Probe non-contact cold-gas thruster micro-thrust rapid measurement device and method

Abstract

A non-contact probe-based micro-thrust testing device and method for cold gas thrusters includes a high-pressure gas source, a one-way valve, a flow meter, a vacuum chamber, a cold gas thruster, an ionization probe, an inverted pendulum assembly, and a host computer. The ionization probe and inverted pendulum assembly are positioned in the plume region of the cold gas thruster's ejected beam. The host computer receives the electrical signals detected by the ionization probe and generated by the inverted pendulum assembly to calculate the thruster's thrust. The high-pressure gas source, one-way valve, and flow meter are sequentially connected to the cold gas thruster via flexible hoses. The ionization probe and inverted pendulum assembly are electrically connected to the host computer. By controlling the high-pressure gas source to establish a correspondence between the magnitude of the ionization probe's electrical signal and the micro-thrust value of the cold gas thruster across its entire range, the micro-thrust value is rapidly obtained based on the actual magnitude of the ionization probe's electrical signal. This invention enables rapid and accurate thrust response, unaffected by reflected beam particles, heat, or plasma.

Description

Technical Field

[0001] This invention relates to the field of micro-thrust measurement, and in particular to a probe-based non-contact rapid measurement device and method for micro-thrust of a cold gas thruster. Background Technology

[0002] Fast-response measurement of microthrust thrust is a crucial performance indicator for drag-free control systems, directly determining the system's real-time suppression capability against non-conservative forces on the spacecraft. In ultra-high-precision missions such as space gravitational wave detection, thrust response delays can lead to compensation lag, coupling environmental disturbances into the measurement frequency band. Therefore, establishing millisecond-level dynamic thrust measurement capabilities is of decisive significance for verifying the time-varying output characteristics of microthrusters, optimizing drag-free control algorithms, and ensuring that spacecraft achieve the required ultra-static and stable environment.

[0003] Existing thrust measurement systems are mostly mainstream pendulum-type systems, which mainly involve mounting a cold gas thruster on the system. The thruster generates cold gas that is sprayed onto a target, and the target's offset, such as displacement or amplitude, is measured. Thrust and other parameters are then calculated from this displacement or amplitude information, as disclosed in Chinese Patent ZL2023110622819. However, measurements using mechanical transmission typically have response times on the order of seconds, making it difficult to achieve fast-response time measurements of thrust in micro-thrust systems. Furthermore, when cold gas thrusters are operating in space, thrust cannot be measured using a pendulum-type test setup; calculating thrust through operating parameters is susceptible to the influence of thruster instability and beam particle reflection from the target. Therefore, achieving fast-response time measurement of micro-thrust from cold gas thrusters is of great significance and importance. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned shortcomings of the prior art and provide a probe-based non-contact cold gas thruster micro-thrust rapid measurement device and method.

[0005] The technical solution of the present invention is: a probe-type non-contact cold gas thruster micro-thrust rapid measurement device, comprising a high-pressure gas source, a one-way valve, a flow meter, a vacuum chamber, a cold gas thruster, an ionization probe, an inverted pendulum assembly, and a host computer.

[0006] The high-pressure gas source is used to generate the high-speed, directional neutral particle beam required by the cold gas thruster.

[0007] The vacuum chamber is used to simulate a vacuum environment. It is hollow inside and has an air inlet at one end.

[0008] The ionization probe is installed inside the vacuum chamber and is used to detect changes in the flow field of the gas ejected from the cold gas thruster.

[0009] The inverted pendulum assembly is located inside the vacuum chamber, and under the action of the beam, the inverted pendulum assembly undergoes deflection displacement.

[0010] The host computer is used to receive the electrical signals detected by the ionization probe and the deflection displacement signal of the inverted pendulum assembly. It integrates a module for calculating the thrust of the cold gas thruster based on the electrical signals detected by the ionization probe, and a module for calculating the thrust of the cold gas thruster based on the displacement signal of the inverted pendulum assembly.

[0011] The outlet of the high-pressure gas source is connected to the inlet of the one-way valve, the outlet of the one-way valve is connected to the inlet of the flow meter, and the outlet of the flow meter is connected to the inlet of the cold gas thruster fixed in the vacuum chamber through a hose. The ionization probe and the inverted pendulum assembly are both set on the airflow path of the jet stream ejected by the cold gas thruster, and are electrically connected to the host computer through wired or wireless means respectively.

