An air-breathing electric thruster for ultra-low Earth orbit satellites

Abstract

This invention discloses an air-breathing electric thruster for ultra-low Earth orbit (ULE) satellites, characterized by: a flow control and storage system, a low-resistance gas isolation and distribution system, a temperature-controlled radio frequency ionization system, an ion optics system, and an electric neutralization system. This air-breathing electric thruster for ULE satellites achieves significant thrust by ionizing and accelerating the captured ULE atmospheric working fluid, ensuring the satellite maintains its ULE orbit (100–300 km). The thrust range is 1–35 mN, specific impulse ≥3500 s, and plume divergence half-angle ≤20°. By providing a very small amount of Xe working fluid (1%–10%), the ignition power and operating power of the thruster are significantly reduced. The temperature-controlled radio frequency ionization system, with its radio frequency coil composed of a microgravity heat pipe, connects a porous phase change energy storage system and a radiative heat dissipation system, reducing the impact of the thermal environment on thruster lifespan reduction. By using a low-resistance gas isolation-distributor, the electric thruster is guaranteed to obtain a sufficient working fluid flow rate to maintain the thruster's self-sustaining discharge, while isolating plasma backflow.

Description

Technical Field

[0001] This invention relates to a satellite propulsion device, specifically to an air-breathing electric thruster for ultra-low Earth orbit satellites. Background Technology

[0002] Currently, countries are racing to launch ultra-low orbit satellites / constellations, vying for ultra-low orbit satellite orbits and communication frequency bands.

[0003] Ultra-low Earth orbit (ULE) satellites, due to their closer proximity to Earth, can easily obtain clearer remote sensing images. For optical payloads, halving the orbital altitude doubles the ground pixel resolution. For SAR payloads, halving the orbital altitude reduces transmission power to one-eighth, significantly improving system sensitivity and radiometric resolution. For LIDAR payloads, halving the orbital altitude reduces transmission power to one-quarter. This helps to significantly reduce the payload cost of Earth observation satellites while meeting the same Earth observation requirements, potentially achieving centimeter-level or even millimeter-level Earth observation accuracy. For ultra-wideband satellite communication systems, significantly lower orbital altitude results in lower data transmission latency and less path loss. ULE satellites can significantly reduce the payload and launch costs of communication satellite constellations, facilitating constellation expansion and boosting the commercial aerospace industry. Furthermore, this technology is also a promising cutting-edge aerospace propulsion technology with applications in Earth's gravity field monitoring, near-space observation, and deep space exploration.

[0004] Air-breathing electric propulsion is an emerging aerospace technology suitable for long-term orbital maintenance of ultra-low Earth orbit satellites (100km–300km), and the air-breathing electric thruster is an important component of this system. This technology has significant implications for both civilian and military applications.

[0005] However, the realization of air-breathing electric propulsion technology faces the following difficulties:

[0006] (1) Ultra-low orbit satellites face the problem of large aerodynamic heat and radiative heat, and the thrusters are prone to failure under the influence of high environmental heat sources and their own heat generation.

[0007] (2) The atmosphere in the ultra-low orbit is a molecular flow, and the pressure of the in-situ working gas passively collected is very low, which is not conducive to the thruster maintaining self-sustaining discharge and stable operation.

[0008] (3) The atmosphere of the ultra-low orbit is rich in atomic oxygen. The corrosive effect of atomic oxygen is detrimental to the thruster components. The strong oxidizing properties of atomic oxygen can cause the thruster with hollow cathode to be poisoned and fail, and will cause the electric neutralization system using hollow cathode to fail.

[0009] (4) Long-term orbit maintenance of ultra-low orbit satellites is a game between energy and drag. Existing air-breathing electric propulsion systems cannot achieve thrust-drag balance and need to be optimized from the perspective of the whole system. Summary of the Invention

[0010] This invention addresses the problems of existing technologies by proposing an air-breathing electric thruster for very low Earth orbit (LEO) satellites. The first objective is to solve the problem of high aerodynamic and radiative heat in LEO satellites, which can easily cause thruster failure under high environmental heat sources and self-generated heat. The second objective is to address the issue that the LEO atmosphere is a molecular flow, resulting in very low pressure of the passively collected in-situ working fluid, which is detrimental to the thruster's ability to maintain self-sustaining discharge and stable operation. The third objective is to address the problem that the abundance of atomic oxygen in the LEO atmosphere can have a corrosive effect on thruster components; the strong oxidizing properties of atomic oxygen can cause poisoning failure in thrusters with hollow cathodes, and can also cause the failure of the charge neutralization system using hollow cathodes. The fourth objective is to address the fact that long-term orbit maintenance of LEO satellites involves a trade-off between energy and drag, and existing air-breathing electric propulsion systems cannot achieve thrust-drag balance, requiring comprehensive optimization from a system-wide perspective.

