Chinese astronauts set new record for extravehicular activities

On September 17, Cai Xuzhe and Chen Dong successfully exited the Wentian laboratory module, setting a record for the shortest interval between extravehicular activities by Chinese astronauts.

As the construction and operation of China's space station progress steadily, astronauts are getting busier and busier in space, and the frequency of their spacewalks is increasing. So what challenges might astronauts face when they frequently go out of the spacecraft? What kind of training and preparation do they need to make?

The second extravehicular activity of the astronauts of the Shenzhou XIV spacecraft

Hidden dangers and treading on thin ice

Astronauts' extravehicular activities are probably one of the most popular space missions. Extravehicular activities, also known as spacewalks, refer to astronauts leaving the interior of a manned spacecraft and entering space. Generally speaking, astronauts' extravehicular activities can complete tasks such as spacecraft external facility maintenance, assisting in the assembly of equipment on orbit, and conducting extravehicular scientific experiments and scientific research exploration.

Due to the lack of cabin wall protection, astronauts face complex and changeable challenges such as temperature, pressure and radiation outside the cabin. Unfortunately, robots and other automated equipment cannot completely replace astronauts in performing extravehicular tasks, so astronauts must go out of the cabin.

Many people watch videos of astronauts going out of the cabin, hoping for "faster action". In fact, extravehicular activities are extremely dangerous and must be carried out with caution. During the first human extravehicular activity, an extremely thrilling scene occurred. In 1965, when Alexi Leonov, a Soviet astronaut and the "first man to walk in space", was performing an extravehicular mission, his space suit swelled due to the pressure difference, and he was unable to return to the cabin for a while. Fortunately, he decisively took the risk to lower the air pressure of the life support system, turned his head forward, and desperately turned his body to return safely.

According to public information, when Liu Boming, an astronaut of the Shenzhou XII spacecraft, was leaving the cabin, he suddenly received an order from the ground: "02, please enter the cabin now. Please temporarily place the foot limiter at the cabin door. 02, please enter the cabin now. Over." This order shows the high risk of the spacewalk mission.

At that time, the ground detected abnormal radiation values ​​in the area near the astronauts. Because the Chinese space station cabin has a multi-layer protective structure that can shield most of the dangerous radiation, the commander asked the astronauts to return to the cabin as soon as possible to avoid it. After the abnormal radiation dissipated, Liu Boming went out of the cabin again and installed the foot limiter on the equipment interface on the outer surface of the node cabin, successfully completing the relevant tasks.

As we can see from that episode, astronauts need to choose the right time for each extravehicular activity to avoid the terrible rays, high-energy particles, high radiation, solar wind, etc., so every extravehicular opportunity is precious. What's more troublesome is that extravehicular activities require close cooperation between astronauts and ground researchers. Some special missions also require the adjustment of the space station's attitude and consideration of conditions such as sunlight and ground-to-space communication technology. Therefore, frequent extravehicular activities are a major test for astronauts and researchers.

Extravehicular activities consume a lot of energy for astronauts, and frequent extravehicular activities place extremely high demands on the astronauts' physical fitness. Because it is inconvenient to control body movements in a weightless environment, astronauts have difficulty exerting force with their feet, and they mainly rely on their hands to grab objects and move carefully.

The second extravehicular activity of the astronauts of the Shenzhou XIV spacecraft

In addition, the mass of the space suit is large and will not change with weightlessness. The greater the mass of an object, the greater its inertia, which increases the difficulty of control. Therefore, it is difficult for astronauts to carry out extravehicular activities as easily as some people imagine. They need to recover and monitor their health after each extravehicular activity, otherwise they may be overwhelmed.

Prepare for complex technology support

The construction of China's space station is progressing in an orderly manner. The astronauts stationed on the station have to exercise every day to prevent muscle atrophy under low gravity conditions, which will affect their normal life and extravehicular work. Before performing extravehicular missions, astronauts first need to simulate the extravehicular procedures and mission execution processes in advance according to the mission manual and ground training content. After that, they prepare the necessary tools according to the mission manual, such as safety ropes, electric screwdrivers, fixers, limiters, etc., and must ensure that the tools can be used normally. Next, the astronauts have to wear extravehicular space suits.

