It has been more than half a month since the first exciting mission of Shenzhou 12 astronauts. There are countless videos and pictures from various channels, but there are few articles that completely record and interpret this incident. The author will try to attract more attention this time.
On the day when the Shenzhou-12 astronauts performed the first extravehicular mission of Tiangong Space Station, the extravehicular time was 6 hours and 46 minutes from 8: 00 (1 1) when Liu Boming opened the airlock door to 14: 57 that afternoon.
Due to various preparations for extravehicular activities, the duration of extravehicular activities is limited. Astronauts get up at three in the morning and enter the extravehicular preparation process at four, which takes two to three hours as planned.
The key point of preparation for extravehicular activities is naturally to wear extravehicular activity suits weighing about 130 kg. Compared with the extravehicular activity suit used in the Shenzhou VII extravehicular activity, the second generation product is used this time.
The advantage of the new generation of extravehicular spacesuit is that the joints of all parts of the body are more flexible. The gloves of the extravehicular spacesuit can even catch objects with a diameter of 0.5 cm, and the independent guarantee time for leaving the cabin has reached 8 hours. The height adaptation range of astronauts has also been relaxed from1.65m to1.8m in Tian Fei generation to1.6m to1.8m. ..
Unlike Shenzhou VII's short mission of several tens of minutes, Tiangong Space Station took more than seven hours to leave the cabin for the first time (including the time to enter and leave the airlock cabin), and the space station assembly flew around the earth for about 90 minutes. During the whole mission, astronauts need to stay in the shadow area for several hours, so the second generation of extravehicular spacesuit is equipped with lighting components and high-definition camera components.
The astronauts who performed the first mission of the space station were Liu Boming No.02 and Tang Hongbo No.03, and commander 0 1 Nie Haisheng sat on the controller console of the core module to provide support.
In the extravehicular mission sequence, Liu Boming is astronaut A, wearing a red striped extravehicular spacesuit. Tang Hongbo is astronaut B, wearing a blue striped extravehicular spacesuit.
Astronauts need to pass through the airlock cabin (node cabin) as a transportation hub when entering and leaving space. Tianhe-1 core cabin is divided into three parts: large column section, small column section and node cabin. The large column section is mainly the working area, and the small column section is the living area. Although the node module is the smallest but powerful, it can not only dock Shenzhou and Tianzhou spacecraft, but also park two 22-ton large experimental modules. At the same time, the node module also acts as an airlock module, which is the way for astronauts to get in and out of space.
There are three airlocks in Tiangong Space Station, and the airlock of Tianhe No.1 node is only one of them. In the experimental module I, which will be launched next year, there is also an air lock dedicated to personnel. After docking with Tianhe-1, the airlock of the experimental cabin is the main airlock, and the two airlocks are backup to each other. Meng Tian Experimental Module II will also be launched next year, and it also has a cargo airlock as the passage for the experimental load to enter and leave the space station.
When two astronauts enter space from the airlock, they need to "close the door of the orbital module connected with the core module of Shenzhou 12, the two-way pressure-bearing door between the small column section of the core module and the airlock module, and the backpack door of the extravehicular spacesuit, and open the door.
After closing the three doors, two astronauts dressed in extravehicular clothing carried out large-flow flushing and oxygen and nitrogen removal in the airlock room.
The so-called large-flow flushing refers to the "space suit large-flow oxygen flushing mode", that is, the air in the space suit is transformed into a pure oxygen environment, and the purpose of oxygen inhalation and nitrogen removal is to prevent the nitrogen in the astronauts from overflowing at 0.4 atmospheric pressure during extravehicular service, thus reducing the risk of decompression sickness.
After completing the sealing inspection and large-flow flushing of each hatch, the airlock enters the pressure relief procedure. Unlike 13 years ago, the Shenzhou VII airlock directly discharged air into space, the Tianhe core airlock chose the recovery mode. It transfers the air in the airlock to the air cylinder in the core cabin adjacent to the cabin, and then returns the air to the airlock when the astronauts return from the mission.
The advantage of this is that it can not only save valuable gas resources, but also eliminate the disturbance of the attitude of the spacecraft caused by the release of gas from the Shenzhou VII airlock into space.
Astronauts spend most of their time in the airlock. They provide power, oxygen supply and ventilation, temperature control and liquid cooling for the extravehicular spacesuit through the umbilical cord. After all the preparations for the extravehicular activity were completed, Liu Boming used the hatch key to open the extravehicular door in the third quadrant of the airlock.
13 years ago, when Shenzhou VII carried out China's first space mission, the door opening process was very bumpy due to the pressure difference inside and outside the airlock. Zhai Zhigang later revealed that I was desperately trying to open the door there and pull it. I really tried my best, but I just couldn't open it. It's too strong. When I pried open the door with a crowbar, it was an idiom "Be elated".
Drawing on the experience of the previous mission, the hatch key of Tianhe No.1 airlock was not set in the center of the hatch like Shenzhou VII, but on one side, and a booster handle was added at the same time, so the hatch opened very smoothly, even the word "easy" was just right.
Just as the astronauts were preparing to leave the cabin, the Tianhe manipulator docked at the outer wall of the small column section of the core cabin also began to operate, and finally moved the end effector at one end of the manipulator to the installation point of the foot limiter.
