Microwave magnetic nozzle thruster without excitation antenna

Abstract

The invention discloses a microwave magnetic nozzle thruster without an excitation antenna, belongs to the field of space electric propulsion, and aims to solve the problems of antenna ablation and performance drift of a conventional microwave magnetic nozzle thruster. The thruster comprises a discharge chamber and a resonant cavity which are coaxially arranged, an air inlet pipe axially penetrates through the center of the thruster, the resonant cavity is coaxially arranged outside the air inlet pipe, the air inlet pipe is communicated with a discharge chamber air path, and the air inlet pipe is isolated from a resonant cavity air path; microwaves are fed into the resonant cavity chamber and are repeatedly reflected by the short-circuit end and the open-circuit end of the resonant cavity chamber to generate standing waves, so that a strong standing wave electric field is formed at the open-circuit end, the strong standing wave electric field ionizes working medium gas in the discharge chamber to form plasmas, and the plasmas are axially accelerated under a divergent magnetic spray pipe characteristic magnetic field applied externally. And plume is formed and jetted out of the thruster, so that thrust is formed.

Description

Technical Field

[0001] The invention relates to a microwave magnetic nozzle thruster without an excitation antenna, belonging to the field of space electric propulsion. Background Art

[0002] Microwave magnetic nozzle thrusters are also commonly called microwave plasma thrusters (ECRTs). They are a new type of space electric propulsion device. The principle is to feed microwave power into a region with a specific magnetic field strength in the thruster discharge chamber. When the electron cyclotron frequency corresponding to the magnetic field strength is consistent with the microwave power frequency, the electrons will continuously obtain energy from the microwave electric field and collide with neutral gases to cause ionization. The plasma generated by ionization converts its internal energy and non-axial kinetic energy into axial kinetic energy to generate thrust under the guidance of the divergent magnetic field of the magnetic nozzle. In the field of space electric propulsion, microwave magnetic nozzle thrusters are different from traditional types of electrothermal, electrostatic and electromagnetic electric thrusters. Their ionization and acceleration process does not rely on DC electrodes, and the plasma plume is electrically neutral, which has significant advantages in the expected life and reliability of the thruster.

[0003] At present, the most mainstream microwave magnetic nozzle thruster in the world uses a cylindrical metal antenna as a waveguide device, which directly probes into the electron cyclotron resonance surface in the magnetic field for energy coupling. In this coupling mode, due to the direct contact between the plasma and the metal antenna, the metal antenna will continue to be sputtered and heated by the plasma, resulting in erosion of the antenna; at the same time, the erosion products will also be deposited on the wall of the discharge chamber and the plane of the microwave feed port, resulting in changes in microwave transmission and plasma discharge characteristics, resulting in changes in the working characteristics of the thruster, thereby reducing reliability and the expected life of the thruster. Summary of the invention

[0004] In order to solve the problems of antenna ablation and performance drift of a conventional microwave magnetic nozzle thruster, the present invention provides a microwave magnetic nozzle thruster without an excitation antenna.

[0005] The microwave magnetic nozzle thruster without excitation antenna described in the present invention comprises a discharge chamber 7 and a resonance chamber 9 which are coaxially arranged, an air inlet pipe 8 is axially arranged through the center of the thruster, the resonance chamber 9 is coaxially arranged outside the air inlet pipe 8, the air inlet pipe 8 is connected with the discharge chamber 7 by air path, and the air inlet pipe 8 is isolated from the resonance chamber 9 by air path;

[0006] The microwave is fed into the resonant cavity 9, and is repeatedly reflected by the short-circuit end and the open-circuit end of the resonant cavity 9 to generate standing waves, thereby forming a strong standing wave electric field at the open-circuit end. The strong standing wave electric field ionizes the working fluid gas in the discharge chamber 7 to form plasma. The plasma is axially accelerated under the characteristic magnetic field of the divergent magnetic nozzle applied externally, forming a plume that is ejected out of the thruster, thereby generating thrust.

[0007] Preferably, it also includes an insulating mounting plate 1, a chamber housing 2, a microwave feeding port 3, a microwave antenna 4, a wall ceramic 6 and a coaxial waveguide 10;

[0008] The chamber housing 2 and the coaxial waveguide 10 are coaxially arranged, and the tail ends of both are fixedly arranged on the insulating mounting plate 1;

[0009] The annular cavity formed by the chamber housing 2 and the head end of the coaxial waveguide 10 serves as the resonant chamber 9, and the chamber housing 2 and the tail end of the coaxial waveguide 10 are in contact and electrically connected to form a short-circuit end of the resonant chamber 9;

[0010] The discharge chamber 7 is constructed by using the wall ceramic 6. The wall ceramic 6 and the coaxial waveguide 10 are coaxially installed by brazing or tight fitting at the bottom. The bottom plate of the wall ceramic 6 has an air inlet hole, which is connected to the air inlet pipe 8. The bottom plate of the wall ceramic 6 serves as an open circuit end of the resonant cavity 9.

