An electron-enhanced radio frequency ion thruster for complex working fluids

Abstract

The application discloses an electron-enhanced radio frequency ion thruster for complex propellants, which comprises, from one side to the other side, a gas supply system, a radio frequency excitation system, an ion optical system, a neutralizer, a power supply processing and control unit for supplying power to each power consumption unit and controlling the operation thereof; the method comprises the following steps: introducing oxygen-containing complex propellant gas into a discharge chamber; starting the radio frequency excitation system to generate radio frequency plasma in the discharge chamber; starting the electron enhancement system to make the cathode emit electron beams into the radio frequency plasma to improve the plasma density and ionization degree; after the plasma is stable, the ion optical system is powered to extract and accelerate ion beam current; and the neutralizer is started to perform electron neutralization on the extracted ion beam current. The problems of high ionization difficulty of complex propellants, significant oxidation of oxygen-containing propellants and low extraction efficiency of complex propellants are solved.

Description

Technical Field

[0001] This invention relates to the field of aerospace electric propulsion technology, and more specifically to an electron-enhanced radio frequency ion thruster for complex working fluids. Background Technology

[0002] Electric propulsion technology, with its advantages of high specific impulse and long lifespan, can significantly increase the payload ratio and reduce transportation costs, and has become the mainstream choice for modern spacecraft propulsion systems. Among them, radio frequency ion thrusters, due to their simple structure, long lifespan, and high reliability, are gradually becoming one of the important development directions.

[0003] However, existing radio frequency ion thrusters mainly rely on rare gases such as xenon, which have stable ionization characteristics but suffer from high cost and complex storage. With the development of new propulsion modes such as air-breathing propulsion and in-situ resource utilization, using air or other complex working fluids as propellants has become a research hotspot.

[0004] The challenge of using air or other complex working fluids as propellants lies in the significant differences in their ionization processes within radio frequency plasmas. On one hand, their complex molecular structures and uneven ionization energy distribution lead to lower ionization efficiency. On the other hand, reactive components such as oxygen can easily cause oxidation and corrosion to critical components like the cathode and neutralizer, affecting system stability and lifespan. Furthermore, the insufficient high-energy electron density in traditional radio frequency discharge methods makes it difficult to effectively excite the multi-stage ionization process of complex working fluids, thus limiting the overall performance of the thruster. Summary of the Invention

[0005] This invention addresses the problems existing in the prior art by proposing an electron-enhanced radio frequency ion thruster for complex working media. The aim is to solve the problems of high ionization difficulty, strong chemical corrosion, and unstable discharge mode when using complex working media.

[0006] To solve its technical problems, the present invention proposes the following technical solutions. An electron-enhanced radio frequency ion thruster for oxygen-containing complex working fluids includes, sequentially arranged from one side to the other: a gas supply system for supplying working fluid gas to the discharge chamber; a discharge chamber for containing the working fluid gas and generating plasma; a radio frequency excitation system for generating an alternating electromagnetic field within the discharge chamber to ionize the working fluid gas and form radio frequency plasma; an ion optics system located downstream of the discharge chamber for extracting and accelerating ions to form a beam; a neutralizer located at the thruster outlet for neutralizing the ion beam; and a power supply processing and control unit for supplying power to each power-consuming unit and controlling its operation. Its key feature is: At the entrance of the discharge chamber, an electron enhancement system is also provided. This system includes a cathode disposed within the discharge chamber and a DC power supply for the cathode. The cathode is used to emit electrons into the discharge chamber to enhance the ionization degree of the radio frequency plasma within the discharge chamber. The cathode adopts the radio frequency self-sustaining discharge principle, has an anti-oxidation configuration, and has no built-in cathode body, enabling it to operate stably in an oxygen-containing plasma environment. On the inner walls of both sides of the discharge chamber, a pair of anode plates are symmetrically arranged. These anode plates are used to accelerate the electrons emitted by the cathode, allowing the electrons to acquire sufficient energy to enhance the plasma ionization efficiency and increase the plasma density.

