1600℃! Safely "playing with fire" in the Dream Sky Cabin

Researchers are checking the equipment. Photo provided by the interviewee

One wants to "play with fire" in the sky, and the other wants to "make elixirs" in the sky. These two scientific experiment cabinets in the Mengtian laboratory module of China's space station can be said to be the most "hot" pair - the combustion science experiment cabinet and the high-temperature materials science experiment cabinet.

Recently, the chief designer of the experimental cabinet and other researchers revealed to China Science Daily how the Dream Space Capsule ignites the hottest fire in space.

1600℃ "Alchemy Furnace"

1600℃! This is the highest operating temperature of the Mengtian cabin high temperature material science experiment cabinet, and it is also the highest temperature that the International Space Station science experiment cabin can reach.

The melting point of copper is 1085℃, the melting point of single crystal silicon is 1410℃... The higher the working temperature of the experimental cabinet, the wider the scope of research can be, and the greater the possibility of revolutionary results. Doing material science research in space is the dream of almost every materials scientist.

"The gravity of the space station is only 0.001 to 0.000001 acceleration, which is likely to produce materials that cannot be prepared on the ground." Liu Xuechao, a researcher at the Shanghai Institute of Ceramics, Chinese Academy of Sciences and chief designer of the scientific experimental system of the high-temperature materials scientific experimental cabinet, said.

However, it is not easy for Chinese scientists to realize their dreams. In the International Space Station, the maximum operating temperature of the Destiny laboratory module of the United States is 1400℃, the Columbus of Europe is 1400℃, the Hope of Japan is 1600℃, and the Science of Russia is 1200℃.

"We didn't have the resources in the past, but now we have a great opportunity. When we launched the project, we made sure that all technical indicators were no lower than similar devices on the International Space Station," said Liu Xuechao.

They did what they said. At present, a series of indicators of the high-temperature material science experiment cabinet are leading in the world - the temperature stability reaches plus or minus 0.2℃, the number of automated samples is 16, and X-ray real-time observation is used for the first time.

The one-time batch processing of 16 samples broke the record of 15 samples in the Japanese GHF material experiment device of Hope. This means that after the astronauts hang up the 16 samples, they do not need to perform any operations for several months. The experiment cabinet will complete all experiments autonomously, greatly improving efficiency and accuracy.

Zhang Minghui, associate researcher at the Shanghai Institute of Ceramics, Chinese Academy of Sciences, and chief designer of the high-temperature material science experiment cabinet scientific experiment system, said that batch experiments are a bit like the magazine of a revolver, which rotates in sequence to conduct experiments. The CCD camera that takes real-time photos of the entire experimental process is like the boy of Taishang Laojun, guarding the "alchemy furnace" at all times.

It is understood that in order to improve the success rate of space experiments, scientists have conducted a large number of matching experiments on the ground, with the ratio of matching experiments to space experiments reaching 95:5. One minute on stage is the result of ten years of hard work off stage. Zhang Minghui said: "We have a heating experiment in the sky, and thousands of trials on the ground."

Multiple measures to ensure absolute safety

"Isn't it too dangerous to 'play with fire' in the space station?" Such doubts have been heard since the first day of the Mengtian Capsule Combustion Science Experiment Cabinet project.

However, the combustion phenomenon is closely related to human life, not to mention that space combustion experiments are expected to produce major scientific results, which is also a hot research direction in the world.

Zheng Huilong, a researcher at the Institute of Engineering Thermophysics of the Chinese Academy of Sciences and chief designer of the scientific experimental system of the Combustion Science Experiment Cabinet, said that space eliminates the influence of convection, which can provide a deep understanding of the combustion mechanism, and is helpful for aerospace engine research, new material synthesis, and PM2.5 production mechanism analysis.