[0011] To solve its technical problems, the present invention proposes the following technical solutions:

[0012] An air-breathing electric thruster for ultra-low Earth orbit (UEO) satellites is characterized by comprising a flow control and supply system, a low-resistance gas isolation and distribution system, a temperature-controlled radio frequency ionization system, an ion optics system, and an electric neutralization system. The air-breathing electric thruster does not include a hollow cathode. The flow control and supply system is used to mix the incoming working fluid in the required proportions and provide a very small amount of Xe working fluid, thereby reducing the thruster's ignition power and operating power. The low-resistance gas isolation and distribution system is used to maintain a low gas resistance level while isolating plasma gas backflow, thereby maintaining the internal gas pressure level of the ceramic discharge chamber 3. The temperature-controlled radio frequency ionization system is used to convert heat... The phase change energy storage material and radiant heat sink of the ultra-low orbit satellite thermal control system are introduced in large quantities, thereby reducing the size of the radiant heat sink to reduce drag. After the gaseous working fluid is fully ionized, it is accelerated and extracted by the ion optical system to form a plume. The electric neutralization system is used to neutralize the plume potential to ensure the overall potential balance of the air-breathing electric thruster. This air-breathing electric thruster can obtain greater thrust by ionizing and accelerating the captured ultra-low orbit atmospheric working fluid, ensuring that the satellite can maintain an ultra-low orbit of 100-300km. For N2 / O2 / Xe mixed working fluid, the thrust range reaches 1.8-35.9mN, the maximum specific impulse is ≥3000s, and the plume divergence half angle is ≤20°.

[0013] Furthermore, the flow control and storage system includes a flow control and storage system module for capturing the incoming flow and a flow control and storage system module for Xe working fluid. The flow control and storage system mixes the incoming working fluid and a small amount of Xe working fluid in the required proportion and supplies them to the thruster and the electric neutralization system. The use of a small amount of Xe working fluid significantly reduces the power required for thruster ignition and self-sustaining discharge, thereby reducing the size of the radio frequency power module and the required solar panel area.

[0014] Furthermore, the flow control and storage system module for capturing incoming flow includes a flow control module 15, a proportional flow control valve 16, a self-locking valve 17, an atmospheric working fluid tank 18, and captured low-Earth orbit atmosphere 19. The captured low-Earth orbit atmosphere 19 is stored in the atmospheric working fluid tank 18 and, under the control of the flow control module 15, the proportional flow control valve 16, and the self-locking valve 17, provides a flow-controlled atmospheric working fluid to the air-breathing thruster and neutralizer. The flow control and storage system module for Xe working fluid includes a flow control module 20, a proportional flow control valve 21, a self-locking valve 22, and an Xe working fluid tank 23. The Xe working fluid in the Xe working fluid tank 23, under the control of the flow control module 20, the self-locking valve 22, and the proportional flow control valve 21, provides a flow-controlled Xe working fluid to the air-breathing thruster and the electric neutralization system.

[0015] Furthermore, the small amount of Xe working fluid specifically refers to mixing the incoming working fluid and Xe working fluid in the required proportion, wherein the proportion of Xe working fluid is less than 10%.

[0016] Furthermore, the low-resistance gas isolation-distribution system includes a gas distributor baffle 5-1, a gas distribution outlet 5-2, an isolator gas channel 5-3, a lower ceramic slot 5-4, an upper ceramic slot 5-5, and an inlet 5-6. By adjusting the width, length, and number of bends of the isolator gas channel 5-3, the flow rate of the captured low-orbit atmosphere 19 under different capture gas pressures can be adapted. The mixed atmosphere / Xe working fluid enters the isolator gas channel 5-3, which is jointly formed by the lower ceramic slot 5-4 and the upper ceramic slot 5-5, through the inlet 5-6. The working fluid enters the ceramic discharge chamber 3 from the gas distribution outlet 5-2, and its ejection direction is changed by the gas distributor baffle 5-1, causing it to diffuse towards the side wall of the ceramic discharge chamber 3.

[0017] Furthermore, the temperature-regulating radio frequency ionization system includes a ceramic discharge chamber 3, a thruster coil 4, a thruster shielding shell 6, an L-shaped matching network 12, a power amplifier 13, and a signal source 14. The thruster coil 4 is composed of a microgravity heat pipe with a special liquid-absorbing core and is connected to the phase change energy storage system and radiative heat dissipation system of the ultra-low orbit satellite thermal control system to regulate the thruster temperature. The signal source 14, power amplifier 13, L-shaped matching network 12, and thruster coil 4 are used to generate radio frequency electromagnetic waves. The signal source 14 provides a sinusoidal signal, which is amplified by the power amplifier 13. After the L-type matching network 12 is configured, the thruster coil 4 generates radio frequency electromagnetic waves, forming a ring electric field in the ceramic discharge chamber 3 to accelerate the ionization of the working gas. The electric field that accelerates the ionization of electrons is provided by the neutralization system. The end face of the shielding shell 6 near the acceleration grid 1 is covered with an anti-oxidation copper film. The surface treatment of this end face is a special consideration for ultra-low orbit satellite thrusters and has a significant impact on stable ignition and operation. The shielding shell 6 as a whole is used to prevent radio frequency electromagnetic waves from leaking out and affecting adjacent electronic components, while also reducing the loss of electromagnetic waves to a certain extent so that they can be used for radio frequency ionization.

