Discharge chamber life estimation method based on low melting point metal ablation

Abstract

The application discloses a discharge chamber life prediction method based on low-melting-point metal ablation, and belongs to the technical field of discharge chamber life evaluation of electric propulsion. Low-melting-point metal materials are used to make experimental discharge chambers of the same size, then the limit life of the discharge chambers is measured, and a limit life database of low-melting-point metal discharge chambers corresponding to conventional material discharge chambers is established according to the limit life; when subsequent full-life experiments of other electric propulsion engineering prototypes are carried out, the information of the database is directly used to calculate the equivalent life required by the experimental thruster made of the low-melting-point metal discharge chamber when the electric propulsion device to be measured reaches the design life requirement, and then the equivalent life experiment is carried out. The application utilizes the characteristics of low-melting-point metal materials, such as low melting point, low strength and short life, to greatly reduce the experimental time and propellant consumption, and to reduce the experimental cost.

Description

Technical Field

[0001] This invention relates to the field of electric propulsion discharge chamber lifetime assessment technology, and in particular to a method for predicting discharge chamber lifetime based on the ablation of low-melting-point metals. Background Technology

[0002] Electric propulsion is an ideal propulsion system for spacecraft such as satellites, spacecraft, space stations, and deep space probes. Among electric thrusters in orbit, the vast majority of failures occur due to the lifespan failure of critical components. Therefore, verifying through ground experiments that their lifespan meets mission requirements is crucial for ensuring the normal execution of space missions.

[0003] There are many key components that limit the lifespan of electric propulsion systems. For example, hollow cathodes are lifespan-limiting components for ion thrusters and Hall thrusters; grids are lifespan-limiting components for ion thrusters and electrospray thrusters; and nozzles are key components for arc-heated thrusters. However, all electrostatic and electromagnetic electric propulsion systems have a discharge chamber. Its function is to generate plasma through ionization, providing charged working fluid for the electrostatic or electromagnetic acceleration process of electric propulsion. In some electromagnetic electric propulsion systems, the ionization and acceleration processes are coupled, and both processes occur within the discharge chamber. During operation, the discharge chamber is bombarded by high-temperature plasma. Ions with high momentum can cause ablation within the discharge chamber cylinder, damaging electrodes and insulating components, leading to discharge chamber failure. A failed discharge chamber can cause plasma leakage, short circuits, and other problems, resulting in risks such as damage to the spacecraft's power supply, plasma sputtering contamination of the spacecraft surface, and thrust failure.

[0004] Verifying the discharge chamber lifetime of an electric thruster typically requires full-life testing. The full lifetime of electric propulsion usually ranges from 2000 to 20000 hours. Conducting these tests consumes significant amounts of water and electricity to maintain and cool the vacuum environment simulation equipment. Some electric propulsion systems using rare gases also require large quantities of rare gases such as xenon and argon, resulting in high time and economic costs. Currently, many electric thrusters with long-life and high-power requirements are constrained by the limitations of ground-based testing equipment and the economic capacity of participating research units, preventing full-life testing. Only partial-life testing is possible, assessing the feasibility of on-orbit application by examining the wear and tear of key components. For example, examining whether the erosion depth of electrodes and grids in the discharge chamber is less than the proportion of the test time to the total lifetime is crucial. However, the erosion rate of key components under plasma bombardment is not constant; the erosion rate of already eroded areas typically increases, reducing the reliability of electric thruster lifetime verification. Therefore, an effective equivalent testing method is urgently needed to provide a more reliable lifetime verification method while maintaining lower experimental costs. Summary of the Invention

[0005] The purpose of this invention is to provide a method for estimating the lifetime of a discharge chamber based on the ablation of low-melting-point metals, thereby improving the problems of long experimental time and high costs of water, electricity and propellants when directly conducting full-life experiments of electric propulsion. By utilizing the low melting point properties of lead, tin, zinc and bismuth, a discharge chamber of the same size can be made using these materials for lifetime experiments, which will significantly shorten the time of the full-life experiment, thereby reducing the cost and time consumption of the experiment.