[0011] The microwave feeding port 3 is disposed at the rear end of the chamber housing 2 , and the microwave antenna 4 extends into the resonance chamber 9 through the microwave feeding port 3 and is connected to the coaxial waveguide 10 .

[0012] Preferably, it also includes a permanent magnet 5 and a magnet fixing ring 11; the permanent magnet 5 is arranged outside the head end of the chamber shell 2, and the permanent magnet 5 is used to generate a divergent magnetic nozzle characteristic magnetic field. The magnet fixing ring 11 is sleeved on the outside of the chamber shell 2, and the axial fixation of the permanent magnet 5 is achieved by the magnet fixing ring 11.

[0013] Preferably, the chamber shell 2 , the coaxial waveguide 10 and the microwave antenna 4 are made of metal devices and are electrically connected to each other. The microwave antenna 4 is electrically connected to the coaxial waveguide 10 as the inner core of the microwave feeding port 3 , and the shielding pole of the microwave feeding port 3 is electrically connected to the chamber shell 2 .

[0014] Preferably, the chamber housing 2 and the coaxial waveguide 10 are made of aluminum or copper metal materials.

[0015] Preferably, the structures are fixedly mounted by bolts.

[0016] Preferably, the length of the resonance chamber 9 is an odd number of times the 1 / 4 wavelength of the microwaves.

[0017] Preferably, the inner surface of the resonance chamber 9 is smoothed.

[0018] Preferably, the wall ceramic 6 is made of quartz or boron nitride.

[0019] Preferably, the microwave feeding port 3 uses an SMA connector or an N-type connector.

[0020] Beneficial effects of the present invention: By using a ceramic discharge chamber coaxial resonator as a microwave coupling device, the microwave coaxial line resonator is a device that can form local plasma discharge without direct contact with a metal waveguide device. Through the coaxial resonant cavity, the fed microwave forms a standing wave strong electric field near the open end to induce local discharge. This technology makes it possible to achieve effective operation of the microwave magnetic nozzle thruster without using direct coupling with a metal antenna.

[0021] The present invention utilizes a microwave coaxial line resonator to replace the coupling method of the traditional cylindrical antenna, completely avoiding the problems of thruster performance drift and shortened life caused by metal antenna erosion and coating. At the same time, the coaxial resonator's ability to capture and store microwaves of a specific frequency, as well as its ability to enhance the local standing wave electric field, significantly reduces the microwave power required for thruster ignition and discharge maintenance, making it possible to reduce the power of the microwave magnetic nozzle thruster. The above working characteristics greatly improve the reliability of the microwave magnetic nozzle thruster of the present invention, broaden the scope of application, and have great application prospects in the fields of micro-nano satellite electric propulsion, high-precision space science exploration, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a front schematic diagram of the thruster of the present invention.

[0023] Figure 2 It is a schematic diagram of the back side of the thruster of the present invention.

[0024] Figure 3 It is a side schematic diagram of the thruster of the present invention.

[0025] Figure 4 It is a schematic diagram of the cross-sectional structure of the thruster of the present invention.

[0026] Figure 5 It is a schematic diagram of the overall working principle of the thruster of the present invention.

[0027] Figure 6 It is a schematic diagram of the local standing wave electric field intensity formed by microwaves in the discharge chamber of the thruster described in the present invention during operation. DETAILED DESCRIPTION

[0028] 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.

[0029] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0030] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0031] Specific implementation method 1: The following is combined Figures 1 to 6 The present embodiment is described. The microwave magnetic nozzle thruster without an excitation antenna in the present embodiment comprises a discharge chamber 7 and a resonance chamber 9 which are coaxially arranged. An air inlet pipe 8 is axially arranged to penetrate the center of the thruster. The resonance chamber 9 is coaxially arranged outside the air inlet pipe 8. The air inlet pipe 8 is connected to the discharge chamber 7 by air path, and the air inlet pipe 8 is isolated from the resonance chamber 9 by air path.

[0032] The microwave is fed into the resonant cavity 9, and is repeatedly reflected by the short-circuit end and the open-circuit end of the resonant cavity 9 to generate standing waves, thereby forming a strong standing wave electric field at the open-circuit end. The strong standing wave electric field ionizes the working fluid gas in the discharge chamber 7 to form plasma. The plasma is axially accelerated under the characteristic magnetic field of the divergent magnetic nozzle applied externally, forming a plume that is ejected out of the thruster, thereby generating thrust.