[0007] Furthermore, the ion optical system includes a screen gate and an accelerating gate, the geometry of which and the applied voltage are configured to effectively extract and focus various ions generated by the ionization of oxygen-containing complex working fluids.

[0008] Furthermore, the geometry of the screen gate and the accelerating gate is as follows: the aperture of the accelerating gate and the screen gate should be set according to the type of working gas, the gate spacing is kept in a range suitable for suppressing arcing between gates (0.6~0.9mm), and both the screen gate and the accelerating gate are made of high temperature resistant, sputter resistant and oxidation resistant materials, and the surface is covered with an oxidation resistant coating to adapt to the working environment of oxygen-containing working fluids.

[0009] Furthermore, the voltages applied to the screen gate and the accelerating gate are as follows: the screen gate voltage is 800 to 1500V, and the accelerating gate voltage is generally 10% of the screen gate voltage.

[0010] Furthermore, the electron emitting end of the cathode extends into the discharge chamber, and its axial position at least partially overlaps with the projection area of ​​the radio frequency antenna on the discharge chamber.

[0011] Furthermore, the working gas is air, carbon dioxide, or a mixture of both. Advantages and effects of the present invention

[0012] 1. Solving the problem of difficult ionization of complex working fluids: By incorporating an electron enhancement system (including cathode and anode plates) within the discharge chamber, electrons are injected into the radio frequency plasma from the cathode, and the anode plates accelerate these electrons to increase their energy. This auxiliary electron injection mechanism significantly improves plasma density and ionization, overcoming the difficulties of high power requirements and low ionization efficiency in radio frequency self-sustaining discharge of complex molecular working fluids. With the help of electron enhancement, complex working fluids that were originally difficult to ionize effectively can now generate plasma efficiently, thereby improving propulsion efficiency.

[0013] 2. Addressing the significant oxidation problem in oxygen-containing working fluids: The cathode adopts the principle of radio frequency self-sustaining discharge and an anti-oxidation configuration, eliminating the need for a built-in cathode body. This allows it to operate stably in oxygen-containing plasma environments, overcoming the technical bottleneck of traditional neutralizers and cathodes being prone to "oxygen poisoning" and electrode corrosion in oxygen-containing environments, significantly extending the thruster's on-orbit lifespan. Both the shielding grid and the accelerating grid are made of high-temperature resistant, sputter-resistant, and oxidation-resistant materials, with an anti-oxidation coating on the surface, further adapting to oxygen-containing working fluid environments. This effectively prevents oxidation and corrosion of key components such as the cathode and neutralizer by active components like oxygen, ensuring system stability and service life.

[0014] 3. Solving the problem of low extraction efficiency for complex working fluids: The ion optics system is optimized by modifying the geometry of the screen grid and accelerating grid, as well as the applied voltage, to improve the electric field distribution in the ion extraction region. This enhances the ability to extract, focus, and directionally extract complex ions, while reducing divergence and backflow losses during extraction. The aperture diameters of the accelerating grid and screen grid are set according to the type of working fluid gas, and the grid spacing is controlled within a range suitable for suppressing arcing between grids (0.6–0.9 mm), thereby ensuring the stability of the ion beam and guaranteeing the thrust efficiency and specific impulse performance of the thruster. Attached Figure Description

[0015] Figure 1 is a schematic diagram of the electron-enhanced radio frequency ion thruster for complex working fluids according to the present invention; Figure 2 This is a functional block diagram of the electron-enhanced radio frequency ion thruster for complex working fluids according to the present invention; Figure 3 is a schematic diagram of the working principle of the existing radio frequency ion thruster. Detailed Implementation Innovation of this invention

[0016] 1. Electron-enhanced discharge technology: Based on radio frequency inductive coupling, an auxiliary electron injection mechanism is introduced. The radio frequency coil generates basic plasma, and high-energy electrons are injected through the built-in cathode. The plasma density is greatly increased through collisional ionization, which solves the problems of high power and low ionization efficiency in radio frequency self-sustaining discharge of complex molecular working fluids.

