When satellites, space probes and other spacecraft are operating in space, they are in a thermal vacuum environment of high vacuum, cold black and solar radiation. Vacuum thermal environment simulation test is a very effective ground test method to simulate the vacuum thermal environment (high vacuum, cold black, solar radiation, high temperature and other environments) of the space.
Vacuum thermal test is the general term of spacecraft thermal balance test and thermal vacuum test. The vacuum thermal environment simulation test of spacecraft has become one of the most important links in the development stage of spacecraft. It can test the rationality of the thermal control design of spacecraft such as satellites, modify the design model, verify the working state of instruments and equipment inside the spacecraft, as well as the matching and working performance between subsystems. At the same time, it can also be used to check the function and manufacturing process of spacecraft, Expose the potential design defects that may exist in the spacecraft and find the early failure of the spacecraft.
In the development stage, all spacecraft must undergo vacuum thermal environment simulation tests. For the spacecraft in the initial sample development stage, it is necessary to carry out the qualification level vacuum thermal test. For the launched spacecraft, whether it is the first launch or repeated launch, it is necessary to carry out the acceptance level vacuum thermal test.
1.Thermal vacuum test
Spacecraft thermal vacuum test can be divided into identification level thermal vacuum test and acceptance level thermal vacuum test.
The qualification level thermal vacuum test is mainly aimed at the spacecraft in the development stage, and its purpose is to assess the structure and working performance of the spacecraft and its ability to withstand environmental stress, and to verify the rationality of its design. The acceptance level thermal direct space test is mainly aimed at the spacecraft that is normal or launched, and the purpose is to expose the potential defects in the material and process manufacturing quality of the spacecraft, so as to improve the reliability of spacecraft flight.
Foreign standards often used in spacecraft thermal vacuum tests include the US military standard mil-std-1540 (versions B, C, D, E) and the European Organization for space standardization standard ECSS-E-10-03A.
There are certain differences in the test methods of thermal vacuum test specified in various versions of the U.S. military standard mil-std-1540. Among them, MIL-STD-1540C-1994 stipulates that the number of cycles of the test is 25, and the total test time is 300 h, which is the most severe test method specified in several versions. Compared with the test method specified in the latest version of MIL-STD-1540E-2002, it has been greatly reduced, and the number of cycles is specified as at least 3, and the total test time is at least 28 H.
2.Development status of vacuum thermal test equipment
The vacuum thermal test equipment is mainly used to simulate the high vacuum, cold black environment and external heat flow environment of space, and to simulate the vacuum thermal test environment such as the thermal balance test and thermal vacuum test of spacecraft components, subsystems and the whole system.
2.1 Equipment composition
Vacuum thermal test equipment is mainly composed of vacuum vessel, vacuum pumping system, heat sink, nitrogen system, external heat flow simulation device (or high-temperature heat source), temperature control system, measurement and control system and auxiliary system (cooling water system, gas source system, etc.). According to the specific use, the size and composition of the equipment are also different.
2.2 Vacuum simulation technology
The vacuum thermal test equipment reaches the specified vacuum degree, which is realized by the vacuum pumping system. The vacuum pumping system is generally composed of mechanical pumps, molecular pumps, cryogenic pumps, valves and other ancillary devices. Mechanical pump as the roughing of the system
Unit, used for vacuum pre pumping; Molecular pump is the high vacuum auxiliary pump of the system. When the vacuum degree of the container is less than 10 Pa, start the molecular pump; As the main vacuum pump of the system, the cryogenic pump performs high vacuum pumping to make the vacuum degree in the container reach the level required by the test.
2.3 Cold black simulation technology
The infinite space environment is equivalent to an absolute blackbody that can absorb any radiation. The space is a cold black environment with a temperature of 3 K and an absorption coefficient of 1. In the vacuum thermal test equipment, it is used to simulate the cold and black environment in space
The device of is called heat sink.
At present, the heat sink usually adopts the tubesheet structure composed of aluminum, red copper or stainless steel, and its surface is coated with black epoxy matt paint with high absorptivity to achieve the optimal heat transfer efficiency. At the same time, 77 K liquid chlorine is used as the cold source, so that the heat sink can meet the requirements specified in the standard that the heat sink temperature is not higher than 100 k, and the internal surface absorptivity coefficient is greater than 0.9. According to the size of spacecraft heat load, liquid helium can also be used as a cold source to achieve a lower heat sink temperature. If only high and low temperature cyclic vacuum thermal test is required, mechanical refrigeration can also be used when the low temperature of the test is not lower than -70 ℃.
DGBELL has been committed to producing environmental reliability test equipment for more than 15 years. We has rich experience in the R & D and production of environmental reliability test equipment. Over the years, it has met various needs of customers and can provide reasonable solutions for various test requirements.
For details of conventional models, please refer to the official website data. In addition, DGBELL can provide customized services for thermal vacuum test chambers. Please feel free to purchase.