Extravehicular space suits are the epitome of "space black technology". In order to isolate the human body from the harsh space environment, its production process requires high requirements, taking into account multiple functions such as thermal insulation, impact protection, radiation protection, humidity control, and pressure regulation. It can be said that extravehicular space suits are equivalent to "small manned spacecraft systems" and are more expensive than gold. Even launching and transporting it into space will cost a lot of money.

Such a sophisticated and complex space suit has a relatively limited service life, and its reliability decreases after each use, which undoubtedly increases the difficulty of astronauts leaving the spacecraft. In August this year, Russian astronauts accidentally discovered a power supply problem with their space suits when leaving the International Space Station, and were forced to terminate their mission early.

With the airlock of the Wentian experimental module put into use, Chinese astronauts have more complete facilities for extravehicular activities and larger space for activities. However, before this, astronauts used the core module node module to extravehicular activities, which was complicated to operate and required "three closings and one opening", namely closing the hatch of the orbital module connecting the spacecraft to the core module, the two-way pressure door between the core module small column and the airlock, and the extravehicular space suit backpack door, and opening the hatch for extravehicular activities.

After closing the multiple doors, the astronauts wear the space suits for high-flow flushing and oxygen inhalation to expel nitrogen. Simply put, the space suits are transformed into a pure oxygen environment. Since the air pressure inside the space station is slightly lower than the standard air pressure, the air pressure inside the space suits is only half of the standard atmospheric pressure on the ground. Astronauts must breathe pure oxygen to expel nitrogen from their bodies as much as possible. Otherwise, nitrogen will overflow abnormally outside the cabin, and the astronauts may suffer from decompression sickness, or even endanger their lives.

If astronauts want to avoid potential hazards such as radiation and space debris outside the cabin in time, they need the help of ground monitoring and command systems, which puts higher demands on space-to-ground communication technology. During the extravehicular mission, energy supply cannot be neglected, the position of the solar panels must be coordinated with the angle of sunlight incidence, and at least one astronaut is required to operate various equipment in the space station to assist, with the collective support of the advanced manufacturing industry behind it.

Half-day extravehicular training for the whole year

"I have left the spacecraft and feel good." On September 27, 2008, Zhai Zhigang left a message after leaving the spacecraft, marking the first time a Chinese person left his footprint in space. Astronauts' extravehicular activities usually last for several hours, but they need to make a hundred times more effort on the ground.

Before flying into space, astronauts will learn basic theoretical knowledge, practice operational skills, and carry out extravehicular procedures and mission training at the scientific research and training center. The entire ground training process is extremely difficult, and the training standards for men and women are the same. It is through day-to-day persistence that they continue to surpass themselves and challenge their limits, laying a solid physical foundation for extravehicular activities.

The extravehicular simulator can simulate the space environment and equipment usage status, create realistic touch, vision and hearing, extravehicular pressure density, etc. It can also create various problems for astronauts and train their ability to deal with emergencies.

If the weightless environment is not realistic enough, astronauts have to experience the neutral buoyancy tank. There is a scaled model of the space station module underwater. Astronauts must wear special training suits with lead blocks, weighing up to 200 kilograms. They train underwater for several hours each time, and they have to repeat it almost every day. The weight control of the training suit is precise and clever, allowing the human body to float underwater, providing a nearly weightless environment, making it easier for astronauts to practice extravehicular activities and exit procedures, and there are also multiple complex single trainings.

Astronauts training underwater

In short, every operation performed by astronauts in space must be honed on Earth, and practice makes perfect, so that they can grow into "hexagonal warriors" with all-round physical fitness, psychological quality, adaptability, and technical skills.

China's space station is under construction, and astronauts are busy. After hard training and careful preparation, each flight crew has undertaken more than one extravehicular mission, and frequent extravehicular missions also face certain risks.

After the Chinese space station is built and put into regular operation in the future, with the technological progress in space environment monitoring, command and control, extravehicular equipment, space suits, etc., and the optimization of astronaut mission processes, the risk of frequent extravehicular activities will be lower and is expected to be reduced. Although the audience may feel regretful, this will be a major advancement in China's manned space technology. I believe that the Chinese people's steps in space will be more stable and farther.