakdown discharge. The initial electrons are constrained by the magnetic field and move back and forth in the magnetic mirror. Relying on the resonance between the microwave electric field and the electron cyclotron, the electrons continuously absorb microwave energy to become high-energy electrons, further ionize the gas, and generate and maintain plasma. After ignition, a large amount of plasma is generated inside discharge chamber A (1) and discharge chamber B (5). Under the action of the magnetic field, the plasma moves into the cavity connection channel (3) to connect the plasma in discharge chamber A (12) and discharge chamber B (6), realize charge exchange, and keep the plasma inside the discharge chamber quasi-neutral. A positive voltage is applied to the positive charge particle extraction system (2), and a negative voltage is applied to the negative charge particle extraction system (4). Under the action of electrostatics, positive charge particles are extracted from the discharge chamber A (12), and negative charge particles are extracted from the discharge chamber B (6), and the plume is self-neutralized downstream of the thruster.

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