Electric arc thruster with long service life and high specific impulse

Abstract

The invention relates to a long-life and high-specific impulse hydrazine arc thruster, which relates to the field of electric thrusters, and comprises a rear shell, a front shell, a gas interface, an electric connector, a belleville spring, a cyclone, a cathode and an anode, the rear shell and the front shell are made of different materials and are fixedly connected through welding; the fuel gas interface is fixedly connected to the rear shell so as to introduce gas which is formed by catalytic decomposition of liquid anhydrous hydrazine into the rear shell; the electric connector is fixedly connected to the end part of the rear shell so as to supply power to the thruster; a plurality of belleville springs are arranged in the rear shell close to the electric connector; the swirler is installed in the front shell so as to convert gas input by the gas connector into circumferential rotational flow, the anode is welded to the front shell, the anode is made of tungsten-rhenium alloy which is low in rhenium content and doped with hafnium carbide, a throat is formed in the anode and integrated with the spray pipe, the sharp end of the cathode extends to the throat, arc discharge is generated between the sharp end of the cathode and the anode, and gas is heated and ionized. The invention has the advantages that the specific impulse can reach 600s, and the service life can reach 1000h.

Description

Technical Field

[0001] This invention relates to the field of electric propulsion technology, and in particular to a long-life, high-specific-impulse hydrazine arc thruster. Background Technology

[0002] With the increasing number of space missions, some satellite models have proposed dual-mode propulsion requirements: using chemical thrusters for orbit changes and high-specific-impulse electric thrusters for north-south position maintenance. If electric propulsion such as ion thrusters and Hall thrusters are used, two separate storage and supply systems are required to power the electric thrusters and chemical thrusters respectively, significantly increasing costs and payload. In this case, using arc thrusters as the electric thrusters for north-south position maintenance is a very suitable choice.

[0003] Although China has conducted extensive research on electric arc thrusters and achieved certain results, there are still no reports of successful on-orbit applications of hydrazine electric arc thrusters. The research on electric arc thrusters in China still has the following shortcomings:

[0004] 1) The power is relatively low, mostly around 1kW. At this power, the specific impulse of the arc thruster is generally within 450s, and the specific impulse advantage is not prominent enough.

[0005] 2) Argon, nitrogen, hydrogen or mixed gases are mostly used as working fluids, and anhydrous hydrazine propellant, which is a mature application in satellites, is rarely used.

[0006] 3) Key processes or materials have not been fully validated, and the cumulative lifespan ignition time is insufficient, failing to meet the lifespan requirements of the satellite model.

[0007] Therefore, to address the above shortcomings, there is a need to provide a long-life, high-specific-impulse hydrazine arc thruster. Summary of the Invention

[0008] (a) Technical problems to be solved

[0009] The technical problem to be solved by this invention is to address the issues of low specific impulse and short cumulative lifespan ignition time in current domestic arc thrusters.

[0010] (II) Technical Solution

[0011] To address the aforementioned technical problems, this invention provides a long-life, high-specific-impulse hydrazine arc thruster, comprising a rear housing, a front housing, a gas inlet, an electrical connector, disc springs, a cyclone separator, a cathode, and an anode. The rear housing and the front housing are made of different materials and are welded together. The gas inlet is fixed to the rear housing to introduce gas catalytically decomposed from liquid anhydrous hydrazine into the rear housing. The electrical connector is fixed to the end of the rear housing to supply power to the thruster. Several disc springs are installed in the rear housing near the electrical connector. The cyclone separator is installed in the front housing to convert the gas input from the gas inlet into a circumferential swirling flow. The anode is welded to the front housing and is made of a tungsten-rhenium alloy with low rhenium content and doped with hafnium carbide. The anode has a throat and is integrated with the nozzle. The sharp end of the cathode extends into the throat and generates an arc discharge between it and the anode, intensely heating the gas to achieve a specific impulse of 600s.

[0012] As a further explanation of the present invention, preferably, the throat diameter in the anode is 0.8 mm, the length is 0.8 mm, the angle of the contraction section is 75°, the angle of the expansion section of the nozzle is 40°, and the angle of the cathode tip is 50°.

[0013] As a further explanation of the present invention, preferably, the hydrocyclone is made of tungsten-rhenium alloy to avoid recrystallization during long-term high-temperature operation, and the part is provided with four Φ0.7mm air inlets to convert the gas into circumferential swirling flow, so as to avoid ablation caused by discharge at a fixed position for a long time.

[0014] As a further explanation of the present invention, preferably, the rear housing and the gas interface are made of 4J29 expansion alloy; the front housing is made of TZM molybdenum alloy material, and the rear housing and the front housing are connected by brazing.