[0033] Combination Figures 1 to 4 To give a specific example, the thruster includes an insulating mounting plate 1, a chamber housing 2, a microwave feed port 3, a microwave antenna 4, a permanent magnet 5, a wall ceramic 6, a discharge chamber 7, an air inlet pipe 8, a resonant chamber 9, a coaxial waveguide 10 and a magnet fixing ring 11;

[0034] The chamber housing 2 and the coaxial waveguide 10 are coaxially arranged, and the tail ends of both are fixedly arranged on the insulating mounting plate 1;

[0035] The annular cavity formed by the chamber housing 2 and the head end of the coaxial waveguide 10 serves as the resonant chamber 9, and the chamber housing 2 and the tail end of the coaxial waveguide 10 are in contact and electrically connected to form a short-circuit end of the resonant chamber 9;

[0036] The discharge chamber 7 is constructed by using the wall ceramic 6. The wall ceramic 6 and the coaxial waveguide 10 are coaxially installed by brazing or tight fitting at the bottom. The bottom plate of the wall ceramic 6 has an air inlet hole, which is connected to the air inlet pipe 8. The bottom plate of the wall ceramic 6 serves as an open circuit end of the resonant cavity 9.

[0037] The microwave feeding port 3 is disposed at the rear end of the chamber housing 2 , and the microwave antenna 4 extends into the resonance chamber 9 through the microwave feeding port 3 and is connected to the coaxial waveguide 10 .

[0038] A permanent magnet 5 is arranged outside the head end of the chamber shell 2 , and the permanent magnet 5 is used to generate a divergent magnetic nozzle characteristic magnetic field. A magnet fixing ring 11 is sleeved outside the chamber shell 2 , and the permanent magnet 5 is axially fixed by the magnet fixing ring 11 .

[0039] The chamber shell 2 , the coaxial waveguide 10 and the microwave antenna 4 are made of metal components and are electrically connected to each other. The microwave antenna 4 is electrically connected to the coaxial waveguide 10 as the inner core of the microwave feeding port 3 , and the shielding pole of the microwave feeding port 3 is electrically connected to the chamber shell 2 .

[0040] The chamber housing 2 and the coaxial waveguide 10 are made of metal materials with high electrical conductivity, such as aluminum, copper, etc.

[0041] The wall ceramic 6 is made of a material with low dielectric loss in the microwave frequency band, such as quartz, boron nitride, etc.

[0042] The length of the resonant cavity 9 is an odd multiple of 1 / 4 wavelength of the microwave, for example, under 2.45 GHz microwave, the cavity length is about 3 mm.

[0043] The inner surface of the resonance chamber 9 is smoothed.

[0044] The microwave feed port 3 uses an SMA connector or an N-type connector.

[0045] Each structure is fixed and installed by bolts.

[0046] When working, the thruster is connected to the spacecraft structure through the insulating mounting plate 1, while the metal components such as the chamber housing 2, coaxial waveguide 10, permanent magnet 5, microwave antenna 4, etc. can be connected to the satellite ground wire or apply different potentials as required, such as on-orbit plasma diagnosis. The microwave feed port 3 is connected to the microwave source via a DC isolator, a microwave coaxial transmission line or a waveguide to avoid damage to the microwave source by charge accumulation. The air intake pipe 8 is connected to the on-board storage and supply devices such as the flow controller, the pressure reducing valve, and the working medium high-pressure gas cylinder.

[0047] The thruster in this embodiment should work in a high vacuum environment. During operation, firstly, a high flow rate of 5 to 10 times the rated flow rate during operation is temporarily supplied to the air inlet pipe 8, and a high power (3 to 5 times the rated power during operation) is applied to the microwave feeding port 3 for ignition. At this time, microwaves of a specific frequency are fed into the resonant chamber 9 from the microwave antenna 4. Since microwaves are reflected at both the short-circuit end and the open-circuit end, the relatively propagated reflected waves form standing waves with axial directions on the surface of the coaxial waveguide 10, and form a strong standing wave electric field in the discharge chamber 7, such as Figure 6As shown. Under the action of strong standing wave electric field and collisionless heating of electrons in the electron cyclotron resonance region of the magnetic field in the discharge chamber, the remaining free electrons in the gas collide with the working fluid gas to form a discharge. After the discharge occurs, the microwave power and the working fluid flow rate are reduced to the rated range in turn. In the divergent magnetic nozzle characteristic magnetic field formed by the permanent magnet 5, the plasma generated in the discharge chamber 7 converts the internal energy and non-axial kinetic energy into axial kinetic energy, and the thruster continues to generate thrust. When the fed-in microwave power and the fed-in working fluid gas flow rate are adjusted, the thrust level of the microwave magnetic nozzle thruster without an excitation antenna described in the present invention will change to achieve thrust regulation. The specific implementation method shall be subject to the actual operation.