[0012] A further technical solution of the present invention is that the high-pressure air source is selected as an air pump.

[0013] A further technical solution of the present invention is as follows: the ionization probe is selected as a self-stabilizing ionization probe, including a base, a cathode, a control electrode, an accelerating electrode, and a collecting electrode. The cathode is located at the center of the base, the control electrode is spirally arranged around the cathode, the accelerating electrode is spirally arranged around the control electrode, and the collecting electrode is spirally arranged around the accelerating electrode. The control electrode, accelerating electrode, and collecting electrode are arranged concentrically. The cathode is connected to a resistor, and the other end of the resistor is grounded, forming a negative feedback loop with the control electrode.

[0014] A further technical solution of the present invention is that it also includes an ambient temperature sensor, wherein the ambient temperature sensor is selected as a PT1000 temperature sensor and is fixedly installed inside the vacuum chamber.

[0015] A further technical solution of the present invention is that the ionization probe and the inverted pendulum assembly are arranged on the central axis of the airflow path of the vacuum chamber inlet, and are equidistant from the central axis.

[0016] A further technical solution of the present invention is as follows: the process of calculating the thrust of the cold gas thruster based on the electrical signal detected by the ionization probe is as follows: during the flight of electrons from the cathode to the accelerating electrode, an electron flow phenomenon will be generated. When the temperature remains constant, the current of the collecting electrode is... I + With cathode emission current I e The proportional relationship between them satisfies the following formula: (1) in, α This is the correction factor for the cathode-emitted electron flow. β This is the correction factor for the collection efficiency of the collecting electrode pair; PThis refers to gas pressure, measured in Torr. r i This is the distance a primordial electron needs to travel in an electric field to obtain the minimum ionization energy, expressed in cm. L e The total length of the original electron flight trajectory is expressed in cm. N 0 The number of collisions between an electron and gas molecules as the electron travels 1 cm in a gas with a pressure of 1 Torr. W For ionization efficiency; When the gas is in a low pressure range, the electron free path is much larger than the electrode spacing, and formula (1) is further simplified to: (2) By organically integrating the current change information with the thrust calibration results, the thrust can be obtained. F The calculation formula is: (3) in, η This is the loss coefficient; γ Specific heat ratio; R This is the universal gas constant, with units of J / (mol·K); M The molar mass of the gas stream is expressed in kg / mol. T 0 This refers to the gas temperature, expressed in Kelvin (K). m The mass of the beam particles is expressed in kg.

[0017] A further technical solution of the present invention is: the inverted pendulum assembly is a gravity compound pendulum, the fixed end of which is mounted on the pendulum frame and the movable end is connected to the pendulum rod. The magnitude of the thrust is calculated by the deflection angle of the pendulum rod and the calibrated stiffness of the flexible pivot, and the calculation formula is as follows: (4) in, F This represents the thrust exerted on the pendulum by the thruster beam, expressed in μN. L t The thrust arm is measured in meters (m). M The mass of the inverted pendulum assembly is expressed in kg. h This represents the distance from the center of mass of the pendulum to the center of the flexible pivot, in meters (m). θ The angle of deflection of the pendulum is expressed in rad. K 0 The stiffness of the flexible pivot is calibrated.

[0018] Another technical solution provided by the present invention is: a method for measuring the micro-thrust of a probe-type non-contact cold gas thruster using a rapid measurement device, comprising the following steps: Step 1: Start the high-pressure gas source, open the check valve and flow meter. Depending on the different operating conditions of the simulated cold gas thruster, the flow rate is monitored by the flow meter to make the high-pressure gas source generate an airflow jet at a certain flow rate.

[0019] Step two: Under the action of the high-pressure gas source, the airflow beam enters the cold gas thruster of the vacuum chamber through the one-way valve and flow meter. The cold gas thruster sprays out the gas under the corresponding operating conditions, and the ionization probe and the inverted pendulum assembly detect the beam particles almost simultaneously.