[0018] Furthermore, the ion optical system includes an accelerating grid 1, a screen grid 2, a fastening device 7, a negative high-voltage terminal 8, a negative high-voltage module 9, a positive high-voltage terminal 10, and a positive high-voltage module 11. The spacing, aperture, and number of apertures of the accelerating grid 1 and the screen grid 2 need to be optimized according to the long-term service orbital altitude and space environment of the ultra-low orbit satellite. The positive high-voltage module 11 provides a positive high voltage of 1000-2000V to the screen grid 2 through the positive high-voltage terminal 10, and the negative high-voltage module 9 provides a voltage of ±200V to the accelerating grid 1 through the negative high-voltage terminal 8. The negative high-voltage module 9 is bipolar. When the thruster ignites, it provides a positive voltage of 200V to introduce external electrons into the ceramic discharge chamber 3 for ignition. When the thruster is working, it provides a negative voltage of 200V, which on the one hand forms a strong electric field with the screen grid 2 to accelerate the formation of positive ions into a plume, and on the other hand shields the external electrons generated by the neutralization system. The fastening device 7 assists in fixing the accelerating grid 1 and the screen grid 2 to the end of the thruster.

[0019] Furthermore, the neutralization system includes a radio frequency (RF) neutralizer copper coil 24, an RF neutralizer shielding shell 25, a collecting electrode 26, a tungsten needle 27, low-orbit atmosphere / Xe working fluid 28, a high-voltage ignition power supply 29, an L-type matching network 30, a power amplifier 31, and a signal source 32. The signal source 32 provides a sinusoidal signal, which, after being amplified by the power amplifier 31 and configured by the L-type matching network 30, generates RF electromagnetic waves by the RF neutralizer copper coil 24, ionizing the low-orbit atmosphere / Xe working fluid 28 within the neutralizer to form plasma. The electrons required for ionization originate from the breakdown discharge of the working fluid between the tungsten needle 27 and the high-voltage ignition power supply 29. Positive ions flow towards the collecting electrode 26, and electrons are ejected. The RF neutralizer shielding shell 25 is used to reduce potential interference from the thruster's electromagnetic field to the neutralizer. This neutralization system is based on the principle of RF discharge, has strong oxidation resistance, and is suitable for ultra-low orbit environments rich in atomic oxygen.

[0020] Advantages and effects of the present invention

[0021] 1. This invention patent provides an air-breathing electric thruster for ultra-low orbit satellites. It can obtain greater thrust by ionizing and accelerating the captured ultra-low orbit atmospheric working fluid, ensuring the satellite maintains its ultra-low orbit (100-300km). For N2 / O2 / Xe mixed working fluid, the thrust range reaches 1-35mN, the specific impulse is ≥3500s, and the plume divergence half angle is ≤20°.

[0022] 2. This invention proposes a temperature-controlled radio frequency ionization system, in which the radio frequency coil is composed of a microgravity heat pipe and is connected to a porous phase change energy storage system and a radiation heat dissipation system. It autonomously regulates part of the ambient aerodynamic heat and the ohmic heat of the radio frequency ionization system, thereby reducing the impact of the thermal environment on the thruster's lifespan.

[0023] 3. The present invention proposes a low-resistance gas isolation-distributor, which can ensure that the electric thruster obtains sufficient working fluid flow rate to maintain the self-sustaining discharge of the thruster when the captured gas pressure is low (0.1~0.4Pa), while isolating plasma backflow.

[0024] 4. The present invention proposes a thruster shielding shell 6 for a temperature self-regulating radio frequency ionization system, which covers the end face of the accelerating grid 1 near the ion optical system with an anti-oxidation copper film to resist the oxidation of atomic oxygen, slow down the formation of local charge accumulation, and reduce the probability of thruster ignition difficulty and sparking during operation.

[0025] 5. This invention proposes a flow control and storage system that significantly reduces the ignition power and operating power of the thruster by providing a very small amount of Xe working fluid (1% to 10%), thereby reducing the mass and volume of the system's radio frequency module, saving energy consumption, and providing optimization space for the drag design of ultra-low orbit satellites. Attached Figure Description

[0026] Figure 1 This is an application effect diagram of the air-breathing electric thruster of the present invention;

[0027] Figure 2 This is a structural diagram of the air-breathing electric thruster of the present invention;

[0028] Figure 3 for Figure 2 A magnified view of a portion of area A;

[0029] Figure 4a Relationship between thrust and total power - Schematic diagram for RF power less than 150W;

[0030] Figure 4b Relationship between thrust and total power - Schematic diagram for RF power greater than 150W;

[0031] Figure 5 This is the working state of the air-breathing electric thruster of the present invention.

