Inductively coupled plasma microthruster with dual antenna configuration

Abstract

The application discloses a kind of inductively coupled plasma micro-propeller of double antenna structure, and its discharge system includes gas source, air inlet valve, antenna, discharge tube and radio frequency power supply.Gas source is directly connected with discharge tube by valve, wherein the valve can control the air intake during discharge;Then two identical helical antennas are connected in series at a certain distance and are wound on the same discharge tube, the output end of radio frequency power supply is connected to the end of antenna away from air inlet through impedance matcher, and the other end of radio frequency power supply and antenna is connected to the same ground.The application has simple structure, small space size and mass, and only needs to work stably at low power and low air intake, realizing micro-newton to millinewton level thrust.It is suitable for equipping in most of the current constellation micro-satellites without propulsion system of nanosatellite and cubic satellite.In addition, the length and spacing of the two antennas in the system are adjustable, and the size of the propeller can be adjusted according to the specific requirements of micro-satellite.

Description

Technical Field

[0001] This invention belongs to the field of plasma propulsion technology, specifically relating to an inductively coupled plasma micro-thruster with a dual-antenna structure. Background Technology

[0002] Currently, with the increasing number of satellite launches and the shift in satellite operation mode from individual to networked operation, launched satellites are gradually becoming smaller (cube satellites) and miniaturized (nanosatellites). This presents a series of challenges for electric propulsion technology used in small satellites, including performance optimization, small size, long service life, and low cost. Since the 1960s, electric propulsion has been used by satellite operators for space station maintenance and orbit modification. Current electric propulsion devices are mainly divided into three categories: electrostatic, electromagnetic, and electrothermal. Electrostatic thrusters are mainly grid ion thrusters, electromagnetic thrusters are mainly Hall thrusters, and electrothermal thrusters are mainly resistance and arc thrusters. The former two types of thrusters have more complex systems and are typically used in large satellites with high power (kilowatt-level) and sufficient propellant. In recent years, small satellite structures of 1U, 1.5U, 2U, and 3U types have been proposed for cube satellites, with masses ranging from 1.33 kg to 4.00 kg. As of June 1, 2022, online nanosatellite databases show that over 3,500 nanosatellites and CubeSats have entered orbit, with CubeSats smaller than 3U accounting for an increasingly larger proportion of microsatellites launched in recent years. However, data shows that the vast majority of microsatellites are not equipped with propulsion systems. Due to the shape, size limitations, and average payload power of microsatellites, propulsion systems require small size, light weight, low power, and simple structure, significantly increasing the difficulty of designing them.

[0003] Therefore, it is necessary to study a highly integrated, low-power, low-thrust, and low-impulse micro-propulsion system suitable for microsatellite orbit maintenance, orbital maneuvering, and attitude control; that is, a micro-thruster is needed.

[0004] In recent years, micro-propulsion systems for use on CubeSats and nanosatellites have been proposed, and many plasma propulsion systems are currently undergoing experimental research on the ground and in space. For example, Hall thrusters and ion thrusters have developed rapidly in recent years; however, they are both electromagnetic propulsion systems, ejecting ion jets that require cathode electrons for neutralization to maintain electrical neutrality. Furthermore, their propulsion devices all require magnets to generate magnetic fields to confine the plasma, making the devices relatively complex. Currently, there is a plasma thruster using inductively coupled discharge, which is an electrothermal micro-propulsion system. Its spatial size and overall mass are very suitable for microsatellite propulsion, with very low impulse pulses, achieving thrust in the microNewton to millinewton range, and an average power consumption of only 10-100W. This makes it ideal for equipping microsatellites for high-precision attitude control and relative orbital position maintenance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an inductively coupled plasma microthruster with a dual-antenna structure. This microthruster features a simple structure, small size and mass, and can operate stably under low power and low air intake conditions, achieving microNewton to millinewton thrust. It is suitable for deployment on most nanosatellites and cubesat satellites currently launched in constellations that lack propulsion systems.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] An inductively coupled plasma micro-thruster with a dual-antenna structure includes a discharge system and a grounding and impedance matching device;

[0008] The discharge system includes a gas source, an air inlet valve, a series antenna, a discharge tube, and a radio frequency power supply.