[0017] 2. Oxygen-resistant electrode neutralization technology: By adopting special anti-oxidation cathode materials and configurations, the technology bottleneck of traditional neutralizers being prone to "oxygen poisoning" and electrode corrosion in oxygen-containing working environments has been overcome, significantly extending the on-orbit life of the thruster.

[0018] 3. High-efficiency acceleration technology for complex working fluids: By optimizing the structural parameters and voltage configuration of the screen grid and acceleration grid in the ion optical system, the electric field distribution in the ion extraction region is improved, enhancing the ability to extract, focus, and directionally extract complex ions, reducing the divergence loss and backflow loss of ions during the extraction process, thereby achieving high-efficiency extraction and stable acceleration of complex working fluid ions, and improving the thrust efficiency and specific impulse performance of the thruster. I. This invention focuses on solving the following three key problems:

[0019] Low ionization efficiency: The complex molecular structure of the working fluid, high ionization energy and uneven distribution make it difficult for traditional radio frequency discharge to generate enough high-energy electrons, resulting in insufficient plasma density and ionization degree.

[0020] Oxidation is a prominent issue: the active oxygen components in the working fluid can easily cause oxidation corrosion ("poisoning") and sputtering erosion to key components such as the cathode and grid, seriously threatening the thruster's lifespan and reliability.

[0021] Discharge and extraction instability: Traditional radio frequency discharge modes have low excitation efficiency for complex working fluids, and the various ions generated (such as O⁺, OH⁺, H₂O⁺, etc.) are prone to divergence, backflow or arcing during extraction acceleration, resulting in a decrease in thrust performance.

[0022] II. Targeted Technical Principles and Solutions 1. Principle of Electron-Enhanced Discharge Technology: (1) Technical Solution: Active Energy Injection to Improve Ionization Efficiency: A dedicated cathode is installed at the entrance of the discharge chamber. This cathode operates based on the principle of radio frequency self-sustaining discharge and is itself a plasma source. The electron-emitting end of the cathode extends into the discharge chamber, and its axial position at least partially overlaps with the projection area of ​​the external radio frequency antenna on the discharge chamber, ensuring spatial coupling. A pair of anode plates are symmetrically arranged on both sides of the inner wall of the discharge chamber. The cathode-anode circuit is powered by a DC power supply. The cathode actively emits electrons, and the anode accelerates the electrons. (2) The electrons emitted by the cathode, after being accelerated by the anode electric field, gain higher energy and are directly injected into the radio frequency discharge region. These high-energy electrons, together with the electrons excited by the radio frequency electric field, interact more effectively with complex working fluid molecules, resulting in more efficient collision ionization, excitation, and dissociation, significantly improving the plasma generation rate and density. Electron injection provides additional ionization energy, enabling the acquisition of high-density plasma at relatively low radio frequency power, thus improving energy utilization efficiency.

[0023] 2. Oxygen-resistant configuration design principle: Material and structural optimization to resist environmental corrosion: (1) Technical solution: Cathode Anti-oxidation Design: A special configuration without an internal cathode and anti-oxidation materials (such as specific ceramics or high-stability metal alloys) are adopted to fundamentally avoid the problem of rapid failure of traditional hot cathodes or hollow cathodes due to oxidation in oxygen-rich environments. Grid System Protection: The screen grid and acceleration grid use high-temperature resistant and sputter-resistant substrate materials (such as molybdenum and carbon-based composite materials), and an anti-oxidation coating (such as boron nitride and iridium oxide) is prepared on their surfaces to resist chemical corrosion and physical sputtering by oxygen ions. ⑵ Working Principle: By eliminating vulnerable structures (such as internal cathodes) and applying anti-oxidation coatings, the direct harmful reaction between active oxygen and key component materials is blocked or slowed down, ensuring the structural integrity and functional stability of the thruster during long-term operation in oxygen-containing working environments.

