Space station construction: It’s easier to get things done with people in the sky

At 20:50 on June 5, astronauts Chen Dong, Liu Yang and Cai Xuzhe of the Shenzhou XIV flight crew entered the Tianhe core module in turn, officially starting a six-month long-term resident flight mission. "Shenzhou XIV" is the first manned flight mission in the construction phase of my country's space station. During the six-month flight mission, the astronauts will assemble the Wentian laboratory module and the Mengtian laboratory module, and finally complete the construction of the T-shaped space station. Therefore, the three astronauts will experience complex working conditions and busy work in the space station. So, what kind of work will the astronauts do during the construction phase of the manned space station?

Schematic diagram of the Tiangong space station after completion

Station building astronauts are irreplaceable

The space stations built by humans in the early days, such as the Soviet Union’s "Salyut" series and the United States’ "Skylab", are all single-cabin space stations that can be launched into orbit in one go using a rocket. Although the construction process in space is not that complicated, astronauts still play an irreplaceable role.

Take Skylab as an example. During the first manned mission, the Apollo manned spacecraft and Skylab-2 failed to dock several times because the capture lock of the spacecraft's docking interface failed. The astronauts had to put on their extravehicular space suits and walk out of the cabin to carry out some repairs before the spacecraft successfully docked with Skylab.

Skylab space station

Although modern manned spacecraft are mature and reliable, some accidents are still unavoidable. In 2004, when the Russian Soyuz manned spacecraft was docking with the International Space Station, it was too fast and had to switch to manual rendezvous and docking, proving that astronauts are still necessary as the "stabilizing force" in the flight of station construction.

In addition, modern multi-module and truss-type space stations require multiple use of rockets to launch each module into space, and then dock and assemble them in orbit into a complete space station.

During the construction process, with the arrival of new modules, the space station will have to carry out multiple rendezvous and docking and module transfer tasks. Not only will astronauts be required to monitor the status of the space station and visiting spacecraft, but they will also have to perform manual rendezvous and docking in real time when necessary, or operate large robotic arms to perform manual module transfers.

After the new module is docked, astronauts will move in and decorate the interior. Generally, a long period of in-orbit installation and debugging work is required.

On the one hand, it is necessary to inspect and monitor the various functions of the space station interface to ensure that all electrical and hydraulic functions are connected and working normally, carry out network connection work between the two compartments, and monitor the long-term sealing of the docking mechanism.

On the other hand, the materials, tools and equipment delivered earlier or later are used to adjust or install equipment in the new module. Therefore, the astronauts are very busy during the construction of the space station.

I can't do without extravehicular equipment

During the construction of the space station, the astronauts' extravehicular assembly work plays a vital role. For example, after the American astronauts boarded the Apollo manned spacecraft and entered the "Skylab", they first installed a new heat shield, and then went out of the cabin with great effort to deploy the solar panels on one side. Therefore, the astronauts are required to participate in the extravehicular assembly work of the space station.

As the construction of space stations becomes more and more complex, astronauts have to do more and more extravehicular work. In particular, the Freedom Space Station project proposed by the United States in the 1980s relied heavily on astronauts' extravehicular assembly work.

An image of the Freedom Space Station proposed by the United States

As a huge double-keel truss space station, the Freedom required astronauts to go out of the cabin to perform a lot of assembly and maintenance work during the construction phase. According to NASA's assessment at the time, the completion of the construction of the space station required astronauts to go out of the cabin to perform hundreds of missions. However, for some reasons, the Freedom did not enter the engineering construction phase and ultimately remained on paper.

As the successor of the Freedom, the current International Space Station can be seen as a hybrid of the later single-keel configuration of the Freedom and the Soviet/Russian Mir Space Station, even if it is not a truss design. If the last flight mission of the US space shuttle in 2011 is taken as the symbol of the basic completion of the International Space Station, astronauts conducted a total of 159 extravehicular activities during the construction of the International Space Station, playing a great role in the construction of the space station.

What do astronauts do during the construction of the space station? During the Shenzhou XIII mission, astronauts went out of the cabin to lift the camera outside the Tianhe core cabin, and the Shenzhou XIV mission will also conduct 2-3 extravehicular activities. In the future, the solar panels installed on the core cabin may be moved to the two ends of the two experimental cabins. These are all complex tasks that require astronauts to go out of the cabin to complete.

The International Space Station is a semi-truss structure and a complex project jointly implemented by multiple countries. During its construction, astronauts went out of the cabin to assemble a huge truss structure, solar cell wings and the Canadian robotic arm mobile service system, and installed numerous extravehicular facilities and scientific experimental payloads for the US Destiny laboratory module, the Japanese Hope laboratory module and the European Columbus laboratory module, and also replaced the control torque gyro and batteries.

In 2021, Russian astronauts performed two extravehicular activities to connect cables on the International Space Station to welcome the arrival of the Science laboratory module.

In July 2021, after the Science laboratory module was launched and successfully docked with the International Space Station, Russian astronauts conducted several extravehicular activities, performing in-orbit inspection and installation tasks such as robotic arms, airlocks, additional radiators and extravehicular payload fixtures.

I am the only one who can handle emergency rescue

Although humans are very vulnerable in outer space, the space station is a complex and sophisticated system that not only requires astronauts to assemble and maintain it on orbit during construction, but also requires astronauts to provide emergency rescue services if a failure occurs.

Manned space missions involve lives at stake, and researchers prepare various contingency plans before each mission. However, emergencies in space are usually "unexpected." For example, if the computer control system of the space station suddenly fails, a fire or false alarm occurs in the manned pressurized compartment, or an unknown gas appears in the compartment or a gas leak is detected, astronauts need to make decisions and handle the situation immediately.

Generally speaking, once such an abnormal situation occurs, it is difficult for the conventional space station control system to provide the best solution, and it may even be a problem that needs to be solved. At this time, only the astronauts can rely on their own knowledge and experience to solve the problem, and only the astronauts on the space station can make judgments and handle it according to the on-site situation. Without the astronauts' subjective initiative to handle emergencies, it is difficult to solve these unexpected things.

During the construction phase of the space station, the various subsystems have not been tested by time and are prone to various problems. Emergency rescue is the most difficult task, the task that requires the most from astronauts, and it is also an occasion where astronauts are the only ones suited to this task.

Russia's Mir space station has experienced two major crises, and astronauts have played an irreplaceable role. In February 1997, a fire broke out on the Mir space station, and the cabin was filled with pungent smoke. The astronauts could not see their hands in front of them. They took down the fire extinguisher on the wall to put out the flames, and then adjusted the air composition and repaired some damaged equipment.

The Mir space station in space

In addition, the "Mir" was hit by the Progress cargo spacecraft, which damaged the solar panels and a large hole in the spectral module, causing the space station to lack power and rotate out of control. Fortunately, the astronauts urgently closed the hatch, cut off the cables at the hatch, and used the spacecraft's engine to initially control the attitude, which brought the "Mir" back to life.

These examples of space station emergency rescue prove that astronauts play an important role in the construction of space stations.