Ultra-stable thermal environment simulator for spacecraft ground test

Abstract

The invention discloses an ultra-stable thermal environment simulator for a spacecraft ground test, which adopts a layered structure, coatings with different emissivity are arranged on the inner surface and the outer surface of each layer, a plurality of radiators are uniformly arranged between the two outermost layers at intervals, the heat absorption surface of each radiator is arranged on the inner layer of the two outermost layers, and the heat absorption surface of each radiator is arranged on the outer layer of the two outermost layers. A heat dissipation surface of the ultra-stable thermal environment simulator penetrates through two outermost outer layers to be exposed outside, an active heat compensator is arranged in the middle of the ultra-stable thermal environment simulator, and each active heat compensator is used for adjusting the heat sink temperature of the ultra-stable thermal environment simulator and restraining thermal disturbance from the outside. Through optimization design, the temperature stability, uniformity and adjustability of the heat sink are improved, so that the thermal boundary simulation precision of the spacecraft assembly is remarkably improved, more accurate thermal management and temperature control are ensured to be realized in a harsh spaceflight environment, and the reliability and stability of spacecraft equipment are effectively guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of spacecraft ground test equipment, and in particular to an ultra-stable thermal environment simulator for spacecraft ground tests. Background Art

[0002] Spacecraft ground vacuum thermal testing is one of the key steps in the spacecraft design process. This type of test can verify the function of spacecraft products, check the manufacturing process, and discover potential early failure problems of equipment in a simulated space vacuum and ultra-low temperature environment. In the process of spacecraft development, both the identification-level thermal vacuum test at the prototype stage and the acceptance-level thermal vacuum test before launch are indispensable and important links. These tests play a vital role in ensuring the reliability and stability of spacecraft in extreme space environments.

[0003] The main equipment for thermal vacuum testing is a vacuum tank, also known as a thermal environment simulator, which can simulate the vacuum and extreme hot and cold environments in outer space, and accurately control, monitor and record the vacuum degree and test piece temperature. The structure of the vacuum tank usually includes a vacuum container, an exhaust system, a temperature assurance system (including a test platform), an equipment control and monitoring system, and an auxiliary system. The heat sink maintains its temperature through liquid nitrogen circulation to simulate extreme temperature conditions in space. However, liquid nitrogen circulation may cause temperature fluctuations, affect the stability of the heat sink, and produce temperature gradients, reducing the test accuracy. In order to meet the high-precision requirements, Qi Songsong and others designed a dedicated temperature-controlled heat sink in 2020, combined with a heater and a temperature control system, to achieve a temperature control accuracy of ±0.5°C. However, for spacecraft that require μK-level temperature control accuracy, such as gravitational wave detection satellites, this accuracy still poses great challenges, limiting the improvement of the accuracy of thermal tests on precision spacecraft.

[0004] The current thermal environment simulator based on circulating liquid nitrogen vacuum tank heat sink has many shortcomings and challenges:

[0005] 1) Insufficient heat sink temperature stability

[0006] The implementation method of vacuum tank heat sink is mainly to maintain the heat sink temperature by circulating liquid nitrogen. This method can simulate the extreme temperature conditions in space, but because the circulation of liquid nitrogen will cause temperature fluctuations, the heat sink temperature will fluctuate greatly, which will affect the accuracy of simulating the real thermal environment.

[0007] 2) Poor uniformity of heat sink temperature

[0008] Since the distribution of pipes in the vacuum tank is difficult to be completely uniform and the heat exchange is uneven during the liquid nitrogen circulation process, there is a significant gradient in the heat sink temperature on a large scale, which affects the simulation accuracy of the thermal boundary of the spacecraft components.

[0009] 3) Heat sink temperature cannot be adjusted

[0010] The temperature of the heat sink in the vacuum tank depends on the temperature of liquid nitrogen (about -180°C) and has no temperature regulation capability. It cannot meet the thermal environment simulation requirements of some space probe instruments (most of which require an ambient temperature of 0 to 25°C), and requires additional thermal environment simulation components, which increases the complexity and cost of the test. Summary of the invention

[0011] The present invention provides an ultra-stable thermal environment simulator for ground testing of spacecraft, aiming to solve technical problems in the prior art such as heat sink temperature fluctuation, excessive gradient and unadjustable heat sink temperature caused by uneven pipeline distribution and uneven heat exchange.