[0020] Step 3: The electrical signal detected by the ionization probe and the offset angle generated by the inverted pendulum assembly under the action of the beam particles are transmitted to the host computer. The host computer records the magnitude of the electrical signal of the ionization probe under the flow rate and calculates the micro-thrust value corresponding to the displacement of the inverted pendulum assembly under the flow rate.

[0021] Step four: Change the high-pressure gas source to another flow output. According to the different operating conditions of the simulated thruster, the flow rate is monitored by the flow meter to make the high-pressure gas source generate an airflow jet under another flow rate. Repeat steps two to three to obtain the electrical signal magnitude of the ionization probe under the other flow rate and the micro-thrust value calculated by the inverted pendulum assembly.

[0022] Step 5: Repeat steps 1 to 4 above, record the magnitude of the ionization probe electrical signal and the micro-thrust value calculated by the inverted pendulum assembly across the full range of the cold gas thruster, and establish the correspondence between the magnitude of the ionization probe electrical signal and the micro-thrust value of the cold gas thruster.

[0023] Step 6: Place the cold gas thruster and ionization probe in the actual test environment, record the beam particle signal detected by the ionization probe and output it to the host computer. Based on the correspondence between the magnitude of the ionization probe electrical signal and the micro-thrust value of the cold gas thruster established in Step 5, quickly obtain the micro-thrust value of the cold gas thruster corresponding to the ionization probe.

[0024] A further technical solution of the present invention is: in the actual test environment, the ionization probe is fixedly set at the lower end of the cold gas thruster outlet at an axial distance of 1 cm to 10 cm.

[0025] A further technical solution of the present invention is that the magnitude of the electrical signal of the ionization probe is the magnitude of the electrical signal at the moment when the current of the collecting electrode of the ionization probe increases to 90% of the steady-state value after the gas flow is generated by the high-pressure gas source.

[0026] Compared with the prior art, the present invention has the following characteristics: This invention employs a probe to measure the plume electrical signal in conjunction with the ground calibration of the pendulum frame of the inverted pendulum assembly, achieving non-contact, stable micro-thrust measurement of the cold gas thruster. The probe measures the plume electrical signal, is insensitive to the heat generated by the thruster, and is unaffected by beam particles reflected from the target material, thus avoiding the influence of the heat and neutral particle beams generated by the cold gas thruster itself. The probe's response to the magnitude of the beam electrical signal is typically on the order of microseconds, enabling rapid thrust response.

[0027] The detailed structure of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0028] Figure 1 This is a structural diagram of a probe-type non-contact cold gas thruster micro-thrust rapid measurement device. Figure 2 This is a structural diagram of a self-stabilizing ionization probe; Figure 3 This is a physical model diagram of a gravitational compound pendulum. Figure 4 The graph shows the relationship between the current at the collecting electrode of the ionization probe and the thrust value of the cold gas thruster. Detailed Implementation

[0029] Example 1, as Figures 1-4 As shown, the probe-type non-contact cold gas thruster micro-thrust rapid measurement device includes a high-pressure gas source 1, a one-way valve 2, a flow meter 3, a vacuum chamber 4, a cold gas thruster 8, an ionization probe 5, an inverted pendulum assembly 6, and a host computer 7.

[0030] The high-pressure gas source 1 is typically an air pump used to generate the high-speed, directional neutral particle beam required by the cold gas thruster 8, so that the cold gas thruster 8 can be in different operating states.

[0031] The vacuum chamber 4 is used to simulate a vacuum environment. It is hollow inside and has an air inlet at one end, capable of generating a vacuum of 1.0 × 10⁻⁶. -4 A vacuum environment of Pa.

[0032] The ionization probe 5 is installed inside the vacuum chamber 4 and is used to detect changes in the flow field of the gas ejected from the cold gas thruster 8. The ionization probe 5 is selected as a four-electrode self-stabilizing ionization probe, such as... Figure 2As shown, the probe includes a base 5-1, a cathode 5-2, a control electrode 5-3, an accelerating electrode 5-4, and a collecting electrode 5-5. The cathode 5-2 is positioned at the center of the base 5-1. The control electrode 5-3 is spirally arranged around the cathode 5-2, the accelerating electrode 5-4 is spirally arranged around the control electrode 5-3, and the collecting electrode 5-5 is spirally arranged around the accelerating electrode 5-4. The control electrode 5-3, accelerating electrode 5-4, and collecting electrode 5-5 are concentrically arranged. The cathode 5-2, control electrode 5-3, accelerating electrode 5-4, and collecting electrode 5-5 are all made of fine tungsten wire with a diameter of 0.1 mm. The overall cross-sectional area of ​​the probe is approximately 0.5 mm². 2 .

