An ultra-stable thermal environment simulator for spacecraft ground testing

Abstract

The application discloses an ultra-stable thermal environment simulator for spacecraft ground test, adopts a layered structure, the inner and outer surfaces of each layer are provided with coating with different emissivity, a plurality of radiators are uniformly arranged between the outermost two layers, the heat absorbing surface of each radiator is arranged in the inner layer of the outermost two layers, the heat dissipating surface of each radiator is exposed outside through the outer layer of the outermost two layers, a main heat compensator is arranged in the middle of each radiator, and the main heat compensator is used for adjusting the heat sink temperature of the ultra-stable thermal environment simulator and inhibiting thermal disturbance from the outside. Through optimization design, the temperature stability, uniformity and adjustability of the heat sink are improved, so that the precision of the thermal boundary simulation of the spacecraft component is remarkably improved, the thermal management and temperature control are more accurate in the harsh space environment, and the reliability and stability of the spacecraft equipment are effectively ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of spacecraft ground test equipment, and particularly relates to an ultra-stable thermal environment simulator for spacecraft ground test. BACKGROUND

[0002] Spacecraft ground vacuum thermal test is one of the key steps in the design process of spacecraft. This kind of test can verify the function of spacecraft products, check the manufacturing process, and find potential early failure problems of equipment in the simulated vacuum and ultra-low temperature environment of space. In the development process of spacecraft, whether it is the identification level thermal vacuum test in the initial stage or the acceptance level thermal vacuum test before launch, it is an indispensable important link. These tests play a crucial role in ensuring the reliability and stability of spacecraft in extreme space environments.

[0003] The main equipment of thermal vacuum test is vacuum tank, also known as thermal environment simulator, which can simulate the vacuum and extreme cold and hot environment in space, and accurately control, monitor and record the vacuum degree and test piece temperature. The structure of vacuum tank usually includes vacuum container, pumping system, temperature guarantee system (including test platform), equipment control and monitoring system and auxiliary system, among which the heat sink maintains the temperature by circulating liquid nitrogen to simulate the extreme temperature conditions in space. However, the liquid nitrogen circulation may cause temperature fluctuations, affecting the stability of the heat sink, and generating temperature gradient, reducing the test accuracy. In order to meet the high precision requirement, Qisong Song et al. designed a special temperature-controlled heat sink in 2020, combined with a heater and a temperature control system, achieving a temperature control accuracy of ±0.5℃. However, for spacecrafts that require μK level temperature control accuracy, such as gravitational wave detection satellites, this accuracy still has great challenges, limiting the improvement of thermal test accuracy of precision spacecrafts.

[0004] Current thermal environment simulators based on circulating liquid nitrogen vacuum tank heat sink have many deficiencies and challenges:

[0005] 1) Insufficient stability of heat sink temperature

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

[0007] 2) Poor uniformity of heat sink temperature

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

[0009] 3) Heat sink temperature is not adjustable

[0010] The temperature of the vacuum tank heat sink depends on the temperature of liquid nitrogen (about -180℃), and has no temperature adjustment capability. It cannot meet the simulation requirements of some space probe instruments (most of which require an ambient temperature of 0-25℃) for thermal environment, and additional design of thermal environment simulation components is required, which increases the complexity and cost of the test. SUMMARY

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

[0012] The application can be implemented by the following technical scheme:

[0013] An ultra-stable thermal environment simulator for spacecraft ground test adopts a layered structure, the inner and outer surfaces of each layer are provided with coating layers with different emissivities, a plurality of radiators are uniformly and spaced apart between the outermost two layers, the heat absorbing surface of each radiator is arranged in the inner layer of the outermost two layers, and the heat dissipating surface is exposed to the outside through the outer layer of the outermost two layers, and a main heat compensator is arranged in the middle,

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

[0015] Further, the heat dissipating surface of each radiator penetrates the outer layer of the outermost two layers and directly faces the vacuum tank heat sink, and the number of radiators is determined by the following formula,

[0016]

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

[0018] Further, the axial cross section of each radiator is arranged in an I-shaped structure, the heat absorbing surface and the heat dissipating surface of each radiator are circular structures, and the center positions of the heat absorbing surface and the heat dissipating surface are connected together through a column structure, and the corresponding main heat compensator is arranged on the column structure.

[0019] Further, the main heat compensator adopts a PID control algorithm to realize temperature control, and the specific control function is as follows

[0020]

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

[0022] Further, the super-stable thermal environment simulator adopts a three-layer structure, which is sequentially recorded as a first layer, a second layer and a third layer from outside to 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 the inner and outer surfaces of the third layer are provided with high-emissivity coatings.

[0024] Further, the super-stable thermal environment simulator adopts a heat insulation installation method between each layer.