[0006] To achieve the above objectives, the present invention provides a method for predicting the lifetime of a discharge chamber based on the ablation of low-melting-point metals, comprising the following steps: S1. Select a conventional electric thruster A1 with known ultimate life and life termination conditions; process a discharge chamber metal component made only of low-melting-point metal that serves only a structural and conductive function; assemble the metal component with other components in the discharge chamber to form a low-melting-point metal discharge chamber. S2. Perform an extreme life test on the electric thruster A2 equipped with the low melting point metal discharge chamber, record the circuit parameters and discharge characteristics in real time during the experiment, determine whether the electric thruster A2 has reached its extreme life, record the corresponding life data, and establish a database; the database stores the correspondence between the extreme life of the low melting point metal discharge chamber electric thruster A2 and the known extreme life of the conventional electric thruster A1. S3. Select a product life data set from the database that is of the same type and similar in size to the conventional electric propulsion experimental prototype B1 under test, and calculate the lifespan of the corresponding low-melting-point metal discharge chamber electric propulsion prototype B2 when the conventional electric propulsion experimental prototype B1 reaches its design lifespan. T B2 ; S4. Process the low-melting-point metal discharge chamber corresponding to the prototype under test according to the method of S1, and assemble it to form the low-melting-point metal discharge chamber electric thruster prototype B2. Repeat the limit life test of S2. The test termination condition is: the low-melting-point metal discharge chamber electric thruster prototype B2 reaches the limit life or the test duration reaches the life duration required for the low-melting-point metal discharge chamber electric thruster prototype B2. T B2 ; S5. If the prototype's testing time reaches T B2 If the lifespan of the test sample meets the standard, it is determined that the lifespan of the sample meets the standard; if it does not meet the standard... T B2 If the prototype reaches its lifespan limit, it is determined that the prototype's lifespan has not met the standard.

[0007] Preferably, in S1, other components include metal oxide ceramic structural parts that serve as insulation, magnetic nozzles that generate a confining magnetic field, magnetic cylinders, excitation coil assemblies, and emitters and heating coils with special functions in the main hollow cathode for emitting electrons; the other components must not be replaced by low-melting-point metal parts.

[0008] Preferably, in S1, the low-melting-point metal is selected from one or more of lead, tin, zinc, and bismuth.

[0009] Preferably, in S2, the circuit parameters and discharge characteristics include discharge voltage, current waveform, plume image, ignition success rate, and whether arcing breakdown occurs.

[0010] Preferably, in S2, the criterion for determining whether the electric thruster A2 has reached its limit lifespan is: If it is an ion thruster, the criteria for judgment are a significant decrease in beam current, grid breakdown or burn-through; If it is a pulsed plasma thruster, the criteria for judgment are short-circuit ignition failure or ignition success rate reduced to below 50%; If it is a magnetic plasma thruster, the criteria for judgment are the loss of thrust and the attenuation of discharge current caused by electrode burn-through.

[0011] Preferably, in S3, the calculation formula is as follows: ; in, This indicates the required lifespan of the low-melting-point metal discharge chamber electric thruster prototype B2. This indicates the minimum lifespan requirement specified in the design specifications for the B1 conventional electric propulsion experimental prototype. This represents the measured ultimate lifespan of electric thruster A2, a type of low-melting-point metal discharge chamber in the database. This indicates the publicly available maximum lifespan of the A1 conventional electric thruster of the same type in the database; If the database contains multiple sets of product data that are the same type and similar in size to the prototype, calculate the corresponding data for each set. The maximum value is selected as the target data.

[0012] Preferably, in S4, during the test, diagnostic equipment is used to detect the failure mode of the experimental prototype. The diagnostic equipment includes a laser displacement sensor and a multimeter. The laser displacement sensor is used to scan the morphology of the ablation end face and the morphology of the deposits, and the multimeter is used to detect the location of the short circuit.

[0013] Preferably, in S5, if the prototype's lifespan reaches the design target, the prototype's discharge chamber is checked for areas with high failure risk, and redundant design is implemented to improve the product's redundant lifespan; if the prototype's lifespan does not meet the target, the lifespan failure modes are analyzed, optimization is performed for the failure modes, and the experiment is repeated until the target is met.

[0014] Therefore, the present invention employs the above-mentioned method for predicting the lifetime of a discharge chamber based on the ablation of low-melting-point metals, which has the following beneficial effects: 1) Taking advantage of the low melting point and poor ablation resistance of metals such as tin, lead, and zinc, the ultimate life of the thruster is estimated by using a discharge chamber of the same size made of these materials, which effectively shortens the duration of the full life experiment; reduces the power consumption of the vacuum chamber and the consumption of cooling water during the experiment, and lowers the economic cost.