[0033] A resistor (not shown in the figure) is connected to cathode 5-2, with the other end of the resistor grounded, forming a negative feedback loop with control electrode 5-3. In the actual operation of the quadrupole self-stabilizing ionization probe 5, cathode 5-2 is first heated to induce electron emission. At this time, the potential of control electrode 5-3 relative to cathode 5-2 is set to negative, effectively stabilizing the number of emitted electrons and ensuring the stability and controllability of the emission process. A stable accelerating electric field is established between accelerating electrode 5-4 and cathode 5-2, under which emitted electrons gain acceleration energy. When electrons collide with the thruster beam during flight, a series of physical reactions occur. Under specific conditions where gas temperature and electron energy remain constant, the number of positive ions generated during the collision is only related to the gas pressure. These generated positive ions are then precisely captured by collector electrode 5-5, forming the current in collector electrode 5-5. Since the time and flow rate of the jet gas ejected from the cold gas thruster 8 to reach the ionization probe 5 are not completely consistent, in order to further improve the accuracy of the detection, the electrical signal magnitude of the ionization probe 5 is set to the electrical signal magnitude at the moment when the current at the collecting electrode of the ionization probe 5 increases to 90% of the steady-state value after the gas flow is generated by the high-pressure gas source 1.

[0034] The inverted pendulum assembly 6 is housed within the vacuum chamber 4. Under the action of the beam of gas ejected from the cold gas thruster 8, the inverted pendulum assembly 6 undergoes deflection displacement. Specifically, the inverted pendulum assembly 6 is configured as a gravity compound pendulum, the physical model of which is shown in the figure below. Figure 3 As shown, the fixed end of the flexible pivot 6-1 is mounted on the pendulum frame (not shown in the figure), and the movable end is connected to the pendulum rod 6-2. The bottom of the pendulum rod 6-2 corresponds to the direction of the incoming beam gas flow, generating thrust under the action of the beam gas. F At that time, the swing arm 6-2 deflects with the center of the flexible pivot 6-1 as the support point.

[0035] The host computer 7 is used to receive the electrical signals detected by the ionization probe 5 and the displacement signals of the inverted pendulum assembly 6. It integrates a module for calculating the thrust of the cold air thruster 8 based on the electrical signals detected by the ionization probe 5, and a module for calculating the thrust of the cold air thruster 8 based on the displacement signals of the inverted pendulum assembly 6.

[0036] The process of calculating the thrust of the cold gas thruster 8 based on the electrical signal detected by the ionization probe 5 is as follows: According to Townsend theory, electrons will generate an electron flow phenomenon during their flight from the cathode 5-2 to the accelerating electrode 5-4. When the temperature remains constant, the current at the collecting electrode 5-5 is... I + With cathode 5-2 emission current I e The proportional relationship between them satisfies the following formula: (1) in, α This is the correction factor for the electron flow emitted from cathode 5-2. β The correction factor for the collection efficiency of ions at collecting electrode 5-5; P This refers to gas pressure, measured in Torr. r i This is the distance a primordial electron needs to travel in an electric field to obtain the minimum ionization energy, expressed in cm. L e The total length of the original electron flight trajectory is expressed in cm. N 0 The number of collisions between an electron and gas molecules as the electron travels 1 cm in a gas with a pressure of 1 Torr. W The ionization efficiency is given. When the gas is in a low pressure range, the electron free path is much larger than the electrode spacing, and formula (1) is further simplified to: (2) It can be seen from formula (2) that when the emission current I e When the pressure remains constant, the magnitude of the pressure P With current at collector 5-5 I + The relationship is linear; therefore, the density of neutral atoms can be indirectly indicated by the magnitude of the current at collector 5-5. Further analysis shows that by observing changes in the current at collector 5-5, the trend of beam atom density changes can be accurately determined. By organically integrating this current change information with the thrust calibration results, the thrust can be obtained. F The calculation formula is: (3) in, η The loss coefficient is set to 0.95 in this embodiment; γ The specific heat ratio is set to 1.667. R This is the universal gas constant, with units of J / (mol·K), and a value of 8.314 J / (mol·K). M The value is the molar mass of the gas flow, expressed in kg / mol, and is 0.083798 kg / mol. T 0 The value is 302.4 K, representing the gas temperature in Kelvin. m The mass of the beam particles is expressed in kg. The thrust is obtained by measuring the change in beam atomic density using a quadrupole self-stabilizing ionization probe 5 via formula (3). F The specific value.