"Our space experiments started late, but that also gives us the advantage of being a latecomer." Zheng Huilong said that the Mengtian Capsule Combustion Science Experiment Cabinet is highly versatile and powerful. Its sensors can measure temperatures as high as 3000°C, and its high-speed camera can take 3000 photos per second. It will be open to scientific research project applications from scientists around the world.

In order to ensure the absolute safety of the combustion experiment, the research team took multiple measures: the largest flame in the experiment was only the amount of burning of three birthday candles, and the combustion chamber could withstand a pressure of 9 atmospheres; the fuel was isolated from oxygen to prevent accidents; the combustion products were filtered and recycled multiple times to ensure the life and health of the astronauts. In addition, the researchers also set up many early warning systems.

The high-temperature materials science experiment cabinet was the first in the world to move an X-ray device to a space station.

Sun Jinchuan, senior engineer of the Lanzhou Institute of Space Technology and Physics of China Aerospace Science and Technology Corporation and deputy chief designer of the scientific experimental system of the high-temperature material science experiment cabinet, said that the X-ray experimental device is the "eagle eyes" of space science experiments, which can obtain real-time image information and data of material samples during the preparation process through visualization means.

In order to prevent X-rays from affecting the health of astronauts, the research and development team designed a shielding and absorption system. Even if the device is operating at full power, the X-ray overflow is far below the national standard.

The high-temperature material science experiment cabinet has also achieved, through technical breakthroughs, an internal temperature of 1600°C and an external temperature of less than 40°C, making the cabinet feel neither cold nor hot, almost the same as the astronauts' body temperature.

Submit a perfect answer

At 3:30 pm on October 31, the Mengtian capsule was launched into space with the Long March 5 carrier rocket. Liu Xuechao, Zheng Huilong and others who were watching the launch in Wenchang, Hainan, ran across the lawn excitedly.

At that moment, they were overwhelmed with emotions.

All technical indicators are no less than those of similar international devices, and many are international firsts, which means that from design to research and development, they must go through a difficult process. In the past six years, they have failed countless times.

Once, the heated ceramic structure broke three times in a row, and each time it had to be redesigned, molded, and tested. Before the last mechanics test, a colleague told Liu Xuechao that he dreamed that the ceramic cracked again last night. Liu Xuechao smiled bitterly and said, "What a coincidence, I had the same dream." Fortunately, the experiment finally passed.

In order to place 16 samples in batches, technical experts from the Shenyang Institute of Automation of the Chinese Academy of Sciences came up with 10 solutions, but they still couldn't fit them in. But they told themselves that they had to fit them in. Finally, through continuous iteration of the design, the space was used to the extreme and the 16 samples were placed in place.

In order to keep the total weight within the standard, the design of the high-temperature material science laboratory cabinet went through five rounds of weight reduction, while ensuring advancement and safety, and reducing weight from every detail. In the last round, Sun Jinchuan said with a smile: "Can you please stop reducing the cabinet? I have lost several kilograms myself."

There were many times when he felt like he couldn't hold on any longer, but he eventually got up and became an invincible cockroach. Looking back, Sun Jinchuan said confidently: "All the specific technologies that we have conquered have become our core technologies."

In this nationwide collaboration, experts from top scientific research institutions also forged a deep friendship. "Without the support of so many units, we would not have been able to complete such a complex project in a short time. This reflects our country's strong design, scientific research and integration capabilities." Zheng Huilong said.

Especially in recent years, in order to ensure that the back wall does not collapse, everyone has no holidays and takes the risk of epidemics to travel for a month. This Spring Festival, research and development teams from all over the country gathered in Beijing to carry out the final debugging before the delivery of the prototype. They worked until one or two in the morning on New Year's Eve and came to the site to work at 8 am on New Year's Day.

"Our entire team has fought hard," said Zheng Huilong. "Since we have undertaken a national mission, we must deliver a perfect answer. This is the spirit of aerospace, and it is also the fundamental reason why my country's aerospace industry can continue to surpass itself."

(Originally published in China Science Daily, 2022-11-30, Page 4)