[0048] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that the features described in conjunction with a single embodiment may be used in other described embodiments.

Claims

1. A microwave magnetic nozzle thruster without excitation antenna, characterized in that: It comprises a discharge chamber (7) and a resonance chamber (9) which are coaxially arranged, an air intake pipe (8) is arranged axially through the center of the thruster, the resonance chamber (9) is coaxially arranged outside the air intake pipe (8), the air intake pipe (8) and the discharge chamber (7) are in gas communication, and the air intake pipe (8) and the resonance chamber (9) are in gas isolation; Microwaves are fed into the resonant chamber (9), and are repeatedly reflected at the short-circuit end and the open-circuit end of the resonant chamber (9) to generate standing waves, thereby forming a strong standing wave electric field at the open-circuit end. The strong standing wave electric field ionizes the working fluid gas in the discharge chamber (7) to form plasma. The plasma is axially accelerated under the characteristic magnetic field of the divergent magnetic nozzle applied externally to form a plume that is ejected from the thruster, thereby generating thrust.

2. According to claim 1, a microwave magnetic nozzle thruster without excitation antenna is characterized in that: It also includes an insulating mounting plate (1), a chamber housing (2), a microwave feed port (3), a microwave antenna (4), a wall ceramic (6) and a coaxial waveguide (10); The chamber housing (2) and the coaxial waveguide (10) are coaxially arranged, and the tail ends of both are fixedly arranged on the insulating mounting plate (1); The annular cavity formed by the chamber housing (2) and the head end of the coaxial waveguide (10) serves as the resonant chamber (9), and the tail ends of the chamber housing (2) and the coaxial waveguide (10) are in contact to achieve electrical connection to form a short-circuit end of the resonant chamber (9); A discharge chamber (7) is constructed by using a wall ceramic (6), the wall ceramic (6) and the coaxial waveguide (10) are coaxially installed by brazing or tight fitting at the bottom, the bottom plate of the wall ceramic (6) has an air inlet hole connected to the air inlet pipe (8), and the bottom plate of the wall ceramic (6) serves as an open circuit end of the resonant cavity (9); A microwave feed port (3) is arranged at the rear end of the chamber housing (2); a microwave antenna (4) extends into the resonant chamber (9) through the microwave feed port (3) and is connected to the coaxial waveguide (10).

3. According to claim 2, a microwave magnetic nozzle thruster without excitation antenna is characterized in that: It also includes a permanent magnet (5) and a magnet fixing ring (11); the permanent magnet (5) is arranged outside the head end of the chamber shell (2), and the permanent magnet (5) is used to generate a divergent magnetic nozzle characteristic magnetic field; the magnet fixing ring (11) is sleeved outside the chamber shell (2), and the permanent magnet (5) is axially fixed by the magnet fixing ring (11).

4. According to claim 2, a microwave magnetic nozzle thruster without excitation antenna is characterized in that: The chamber shell (2), the coaxial waveguide (10) and the microwave antenna (4) are made of metal components and are electrically connected to each other; the microwave antenna (4) is electrically connected to the coaxial waveguide (10) as the inner core of the microwave feed port (3); and the shielding electrode of the microwave feed port (3) is electrically connected to the chamber shell (2).

5. The microwave magnetic nozzle thruster without excitation antenna according to claim 4, characterized in that: The chamber shell (2) and the coaxial waveguide (10) are made of aluminum or copper metal materials.

6. A microwave magnetic nozzle thruster without excitation antenna according to claim 1 or 2, characterized in that: Each structure is fixed and installed by bolts.

7. A microwave magnetic nozzle thruster without excitation antenna according to claim 1 or 2, characterized in that: The length of the resonant cavity (9) is an odd number of times the 1 / 4 wavelength of the microwave.

8. The microwave magnetic nozzle thruster without excitation antenna according to claim 1 or 2, characterized in that: The inner surface of the resonance chamber (9) is smoothed.

9. The microwave magnetic nozzle thruster without excitation antenna according to claim 2, characterized in that: The wall ceramic (6) is made of quartz or boron nitride.

10. The microwave magnetic nozzle thruster without excitation antenna according to claim 2, characterized in that: The microwave feed port (3) uses an SMA connector or an N-type connector.

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