[0037] The process of calculating the thrust of the cold gas thruster 8 based on the displacement signal of the inverted pendulum assembly 6 is as follows: By accurately measuring the deflection angle of the pendulum rod 6-2 and combining it with the calibration stiffness of the flexible pivot 6-1, the magnitude of the thrust generated by the beam gas is calculated. The calculation formula is as follows: (4) in, F 摆 This represents the thrust applied to the swing arm 6-2 by the beam of the cold air thruster 8, in μN; L t The thrust arm is measured in meters (m). M This indicates the total mass of the inverted pendulum assembly 6, expressed in kg. h This represents the distance from the center of mass of the pendulum 6-2 to the center of the flexible pivot 6-1, in meters. θ The deflection angle of the pendulum 6-2 is expressed in rad. K 0 The stiffness of the flexible pivot 6-1 is calibrated. When the oscillation amplitude of the gravity-driven pendulum 6 is small, θ ≈ sin(θ) .

[0038] The outlet of the high-pressure gas source 1 is connected to the inlet of the one-way valve 2. The outlet of the one-way valve 2 is connected to the inlet of the flow meter 3. The outlet of the flow meter 3 is connected to the inlet of the cold gas thruster 8 fixed in the vacuum chamber 4 through a hose. The ionization probe 5 and the inverted pendulum assembly 6 are both set on the airflow path of the jet of the cold gas thruster 8 and are electrically connected to the host computer 7 by wired or wireless means respectively.

[0039] In this embodiment, the mass flow rate adjustment range of the cold gas thruster 8 is set between 0.3 and 20.0 sccm. Within the small flow rate range of 0.3 to 2.0 sccm, the adjustment step size is 0.1 sccm to ensure that subtle changes in thrust within this range can be captured. When the mass flow rate exceeds 2.0 sccm, the adjustment step size is adjusted to 0.5 sccm. The entire test process covers multiple different operating conditions, providing reliable data support for a comprehensive and accurate analysis of the performance of the cold gas thruster 8. The results are shown in Table 1 below, which compares the measured values ​​of the inverted pendulum assembly 6 and the theoretical estimates of the ionization probe 5 under typical operating conditions of the cold gas thruster 8. The measured thrust value of the inverted pendulum assembly 6 is calculated by formula (4), and the theoretically estimated thrust value of the ionization probe 5 is calculated by formula (3).

[0040] Table 1. Comparison of measured values ​​and theoretical estimates of the inverted pendulum assembly under typical operating conditions. 0.3 6.91 6.76 2.22% 0.5 11.52 11.76 2.03% 0.7 16.13 15.72 2.64% 1.0 23.05 22.19 3.86% 1.3 29.96 29.35 2.06% 1.5 34.57 33.82 2.21% 2.0 46.09 44.92 2.62% 2.5 57.61 57.16 0.78% 3.0 69.14 68.18 1.40% 3.5 80.66 79.89 0.96% 4.0 92.18 89.83 2.62% 4.5 103.70 104.70 0.95% 5.0 115.23 117.64 2.05% 6.0 138.27 134.51 2.79% 7.0 161.32 157.63 2.34% 8.0 184.36 179.33 2.81% 9.0 207.41 203.06 2.14% 10.0 230.45 226.86 1.58% 12.0 276.54 275.04 0.55% 14.0 322.63 320.47 0.68% 16.0 368.73 361.56 1.98% 18.0 414.82 409.75 1.24% 20.0 460.91 459.21 0.37% Table 1 shows that the maximum error between the measured value and the theoretical estimate is 3.86%, and it decreases with increasing mass flow rate. In the low flow rate range, the error mainly comes from two parts. Firstly, the gas rarefaction effect is significant at low flow rates, increasing the molecular mean free path and causing the actual flow to deviate significantly from the ideal, thus reducing the applicability of the theoretical model. As the flow rate increases to 20.0 sccm, the error gradually decreases, indicating that the theoretical model and the calibration model match well at high flow rates. Secondly, interference factors such as hose connections in the thrust measurement device lead to errors in the measurement results, especially at low flow rates. However, despite the above limitations, the measured thrust results calculated by the inverted pendulum assembly 6 provide a relatively accurate thrust-mass flow rate mathematical model for the performance calibration of the cold gas thruster, demonstrating the excellent stability and repeatability of the cold gas thruster, and providing a basis for using the ionization probe 5 to measure the thrust of the cold gas thruster 8.