[0009] The gas source is directly connected to the discharge tube and is controlled by the air inlet valve;

[0010] The series antenna is connected to the impedance matching device and wound around the surface of the discharge tube to excite plasma and heat the gas entering the discharge tube from the gas source.

[0011] The impedance matching device is connected to the output terminal of the radio frequency power supply;

[0012] The grounding is connected to the series antenna and the radio frequency power supply respectively to form a complete circuit loop;

[0013] The frequency of the radio frequency power supply is 13.56MHz;

[0014] Two identical antennas are connected in series to form a series antenna, and wound on the same discharge tube for use in the discharge system, which excites higher plasma parameters and generates thrust.

[0015] The plasma parameters include plasma density and electron temperature;

[0016] The thrust is the thrust generated by the inductively coupled plasma micro-thruster after heating the gas with plasma.

[0017] Furthermore, one end of the gas source is supplied with gas, and the other end is connected to the discharge tube. The gas is air, nitrogen, or an inert gas.

[0018] Furthermore, the discharge tube is a quartz tube or an alumina ceramic tube.

[0019] Furthermore, the series antenna includes a capacitively coupled antenna, an inductively coupled antenna, an inductive-capacitively coupled antenna, or a helical wave antenna.

[0020] Furthermore, the tandem antenna uses copper or tungsten.

[0021] Furthermore, the series antenna connects two antennas of identical shape, size, and material to the circuit of the discharge system in series.

[0022] Furthermore, the discharge tube uses a high-temperature resistant insulating material tube.

[0023] Furthermore, the gas is argon, helium, or xenon.

[0024] In the dual-antenna structure of the inductively coupled plasma micro-thruster, the antenna consists of two multi-turn radio frequency single-loop antennas connected in series with a spacing of 4cm; other antenna types can be capacitively coupled antennas, inductively coupled antennas, inductive-capacitive coupled antennas, or helical wave antennas; other antenna spacing can be 2cm, 6cm, or 8cm.

[0025] Beneficial effects:

[0026] The inductively coupled plasma micro-thruster with dual antenna structure of the present invention has very small spatial size and overall mass. In one embodiment, its size is 100×16×16 (unit: mm).

[0027] The dual-antenna inductively coupled plasma micro-propulsion system described herein, compared to chemical propulsion systems, avoids clogging and utilizes small-sized nozzle throats to achieve minute thrust. Compared to electromagnetic micro-electric propulsion systems, it has a simpler structure and higher reliability. Furthermore, compared to single-antenna inductively coupled plasma thrusters, it boasts higher plasma parameters and the ability to generate supersonic ion beams, resulting in higher propellant utilization. When used for precise control of microsatellite attitude and orbital position, this micro-thruster generates more accurate thrust. Additionally, while electric propulsion offers advantages of high specific impulse and low thrust, traditional electric thrusters require significant electrical power (1-2 kW). The dual-antenna inductively coupled plasma micro-thruster described herein has low power consumption; in one embodiment, the average power consumption is only 10-100 W, achieving thrust in the micronewton to millinenewton range, making it ideal for high-precision attitude control and relative orbital position maintenance for power-constrained microsatellites. Attached Figure Description

[0028] To more clearly illustrate the technical solution of the present invention, a brief description of the accompanying drawings in an example is provided below.

[0029] Figure 1 This is a schematic diagram of an inductively coupled plasma propulsion system with a multi-turn radio frequency single-loop dual-antenna structure (unit: mm).

[0030] Figure 1 In the middle: 1-Gas source, 2-Inlet valve, 3-Series antenna, 4-Ground, 5-Discharge tube, 6-RF power supply, 7-Impedance matching device, 8-Plasma jet.

[0031] Figure 2 This is a schematic diagram of a direct thrust measurement method for an inductively coupled plasma thruster with a dual-antenna structure; where (a) is the position of the thruster when it is stationary during ignition, and (b) is the position change of the thruster after ignition.