[0012] The present invention can be achieved through the following technical solutions:

[0013] An ultra-stable thermal environment simulator for spacecraft ground tests adopts a layered structure, wherein the inner and outer surfaces of each layer are provided with coatings of different emissivity, and a plurality of radiators are evenly spaced between the two outermost layers, wherein the heat absorption surface of each radiator is provided in the inner layer of the two outermost layers, and the heat dissipation surface thereof passes through the outer layers of the two outermost layers and is exposed to the outside, and an active heat compensator is provided in the middle thereof.

[0014] Each of the active thermal compensators is used to adjust the heat sink temperature of the ultra-stable thermal environment simulator and suppress thermal disturbances from the outside.

[0015] Furthermore, the heat dissipation surface of each radiator passes through the outer layers of the two outermost layers and directly faces the vacuum tank heat sink. The number of radiators is determined using the following formula:

[0016]

[0017] Where n is the number of radiators, Q is the heat dissipation capacity of the ultra-stable thermal environment simulator, and S i is the heat dissipation area of ​​the ith radiator, and σ is the Stefan-Boltzmann constant 5.67e -8 , ε is the emissivity, T0 is the heat sink temperature of the vacuum tank, T r is the target temperature.

[0018] Furthermore, the axial cross-section of each radiator is set to an I-shaped structure, and its heat absorption surface and heat dissipation surface both adopt a circular structure. Their center positions are connected together through a column structure, and the corresponding active thermal compensator is arranged on the column structure.

[0019] Furthermore, the active heat compensator uses a PID control algorithm to achieve temperature control. The specific control function is as follows:

[0020]

[0021] Where u is the controller output command, e(t) is the difference function between the current temperature and the target temperature, Kp, KI, and KD are the proportional coefficient, integral coefficient, and differential coefficient, respectively.

[0022] Furthermore, the ultra-stable thermal environment simulator adopts a three-layer structure, which is sequentially referred to as the first layer, the second layer and the third layer from the outside to the inside.

[0023] The outer surface of the first layer is provided with a low emissivity coating, and the inner surface is provided with a high emissivity coating; the outer surface of the second layer is provided with a low emissivity coating, and the inner surface is provided with a high emissivity coating; and both the inner and outer surfaces of the third layer are provided with high emissivity coatings.

[0024] Furthermore, each level of the ultra-stable thermal environment simulator is installed in a heat-insulating manner.

[0025] The beneficial technical effects of the present invention are:

[0026] The ultra-stable thermal environment simulator developed by the present invention is suitable for spacecraft components that require extremely high temperature control accuracy. The ultra-stable thermal environment simulator is based on a multi-layer structure, which effectively suppresses external thermal disturbances by optimizing the thermal radiation characteristics of each layer; at the same time, a cross-layer adaptive radiator is designed to achieve efficient internal heat dissipation; in addition, an active thermal compensator is set on the radiator, which can accurately adjust the temperature scale and temperature gradient of the heat sink to ensure the temperature control stability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the overall structure of the ultra-stable thermal environment simulator of the present invention;

[0028] Figure 2 It is a schematic diagram of a multi-layer structure thermal network model of the present invention;

[0029] Figure 3 It is a schematic diagram of the radiation characteristics of the three-layer structure of the present invention;

[0030] Figure 4 It is a structural schematic diagram of the cross-level adaptive radiator of the present invention;

[0031] Figure 5 Schematic diagram of steady-state temperature distribution of the third layer in the non-temperature-controlled object embodiment of the present invention;

[0032] Figure 6 It is a schematic diagram of the temperature change of the heat sink of the vacuum tank in the non-temperature-controlled object embodiment of the present invention;

[0033] Figure 7 It is a schematic diagram of the instantaneous temperature fluctuation curve of the third layer in the embodiment of the non-temperature-controlled object of the present invention;