[0024] 3. Principle of High-Efficiency Acceleration Technology for Complex Working Fluids: (1) Technical Solution: Optimization of Ion Optical System Parameters: Coordinated design of the aperture diameter and grid spacing (preferably 0.6–0.9 mm) of the screen grid and accelerating grid. Voltage Configuration Optimization: Setting a high screen grid voltage (800–1500 V) and providing a suitable accelerating grid voltage (typically -10% of the screen grid voltage) to form a strong and stable extraction electric field. (2) Working Principle: Enhanced Extraction Capability: The optimized geometric parameters combined with the high-voltage screen grid form a sufficiently strong initial electric field downstream of the discharge chamber, effectively overcoming the plasma sheath barrier and achieving efficient extraction of various ions. Optimized Focusing and Beam Quality: Precisely controlled grid spacing and voltage ratio can form a good ion focusing lens effect, reduce the divergence angle of the ion beam, and suppress ion backflow caused by the bipolar current effect. Optimized spacing and voltage coordination expands the safe operating area to prevent backflow breakdown (arson) between grids, ensuring the electrical stability of the ion extraction process under complex working fluids.

[0025] In summary, through the above-described collaborative design, this invention achieves efficient ionization, corrosion-resistant operation, and stable acceleration of complex oxygen-containing working fluids, significantly improving the thrust density, specific impulse, and lifespan of the thruster. It provides a feasible thruster solution for advanced space missions such as air-breathing electric propulsion and in-situ resource utilization (ISRU) propulsion based on water or atmospheric resources.

[0026] Based on the above principles, this invention designs an electron-enhanced radio frequency ion thruster for complex working fluids, such as... Figure 1 , Figure 2As shown, the system includes, arranged sequentially from one side to the other: a gas supply system for supplying working gas to the discharge chamber; a discharge chamber for containing the working gas and generating plasma; a radio frequency excitation system for generating an alternating electromagnetic field within the discharge chamber to ionize the working gas and form radio frequency plasma; an ion optics system located downstream of the discharge chamber for extracting and accelerating ions to form a beam; a neutralizer located at the thruster outlet for neutralizing the ion beam; and a power supply processing and control unit for supplying power to each power-consuming unit and controlling its operation. Its features are: At the entrance of the discharge chamber, an electron enhancement system is also provided. This system includes a cathode disposed within the discharge chamber and a DC power supply for the cathode. The cathode is used to emit electrons into the discharge chamber to enhance the ionization degree of the radio frequency plasma within the discharge chamber. The cathode adopts the radio frequency self-sustaining discharge principle, has an anti-oxidation configuration, and has no built-in cathode body, enabling it to operate stably in an oxygen-containing plasma environment. On the inner walls of both sides of the discharge chamber, a pair of anode plates are symmetrically arranged. These anode plates are used to accelerate the electrons emitted by the cathode, allowing the electrons to acquire sufficient energy to enhance the plasma ionization efficiency and increase the plasma density.

[0027] Additional notes: contrast Figure 1 and Figure 3 This invention adds an antioxidant cathode ③ and an anode plate ④, and optimizes the screen gate ① and the acceleration gate ②.

[0028] like Figure 1 , Figure 2 As shown, the ion optical system includes a screen grid and an accelerating grid. The geometry of the screen grid and the accelerating grid, as well as the applied voltage, are configured to effectively extract and focus various ions generated by the ionization of oxygen-containing complex working fluids.

[0029] like Figure 1 , Figure 2 As shown, the geometry of the screen gate and the accelerating gate is as follows: the aperture of the accelerating gate and the screen gate should be set according to the type of working gas, the gate spacing is kept in a range suitable for suppressing arcing between gates (0.6~0.9mm), and both the screen gate and the accelerating gate are made of high temperature resistant, sputter resistant and oxidation resistant materials, and the surface is covered with an anti-oxidation coating to adapt to the working environment of oxygen-containing working fluids.

[0030] like Figure 1 , Figure 2 As shown, the applied voltages to the screen gate and the acceleration gate are: the screen gate voltage is 800-1500V, and the acceleration gate voltage is generally 10% of the screen gate voltage.

[0031] like Figure 1 , Figure 2 As shown, the electron emitting end of the cathode extends into the discharge chamber, and its axial position at least partially overlaps with the projection area of ​​the radio frequency antenna on the discharge chamber.