[0032] Figure 2 In the middle: 9-vacuum chamber wall, 10-laser displacement sensor, 11-suspension device. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0034] like Figure 1As shown, the inductively coupled plasma micro-thruster with a dual-antenna structure of the present invention includes a discharge system, a grounding device 4, and an impedance matching device 7. The discharge system includes a gas source 1, an inlet valve 2, a series antenna 3, a discharge tube 5, and a radio frequency power supply 6. The gas source 1 is directly connected to the discharge tube 5 and is controlled by the inlet valve 2; the series antenna 3 is connected to the impedance matching device 7 and is wound around the surface of the discharge tube 5 to excite plasma and heat the gas entering the discharge tube 5 from the gas source 1.

[0035] The impedance matching device 7 is connected to the output terminal of the RF power supply 6; the grounding device 4 is connected to the series antenna 3 and the RF power supply 6 respectively, to form a complete circuit loop.

[0036] Two identical antennas are connected in series to form a series antenna 3, and wound around the same discharge tube 5 to form an inductively coupled plasma discharge system. This discharge system, as a subsystem of the micro-thruster, can generate higher plasma parameters, thus producing greater thrust. The discharge system is the main factor determining the thrust magnitude; this invention primarily improves the thrust of the micro-thruster by increasing the plasma parameters of the discharge system.

[0037] The frequency of the radio frequency power supply 6 is 13.56MHz.

[0038] One end of the gas source 1 is supplied with gas, and the other end is connected to the discharge tube 5. The gas used can be air, nitrogen, or an inert gas, typically argon, helium, or xenon. The gas pressure in the discharge tube and vacuum chamber is controlled to be 6.1 × 10⁻⁶. -1 Pa.

[0039] The discharge tube 5 is made of quartz tube, alumina ceramic tube, or other high-temperature resistant insulating material.

[0040] The tandem antenna 3 uses copper, tungsten, or other metal materials.

[0041] A dual-antenna structure is formed by using two multi-turn radio frequency single-loop antennas with a spacing of 4cm to form a series antenna.

[0042] The series antenna 3 is wound around the surface of the discharge tube 5. The series antenna 3 can be a common plasma excitation antenna such as a capacitively coupled antenna, an inductively coupled antenna, an inductively coupled antenna, or a helical wave antenna.

[0043] The intake air volume in the discharge tube 5 is controlled by the intake valve 2.

[0044] The miniature thruster was placed inside the vacuum chamber, and a vacuum was created to bring the air pressure to the specified value of 4.4 × 10⁻⁶. -4 Pa.

[0045] Preferred, such as Figure 1As shown, the inductively coupled plasma micro-thruster with dual antenna structure of the present invention has very small spatial size and overall mass. In one embodiment, its size is 100×16×16 (unit: mm).

[0046] Turn on the RF power supply 6 and adjust the power level. Adjust the impedance matching device 7 to reduce the reflected power to 0, controlling the power between 10-100W. This generates plasma within the discharge tube 5. Ions in the plasma collide with the neutral gas through charge exchange, generating heat that heats the neutral gas. The neutral gas expands and ejects a plasma jet 8 to the other end, generating thrust. The plasma jet 8 is not a component of the plasma thruster; it is generated by ions in the plasma produced by the discharge colliding with the neutral gas through charge exchange, heating the neutral gas, and ejecting it to the other end.

[0047] By measuring the distance change between the inductively coupled plasma micro-thruster with a dual-antenna structure and the vacuum chamber wall using a laser displacement sensor, the thrust can be directly measured, enabling precise position adjustment of the microsatellite.

[0048] The following is combined Figure 2 Specifically, this invention describes a control model for the dual-antenna structure inductively coupled plasma micro-thruster used in high-precision position adjustment of microsatellites to achieve displacement changes.