[0015] 2) By conducting extreme life tests on low-melting-point metal discharge chambers of the same size and conventional electric propulsion discharge chambers, and establishing a database of the experimental results, reference data can be provided for subsequent life tests of similar electric propulsion systems. Subsequent experiments only need to use low-melting-point metal discharge chambers for shorter full-life tests to verify their reliability.

[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0017] Figure 1 This is a flowchart of the technical solution of an embodiment of the present invention; Figure 2 This refers to the ablation quality and ablation volume ratio of the lead-based discharge chamber assembly and the copper-based discharge chamber assembly in this embodiment of the invention. Detailed Implementation

[0018] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0019] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0020] Example 1 This invention provides a method for predicting the lifetime of a discharge chamber based on the ablation of low-melting-point metals. The technical solution process is as follows: Figure 1 As shown, it includes the following steps: S1. Select a conventional electric thruster A1 with known ultimate life and life-end conditions; fabricate a discharge chamber metal component made solely of low-melting-point metals, serving only structural and conductive functions; assemble this metal component with other components in the discharge chamber to form a low-melting-point metal discharge chamber; low-melting-point metals include lead, tin, zinc, and bismuth. Other components, including insulating metal oxide ceramic structural parts, magnetic nozzles generating confining magnetic fields, magnetic cylinders, excitation coil assemblies, and emitters with special functions in the main hollow cathode for emitting electrons, heating coils, etc., must not be replaced with low-melting-point metal components.

[0021] It should also be noted that, since low-melting-point metals generally have low hardness, low-melting-point metal materials should be carefully selected when manufacturing components that require a certain structural strength. For example, the grid of an ion thruster is a multi-faceted grid, usually a dual-grid grid, but there are also triple-grid or quadruple-grid grids. During operation, it is necessary to ensure that each beam aperture is aligned. This requires that the grid has a certain rigidity during transportation and assembly, so that it will not deform due to the torque of the screws used in the operating procedures or the pressure of the hands of researchers when handling it. Therefore, it is not advisable to use lead, which is too soft, but rather to choose a lower-melting-point metal such as tin, which is harder.

[0022] S2. Perform an extreme life test on the electric thruster A2 equipped with the low melting point metal discharge chamber, and record the circuit parameters and discharge characteristics during the experiment in real time, such as the discharge voltage, current waveform, plume image, ignition success rate (applicable to pulse electric propulsion), whether arcing and breakdown occur, etc. Based on this information, determine whether the electric thruster A2 has reached its extreme life, record the corresponding life data, and terminate the experiment in time to avoid damage to the power supply equipment.

[0023] The criteria for determining whether electric thruster A2 has reached its lifespan limit are as follows: for ion thrusters, the criteria are a significant decrease in beam current, grid breakdown, or burn-through; for pulsed plasma thrusters, the criteria are short-circuit ignition failure or a ignition success rate reduced to below 50%; for magnetoplasm thrusters, the criteria are electrode burn-through leading to thrust loss and discharge current decay. After recording the lifespan data, a database was established, storing the correspondence between the lifespan limit of the low-melting-point metal discharge chamber electric thruster A2 and the known lifespan limit of the conventional electric thruster A1, providing a reference for subsequent experiments.

[0024] S3. Select a product life data set from the database that is of the same type and similar in size to the conventional electric propulsion experimental prototype B1 under test, and calculate the lifespan of the corresponding low-melting-point metal discharge chamber electric propulsion prototype B2 when the conventional electric propulsion experimental prototype B1 reaches its design lifespan. T B2 The calculation formula is as follows: ; in, This indicates the required lifespan of the low-melting-point metal discharge chamber electric thruster prototype B2. This indicates the minimum lifespan requirement specified in the design specifications for the B1 conventional electric propulsion experimental prototype. This represents the measured ultimate lifespan of electric thruster A2, a type of low-melting-point metal discharge chamber in the database. This indicates the publicly available maximum lifespan of the A1 conventional electric thruster of the same type in the database.