[0015] As a further illustration of the present invention, preferably, the outer surfaces of the anode, the rear housing, and the front housing are coated with a TiC-based ceramic heat dissipation coating by plasma spraying, and the coating thickness is 0.06 to 0.12 mm.

[0016] As a further explanation of the present invention, preferably, a catalytic bed is fixedly connected to the gas interface via a pipeline, and the catalytic bed contains 3.2g to 3.7g of 30-40 mesh catalyst and 4.8g to 5.3g of 18-24 mesh catalyst to operate at the rated flow rate for more than 1000 hours.

[0017] As a further explanation of the present invention, preferably, the inner diameter of the inlet of the catalytic bed pre-chamber is 1.0 mm, and the inner diameter of the transition section is 3.0 mm.

[0018] As a further explanation of the present invention, preferably, a thermal control device is fixedly connected to the outside of the catalyst bed to heat the catalyst bed to 150°C.

[0019] As a further explanation of the present invention, preferably, an injector is fixedly connected upstream of the catalyst bed, and the injector has several capillaries with an inner diameter of 1.0 mm and a wall thickness of 0.2 mm built in to improve the injector's anti-fouling ability.

[0020] As a further illustration of the present invention, preferably, the injector adopts a non-perforated support rod structure to reduce heat conduction from the catalytic bed to the solenoid valve.

[0021] (III) Beneficial Effects

[0022] The above-described technical solution of the present invention has the following advantages:

[0023] 1. Previous domestic research on electric arc thrusters mostly used argon, nitrogen, hydrogen or mixed gases as working fluids. The electric arc thruster of this invention aims to achieve on-board application, selects anhydrous hydrazine as propellant, and shares the storage and supply system with the mature single-component chemical thrusters used on satellites, which has a wider prospect for on-board application and promotion.

[0024] 2. Previous domestic research on electric arc thrusters had relatively low power, generally around 1kW, and specific impulse within 450s. The electric arc thruster of this invention has a rated power of 2kW, a rated specific impulse of 600s, and a rated thrust of 280mN. The power and performance indicators of the thruster have been significantly improved.

[0025] 3. Previous domestic arc thrusters were all ground-based prototypes, lacking sufficient verification of key processes and materials, and failing to undergo engineering application testing. Their cumulative lifespan and ignition time were insufficient, failing to meet the lifespan requirements of satellite models. The arc thruster of this invention has a designed lifespan of 1000 hours, has overcome numerous technical challenges in engineering applications, and its key processes and materials have been fully verified. It has already been delivered to satellite models for use. Attached Figure Description

[0026] Figure 1 This is an assembly rendering of the present invention;

[0027] Figure 2 This is a cross-sectional view of the thruster body of the present invention.

[0028] In the diagram: 1. Support; 2. Gas generator; 3. Solenoid valve; 4. Injector; 5. Thermal control device; 6. Catalytic bed; 7. Thrust body; 71. Rear housing; 72. Front housing; 73. Gas interface; 74. Electrical connector; 75. Disc spring; 76. Cyclone separator; 77. Cathode; 78. Anode. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] A long-life, high-specific-impulse hydrazine arc thruster, combined with Figure 1 , Figure 2 It includes a gas generator 2 and a thruster body 7, which are fixed to the satellite by a split bracket 1.

[0031] Combination Figure 1 , Figure 2 The gas generator 2 includes a solenoid valve 3, an injector 4, a thermal control device 5, and a catalytic bed 6. The solenoid valve 3 is fixed to the inlet end of the injector 4 to control the injection or interruption of liquid anhydrous hydrazine. The injector 4 has a GH3030 capillary tube with an inner diameter of 1.0 mm and a wall thickness of 0.2 mm inside to improve its anti-fouling ability and prevent capillary blockage. The injector 4 adopts a non-perforated support rod structure, which effectively reduces the heat conduction from the catalytic bed 6 to the solenoid valve 3 compared to existing cylindrical surface perforated connection structures, allowing the temperature of the solenoid valve 3 to drop to within the allowable operating range. The thermal control device 5 is fixed to the outside of the catalytic bed 6 to heat the catalytic bed to 150°C. The catalytic bed 6 contains 3.2 g to 3.7 g of 30-40 mesh catalyst and 4.8 g to 5.3 g of 18-24 mesh catalyst. This loading amount is sufficient for operation for more than 1000 hours at a rated flow rate of 48 mg / s. The inlet inner diameter of the catalytic bed 6 is 1.0 mm, and the transition section inner diameter is 3.0 mm. By increasing the inlet inner diameter and the transition section inner diameter of the catalytic bed 6, blockage of the inlet chamber can be prevented and the thruster life can be improved.