[0032] 1: Acceleration grid; 2: Screen grid; 3: Ceramic discharge chamber; 4: Thrust coil; 5: Low-resistance gas isolation-distribution system; 5-1: Gas distributor baffle; 5-2: Plasma gas distributor outlet; 5-3: Isolator gas passage; 5-4: Lower ceramic slot; 5-5: Upper ceramic slot; 5-6: Inlet nozzle; 6: Thrust shielding shell; 7: Fastening device; 8: Negative high-voltage terminal; 9: Negative high-voltage module; 10: Positive high-voltage terminal; 11: Positive high-voltage module; 12: L-type matching network; 13: Power amplifier; 14: Signal source; 15: Flow control module; 16: Proportional flow control valve; 17: Self-locking valve; 18: Atmospheric working fluid tank; 19: Captured low-Earth orbit atmosphere; 20: Flow control module; 21: Proportional flow control valve; 22: Self-locking valve; 23: Xe working fluid tank; 24: RF neutralizer copper coil; 25: RF neutralizer shielding shell; 26: Collection plate; 27: Tungsten needle; 28: Low-Earth orbit atmosphere / Xe working fluid; 29: High-voltage ignition power supply; 30: L-type matching network; 31: Power amplifier; 32: Signal source. Detailed Implementation

[0033] Design principle of the invention

[0034] 1. The innovative feature of this patent is its long-term usability of an air-breathing electric thruster for orbital altitudes of 100–300 km. To date, there are no precedents, either domestically or internationally, for ultra-low Earth orbit satellites operating for extended periods in the 100–300 km range, nor for electric thrusters designed for long-term use at this altitude. This invention fills a gap in the domestic and international market.

[0035] 2. Design principle for addressing the problem of high aerodynamic and radiative heat in ultra-low Earth orbit (UEO) satellites, and the susceptibility of thrusters to failure under the combined effects of high ambient heat sources and their own heat generation: In the vacuum environment of space, heat transfer in thrusters primarily occurs through thermal radiation and conduction. Traditional thrusters operate at relatively high orbital altitudes where ambient aerodynamic heat is not significant, allowing for effective heat dissipation through sufficient radiative heat sinks. However, UEO satellites experience substantial aerodynamic and radiative heat, compounded by the heat generated by the thrusters, making heat dissipation a critical issue. Furthermore, relying on large radiative heat sinks to improve heat dissipation efficiency would increase drag, which is not advisable. Therefore, a trade-off exists between heat dissipation and drag reduction.

[0036] This invention utilizes the temperature gradient of the air-breathing electric thruster itself, and through a microgravity heat pipe formed by the thruster coil 4 of the "temperature self-regulating radio frequency ionization system," transfers heat to the phase change energy storage material and radiant heat sink of the ultra-low orbit satellite thermal control system (such as...). Figure 1 The thruster coil 4 serves both ionization and heat conduction purposes. The phase change energy storage material of the satellite's thermal control system absorbs some of the heat, thereby reducing the size of the radiant heat sink and lowering drag. Simultaneously, the heat stored in the phase change material can also be used for the overall thermal management of the ultra-low Earth orbit satellite, acting as a buffer element within the thermal management system.

[0037] 3. Design principle to address the problem that the atmospheric flow in ultra-low orbit is molecular, and the pressure of the passively collected in-situ working propellant is very low, which is not conducive to the thruster maintaining self-sustaining discharge and stable operation: Traditional gas isolators are usually designed based on Paschen's law, using a very small orifice diameter to isolate plasma backflow according to the gas pressure in the discharge chamber. However, the small orifice diameter increases gas resistance, reduces the gas pressure in the discharge chamber, and affects the stability of self-sustaining discharge.

[0038] This invention adjusts the width, length, and number of bends of the isolator gas channel 5-3 of the "low-resistance gas isolation-distribution system" to adapt to the flow supply of low-orbit atmosphere 19 captured under different capture gas pressures, while maintaining a large width of the isolator gas channel 5-3. This isolates the backflow from the plasma gas distributor outlet 5-2 to the inlet 5-6 while maintaining a low gas resistance level, thereby maintaining the gas pressure level inside the ceramic discharge chamber 3 and ensuring the stability of the self-sustaining plasma discharge inside the ceramic discharge chamber 3.

[0039] 4. Addressing the issue of abundant atomic oxygen in the ultra-low orbit atmosphere, the corrosive effect of atomic oxygen is detrimental to thruster components, and the strong oxidizing properties of atomic oxygen can lead to poisoning failure of thrusters with hollow cathodes, causing the failure of electric neutralization systems using hollow cathodes. The design principle is as follows: commonly used millinew-level Hall electric propulsion systems and Kaufman electric propulsion systems use hollow cathodes. However, materials such as lanthanum hexaboride and barium tungsten in the hollow cathode will form a dense oxide film when they come into contact with atomic oxygen, preventing the release of electrons and causing the hollow cathode to poison and fail, thus causing the electric propulsion system to fail.

[0040] The "electro-neutralization system" of this invention is an electro-neutralization system for an air-breathing electric thruster based on the principle of radio frequency ionization. Since the air-breathing electric thruster does not include the aforementioned hollow cathode, and the electro-neutralization system employs a completely different working principle from the hollow cathode, the entire air-breathing electric thruster can resist the strong oxidizing effect of ultra-low orbit atomic oxygen. Furthermore, it is particularly emphasized that the thruster shielding shell 6 of the "temperature-self-regulating radio frequency ionization system" must be covered with an anti-oxidation copper film on the end face near the acceleration grid 1. This is a special consideration for ultra-low orbit satellite thrusters, as it has a significant impact on stable ignition and operation.