[0034] Figure 8 It is a schematic diagram of the temperature field distribution of the controlled object in the embodiment of the temperature-controlled object of the present invention;

[0035] Fig. 9 It is a schematic diagram of the temperature field distribution of the third layer in the embodiment of the temperature-controlled object of the present invention;

[0036] Fig.10 It is a schematic diagram of an instantaneous temperature fluctuation curve of a controlled object in an embodiment of a temperature-controlled object of the present invention;

[0037] Fig.11 Schematic diagram of instantaneous temperature fluctuation curve of the third layer in the temperature-controlled object embodiment of the present invention. DETAILED DESCRIPTION

[0038] The specific implementation of the present invention is described in detail below with reference to the accompanying drawings and preferred embodiments.

[0039] Aiming at the thermal disturbance and temperature gradient problems faced by vacuum tank heat sinks, such as Figure 1 As shown, the present invention provides an ultra-stable thermal environment simulator for ground tests of spacecraft, which adopts a layered structure, and the inner and outer surfaces of each layer are provided with coatings of different emissivity, and a plurality of radiators are evenly spaced between the two outermost layers, and the heat absorption surface of each radiator is provided in the inner layer of the two outermost layers, and its heat dissipation surface passes through the outer layers of the two outermost layers and is exposed to the outside, and an active thermal compensator is provided in the middle, and each active thermal compensator is used to adjust the heat sink temperature of the ultra-stable thermal environment simulator and suppress thermal disturbances from the outside. In this way, through the multi-layer structure and radiation heat exchange regulation, external thermal disturbances are suppressed step by step, and the internal temperature of the simulator is effectively kept stable, and the internal heat is dissipated to the external heat sink through the radiator, realizing precise temperature control and thermal management.

[0040] The details are as follows:

[0041] 1. Multi-layer structure design based on different radiation characteristics

[0042] The ultra-stable thermal environment simulator adopts a three-layer structure, which is the first, second and third layers from the outside to the inside. It gradually suppresses the thermal disturbance from the outside (vacuum tank heat sink) while taking into account the heat dissipation efficiency. Its thermal network model is as follows: Figure 2 shown.

[0043] The transfer function relationship between the vacuum tank heat sink temperature T0 and the third layer temperature T3 is as follows:

[0044]

[0045] The amplitude-frequency characteristic is:

[0046]

[0047] The phase-frequency characteristic is:

[0048]

[0049] in:

[0050] a=(R1C1ω+R1C2ω+R1C3ω+R2C2ω+R2C3ω+R3C3ω)-R1C1R2C2R3C3ω 3

[0051] b=(1-(R1C1R2C2+R1C1R2C3+R1C1R3C3+R2C2R3C3+R3C3R1C2)ω 2 )

[0052] From the above calculation formula, it can be seen that when the fluctuation amplitude of the temperature T0 with a frequency of ω is transmitted to the third layer, the temperature fluctuation amplitude is attenuated to the original |H(jω)| (hereinafter referred to as the attenuation ratio), and its specific value is determined by the system parameter RC and the signal frequency ω. When the specific structural size parameters of the ultra-stable environment simulator are clear, the anti-interference characteristics of the simulator can be designed by adjusting the thermal resistance R between the layers, such as Figure 3 In order to improve the temperature uniformity of the simulator, further suppress the thermal disturbance from the outside, and effectively reduce the temperature gradient in the simulator space, the installation method between each level adopts thermal insulation installation to reduce direct heat conduction.

[0053] The radiation characteristics of each layer are designed as follows:

[0054] 1) A low-emissivity coating is designed on the outer surface of the first layer to reduce thermal disturbance from the heat sink of the vacuum tank, and a high-emissivity coating is designed on the inner surface to improve the temperature uniformity of the second layer structure;

[0055] 2) The outer surface of the second layer is designed with a low-emissivity coating to further reduce thermal disturbances from the outside, and the inner surface is designed with a high-emissivity coating to improve the temperature uniformity of the third layer structure;

[0056] 3) A high emissivity coating is designed on the outer surface of the third layer to enhance the heat exchange between the third layer and the second layer, and a high emissivity coating is designed on the inner surface to further improve the heat dissipation efficiency inside the simulator.

