A microwave magnetic nozzle thruster without a driven antenna

Abstract

The application discloses a microwave magnetic nozzle thruster without an exciting antenna, belongs to the field of space electric propulsion, and aims at solving the problems of antenna ablation and performance drift of a conventional microwave magnetic nozzle thruster. The microwave magnetic nozzle thruster comprises a discharge chamber and a resonance chamber which are coaxially arranged, a gas inlet pipe is arranged through the center of the thruster in an axial direction, the resonance chamber is coaxially arranged outside the gas inlet pipe, the gas inlet pipe is in communication with the discharge chamber in a gas path, and the gas inlet pipe is isolated from the resonance chamber in a gas path; microwaves are fed into the resonance chamber, repeatedly reflected through a short-circuit end and an open-circuit end of the resonance chamber to generate a standing wave, so that a strong standing wave electric field is formed at the open-circuit end; the strong standing wave electric field ionizes working gas in the discharge chamber to form plasma; the plasma is axially accelerated under a characteristic magnetic field of a divergent magnetic nozzle which is externally applied, forms a plume jet and is ejected out of the thruster, so that a thrust is formed.

Description

TECHNICAL FIELD

[0001] The present application relates to a microwave magnetic nozzle thruster without excitation antenna, belonging to the field of space electric propulsion. BACKGROUND

[0002] The microwave magnetic nozzle thruster, also commonly known as microwave plasma thruster (ECRT), is a new type of space electric propulsion device. The principle is to feed microwave power into the region with a specific magnetic field strength in the discharge chamber of the thruster. When the electron cyclotron frequency corresponding to the magnetic field strength is consistent with the frequency of the microwave power, the electrons will continuously gain energy from the microwave electric field and collide with the neutral gas to cause ionization. The plasma generated by ionization is accelerated axially under the guidance of the divergent magnetic field of the magnetic nozzle, and the internal energy and non-axial kinetic energy are converted into axial kinetic energy to generate thrust. In the field of space electric propulsion, the microwave magnetic nozzle thruster is different from traditional electric heaters, electrostatic and electromagnetic electric thrusters. Its ionization and acceleration process does not depend on direct current electrodes, and the plasma plume is electrically neutral, which has significant advantages in expected life and reliability of the thruster.

[0003] The most mainstream microwave magnetic nozzle thruster in the world currently uses a cylindrical metal antenna as a waveguide device, which directly penetrates into the electron cyclotron resonance plane in the magnetic field for energy coupling. In this coupling mode, since the plasma is in direct contact with the metal antenna, the metal antenna will be continuously affected by sputtering and heating of the plasma, resulting in erosion of the antenna. At the same time, the erosion products will also deposit on the discharge chamber wall and the microwave feed-in port plane, causing changes in microwave transmission and plasma discharge characteristics, resulting in changes in the working characteristics of the thruster, thereby reducing the reliability and expected life of the thruster. SUMMARY

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

[0005] The microwave magnetic nozzle thruster without excitation antenna provided by the present application comprises a discharge chamber 7 and a resonant cavity 9 arranged coaxially, and a gas inlet pipe 8 is arranged through the center axis of the thruster. The resonant cavity 9 is arranged coaxially outside the gas inlet pipe 8. The gas inlet pipe 8 is in gas communication with the discharge chamber 7, and the gas inlet pipe 8 is gas isolated from the resonant cavity 9.

[0006] Microwave is fed into the resonant cavity 9, and standing waves are generated by repeated reflection of the short-circuit end and open-circuit end of the resonant cavity 9, thereby forming a strong standing wave electric field at the open-circuit end. The strong standing wave electric field ionizes the working gas in the discharge chamber 7 to form plasma. The plasma is accelerated axially under the action of the divergent magnetic field of the external characteristic magnetic nozzle, and the plasma plume is ejected out of the thruster to form thrust.