[0041] 5. Solving the long-term orbital maintenance problem for ultra-low Earth orbit (ULE) satellites involves a trade-off between energy and drag. Existing air-breathing electric propulsion systems cannot achieve a balance between thrust and drag, requiring a design principle that optimizes the entire system: The energy-drag trade-off in long-term ULE satellite orbital maintenance is a unique problem for orbital altitudes of 100–300 km. Existing satellites at other orbital altitudes do not have this problem, and no satellite has ever been permanently stationed at this altitude. Therefore, considering and solving this problem is a completely new endeavor.

[0042] The "flow control and storage system" of the present invention significantly reduces the ignition power and operating power of the thruster by mixing the incoming working fluid and providing a very small amount of Xe working fluid (1% to 10%), thereby reducing the mass and volume of the system's L-type matching network 12, power amplifier 13, and signal source 14, saving energy consumption, and providing optimization space for the drag design of ultra-low orbit satellites.

[0043] Based on the above-mentioned inventive principles, this invention designs an air-breathing electric thruster for ultra-low Earth orbit satellites, such as... Figure 1 , Figure 2 , Figure 3As shown, its features include: a flow control and storage system, a low-resistance gas isolation-distribution system, a temperature-controlled radio frequency ionization system, an ion optics system, and an electric neutralization system; the air-breathing electric thruster does not include a hollow cathode; the flow control and storage system is used to mix the incoming working fluid and provide a very small amount of Xe working fluid in the required proportion, thereby reducing the thruster's ignition power and operating power; the low-resistance gas isolation-distribution system is used to maintain a low resistance level while isolating plasma gas backflow, thereby maintaining the internal gas pressure level of the ceramic discharge chamber 3; the temperature-controlled radio frequency ionization system is used to transfer heat to the ultra-low orbit satellite. The phase change energy storage material of the thermal control system and the radiant heat sink reduce the size of the radiant heat sink and lower the drag. After the gaseous working fluid is fully ionized, it is accelerated and extracted by the ion optical system to form a plume. The electric neutralization system is used to neutralize the plume potential and ensure the overall potential balance of the air-breathing electric thruster. This air-breathing electric thruster can obtain greater thrust by ionizing and accelerating the captured ultra-low orbit atmospheric working fluid, ensuring that the satellite can maintain an ultra-low orbit of 100-300km. For N2 / O2 / Xe mixed working fluid, the thrust range reaches 1.8-35.9mN, the maximum specific impulse is ≥3000s, and the plume divergence half angle is ≤20°.

[0044] Supplementary Note 1

[0045] The aforementioned "temperature-regulating radio frequency ionization system, used to introduce heat into the phase change energy storage material and radiant heat sink of the ultra-low orbit satellite thermal control system" is as follows: Figure 1 As shown, the air-breathing electric thrust gas is connected to the phase change energy storage material of the satellite system. The temperature-regulating radio frequency ionization system of the air-breathing electric thrust gas transfers heat to the radiant heat sink of the satellite system through the phase change energy storage material.

[0046] Furthermore, the flow control and storage system includes a flow control and storage system module for capturing the incoming flow and a flow control and storage system module for Xe working fluid. The flow control and storage system mixes the incoming working fluid and a small amount of Xe working fluid in the required proportion and supplies them to the thruster and the electric neutralization system. The use of a small amount of Xe working fluid significantly reduces the power required for thruster ignition and self-sustaining discharge, thereby reducing the size of the radio frequency power module and the required solar panel area.

[0047] Furthermore, such as Figure 2As shown, the flow control and storage system module for capturing incoming flow includes a flow control module 15, a proportional flow control valve 16, a self-locking valve 17, an atmospheric working fluid tank 18, and captured low-Earth orbit atmosphere 19. The captured low-Earth orbit atmosphere 19 is stored in the atmospheric working fluid tank 18 and, under the control of the flow control module 15, the proportional flow control valve 16, and the self-locking valve 17, provides a flow-controlled atmospheric working fluid to the air-breathing thruster and neutralizer. The flow control and storage system module for Xe working fluid includes a flow control module 20, a proportional flow control valve 21, a self-locking valve 22, and an Xe working fluid tank 23. The Xe working fluid in the Xe working fluid tank 23, under the control of the flow control module 20, the self-locking valve 22, and the proportional flow control valve 21, provides a flow-controlled Xe working fluid to the air-breathing thruster and the electric neutralization system.

[0048] Furthermore, the small amount of Xe working fluid specifically refers to mixing the incoming working fluid and Xe working fluid in the required proportion, wherein the proportion of Xe working fluid is less than 10%.