[0025] If the database contains multiple sets of product data that are of the same type and similar in size to the sample under test, calculate the corresponding data for each set. The maximum value is selected as the target data. In summary, the conditions for the tested electric thruster to meet the lifespan standard are: ; In the formula, This indicates the maximum lifespan that a prototype using low-melting-point metal electrodes can achieve in experiments.

[0026] In S3, the equipment typically required includes a product prototype converted into a low-melting-point metal discharge chamber, a vacuum environment simulation system, a power supply and ignition control system, gas working fluid supply and flow measurement equipment, voltage and current probes and oscilloscopes, camera equipment, and tools required for installation and maintenance. The vacuum environment simulation system typically includes a single-stage or multi-stage vacuum environment simulation chamber, a multi-stage vacuum pump set, control equipment, and a cooling system.

[0027] S4. Process the low-melting-point metal discharge chamber corresponding to the prototype under test according to the method of S1, and assemble it to form the low-melting-point metal discharge chamber electric thruster prototype B2. Repeat the limit life test of S2. The test termination condition is: the low-melting-point metal discharge chamber electric thruster prototype B2 reaches the limit life or the test duration reaches the life duration required for the low-melting-point metal discharge chamber electric thruster prototype B2. T B2 During the testing process, diagnostic equipment was used to detect the failure modes of the experimental prototype. The diagnostic equipment included a laser displacement sensor and a multimeter. The laser displacement sensor was used to scan the morphology of the ablation end face and the deposit morphology, and the multimeter was used to detect the location of short circuits, etc., to specifically detect the failure modes of the experimental prototype.

[0028] S5. If the prototype's testing time reaches T B2 If the prototype's lifespan is within the acceptable range, then it is determined that the prototype's lifespan meets the standard; if T B2 If the prototype reaches its lifespan limit, it is determined that the prototype's lifespan has not met the standard. If the prototype's lifespan meets the design target, the discharge chamber of the prototype is checked for areas with high failure risk, and redundancy design is implemented to improve the product's redundant lifespan. If the prototype's lifespan does not meet the standard, the failure modes are analyzed, optimization is performed for the failure modes, and the experiment is repeated until the standard is met.

[0029] Based on the above method, this embodiment further conducted experimental verification. A linear working fluid pulsed plasma thruster was selected for the experiment, using copper and lead as ablation materials respectively. Ablation experiments were conducted under the same operating conditions, and the ablation mass of the copper and lead discharge chamber components under different operating voltages was measured. The ratio of their ablation volumes was calculated accordingly. The results are as follows: Figure 2 As shown.

[0030] The results show that the ablation quality of lead, with its lower melting point, is significantly higher than that of copper working fluid under different operating voltages. At operating voltages of 1200V, 1350V, and 1500V, the ablation volume of lead is 9.58, 16.58, and 13.36 times that of copper, respectively. Since the ablation ratios differ under different operating voltages, it is necessary to measure the loss rate ratio of the ionization chamber material for different operating voltages in actual experiments.

[0031] The experiment verified the feasibility of using low-melting-point metal materials to accelerate the lifetime assessment of the discharge chamber, and showed that the ablation ratio under different working conditions is not universal. Therefore, it is necessary to establish a comparative database of the ultimate lifetime of low-melting-point discharge chambers and conventional discharge chambers under different working conditions.

[0032] Therefore, the present invention adopts the above-mentioned method for estimating the lifetime of a discharge chamber based on the ablation of low-melting-point metals. It utilizes the inherent properties of low-melting-point metals to create a short-life electric propulsion discharge chamber. By conducting extreme lifetime experiments on low-melting-point metal discharge chambers of the same size and conventional electric propulsion discharge chambers, and establishing a database of experimental results, the present invention provides reference data for subsequent lifetime experiments of similar electric propulsion systems, effectively shortening the duration of the full lifetime experiment and reducing economic costs.