[0007] Preferably, the device further comprises an insulating mounting plate 1, a chamber shell 2, a microwave feed port 3, a microwave antenna 4, a wall ceramic 6 and a coaxial waveguide 10.

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

[0009] The annular cavity formed by the head ends of the chamber shell 2 and the coaxial waveguide 10 serves as a resonant cavity 9, and the tail ends of the chamber shell 2 and the coaxial waveguide 10 are in contact to achieve electrical connection to constitute a short-circuit end of the resonant cavity 9.

[0010] The wall ceramic 6 is used to construct a discharge chamber 7, and the wall ceramic 6 is coaxially arranged with the coaxial waveguide 10 through brazing or tight fitting, the bottom plate of the wall ceramic 6 has an air inlet hole in communication with 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.

[0011] The microwave feed port 3 is arranged at the tail end of the chamber shell 2, the microwave antenna 4 extends into the resonant cavity 9 through the microwave feed port 3 and is connected with the coaxial waveguide 10.

[0012] Preferably, the device further comprises 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 is used to generate a divergent magnetic nozzle characteristic magnetic field, and the magnet fixing ring 11 is sleeved outside the chamber shell 2 to axially fix the permanent magnet 5.

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

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

[0015] Preferably, the structures are fixedly installed through bolts.

[0016] Preferably, the length of the resonant cavity 9 is an odd multiple of 1 / 4 wavelength of the microwave.

[0017] Preferably, the inner surface of the resonant cavity 9 is smooth.

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

[0019] Preferably, the microwave feed port 3 is selected from an SMA joint or an N-type joint.

[0020] The beneficial effects of the present application: by using the ceramic discharge chamber coaxial resonator as the microwave coupling device, the microwave coaxial line resonator is a device capable of forming local plasma discharge without direct contact with metal waveguide devices. It forms a standing wave strong electric field near the open end of the coaxial resonant cavity to induce local discharge. This technology makes it possible to realize the effective work of the microwave magnetic nozzle thruster without using metal antenna direct coupling.

[0021] The present application uses a microwave coaxial line resonator to replace the coupling mode of the traditional cylindrical antenna, completely avoiding the problem of performance drift and shortening of the service life of the thruster caused by metal antenna erosion and coating. At the same time, the coaxial resonator has the ability to capture, store energy, and enhance the local standing wave electric field for specific frequency microwaves, significantly reducing the microwave power required to ignite and maintain the discharge of the thruster, making it possible to miniaturize the microwave magnetic nozzle thruster. The above working characteristics greatly improve the reliability of the microwave magnetic nozzle thruster of the present application, broaden its application range, and have great application prospects in micro-nano satellite electric propulsion, high-precision space scientific exploration, and other fields. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is the front view of the thruster described in the present application.

[0023] Figure 2 is the back view of the thruster described in the present application.

[0024] Figure 3 is the side view of the thruster described in the present application.

[0025] Figure 4 is the cross-sectional structure diagram of the thruster described in the present application.

[0026] Figure 5 is the overall working principle diagram of the thruster described in the present application.

[0027] Figure 6 is the local standing wave electric field intensity diagram formed by the microwave in the discharge chamber of the thruster described in the present application. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

[0029] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0030] The application will be further described below in conjunction with the drawings and specific embodiments, but not as a limitation of the application.

[0031] Specific embodiment one: the following will be described in conjunction with Figures 1 to 6 In this embodiment, the microwave magnetic nozzle thruster without excitation antenna includes a discharge chamber 7 and a resonant chamber 9 coaxially arranged, and a gas inlet pipe 8 is arranged through the center axis of the thruster. The resonant chamber 9 is coaxially arranged outside the gas inlet pipe 8. The gas inlet pipe 8 is in gas communication with the discharge chamber 7, and the gas inlet pipe 8 is isolated from the resonant chamber 9 in gas communication.