[0049] Furthermore, such as Figure 2 , Figure 3 As shown, the low-resistance gas isolation-distribution system includes a gas distributor baffle 5-1, a gas distribution outlet 5-2, an isolator gas channel 5-3, a lower ceramic slot 5-4, an upper ceramic slot 5-5, and an inlet 5-6. By adjusting the width, length, and number of bends of the isolator gas channel 5-3, the flow rate of the captured low-orbit atmosphere 19 under different capture gas pressures can be adapted. The mixed atmosphere / Xe working fluid enters the isolator gas channel 5-3, which is composed of the lower ceramic slot 5-4 and the upper ceramic slot 5-5, through the inlet 5-6. The working fluid enters the ceramic discharge chamber 3 from the gas distribution outlet 5-2, and its ejection direction is changed by the gas distributor baffle 5-1, causing it to diffuse towards the side wall of the ceramic discharge chamber 3.

[0050] Furthermore, such as Figure 2As shown, the temperature-regulating radio frequency ionization system includes a ceramic discharge chamber 3, a thruster coil 4, a thruster shielding shell 6, an L-shaped matching network 12, a power amplifier 13, and a signal source 14. The thruster coil 4 is composed of a microgravity heat pipe with a special liquid-absorbing core and is connected to the phase change energy storage system and radiative heat dissipation system of the ultra-low orbit satellite thermal control system to regulate the thruster temperature. The signal source 14, power amplifier 13, L-shaped matching network 12, and thruster coil 4 are used to generate radio frequency electromagnetic waves. The signal source 14 provides a sinusoidal signal, which is amplified by the power amplifier 13 and the L-shaped matching network 14. After the matching network 12 is configured, the thruster coil 4 generates radio frequency electromagnetic waves, forming a ring electric field in the ceramic discharge chamber 3 to accelerate the ionization of the working gas. The electric field that accelerates the ionization of electrons is provided by the neutralization system. The end face of the shielding shell 6 near the acceleration grid 1 is covered with an anti-oxidation copper film. The surface treatment of this end face is a special consideration for ultra-low orbit satellite thrusters and has a significant impact on stable ignition and operation. The shielding shell 6 as a whole is used to prevent radio frequency electromagnetic waves from leaking out and affecting adjacent electronic components, while also reducing the loss of electromagnetic waves to a certain extent so that they can be used for radio frequency ionization.

[0051] Furthermore, such as Figure 2 As shown, the ion optical system includes an accelerating grid 1, a screen grid 2, a fastening device 7, a negative high-voltage terminal 8, a negative high-voltage module 9, a positive high-voltage terminal 10, and a positive high-voltage module 11. The spacing, aperture, and number of apertures between the accelerating grid 1 and the screen grid 2 need to be optimized according to the long-term service orbital altitude and space environment of the ultra-low orbit satellite. The positive high-voltage module 11 provides a positive high voltage of 1000-2000V to the screen grid 2 through the positive high-voltage terminal 10, and the negative high-voltage module 9 provides a voltage of ±200V to the accelerating grid 1 through the negative high-voltage terminal 8. The negative high-voltage module 9 is bipolar. When the thruster ignites, it provides a positive voltage of 200V to introduce external electrons into the ceramic discharge chamber 3 for ignition. When the thruster is working, it provides a negative voltage of 200V, which on the one hand forms a strong electric field with the screen grid 2 to accelerate the formation of positive ions into a plume, and on the other hand shields the external electrons generated by the neutralization system. The fastening device 7 assists in fixing the accelerating grid 1 and the screen grid 2 to the end of the thruster.

[0052] Furthermore, such as Figure 2As shown, the neutralization system includes a radio frequency (RF) neutralizer copper coil 24, an RF neutralizer shielding shell 25, a collecting electrode 26, a tungsten needle 27, low-orbit atmosphere / Xe working fluid 28, a high-voltage ignition power supply 29, an L-type matching network 30, a power amplifier 31, and a signal source 32. The signal source 32 provides a sinusoidal signal, which, after being amplified by the power amplifier 31 and configured by the L-type matching network 30, generates RF electromagnetic waves through the RF neutralizer copper coil 24, ionizing the low-orbit atmosphere / Xe working fluid 28 within the neutralizer to form plasma. The electrons required for ionization originate from the breakdown discharge of the working fluid between the tungsten needle 27 and the high-voltage ignition power supply 29. Positive ions flow towards the collecting electrode 26, and electrons are ejected. The RF neutralizer shielding shell 25 is used to reduce the potential interference of the thruster's electromagnetic field on the neutralizer. This neutralization system is based on the principle of RF discharge, has strong oxidation resistance, and is suitable for ultra-low orbit environments rich in atomic oxygen.

[0053] Example 1: Operation Procedure of Air-breathing Electric Thruster

[0054] This embodiment describes the operation process of an air-breathing electric thruster, specifically including the following aspects:

[0055] (1) Thruster ignition includes three methods as follows:

[0056] (a) Thruster-Neutralizer Synchronous Ignition: The thruster flow control system is activated, radio frequency power is applied, and the neutralizer is started. At the instant the neutralizer successfully ignites, the thruster ignites due to the electron avalanche effect. This method requires specific positioning and angles between the neutralizer and the thruster; they should not be too far apart. The radio frequency power and ignition flow rate are also relatively high during ignition. The probability of failure increases significantly when the neutralizer's own temperature is high.