[0033] 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 preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for predicting the lifetime of a discharge chamber based on the ablation of low-melting-point metals, characterized in that, Includes the following steps: S1. Select a conventional electric thruster A1 with known ultimate life and life termination conditions; process a discharge chamber metal component made only of low-melting-point metal that serves only a structural and conductive function; assemble the metal component with other components in the discharge chamber to form a low-melting-point metal discharge chamber. S2. Perform an extreme life test on the electric thruster A2 equipped with the low melting point metal discharge chamber, record the circuit parameters and discharge characteristics in real time during the experiment, determine whether the electric thruster A2 has reached its extreme life, record the corresponding life data, and establish a database; the database stores the correspondence between the extreme life of the low melting point metal discharge chamber electric thruster A2 and the known extreme life of the conventional electric thruster A1. S3. Select a product life data set from the database that is of the same type and similar in size to the conventional electric propulsion experimental prototype B1 under test, and calculate the lifespan of the corresponding low-melting-point metal discharge chamber electric propulsion prototype B2 when the conventional electric propulsion experimental prototype B1 reaches its design lifespan. T B2 ; S4. Process the low-melting-point metal discharge chamber corresponding to the prototype under test according to the method of S1, assemble it to form the low-melting-point metal discharge chamber electric thruster prototype B2, and repeat the limit life test of S2. The test termination condition is: the low-melting-point metal discharge chamber electric thruster prototype B2 reaches the limit life or the test duration reaches the life duration required for the low-melting-point metal discharge chamber electric thruster prototype B2. T B2 ; S5. If the prototype's testing time reaches T B2 If the lifespan of the test sample meets the standard, it is determined that the lifespan of the sample meets the standard; if it does not meet the standard... T B2 If the prototype reaches its lifespan limit, it is determined that the prototype's lifespan has not met the standard.

2. The method for predicting the lifetime of a discharge chamber based on the ablation of low-melting-point metals according to claim 1, characterized in that, In S1, other components include metal oxide ceramic structural parts that serve as insulation, magnetic nozzles that generate a confining magnetic field, magnetic cylinders, excitation coil assemblies, and emitters and heating coils with special functions in the main hollow cathode for emitting electrons; these other components must not be replaced by low-melting-point metal parts.

3. The method for predicting the lifetime of a discharge chamber based on the ablation of low-melting-point metals according to claim 1, characterized in that, In S1, the low-melting-point metal is selected from one or more of lead, tin, zinc, and bismuth.

4. The method for predicting the lifetime of a discharge chamber based on the ablation of low-melting-point metals according to claim 1, characterized in that, In S2, the circuit parameters and discharge characteristics include discharge voltage, current waveform, plume image, ignition success rate, and whether arcing breakdown occurs.

5. The method for predicting the lifetime of a discharge chamber based on the ablation of low-melting-point metals according to claim 4, characterized in that, In S2, the criterion for determining whether the electric thruster A2 has reached its limit lifespan is: If it is an ion thruster, the criteria for judgment are a significant decrease in beam current, grid breakdown or burn-through; If it is a pulsed plasma thruster, the criteria for judgment are short-circuit ignition failure or ignition success rate reduced to below 50%; If it is a magnetic plasma thruster, the criteria for judgment are the loss of thrust and the attenuation of discharge current caused by electrode burn-through.

6. The method for predicting the lifetime of a discharge chamber based on the ablation of low-melting-point metals according to claim 1, characterized in that, In S3, the calculation formula is as follows: ； in, This indicates the required lifespan of the low-melting-point metal discharge chamber electric thruster prototype B2. This indicates the minimum lifespan requirement specified in the design specifications for the B1 conventional electric propulsion experimental prototype. This represents the measured ultimate lifespan of electric thruster A2, a type of low-melting-point metal discharge chamber in the database. This indicates the publicly available maximum lifespan of the A1 conventional electric thruster of the same type in the database; If the database contains multiple sets of product data that are the same type and similar in size to the prototype, calculate the corresponding data for each set. The maximum value is selected as the target data.

7. The method for predicting the lifetime of a discharge chamber based on the ablation of low-melting-point metals according to claim 1, characterized in that, In S4, diagnostic equipment is used to detect the failure mode of the experimental prototype during the test. The diagnostic equipment includes a laser displacement sensor and a multimeter. The laser displacement sensor is used to scan the morphology of the ablation end face and the morphology of the deposits, and the multimeter is used to detect the location of the short circuit.

8. The method for predicting the lifetime of a discharge chamber based on the ablation of low-melting-point metals according to claim 1, characterized in that, In S5, if the prototype's lifespan reaches the design target, the system checks whether there are high-risk areas for failure in the prototype's discharge chamber and implements redundant design to improve the product's redundant lifespan. If the prototype's lifespan does not meet the target, the system analyzes the failure modes, optimizes the failure modes, and repeats the experiment until the target is met.

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