[0032] Microwaves are fed into the resonant chamber 9, and standing waves are generated by repeated reflection of the short-circuit end and open-circuit end of the resonant chamber 9, so that a strong standing wave electric field is formed at the open-circuit end. The strong standing wave electric field ionizes the working gas in the discharge chamber 7 to form plasma. The plasma is axially accelerated under the external applied divergent magnetic nozzle characteristic magnetic field to form a plume jet out of the thruster, thereby forming thrust.

[0033] In conjunction with Figures 1 to 4 A specific example is given. The thruster includes an insulating mounting plate 1, a chamber shell 2, a microwave feed port 3, a microwave antenna 4, a permanent magnet 5, a wall ceramic 6, a discharge chamber 7, a gas inlet pipe 8, a resonant chamber 9, a coaxial waveguide 10, and a magnet fixing ring 11.

[0034] The chamber shell 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 head ends of the chamber shell 2 and the coaxial waveguide 10 serves as the resonant chamber 9, and the tail ends of the chamber shell 2 and the coaxial waveguide 10 are in contact to achieve electrical connection to constitute the short-circuit end of the resonant chamber 9.

[0036] The wall ceramic 6 is used to construct the discharge chamber 7. The wall ceramic 6 is coaxially mounted with the coaxial waveguide 10 through brazing or tight fitting at the bottom. The bottom plate of the wall ceramic 6 has an air inlet hole in communication with the gas inlet pipe 8, and the bottom plate of the wall ceramic 6 serves as the open-circuit end of the resonant chamber 9.

[0037] The microwave feed port 3 is arranged at the tail end of the chamber shell 2, and the microwave antenna 4 extends into the resonant chamber 9 through the microwave feed port 3 and is connected with the coaxial waveguide 10.

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

[0039] The chamber shell 2, the coaxial waveguide 10 and the microwave antenna 4 are made of metal 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 pole of the microwave feed port 3 is electrically connected to the chamber shell 2.

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

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

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

[0043] The inner surface of the resonant chamber 9 is smooth.

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

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

[0046] The thruster is connected to the spacecraft structure through the insulating mounting plate 1 when working, and the metal devices such as the chamber shell 2, the coaxial waveguide 10, the permanent magnet 5, the microwave antenna 4, etc. can be connected to the satellite ground or applied with different potentials according to requirements such as in-orbit plasma diagnosis. The microwave feed port 3 is connected to the microwave source through a direct-current isolator, a microwave coaxial transmission line or a waveguide to avoid damage to the microwave source caused by charge accumulation. The gas inlet pipe 8 is connected to the on-board storage and supply devices such as a flow controller, a pressure reducing valve and a working medium high-pressure cylinder.

[0047] The thruster in this embodiment should work in a high-vacuum environment. When running, first, a flow rate of 5-10 times the rated flow rate of the working medium is temporarily supplied to the gas inlet pipe 8, and a high power (3-5 times the rated power of the working medium) is applied to the microwave feed port 3 to ignite. At this time, microwaves of a specific frequency are fed into the resonant chamber 9 from the microwave antenna 4. Since the microwaves are reflected at both the short-circuit end and the open-circuit end, the reflected waves propagate in the opposite direction and form a standing wave on the surface of the coaxial waveguide 10 in the axial direction, and a strong standing wave electric field is formed in the discharge chamber 7, as shown in Figure 6The remaining free electrons in the gas collide with the working gas to form discharge under the action of the non-collision heating of the electrons in the strong standing wave electric field and the electron cyclotron resonance region on the magnetic field in the discharge chamber. After the discharge is generated, the microwave power and the working gas flow are reduced to the rated range in turn. The plasma generated in the discharge chamber 7 is converted into axial kinetic energy in the divergent magnetic nozzle characteristic magnetic field formed by the permanent magnet 5, and the thruster continuously generates thrust. When the input microwave power and the working gas flow are adjusted, the thrust level of the microwave magnetic nozzle thruster with non-excited antenna of the present application changes to realize the regulation of the thrust. The specific implementation is subject to the actual operation.