[0032] like Figure 1 , Figure 2 As shown, the working gas is air, carbon dioxide, or a mixture of both.

[0033] Based on the above-mentioned electron-enhanced radio frequency ion thruster for complex working fluids, this invention designs a method for using an electron-enhanced radio frequency ion thruster, characterized by comprising the following steps: Step 1: Introduce a complex working gas containing oxygen into the discharge chamber; Step 2: Start the radio frequency excitation system to generate radio frequency plasma in the discharge chamber; Step 3: Activate the electron enhancement system to inject electrons emitted by the cathode into the radio frequency plasma, thereby increasing the plasma density and ionization. Step 4: After the plasma stabilizes, power is applied to the ion optical system to extract and accelerate the ion beam. Step 5: Activate the neutralizer to perform electron neutralization on the extracted ion beam.

[0034] It should be emphasized that the above specific embodiments are merely explanations of the present invention and are not intended to limit the present invention. After reading this specification, those skilled in the art can make modifications to the above embodiments without contributing any inventive step, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. An electron-enhanced radio frequency ion thruster for complex working fluids, comprising, arranged sequentially from one side to the other: a gas supply system for supplying working fluid gas to the discharge chamber; a discharge chamber for containing the working fluid gas and generating plasma; a radio frequency excitation system for generating an alternating electromagnetic field within the discharge chamber to ionize the working fluid gas and form radio frequency plasma; an ion optics system disposed downstream of the discharge chamber for extracting and accelerating ions to form a beam; a neutralizer disposed at the thruster outlet for neutralizing the ion beam; and a power supply processing and control unit for supplying power to each power-consuming unit and controlling its operation, characterized in that: At the entrance of the discharge chamber, an electron enhancement system is also provided. This system includes a cathode disposed within the discharge chamber and a DC power supply for the cathode. The cathode is used to emit electrons into the discharge chamber to enhance the ionization degree of the radio frequency plasma within the discharge chamber. The cathode adopts the radio frequency self-sustaining discharge principle, has an anti-oxidation configuration, and has no built-in cathode body, enabling it to operate stably in an oxygen-containing plasma environment. On the inner walls of both sides of the discharge chamber, a pair of anode plates are symmetrically arranged. These anode plates are used to accelerate the electrons emitted by the cathode, allowing the electrons to acquire sufficient energy to enhance the plasma ionization efficiency and increase the plasma density.

2. The electron-enhanced radio frequency ion thruster for complex working fluids according to claim 1, characterized in that: The ion optical system includes a screen gate and an accelerating gate, the geometry of which and the applied voltage are configured to effectively extract and focus a variety of ions generated by the ionization of oxygen-containing complex working fluids.

3. The electron-enhanced radio frequency ion thruster for complex working fluids according to claim 2, characterized in that: The geometry of the screen gate and the accelerating gate is as follows: the aperture of the accelerating gate and the screen gate should be set according to the type of working gas, the gate spacing is kept in the range of 0.6 to 0.9 mm suitable for suppressing arcing between gates, and both the screen gate and the accelerating gate are made of high temperature resistant, sputter resistant and oxidation resistant materials, and the surface is covered with an anti-oxidation coating to adapt to the working environment of oxygen-containing working fluids.

4. The electron-enhanced radio frequency ion thruster for complex working fluids according to claim 2, characterized in that: The voltages applied to the screen gate and the accelerating gate are as follows: the screen gate voltage is 800-1500V, and the accelerating gate voltage is generally 10% of the screen gate voltage.

5. The electron-enhanced radio frequency ion thruster for complex working fluids according to claim 1, characterized in that: The electron emitting end of the cathode extends into the discharge chamber, and its axial position at least partially overlaps with the projection area of ​​the radio frequency antenna on the discharge chamber.

6. An electron-enhanced radio frequency ion thruster for complex working fluids according to any one of claims 1 to 5, characterized in that: The working gas is air, carbon dioxide, or a mixture of both.

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