[0041] Example 2 is the same as Example 1 in basic content, except that the probe non-contact cold gas thruster micro-thrust rapid measurement device also includes an ambient temperature sensor. The ambient temperature sensor is a PT1000 temperature sensor, which is fixedly installed in the vacuum chamber 4 to measure the temperature inside the vacuum chamber 4.

[0042] Example 3 is the same as Example 1 in its basic content, except that: the probe non-contact cold gas thruster micro-thrust rapid measurement device, the ionization probe 5 and the inverted pendulum assembly 6 are set on the central axis of the airflow path of the cold gas thruster 8, and are equidistant from the central axis.

[0043] Example 4, a method for measuring the micro-thrust of a probe-based non-contact cold gas thruster using the rapid micro-thrust measurement device described in Examples 1 to 3, includes the following steps: Step 1: Start the high-pressure gas source 1, open the one-way valve 2 and the flow meter 3. According to the different operating conditions of the simulated cold air thruster 8, the high-pressure gas source 1 generates an airflow at a certain flow rate by monitoring the flow rate through the flow meter 2.

[0044] Step 2: Under the action of high-pressure gas source 1, the airflow beam enters the cold gas thruster 8 of vacuum chamber 4 through one-way valve 2 and flow meter 3. The cold gas thruster 8 ejects gas under the corresponding working conditions, and the ionization probe 5 and the inverted pendulum assembly 6 detect the beam particles almost simultaneously.

[0045] Step 3: The electrical signal detected by the ionization probe 5 and the offset angle generated by the inverted pendulum assembly 6 under the action of the beam particles are transmitted to the host computer 7. The host computer 7 records the magnitude of the electrical signal of the ionization probe 5 under the flow rate and calculates the micro-thrust value corresponding to the displacement of the inverted pendulum assembly 6 under the flow rate.

[0046] Step four: The high-pressure gas source 1 is changed to another flow output. According to the different working conditions of the simulated thruster, the flow is monitored by the flow meter 2, so that the high-pressure gas source 1 generates an airflow jet under another flow. Steps two to three are repeated to obtain the electrical signal magnitude of the ionization probe 5 under the other flow and the micro-thrust value calculated by the inverted pendulum assembly 6.

[0047] Step 5: Repeat steps 1 to 4 above, record the magnitude of the electrical signal of the ionization probe 5 and the micro-thrust value calculated by the inverted pendulum assembly 6 within the full range of the cold air thruster 8, and establish the correspondence between the magnitude of the electrical signal of the ionization probe 5 and the micro-thrust value of the cold air thruster 8.

[0048] In this embodiment, the mass flow rate adjustment range of the high-pressure gas source 1 is set between 0.3 and 20.0 sccm. Within this range, there are 54 operating conditions. Each operating condition is tested 5 times and the average value is taken. The relationship between the current of the ionization probe 5 collector and the thrust value of the cold gas thruster is obtained as follows: Figure 4 As shown.

[0049] Step 6: Place the cold gas thruster 8 and ionization probe 5 in the actual test environment, record the beam particle signal detected by the ionization probe 5 and output it to the host computer 7. Based on the correspondence between the electrical signal magnitude of the ionization probe 5 and the micro-thrust value of the cold gas thruster 8 established in Step 5, quickly obtain the micro-thrust value of the cold gas thruster 8 corresponding to the ionization probe 5.