[0048] While the application has been described with reference to particular embodiments, it will be understood that the examples are merely illustrative of the principles and applications of the present application. It will be understood that various modifications can be made to the illustrative embodiments, and other arrangements can be devised without departing from the spirit and scope of the present application as defined by the appended claims. It will be understood that the features of the various embodiments can be combined with each other, in different ways than as described herein. It will be understood that features described with reference to one embodiment can be used in other embodiments.

Claims

1. A microwave magnetic midget thrust er without an exciting antenna, characterized in that, The application relates to a microwave plasma thruster, which comprises an insulating mounting plate (1), a chamber shell (2), a microwave feeding port (3), a microwave antenna (4), wall ceramic (6), a coaxial waveguide (10), a coaxially arranged discharge chamber (7) and a resonant chamber (9), and a permanent magnet (5) and a magnet fixing ring (11); a gas inlet pipe (8) is arranged through the center of a thruster in an axial direction; the resonant chamber (9) is coaxially arranged outside the gas inlet pipe (8); the gas inlet pipe (8) is in air communication with the discharge chamber (7); and the gas inlet pipe (8) is in air isolation with the resonant chamber (9). Microwaves are fed into the resonant chamber (9) and repeatedly reflected by the short-circuit end and the open-circuit end of the resonant chamber (9) to generate a standing wave, so that a strong standing wave electric field is formed at the open-circuit end; the strong standing wave electric field ionizes working gas in the discharge chamber (7) to form plasma; the plasma is accelerated in an axial direction under the characteristic magnetic field of a divergent magnetic nozzle to form a plume jet to be ejected from the thruster, so that thrust is formed. The chamber shell (2) and the coaxial waveguide (10) are coaxially arranged, and the tail ends of the chamber shell (2) and the coaxial waveguide (10) are fixedly arranged on the insulating mounting plate (1). The tail ends of the chamber shell (2) and the coaxial waveguide (10) are in electrical connection to form a short-circuit end of the resonant chamber (9). The wall ceramic (6) is used to construct the discharge chamber (7); the wall ceramic (6) is coaxially arranged with the coaxial waveguide (10) through brazing or tight fitting; the bottom plate of the wall ceramic (6) has an air inlet hole and is in air communication with the gas inlet pipe (8); and the bottom plate of the wall ceramic (6) serves as an open-circuit end of the resonant chamber (9). The microwave feeding port (3) is arranged at the tail end of the chamber shell (2); the microwave antenna (4) extends into the resonant chamber (9) through the microwave feeding port (3) and is connected with the coaxial waveguide (10). The permanent magnet (5) is arranged outside the head end of the chamber shell (2) and is used to generate a characteristic magnetic field of a divergent magnetic nozzle; and the magnet fixing ring (11) is arranged outside the chamber shell (2) and is used to axially fix the permanent magnet (5).

2. A microwave magnetic midget engine of claim 1, characterized in that The chamber shell (2), the coaxial waveguide (10) and the microwave antenna (4) are metal devices and are in electrical connection with each other; the microwave antenna (4) is electrically connected with the coaxial waveguide (10) as an inner core of the microwave feeding port (3); and the shielding pole of the microwave feeding port (3) is electrically connected with the chamber shell (2).

3. A microwave magnetic midget engine of claim 2, characterized in that The chamber shell (2) and the coaxial waveguide (10) are made of aluminum or copper.

4. A microwave magnetic midget engine of claim 1, wherein The structures are fixedly arranged through bolts.

5. A microwave magnetic midget engine of claim 1, wherein The length of the resonant chamber (9) is an odd multiple of 1 / 4 wavelength of microwaves.

6. A microwave magnetic midget thrust er of claim 1, wherein The inner surface of the resonant chamber (9) is smooth.

7. A microwave magnetic midget engine of claim 1, wherein The wall ceramic (6) is made of quartz or boron nitride.

8. A microwave magnetic midget engine of claim 1, wherein The microwave feeding port (3) is selected from SMA joints and N-type joints.

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