Beijing, May 15 — In the face of extreme temperature differences, how can the “Tianwen-1” and “storm suits” solve the problem of “two heavens of ice and fire”?
Authors: Chaokai Guo, Pinto Yuan, Yuan
On May 15, the “Tianwen-1” landing rover successfully landed on Mars. “Tianwen-1” can cross “thousands of rivers and mountains” on this long journey, and there is a “magic weapon” that must be mentioned, that is, the silver “storm suit” on its body.
The application orbit of this “storm suit” is mainly in the three sections of the geofire transfer orbit, the Mars capture orbit and the Mars berthing orbit. From the moment it left Earth and entered space to the flight journey to Mars, “Tianwen-1” “rode the wind and waves” under the protection of this “storm suit”.
The “storm suit” can withstand temperature differences of more than 200 degrees
The “storm suit” of “Tianwen-1” is known as low absorption-low emission thermal control coating, which is a thermal control material coated on the outer surface of the spacecraft, which effectively reduces the temperature impact of the space environment on the interior of the spacecraft through its own ability to reflect the solar spectrum radiation and its own infrared radiation characteristics. This “storm jacket” was carefully developed by the 529 Factory of the Fifth Academy of China Aerospace Science and Technology Corporation after two years, and its successful development contains a number of independent key technologies.
In its orbit closer to Mars, Tianwen-1 undergoes multiple temperature cycles, with a maximum temperature of 100 °C and a minimum temperature of -120 °C. The temperature difference of more than 200 degrees has a great impact on the normal operation of the internal equipment of “Tianwen-1”.
In addition, the high vacuum characteristics of space make “Tianwen-1” unable to transfer heat through heat convection or heat conduction like an airplane under continuous irradiation in the face of the sun, so the surface temperature of its sunny side will continue to rise, resulting in a huge temperature difference with the back sun. Under such working conditions, the temperature inside the landing rover is seriously unbalanced, so that the “internal organs” inside the “Tianwen-1” are either in a cold environment and some are in a high temperature environment. At the same time, the continuous high-energy ultraviolet and ionizing radiation in space can also cause loss damage to its appearance.
Therefore, it is especially necessary to wear a special “storm suit” for the “Tianwen-1”. Experts pointed out that this “storm suit” also has to resist high-energy ultraviolet irradiation, atomic oxygen bombardment and a variety of high-energy particles and ionizing radiation attacks in space, becoming an all-round external protective barrier for spacecraft, which can be described as the “Tianwen-1” full-effect protective clothing during the fire journey.
Special coatings solve the “two heavens of ice and fire” problem
The “storm suit” of the “Tianwen-1” adopts a type that has never been seen in China’s previous field of thermal control coatings. Plant 529 experts said that thermal control coatings with low absorption alone are common, but thermal control coatings with both low absorption and low emission functions are extremely rare.
In order to develop this “storm suit”, the R&D team first determined the two key technical indicators of low absorption and low emission of the thermal control coating according to the external heat flow characteristics of the whole process of “Tianwen-1” in orbit by the overall thermal control designer, and then took these two technical indicators as the starting point to carry out a series of research and development work such as the design, simulation, preparation, testing and engineering implementation of the coating. After repeated trials, the R&D team finally successfully broke through a number of key technologies for the development of low-absorption and low-emission coatings, and tailored this silver shiny “storm suit” for “Tianwen-1”.
Similar to other heat-controlled coatings, this “storm suit” has a low absorption feature, and through a very low solar absorption ratio, it can effectively reflect most of the energy irradiated by the sun for a long time. In this way, the problem of “ice and fire” within the “Tianwen-1” can be effectively solved.
The difference is that the new “storm suit” not only has low absorption but also low emission, which is significantly different from other thermal control coatings that dissipate heat externally through high emissivity. According to the researchers, the reason for this design is that the journey of “Tianwen-1” is in a deep cold environment in space, and the heat generated by its internal engine will always be consumed to the outside world. The flight time of nearly 10 months has made the fuel consumption of the outside cold environment extremely high, and too much reserve fuel will increase the weight of “Tianwen-1”, which will bring a weight burden to the “Kekejiao” spacecraft.
Therefore, by reducing the infrared emissivity of the thermal control coating and reducing the radiation leakage from the cabin to the outside in the vacuum environment, the R&D personnel successfully realized the temperature guarantee for the normal operation of the equipment inside the landing rover, ensuring the safety and comfort of the journey of “Tianwen-1”. (End)