[0032] Combination Figure 1 , Figure 2 The thruster body 7 includes a rear housing 71, a front housing 72, a gas inlet 73, an electrical connector 74, a disc spring 75, a cyclone separator 76, a cathode 77, and an anode 78. The rear housing 71 and the front housing 72 are made of different materials and are fixed together by welding. The gas inlet 73 is fixed to the rear housing 71 and connected to the catalytic bed 6 through a pipe. The electrical connector 74 is fixed to the end of the rear housing 71 to supply power to the thruster. Several disc springs 75 are installed in the rear housing 71 near the electrical connector 74. The cyclone separator 76 is installed in the front housing 72 to convert the gas input from the gas inlet 73 into a circumferential swirling flow. The anode 78 is welded to the front housing 72 outside the cyclone separator 76. The cathode 77 is connected to the electrical connector 74 and extends toward the anode 78.

[0033] Combination Figure 1 , Figure 2 The rear housing 71 and gas interface 73 are made of 4J29 expansion alloy with low thermal conductivity, which reduces heat conduction to the electrical connector 74. The front housing 72 is made of high-temperature resistant TZM molybdenum alloy. The anode 78 and the front housing 72 are welded by plasma diffusion welding (SPS), the front housing 72 and the rear housing 71 are brazed, the rear housing 71 and the electrical connector 74 are brazed with electron beam welding, and the rear housing 71 and the gas interface 73 are electron beam welded. In addition, the outer surfaces of the rear housing 71 and the front housing 72 are coated with a plasma-sprayed TiC-based ceramic heat dissipation coating with a coating thickness of 0.06-0.12 mm, which improves the emissivity of the housing surface and reduces the housing temperature.

[0034] Combination Figure 1 , Figure 2 Four disc springs 75 are configured between the electrical connector 74 and the cathode 77 for axial positioning. The disc springs 75 have the following specifications: outer diameter 14mm, inner diameter 7.2mm, thickness 0.5mm, and are made of 50CrVA material, allowing for long-term stable operation in high-temperature environments. The hydrocyclone 76 is made of tungsten-rhenium alloy (WRe25, 25% rhenium) and has four Φ0.7mm air inlets, which convert the airflow into circumferential delivery downstream. The use of tungsten-rhenium alloy material avoids recrystallization of parts, preventing surface protrusion. The swirling air intake causes the arc to adhere and rotate, avoiding prolonged discharge in a fixed location that could lead to ablation.

[0035] Combination Figure 1 , Figure 2 The anode 78 is made of a tungsten-rhenium alloy (W-4Re-HfC) with low rhenium content and doped with hafnium carbide, integrally molded with the nozzle, exhibiting excellent high-temperature performance, high thermal conductivity, and resistance to high-temperature creep. The throat diameter within the anode 78 is 0.8 mm, the length is 0.8 mm, the contraction angle is 75°, and the expansion angle of the nozzle is 40°. The cathode 77 has a pointed end away from the electrical connector 74 that extends into the anode 78, with a tip angle of 50°.

[0036] The working principle of this invention is as follows: The gas generator 2 is connected to the hydrazine storage and supply system. After receiving an electrical signal, the solenoid valve 3 opens, and the liquid hydrazine propellant flows from the solenoid valve 3 into the injector 4 through the throttling effect of fluid damping. After secondary throttling through the capillary tube of the injector 4, the liquid hydrazine enters the catalyst bed 6 through the capillary tube and is atomized. After contacting the catalyst, which has been heated by the thermal control device 5, a decomposition reaction occurs, and the heat generated is finally transformed into a mixture of nitrogen, ammonia, and hydrogen, providing high-energy gas feedstock for subsequent electric arc heating. By using a large-diameter capillary tube and support rod structure in the injector 4, on the one hand, uniform injection of propellant is ensured, and on the other hand, the structural design reduces the heat conduction from the catalyst bed 6 to the solenoid valve 3, avoiding heat loss from the catalyst bed 6 and maintaining decomposition efficiency. At the same time, the catalyst loading of the gas generator 2 is precisely controlled, optimizing the porosity and reaction area of ​​the catalyst bed 6, allowing for more complete decomposition of anhydrous hydrazine and generating high-temperature, high-energy gas, providing high-quality high-energy feedstock for electric arc heating.

