"3, 2, 1 ignition, ignition......." At 01:56 on May 10, the Long March 7 remote 5 carrier rocket carrying the Tianzhou 4 cargo spacecraft was ignited and launched at the Wenchang space launch site. The raging flame was like a light in the night, illuminating China's manned space dream again. This was the first launch mission of China's space station construction from the key technology verification stage to the on orbit construction stage.
Tianzhou 4 cargo spacecraft is a cargo spacecraft specially developed for manned spaceflight in China at the present stage. It is like "sky express". Its main task is to transport goods and add propellant for the manned space station project, and bring the waste of the space station back to the atmosphere for burning.
In order to deliver express to space, express packing boxes are naturally needed. During the transportation of "space express", some materials with strong temperature sensitivity, such as basic support and medical testing, need to be packed in special boxes - a "sky refrigerator" made of special materials and called low-temperature lock cabinet.
Compared with the refrigerator in our daily home, the material selection of "sky refrigerator" should have the characteristics of "light weight, small volume and absolute flame retardant", which is because it not only undertakes the basic functions of excellent thermal insulation, stability and safety, but also needs to have the special mission of "minimizing weight, improving the degree and realizing the space utilization efficiency in the spacecraft".
In recent years, aerogel gel, a thermal insulation material used in national defense equipment, energy conservation, environmental protection and petrochemical industry, has repeatedly appeared in front of the public. Can it also complete the special answer of "space refrigerator" low-temperature lock cabinet?
This is known as "magic material that changes the world". It is a material with three-dimensional nano porous network structure composed of colloidal particles or polymer molecules. It has unique properties such as low density, low thermal conductivity, high thermal stability, high adsorption and sound insulation.
When we got the technical indicators of thermal insulation materials for low-temperature lock cabinets, the scientific research team that has been deeply involved in the research field of aerogel gel materials for many years still had a sweat - according to the application requirements of low-temperature lock cabinets, the required thermal conductivity is lower than the existing aerogel gel! For a while, the team fell into the dilemma of "no material available".
In order to ensure the special mission of "space refrigerator", the aerogel gel team of institute 306 of the third Academy of Aerospace Science and industry of China gathered intelligence to tackle key problems and climb new heights.
Through in-depth discussion, the team proposed a solution: take the existing aerogel gel material as the base material, and "vacuum" the existing aerogel gel material through a special process to prepare a vacuum insulation board. After verification, the thermal conductivity of this kind of plate is reduced to half of the original aerogel gel material. On the basis of meeting the requirements of thermal conductivity index, it also has excellent air separation and puncture resistance.
Vacuum insulation panel, English name is vacuum insulation panel, abbreviated as "VIP", so it is also jokingly called "VIP" material on Tianzhou by team members.
In April 2017, this material was first used in the low-temperature lock cabinet of tianzhou-1 cargo spacecraft; In May 2021, the upgraded version of "VIP" with larger single chip size was applied on Tianzhou II again, and its thermal insulation performance was further improved.
For the vacuum insulation board used by Tianzhou 4 this time, the user has put forward more stringent requirements for the performance and stability of the product. However, in recent years, with the scientific research team working hard to tackle key problems and develop new research on the material life, one of the key technical indicators of aerogel gel, the performance of aerogel gel has remained stable since its inception in 2015, and its reliability has withstood the test of time.
With the "space trip" of the tianzhou-4 cargo spacecraft, in the future, the team will be more confident to develop more and better advanced materials and products, provide a strong guarantee for the establishment of China's aerospace cargo system, and make new contributions to China's deep space exploration industry!
(text / Tian Shaoxing, Sheng Jinhua, 306 Institute of the third Academy of Aerospace Science and industry of China)