Thermal vacuum test chamber is mainly used as a ground test to simulate the vacuum, cold black and solar radiation environment of spacecraft in space. This kind of test is performed on single machines (components), subsystems and the entire spacecraft. During the simulation test, the specimen is mostly in working condition and its working parameters and environmental parameters are measured.
A ground test that simulates the vacuum, cold darkness and solar radiation environment of a spacecraft in space. This test is performed on individual machines (components), subsystems and the entire spacecraft. During the simulation test, the specimen is mostly in working condition and its working parameters and environmental parameters are measured.
Vacuum environment simulation
The vacuum degree of the environment where the spacecraft is located is 13.3~13.3×10-10 mPa (10-4~10-14 mmHg). From the perspective of heat transfer, the vacuum degree of 13.3 mPa is sufficient for the spacecraft. Need for simulation of thermophysical properties effects. In order to save test costs, the vacuum degree used in thermal vacuum testing is usually set to be better than 13.3 mPa. In order to assess and study the dry friction and cold welding performance of certain moving parts and extension mechanisms, and to study the sublimation, weight loss, aging and other effects of materials under vacuum conditions, it is necessary to use a combination of higher vacuum and other space environmental factors. When the test is carried out, a vacuum degree of 13.3×10-1~13.3×10-10 mPa (10-5~10-14 mmHg) can be obtained in a small and medium-sized space simulator.
Cold and dark environment simulation
The thermal background temperature of the universe is 4K and the absorption coefficient is 1, which is equivalent to an ideal black body. When simulating this heat sink effect on the ground, a black radiation screen cooled by liquid nitrogen is usually used. The simulated temperature of the screen is lower than 100K and the absorption coefficient is greater than 0.9. When the characteristic size ratio between the simulation chamber and the spacecraft is greater than 2:1, the thermal simulation error is less than 1%, and such errors can be corrected through theoretical calculations. For the calibration test of the remote sensor, the background temperature of the heat sink should be lower than 20K.
Solar irradiation simulation
Solar electromagnetic radiation is equivalent to a 6000K black body radiation and is the main external heat source of the spacecraft. Earth-circling spacecraft are also subject to Earth albedo and Earth infrared radiation in orbit. Solar simulators usually use carbon arc lamps or high-voltage short-arc xenon lamps as light sources, and are equipped with off-axis, coaxial or divergent optical systems to create a certain irradiation intensity, spectrum, uniformity and collimation angle to simulate sunlight. intensity and energy spectrum distribution. Since the manufacturing and testing of solar simulators are very expensive, heat flux simulation methods are often used instead of solar simulations for most spacecraft with less complex shapes. The heaters used include infrared heaters, quartz lamp arrays, cage resistance sheets, patch resistance heaters, electric heating tubes and their combinations. The disadvantage of this method is that it cannot simulate the energy spectrum and collimation of sunlight. For spacecraft with complex shapes and special components such as solar cell wings, solar sensors, and large antenna structures, solar simulators are still needed for irradiation tests.
Standards for thermal vacuum testing:
"GJB 3758-99 Thermal Simulation Method for Satellite Vacuum Thermal Test"
At present, there are very few laboratories that can conduct thermal vacuum tests. They mainly include the Environmental Reliability and Electromagnetic Compatibility Test Center, the Aerospace Environmental Reliability Test and Inspection Center, etc.
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