[0037] The thruster body 7 receives high-temperature gas from the gas generator 2 and electrical energy from the electrical connector 74. When this electrical energy passes through an electric arc formed between the cathode 77 and the anode 78, which also serves as the thrust nozzle, it is converted into thermal energy of the gas through ohmic dissipation. The gas is heated to tens of thousands of degrees Celsius, forming partially ionized gas, which is then accelerated in the nozzle expansion section, converting its thermal energy into kinetic energy. In conjunction with the swirler 76, the airflow is converted into circumferential rotation, forming a "rotating airflow sheath," making the arc discharge more stable, concentrating and uniformly distributing heat to the gas, and reducing heat loss. Correspondingly, the gas temperature and pressure decrease, ultimately ejecting as a supersonic jet, generating thrust. Because the temperature at the center of the electric arc can reach over ten thousand degrees Celsius, far exceeding the combustion temperature of the propellant in a chemical thruster, a specific impulse of 600 seconds can be achieved.

[0038] In summary, by optimizing the structure and materials of the gas generator 2 and the thruster body 7, this invention enables the arc thruster to achieve a rated specific impulse of 600s, a rated thrust of 280mN, and a lifespan of 1000 hours. This significantly improves the thruster's power, performance, lifespan, and other indicators, enabling its application in space.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A long-life, high-specific-impulse hydrazine arc thruster, characterized in that: The assembly includes a rear housing (71), a front housing (72), a gas inlet (73), an electrical connector (74), a disc spring (75), a cyclone separator (76), a cathode (77), and an anode (78). The rear housing (71) and the front housing (72) are made of different materials and are fixed together by welding. The gas inlet (73) is fixed to the rear housing (71) to introduce gas that has been catalytically decomposed from liquid anhydrous hydrazine into the rear housing (71). The electrical connector (74) is fixed to the end of the rear housing (71) to supply power to the thruster. Several disc springs are also included. A spring (75) is installed in the rear housing (71) near the electrical connector (74); a cyclone separator (76) is installed in the front housing (72) to convert the gas input from the gas interface (73) into a circumferential swirling flow; an anode (78) is welded to the front housing (72); the anode (78) is made of a tungsten-rhenium alloy with low rhenium content and doped with hafnium carbide; a throat is provided in the anode (78) and it is integrated with the nozzle; a cathode (77) has a sharp end that extends into the throat and generates an electric arc discharge between it and the anode to intensely heat the gas so that the specific impulse reaches 600s.

2. The long-life, high-specific-impulse hydrazine arc thruster according to claim 1, characterized in that: The throat diameter of the anode (78) is 0.8 mm, the length is 0.8 mm, the angle of the contraction section is 75°, and the angle of the expansion section of the nozzle is 40°; the tip angle of the cathode (77) is 50°.

3. The long-life, high-specific-impulse hydrazine arc thruster according to claim 2, characterized in that: The hydrocyclone (76) uses tungsten rhenium alloy to avoid recrystallization during long-term high-temperature operation. The part has four Φ0.7mm air inlets to convert the gas into circumferential swirling flow, so as to avoid ablation caused by long-term discharge at a fixed position.

4. The long-life, high-specific-impulse hydrazine arc thruster according to claim 3, characterized in that: The rear housing (71) and gas interface (73) are made of 4J29 expansion alloy; the front housing (72) is made of TZM molybdenum alloy material, and the rear housing (71) and the front housing (72) are connected by brazing.

5. A long-life, high-specific-impulse hydrazine arc thruster according to claim 4, characterized in that: The outer surfaces of the anode (78), the rear housing (71) and the front housing (72) are coated with a TiC-based ceramic heat dissipation coating by plasma spraying, with a coating thickness of 0.06 to 0.12 mm.

6. The long-life, high-specific-impulse hydrazine arc thruster according to claim 1, characterized in that: A catalytic bed (6) is fixedly connected to the gas interface (73) via a pipeline. The catalytic bed (6) contains 3.2g to 3.7g of 30-40 mesh catalyst and 4.8g to 5.3g of 18-24 mesh catalyst to operate for more than 1000 hours at the rated flow rate.

7. A long-life, high-specific-impulse hydrazine arc thruster according to claim 6, characterized in that: The inner diameter of the inlet of the catalytic bed (6) is 1.0 mm, and the inner diameter of the transition section is 3.0 mm.

8. A long-life, high-specific-impulse hydrazine arc thruster according to claim 7, characterized in that: A thermal control device (5) is fixedly connected to the catalyst bed (6) to heat the catalyst bed (6) to 150°C.

9. A long-life, high-specific-impulse hydrazine arc thruster according to claim 8, characterized in that: An injector (4) is fixed upstream of the catalyst bed (6). The injector (4) has several capillary tubes with an inner diameter of 1.0 mm and a wall thickness of 0.2 mm inside to improve the anti-fouling ability of the injector (4).

10. A long-life, high-specific-impulse hydrazine arc thruster according to claim 9, characterized in that: The injector (4) adopts a non-perforated support rod structure to reduce heat conduction from the catalyst bed (6) to the solenoid valve (3).

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