[0057] In this way, the large-scale effect of radiation heat transfer is used to build a uniform thermal environment for the second and third layers. A high-emissivity coating is designed on the inner surface of the first layer to optimize the uniformity of radiation heat transfer between the first and second layers; a high-emissivity coating is designed on the inner surface of the second layer to optimize the uniformity of radiation heat transfer between the second and third layers; and a high-emissivity coating is designed on both the inner and outer surfaces of the third layer to enhance the heat transfer efficiency between the simulator and the second layer and improve the heat dissipation capacity.

[0058] 2. Cross-level adaptive radiator design

[0059] Although the hierarchical ultra-stable thermal environment simulator structure can effectively suppress thermal disturbances from the outside, it cannot dissipate the heat inside the environment simulator. To address this problem, a cross-layer radiator is designed, with the heat absorption section installed on the second layer, and the heat dissipation end crossing the first layer directly facing the vacuum tank heat sink to dissipate the heat.

[0060] The cross-level adaptive radiator is shaped like Figure 4 As shown, its axial cross section is set to an I-shaped structure, and its heat absorption surface and heat dissipation surface are both circular structures, and their center positions are connected together by a column structure. It can be divided into three parts: top, middle, and bottom, and the material is a high thermal conductivity metal (such as copper). The outer surface of the top is designed with a high emissivity coating as a heat dissipation surface, and the outer surfaces of the remaining parts are heat-insulated, and the bottom is installed on the second layer as a heat absorption surface. The top crosses the first layer and directly faces the vacuum tank heat sink to dissipate the heat.

[0061] The total area of ​​the heat dissipation surface of the radiator determines the total heat dissipation capacity of the ultra-stable thermal environment simulator. The specific calculation formula is as follows:

[0062]

[0063] Where n is the number of radiators, Q is the heat dissipation capacity of the thermal environment simulator, S i is the heat dissipation area of ​​the ith radiator, and σ is the Stefan-Boltzmann constant 5.67e -8 , ε is the emissivity, T0 is the temperature of the vacuum tank heat sink, such as -180℃, T r is the target temperature.

[0064] Number of radiators n and heat dissipation area S i It can be designed according to the requirements. In general, as the number n increases, the temperature gradient of the entire simulator heat sink decreases; as the radiator heat dissipation area Si increases, the heat dissipation efficiency of the simulator will gradually increase.

[0065] 3. Active thermal compensator

[0066] Active thermal compensators are designed in the middle of the cross-level adaptive radiators. On the one hand, they can adjust the temperature value of the heat sink of the thermal environment simulator, and on the other hand, they can suppress thermal disturbances from the outside.

[0067] The PID control algorithm is used in combination with the nearby temperature sensor to form a closed-loop control to improve the system's adaptability. The specific control function is as follows:

[0068]

[0069] Where u is the controller output command, e is the difference between the current temperature and the target temperature, Kp, KI, and KD are the proportional coefficient, integral coefficient, and differential coefficient, respectively.

[0070] 4. Simulation verification

[0071] Taking the KM2.5 vacuum tank as an example, the designed ultra-stable environment simulator is as follows Figure 1 As shown in the figure, the dimensions of the first, second and third layers are 2m×2m×1m, 1.9m×1.9m×0.9m and 1.8m×1.8m×0.8m respectively. There are 16 cross-level radiators, and the radius of the heat dissipation surface of the radiator is 0.2m.

[0072] 1) No temperature control object

[0073] In the simulation calculation, the temperature fluctuation curve of the vacuum tank heat sink is set as follows Figure 6 As shown in Figure 1, the temperature fluctuation range is -183 to -177°C. The temperature control target of the radiator thermal compensator is set to 20°C. After the system is stable, the temperature field distribution of the simulator heat sink (third layer) is as follows: Figure 5 As shown in Figure 1, the temperature range is 19.63-19.66°C, and the temperature gradient is less than 0.1°C. The instantaneous temperature fluctuation curve of the third layer is shown in Figure 1. Figure 7 As shown in the figure, the temperature fluctuation amplitude is less than 0.001°C, which is very stable. This shows that even under the condition of large disturbance of the vacuum tank heat sink, the ultra-stable thermal environment simulator can achieve high temperature stability and temperature uniformity.