[0057] (b) Pulsed gas gate discharge ignition: The neutralizer is activated, radio frequency power is applied, and the thruster flow control system is turned on to provide a large airflow impact, thus igniting the thruster. This method requires high radio frequency power for ignition, and the frequent supply of large instantaneous gas flows has a certain impact on the mechanical structure and service life of the flow control valve. However, this method is relatively reliable.

[0058] (c) Electron ignition by gate potential difference: The neutralizer is activated, the thruster flow control system is turned on, radio frequency power is applied, and an accelerating gate positive voltage is applied to introduce electrons into the neutralizer, thus igniting the thruster. This method is commonly used for ignition of large-diameter thrusters. It has low requirements for propellant flow rate and radio frequency power, and only needs to consider the polarity reversal of the accelerating gate electrode. This method has high reliability.

[0059] (2) After successful ignition, the thruster can achieve the optimal working state under different thrust values ​​by adjusting the main parameters such as grid voltage, working fluid flow rate, and radio frequency.

[0060] (3) When the thruster is shut down, the following steps are included: (a) reducing and turning off the radio frequency power of the temperature self-regulating radio frequency ionization system; (b) turning off the gate power of the ion optics system; (c) turning off the charge neutralization system; and (d) turning off the flow control and storage system.

[0061] Example 2: Verification of Thrust Range and Maximum Specific Impulse

[0062] Taking the atmospheric composition at an orbital altitude of 150 km as an example, considering the recombination of atomic oxygen, the working fluid combination used in the experiment was 4 sccm Xe + 22.5 sccm N2 + 22.5 sccm O2. The relationship between its thrust and total power is shown in [reference needed]. Figure 4a , 4b When the thruster ignites at the maximum working fluid flow rate provided by the flow control and storage system, it operates in low-power mode when the RF power provided by power amplifier 13 is below 150W, and in high-power mode when the RF power provided by power amplifier 13 is above 150W. In both low-power and high-power operating modes, the thrust of the thruster can cover a range of 1.8mN to 35.9mN (see...). Figure 4a and 4b Calculations show that the thruster's specific impulse ranges from 174s to 3471.2s, with specific impulses above 5mN exceeding 479.64s, and a specific impulse of 9.76mN reaching 941.5s. When operating at its maximum thrust limit of 35.9mN, the total thruster power is 2074.3W, and the electric neutralization system power is 30W. The operating status of the air-breathing electric thruster is shown in [reference needed]. Figure 5 .

[0063] 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 air-breathing electric thruster for ultra-low Earth orbit satellites, characterized in that: The system includes a flow control and storage system, a low-resistance gas isolation-distribution system, a temperature-controlled radio frequency ionization system, an ion optics system, and an electric neutralization system; the air-breathing electric thruster does not include a hollow cathode; the flow control and storage system is used to mix the incoming working fluid and provide a very small amount of Xe working fluid in the required proportion, thereby reducing the ignition power and operating power of the thruster; the low-resistance gas isolation-distribution system is used to maintain a low gas resistance level while isolating plasma gas backflow, thereby maintaining the gas pressure level inside the ceramic discharge chamber (3); the temperature-controlled radio frequency ionization system is used to introduce heat into the ultra-low orbit satellite thermal control system. The system incorporates phase change energy storage materials and radiant heat sinks, thereby reducing the size of the radiant heat sink to lower drag. After fully ionizing the gaseous working fluid, it is accelerated and extracted by the ion optical system to form a plume. The electric neutralization system is used to neutralize the plume potential, ensuring the overall potential balance of the air-breathing electric thruster. This air-breathing electric thruster can obtain greater thrust by ionizing and accelerating the captured ultra-low orbit atmospheric working fluid, ensuring the satellite can maintain an ultra-low orbit of 100~300km. For N2 / O2 / Xe mixed working fluid, the thrust range reaches 1.8~35.9mN, the maximum specific impulse is ≥3000s, and the plume divergence half angle is ≤20°. The flow control and storage system includes a flow control and storage system module for capturing incoming flow and a flow control and storage system module for Xe working fluid. The flow control and storage system mixes the incoming working fluid and a small amount of Xe working fluid in the required proportion and supplies them to the thruster and the electric neutralization system. The use of a small amount of Xe working fluid significantly reduces the power required for thruster ignition and self-sustaining discharge, thereby reducing the size of the radio frequency power module and the required solar panel area. The flow control and storage system module for capturing incoming flow includes a flow control module (15), a proportional flow control valve (16), a self-locking valve (17), an atmospheric working fluid tank (18), and captured low-Earth orbit atmosphere (19). The captured low-Earth orbit atmosphere (19) is stored in the atmospheric working fluid tank (18) and, through the control of the flow control module (15), the proportional flow control valve (16), and the self-locking valve (17), provides a flow-controlled atmospheric working fluid for the air-breathing thruster and neutralizer. The flow control and storage system module for Xe working fluid includes a flow control module (20), a proportional flow control valve (21), a self-locking valve (22), and an Xe working fluid tank (23). The Xe working fluid in the Xe working fluid tank (23), through the control of the flow control module (20), the self-locking valve (22), and the proportional flow control valve (21), provides a flow-controlled Xe working fluid for the air-breathing thruster and the electric neutralization system. The small amount of Xe working fluid specifically refers to the mixing of the incoming working fluid and Xe working fluid in the required proportion, wherein the proportion of Xe working fluid is less than 10%.