[0050] Example 5 is the same as Example 4 in basic content, except that: in order to reduce the error in the measurement process, the ionization probe 5 is fixedly set at the lower side of the outlet of the cold gas thruster 8 in the actual test environment.

[0051] Through the combined calibration calculation of the ionization probe 5 and the inverted pendulum assembly 6, after each detection, without the need for complex calculations, the micro-thrust value of the cold gas thruster 8 can be quickly obtained simply by knowing the electrical signal of the non-contact ionization probe 5, thus realizing real-time measurement of on-orbit thrust.

Claims

1. A probe-based non-contact rapid measurement device for micro-thrust in a cold gas thruster, characterized by: It includes a high-pressure gas source, a one-way valve, a flow meter, a vacuum chamber, a cold gas thruster, an ionization probe, an inverted pendulum assembly, and a host computer; The high-pressure gas source is used to generate the high-speed, directional neutral particle beam required by the cold gas thruster. The vacuum chamber is used to simulate a vacuum environment. It is hollow inside and has an air inlet at one end. The ionization probe is installed inside the vacuum chamber and is used to detect changes in the flow field of the gas ejected from the cold gas thruster. The inverted pendulum assembly is located inside the vacuum chamber, and under the action of the beam, the inverted pendulum assembly undergoes deflection displacement; The host computer is used to receive the electrical signals detected by the ionization probe and the deflection displacement signal of the inverted pendulum assembly. It integrates a module for calculating the thrust of the cold gas thruster based on the electrical signals detected by the ionization probe, and a module for calculating the thrust of the cold gas thruster based on the displacement signal of the inverted pendulum assembly. The outlet of the high-pressure gas source is connected to the inlet of the one-way valve, the outlet of the one-way valve is connected to the inlet of the flow meter, and the outlet of the flow meter is connected to the inlet of the cold gas thruster fixed in the vacuum chamber through a hose. The ionization probe and the inverted pendulum assembly are both set on the airflow path of the jet stream ejected by the cold gas thruster, and are electrically connected to the host computer through wired or wireless means respectively.

2. The probe-type non-contact cold gas thruster micro-thrust rapid measurement device as described in claim 1, characterized in that: The high-pressure air source is selected as an air pump.

3. The probe-type non-contact cold gas thruster micro-thrust rapid measurement device as described in claim 1, characterized in that: The ionization probe is selected as a self-stabilizing ionization probe, including a base, a cathode, a control electrode, an accelerating electrode, and a collecting electrode. The cathode is located at the center of the base, the control electrode is spirally arranged around the cathode, the accelerating electrode is spirally arranged around the control electrode, and the collecting electrode is spirally arranged around the accelerating electrode. The control electrode, accelerating electrode, and collecting electrode are arranged concentrically. The cathode is connected to a resistor, and the other end of the resistor is grounded, forming a negative feedback loop with the control electrode.

4. The probe-type non-contact cold gas thruster micro-thrust rapid measurement device as described in claim 1, characterized in that: It also includes an ambient temperature sensor, which is a PT1000 temperature sensor that is fixedly installed inside the vacuum chamber.

5. The probe-type non-contact cold gas thruster micro-thrust rapid measurement device as described in claim 1, characterized in that: The ionization probe and the inverted pendulum assembly are positioned on the central axis of the airflow path at the vacuum chamber inlet, and are equidistant from the central axis.

6. The probe-type non-contact cold gas thruster micro-thrust rapid measurement device as described in claim 1, characterized in that: The process of calculating the thrust of the cold gas thruster based on the electrical signal detected by the ionization probe is as follows: During the flight of electrons from the cathode to the accelerating electrode, an electron flow phenomenon will be generated. When the temperature remains constant, the collecting electrode current... I + With cathode emission current I e The proportional relationship between them satisfies the following formula: （1） in, α This is the correction factor for the cathode-emitted electron flow. β This is the correction factor for the collection efficiency of the collecting electrode pair; P This refers to gas pressure, measured in Torr. r i This is the distance a primordial electron needs to travel in an electric field to obtain the minimum ionization energy, expressed in cm. L e The total length of the original electron flight trajectory is expressed in cm. N 0 The number of collisions between an electron and gas molecules as the electron travels 1 cm in a gas with a pressure of 1 Torr. W For ionization efficiency; When the gas is in a low pressure range, the electron free path is much larger than the electrode spacing, and formula (1) is further simplified to: （2） By organically integrating the current change information with the thrust calibration results, the thrust can be obtained. F The calculation formula is: （3） in, η This is the loss coefficient; γ Specific heat ratio; R This is the universal gas constant, with units of J / (mol·K); M The molar mass of the gas stream is expressed in kg / mol. T 0 This refers to the gas temperature, expressed in Kelvin (K). m The mass of the beam particles is expressed in kg.