[0049] To achieve precise position adjustment, a miniature thruster is mounted on a suspension device 11 equipped with a laser displacement sensor 10. This suspension device 11 is mounted on the vacuum chamber wall 9, ensuring that the reading of the laser displacement sensor 10 remains constant when it is irradiated by the vacuum chamber wall 9. The laser displacement sensor is then calibrated for thrust and displacement, with the result being A μN / μm. The displacement change of the suspension device 11 is determined by utilizing the change in the reading of the laser displacement sensor 10. Figure 2 In (a), the micro-thruster is stationary and suspended on the suspension device 11, and the reading of the laser displacement sensor 10 is L1. Figure 2 (b) shows the position change of the suspension device 11 after the micro-thruster is ignited. The entire suspension device 11 moves in the opposite direction to the plasma jet, and the reading of the laser displacement sensor 10 decreases to L2. At this time, the thrust F generated by this micro-thruster can be measured using the relationship:

[0050] F = A × (L1 - L2)

[0051] Where A is Figure 2 The calibration results of the displacement of the laser displacement sensor and the thrust of the thruster are given in μN / μm.

[0052] This allows us to determine the relationship between the power and thrust of a micro-thruster, ultimately leading to the establishment of a precise thrust control model.

[0053] The specific embodiments described above provide a further detailed explanation of the technical solution of the present invention. Any modifications or substitutions made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A dual-antenna structure inductively coupled plasma micro-thruster, characterized in that, It can operate stably under low power and low air intake, achieving thrust from microNewtons to millinenewtons. Includes a discharge system, grounding (4) and impedance matching device (7); The discharge system includes a gas source (1), an air inlet valve (2), a series antenna (3), a discharge tube (5), and a radio frequency power supply (6). The gas source (1) is directly connected to the discharge tube (5) and is controlled by the air inlet valve (2); The series antenna (3) is connected to the impedance matching device (7) and wound around the surface of the discharge tube (5) to excite plasma and heat the gas entering the discharge tube (5) from the gas source (1); The impedance matching device (7) is connected to the output terminal of the radio frequency power supply (6); The grounding (4) is connected to the series antenna (3) and the radio frequency power supply (6) respectively to form a complete circuit loop; The frequency of the radio frequency power supply (6) is 13.56 MHz; Two identical antennas are connected in series to form a series antenna (3), and wound on the same discharge tube (5) to excite higher plasma parameters and generate thrust in the discharge system; The plasma parameters include plasma density and electron temperature; The thrust is the thrust generated by the inductively coupled plasma micro-thruster after heating the gas with plasma; The thruster nozzle generates a supersonic ion beam; the thrust is directly measured by measuring the distance change between the inductively coupled plasma micro-thruster with a dual-antenna structure and the vacuum chamber wall using a laser displacement sensor.

2. The inductively coupled plasma micro-thruster with a dual-antenna structure according to claim 1, characterized in that: The gas source (1) is supplied with gas at one end and connected to the discharge tube (5) at the other end. The gas is air, nitrogen or inert gas.

3. The inductively coupled plasma micro-thruster with a dual-antenna structure according to claim 1, characterized in that: The discharge tube (5) is a quartz tube or an alumina ceramic tube.

4. The inductively coupled plasma micro-thruster with a dual-antenna structure according to claim 1, characterized in that: The series antenna (3) includes a capacitively coupled antenna, an inductively coupled antenna, an inductive-capacitively coupled antenna, or a helical wave antenna.

5. The inductively coupled plasma micro-thruster with a dual-antenna structure according to claim 1, characterized in that: The tandem antenna (3) uses copper or tungsten.

6. The inductively coupled plasma micro-thruster with a dual-antenna structure according to claim 1, characterized in that: The series antenna (3) connects two antennas of identical shape, size and material to the circuit of the discharge system in series.

7. The inductively coupled plasma micro-thruster with a dual-antenna structure according to claim 1, characterized in that: The discharge tube (5) is made of a high-temperature resistant insulating material.

8. The inductively coupled plasma micro-thruster with a dual-antenna structure according to claim 1, characterized in that: The gas is argon, helium, or xenon.

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