[0074] 2) There is a temperature control object

[0075] A temperature control object is placed in the ultra-stable environment simulator. The size is 1m×1m×0.6m, the material is aluminum alloy, the outer surface emissivity is 0.85, and the heat source of the temperature control object itself is 20W. Figure 6 Similarly, after the system stabilizes, the temperature field distribution of the controlled object and the third layer is as follows: Figure 8 , 9 As shown, the temperature range of the controlled object is 19.17~19.21℃, and the temperature gradient is less than 0.1℃; the temperature range of the third layer is 15.71~16.39℃, and the temperature gradient is less than 0.1℃; the instantaneous temperature fluctuation curves of the controlled object and the third layer are as follows Fig.10 , 11 As shown, the temperature fluctuation amplitude of the controlled object is less than 0.001°C, and the temperature fluctuation of the third layer of heat sink is less than 0.001°C, which is very stable.

[0076] Although specific embodiments of the present invention are described above, those skilled in the art should understand that these are merely examples and that various changes or modifications may be made to these embodiments without departing from the principles and essence of the present invention. Therefore, the scope of protection of the present invention is limited by the appended claims.

Claims

1. An ultra-stable thermal environment simulator for spacecraft ground testing, characterized in that: A layered structure is adopted, and the inner and outer surfaces of each layer are provided with coatings of different emissivity. A plurality of radiators are evenly spaced between the two outermost layers. The heat absorption surface of each radiator is provided in the inner layer of the two outermost layers, and the heat dissipation surface thereof passes through the outer layers of the two outermost layers and is exposed to the outside. An active heat compensator is provided in the middle. Each of the active thermal compensators is used to adjust the heat sink temperature of the ultra-stable thermal environment simulator and suppress thermal disturbances from the outside.

2. The ultra-stable thermal environment simulator for spacecraft ground testing according to claim 1, characterized in that: The heat dissipation surface of each radiator passes through the outer layers of the two outermost layers and directly faces the vacuum tank heat sink. The number of radiators is determined using the following formula: Where n is the number of radiators, Q is the heat dissipation capacity of the ultra-stable thermal environment simulator, and S i is the area of ​​the heat dissipation surface of the ith radiator, and σ is the Stefan-Boltzmann constant 5.67e -8 , ε is the emissivity, T0 is the heat sink temperature of the vacuum tank, T r is the target temperature.

3. The ultra-stable thermal environment simulator for spacecraft ground testing according to claim 2, characterized in that: The axial cross-section of each radiator is set to an I-shaped structure, and its heat absorption surface and heat dissipation surface both adopt a circular structure. Their center positions are connected together through a column structure, and the corresponding active thermal compensator is arranged on the column structure.

4. The ultra-stable thermal environment simulator for spacecraft ground testing according to claim 2, characterized in that: The active heat compensator uses PID control algorithm to achieve temperature control. The specific control function is as follows Where u is the controller output command, e(t) is the difference function between the current temperature and the target temperature, Kp, KI, and KD are the proportional coefficient, integral coefficient, and differential coefficient, respectively.

5. The ultra-stable thermal environment simulator for spacecraft ground testing according to claim 1, characterized in that: The ultra-stable thermal environment simulator adopts a three-layer structure, which is marked as the first layer, the second layer and the third layer from the outside to the inside. The outer surface of the first layer is provided with a low emissivity coating, and the inner surface is provided with a high emissivity coating; the outer surface of the second layer is provided with a low emissivity coating, and the inner surface is provided with a high emissivity coating; and both the inner and outer surfaces of the third layer are provided with high emissivity coatings.

6. The ultra-stable thermal environment simulator for spacecraft ground testing according to claim 1, characterized in that: The various levels of the ultra-stable thermal environment simulator are installed in a heat-insulating manner.

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