7. The probe-type non-contact cold gas thruster micro-thrust rapid measurement device as described in claim 1, characterized in that: The inverted pendulum assembly is a gravity compound pendulum, with its fixed end of the flexible pivot mounted on the pendulum frame and its movable end connected to the pendulum rod. The thrust is calculated using the deflection angle of the pendulum rod and the calibrated stiffness of the flexible pivot, using the following formula: （4） in, F This represents the thrust exerted on the pendulum by the thruster beam, expressed in μN. L t The thrust arm is measured in meters (m). M The mass of the inverted pendulum assembly is expressed in kg. h This represents the distance from the center of mass of the pendulum to the center of the flexible pivot, in meters (m). θ The angle of deflection of the pendulum is expressed in rad. K 0 The stiffness of the flexible pivot is calibrated.

8. A method for measuring the micro-thrust of a probe-type non-contact cold gas thruster using the rapid measurement device according to any one of claims 1-7, characterized in that: Includes the following steps, Step 1: Start the high-pressure gas source, open the check valve and flow meter. Depending on the different operating conditions of the simulated cold gas thruster, monitor the flow rate through the flow meter to make the high-pressure gas source generate an airflow jet at a certain flow rate. Step 2: Under the action of the high-pressure gas source, the airflow beam enters the cold gas thruster of the vacuum chamber through the one-way valve and flow meter. The cold gas thruster sprays out the gas under the corresponding working conditions, and the ionization probe and the inverted pendulum assembly detect the beam particles almost simultaneously. Step 3: The electrical signal detected by the ionization probe and the offset angle generated by the inverted pendulum assembly under the action of the beam particles are transmitted to the host computer. The host computer records the magnitude of the electrical signal of the ionization probe under the flow rate and calculates the micro-thrust value corresponding to the displacement of the inverted pendulum assembly under the flow rate. Step 4: Change the high-pressure gas source to another flow output. According to the different working conditions of the simulated thruster, the flow rate is monitored by the flow meter to make the high-pressure gas source generate an airflow jet under another flow rate. Repeat steps 2 to 3 to obtain the electrical signal magnitude of the ionization probe under the other flow rate and the micro-thrust value calculated by the inverted pendulum assembly. Step 5: Repeat steps 1 to 4 above, record the magnitude of the ionization probe electrical signal and the micro-thrust value calculated by the inverted pendulum assembly within the full range of the cold gas thruster, and establish the correspondence between the magnitude of the ionization probe electrical signal and the micro-thrust value of the cold gas thruster. Step 6: Place the cold gas thruster and ionization probe in the actual test environment, record the beam particle signal detected by the ionization probe and output it to the host computer. Based on the correspondence between the magnitude of the ionization probe electrical signal and the micro-thrust value of the cold gas thruster established in Step 5, quickly obtain the micro-thrust value of the cold gas thruster corresponding to the ionization probe.

9. The method for measuring micro-thrust using the probe-based non-contact cold gas thruster rapid measurement device as described in claim 8, characterized in that: In the actual test environment, the ionization probe is fixed at the lower end of the cold gas thruster outlet at an axial distance of 1 cm to 10 cm.

10. The method for measuring micro-thrust using the probe-based non-contact cold gas thruster rapid measurement device as described in claim 8, characterized in that: The magnitude of the electrical signal of the ionization probe is the electrical signal magnitude at the moment when the current at the collecting electrode of the ionization probe increases to 90% of the steady-state value after the gas flow is generated by the high-pressure gas source.

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