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

[0026] The super-stable thermal environment simulator developed by the present application is suitable for spacecraft components with extremely high temperature control precision. The super-stable thermal environment simulator is based on a multi-layer structure, and by optimizing the thermal radiation characteristics of each layer, external thermal disturbance is effectively suppressed; at the same time, a cross-layer adaptive radiator is designed to achieve efficient dissipation of internal heat; in addition, an active thermal compensator is provided on the radiator, which can accurately adjust the temperature scale and temperature gradient of the heat sink, ensuring the temperature control stability of the system. BRIEF DESCRIPTION OF DRAWINGS

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

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

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

[0030] Figure 4 It is a schematic diagram of the structure of the cross-layer adaptive radiator of the present application;

[0031] Figure 5 It is a schematic diagram of the steady-state temperature distribution of the third layer in the no temperature control object embodiment of the present application;

[0032] Figure 6 It is a schematic diagram of the vacuum tank heat sink temperature change in the no temperature control object embodiment of the present application;

[0033] Figure 7 It is a schematic diagram of the transient temperature fluctuation curve of the third layer in the no temperature control object embodiment of the present application;

[0034] Figure 8 Schematic diagram of the temperature field distribution of the controlled object in the embodiment of the present invention;

[0035] Figure 9 Schematic diagram of the temperature field distribution of the third layer in the embodiment of the temperature-controlled object of the present invention;

[0036] Figure 10 Schematic diagram of instantaneous temperature fluctuation curve of a controlled object in an embodiment of a temperature-controlled object of the present invention;

[0037] Figure 11 Schematic diagram of the 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 spacecraft ground testing. It employs a layered structure, with the inner and outer surfaces of each layer coated with coatings of varying emissivity. Multiple radiators are evenly spaced between the two outermost layers. Each radiator's heat-absorbing surface is located within the inner layer of the two outermost layers, while its heat-dissipating surface passes through the outer layers of the two outermost layers and is exposed to the outside. Active thermal compensators are located within the simulator's center, each used to adjust the ultra-stable thermal environment simulator's heat sink temperature and suppress external thermal disturbances. This multi-layered structure and radiative heat exchange regulation effectively suppress external thermal disturbances, effectively maintaining the simulator's internal temperature stable. The radiators dissipate internal heat to an external heat sink, achieving 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 divided into 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 characteristics are:

[0046]

[0047] The phase-frequency characteristic is:

[0048]

[0049] wherein:

[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, when the temperature T0 fluctuation amplitude of frequency 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 the specific value is determined by the system parameters R-C and the signal frequency ω. When the specific structure size parameters of the super-stable environment simulator are clear, the anti-interference characteristics of the simulator can be designed by adjusting the thermal resistance R between the layers, as shown in the following formula: Figure 3 In order to improve the temperature uniformity of the simulator, further suppress the thermal disturbance from the outside world, and effectively reduce the temperature gradient in the space of the simulator, the installation mode between each layer is heat insulation installation, which reduces direct heat conduction.

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

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

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

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

[0058] 2. Cross-layer adaptive radiator design

[0059] The super-stable thermal environment simulator structure of the hierarchical structure can effectively suppress the thermal disturbance from the outside, but cannot realize the dissipation of heat inside the environment simulator. In view of this problem, a cross-layer radiator is designed, the heat absorption section of which is installed in the second layer, and the heat dissipation end directly faces the vacuum tank heat sink across the first layer to dissipate heat.

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

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

[0062]

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

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

[0065] 3. Active heat compensator

[0066] An active heat compensator is designed in the middle part of the cross-layer adaptive radiator, which can adjust the heat sink temperature value of the thermal environment simulator on the one hand, and can suppress the thermal disturbance from the outside on the other hand.

[0067] PID control algorithm is adopted, and a closed-loop control is formed in combination with the nearby temperature sensor to improve the adaptive ability of the system, and 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 KM2.5 vacuum tank as an example, the designed ultra-stable environment simulator is as follows Figure 1 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-layer radiators, each with a 0.2m radius.

[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 stabilizes, the temperature field distribution of the simulator heat sink (third layer) is as follows: Figure 5 As shown in Figure 2, 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 2. 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 Figure 10 、 11 As shown in the figure, the temperature fluctuation amplitude of the controlled object is less than 0.001°C, and the temperature fluctuation of the third layer 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. A super-thermal environment simulator for spacecraft ground testing, characterized by: It adopts a layered structure, with coatings of different emissivity on the inner and outer surfaces of each layer. Multiple radiators are evenly spaced between the two outermost layers. The heat absorption surface of each radiator is set on 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. Active thermal compensators are set 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; 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; the inner and outer surfaces of the third layer are both provided with a high-emissivity coating; The various levels of the ultra-stable thermal environment simulator are installed in a heat-insulating manner.

2. The ultra-stable thermal environment simulator for spacecraft ground testing of claim 1, wherein: The heat dissipation surface of each radiator passes through the outer layers of the two outermost layers and directly faces the heat sink of the vacuum tank. 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 super-stable thermal environment simulator, S i is the area of the heat dissipation surface of the i-th radiator, σ is the Stefan-Boltzmann constant 5.67e -8 , ε is the emissivity, T0 is the heat sink temperature of the vacuum tank, and T r is the target temperature.

3. The ultra-stable thermal environment simulator for spacecraft ground testing of claim 2, wherein: 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 set on the column structure.

4. The ultra-stable thermal environment simulator for spacecraft ground testing of claim 2, wherein: The active thermal 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.

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