2. The air-breathing electric thruster for a very low Earth orbit satellite according to claim 1, characterized in that: The low-resistance gas isolation-distribution system includes a gas distributor baffle (5-1), a gas distribution outlet (5-2), an isolator gas channel (5-3), a lower ceramic slot (5-4), an upper ceramic slot (5-5), and an air inlet (5-6). By adjusting the width, length, and number of bends of the isolator gas channel (5-3), the flow rate of low-orbit atmosphere (19) captured under different capture gas pressures can be adapted. The mixed atmosphere / Xe working fluid enters the isolator gas channel (5-3) composed of the lower ceramic slot (5-4) and the upper ceramic slot (5-5) through the air inlet (5-6). The working fluid enters the ceramic discharge chamber (3) from the gas distribution outlet (5-2) and changes its ejection direction through the gas distributor baffle (5-1) so that it diffuses toward the side wall of the ceramic discharge chamber (3).

3. The air-breathing electric thruster for a very low Earth orbit satellite according to claim 1, characterized in that: The temperature-regulating radio frequency ionization system includes a ceramic discharge chamber (3), a thruster coil (4), a thruster shielding shell (6), an L-type matching network (12), a power amplifier (13), and a signal source (14). The thruster coil (4) is composed of a microgravity heat pipe with a special liquid-absorbing core and is connected to the phase change energy storage system and the radiation heat dissipation system of the ultra-low orbit satellite thermal control system to regulate the thruster temperature. The signal source (14), power amplifier (13), L-type matching network (12), and thruster coil (4) are used to generate radio frequency electromagnetic waves. The signal source (14) provides a sinusoidal signal, which is transmitted through the power amplifier (13). After the amplification and L-type matching network (12) are configured, the thruster coil (4) generates radio frequency electromagnetic waves, forming a ring electric field in the ceramic discharge chamber (3) to accelerate the ionization of the working gas. The electric field that accelerates the ionization of electrons is provided by the electric neutralization system. The end face of the shielding shell (6) near the acceleration grid (1) is covered with an anti-oxidation copper film. The surface treatment of this end face is a special consideration for the ultra-low orbit satellite thruster and has a significant impact on stable ignition and operation. The shielding shell (6) as a whole is used to prevent the leakage of radio frequency electromagnetic waves from affecting adjacent electronic components, and at the same time, it can reduce the loss of electromagnetic waves to a certain extent so that they can be used for radio frequency ionization.

4. The air-breathing electric thruster for a very low Earth orbit satellite according to claim 1, characterized in that: The ion optical system includes an accelerating grating (1), a screen grating (2), a fastening device (7), a negative high-voltage terminal (8), a negative high-voltage module (9), a positive high-voltage terminal (10), and a positive high-voltage module (11). The spacing, aperture, and number of apertures between the accelerating grating (1) and the screen grating (2) need to be optimized according to the long-term service orbital altitude and space environment of the ultra-low orbit satellite. The positive high-voltage module (11) provides a positive high voltage of 1000~2000V to the screen grating (2) through the positive high-voltage terminal (10), and the negative high-voltage module (9) provides a positive high voltage of 1000~2000V to the screen grating (2) through the positive high-voltage terminal (10). The negative high voltage terminal (8) provides a voltage of ±200V to the acceleration grid 1; the negative high voltage module (9) is bipolar. When the thruster is ignited, it provides a positive voltage of 200V to introduce external electrons into the ceramic discharge chamber 3 for ignition; when the thruster is working, it provides a negative voltage of 200V, which on the one hand forms a strong electric field with the screen grid (2) to accelerate the formation of positive ions into a plume, and on the other hand shields the external electrons generated by the electric neutralization system; the fastening device (7) assists in fixing the acceleration grid (1) and the screen grid (2) to the end of the thruster.

5. The air-breathing electric thruster for a very low Earth orbit satellite according to claim 1, characterized in that: The neutralization system includes a radio frequency neutralizer copper coil (24), a radio frequency neutralizer shielding shell (25), a collecting electrode plate (26), a tungsten needle (27), low-orbit atmosphere / Xe working fluid (28), a high-voltage ignition power supply (29), an L-type matching network (30), a power amplifier (31), and a signal source (32). The signal source (32) provides a sinusoidal signal, which is amplified by the power amplifier (31) and configured by the L-type matching network (30). The radio frequency neutralizer copper coil (24) generates radio frequency electromagnetic waves, which ionize the low-orbit atmosphere / Xe working fluid (28) in the neutralizer to form plasma. The electrons required for ionization come from the breakdown discharge of the working fluid between the tungsten needle (27) and the high-voltage ignition power supply (29). Positive ions flow to the collecting electrode plate (26), and electrons are ejected. The radio frequency neutralizer shielding shell (25) is used to reduce the potential interference of the thruster electromagnetic field to the neutralizer. This neutralization system is based on the principle of radio frequency discharge, has strong anti-oxidation ability, and is suitable for ultra-low orbit environments rich in atomic oxygen.

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