After Liu Boming opened the cabin door, he first added a protective cover on the cabin door, in order to prevent the cabin door from rubbing and damage the air tightness between the extravehicular spacesuit and the cabin door itself.
Then Liu Boming held the foot stopper in one hand and leaned out of the cabin with the circular handrail in the other hand, butting the foot stopper to one side of the end effector of the mechanical arm. Then, the extravehicular console for installing equipment and tools is installed on one side of the foot limiter.
After the foot limiter is installed, the ground flight control center issues the command "Please grasp the circular handrail and control the attitude of the assembly".
Speaking of attitude control, it should be mentioned that the space station implemented a wide range of attitude control, that is, from "continuous yaw flight" to "three-axis stable landing", when astronauts made preparations before the cabin.
Tiangong Space Station usually flies in continuous yaw mode. In this mode, the space station assembly can adjust its flight attitude at any time, quickly and flexibly receive the illumination from the best angle of the sun, and obtain sufficient power supply to the maximum extent.
The reason why the extravehicular mission is switched to the three-axis stable mode is that when the angle between the sun incident vector and the orbital plane is less than a certain angle, the flight attitude needs to be changed to ensure the energy balance and safe flight of the space station assembly.
Thermal control management is closely related to safe flight, especially the thermal control management of Shenzhou 12 manned spacecraft, because the node module is in a vacuum state during the extravehicular task, the door of the orbital module is closed, and there is no ventilation duct connected with shenzhou spaceship. In this case, if we continue to fly in a continuous yaw mode, the thermal control management pressure of Shenzhou manned spacecraft will be even greater.
Tiangong Space Station adopts an attitude control scheme without propellant consumption. There are six control moment gyroscopes in the front cone section of the large column section of the core cabin, and each gyro has a high-speed rotating rotor. By changing the rotating shaft of the rotor, the attitude control of the space station can be realized, and only electric energy is consumed without propellant.
While the attitude of the space station assembly was controlled, Nie Haisheng, who was in charge of the core module, reminded Liu Boming to open the mask of the extravehicular service. At this time, the space station has moved to the shadow area.
Nie Haisheng's "mask" refers to the outermost "filter window" in the four-layer structure of the extravehicular service cabin window, which acts like sunglasses and is mainly used in sunny areas, but needs to be opened in shadow areas.
The four-layer structure of extravehicular service window is filter window, protective window, pressure window and pressure window in turn.
The protective surface window can be replaced in orbit to prevent the surface window structure from being damaged by friction and extrusion, and nitrogen gas is filled between the two pressure surface windows for heat insulation and fog prevention.
As an independent spacecraft in space, the extravehicular spacesuit also needs complete protection capabilities, especially in the environment with a temperature difference of 200 degrees Celsius. Ensuring the safety of astronauts is the top priority of the extravehicular mission. Through passive thermal control means based on multi-layer thermal protection structure and active thermal control means based on water sublimator, the extravehicular space suit has formed all-factor protection capabilities of vacuum protection, high and low temperature protection and radiation protection through various technical means.
After the console outside the space station was installed, the robotic arm immediately moved to the "upper arm point", then Liu Boming boarded the foot limiter installed on the side of the end effector of the robotic arm, and then reported to the ground that "the robotic arm has been installed and there is no connection with the cabin at present".
Then the mechanical arm continues to move to the "equipment connection point", where Liu Boming, standing on the mechanical arm, will fix the main body of the emergency device and test the emergency braking device. The operation button of the device is very conspicuous, just on the extravehicular operation platform.
At the same time, 03 astronaut Tang Hongbo also issued the instruction of "please leave the cabin and carry out autonomous transfer outside the cabin".
The practical task of the two astronauts leaving the cabin this time is to lift panorama camera A, which is located near the control moment gyro between the big column section and the small column section in the fourth quadrant of the core module.
Unlike Liu Boming, who moved by mechanical arm, Tang Hongbo climbed to the working point by the handrail of the main road.
The two astronauts are divided into two ways, and the transfer difficulty is different. The transfer of mechanical arm tests the psychological control ability more, and the autonomous crawling transfer requires higher physical fitness.
Tang Hongbo first started from the long handrail across the cabin (airlock cabin and small column section), then moved to the fourth quadrant of the small column section through the longitudinal handrail, and then moved to the operation point through a series of transverse handrails. Each handrail on the outer surface of the space station has its own number. In the process of astronauts' autonomous extravehicular transfer, an anti-drift hook is always tied to the handrail to ensure absolute safety.
Every key position on the autonomous transfer path has a node cabin (airlock cabin) bearing signpost, which is to ensure that astronauts can quickly judge the bearing when encountering sudden danger, so as to return to the airlock cabin as the only life-saving passage.
Theoretically, people would think that Liu Boming, the 02 astronaut who transferred the mechanical arm, would arrive at the work site first, but in fact, Tang Hongbo, the 03 astronaut who crawled and transferred autonomously, arrived at the work site first.
This is because the mechanical arm assisted astronaut's large-scale transfer function was put into use for the first time. For safety reasons, the parameters were set conservatively, and only one-fifth of the design transfer speed was used.
When Tang Hongbo reached the operating point, he waved to Liu Boming standing on the mechanical arm. At this time, Tianhe and the mechanical arm have moved to the midpoint 3, and Liu Boming is only "one step away" from reaching the operating point. Here, he moved the operating platform to the left side of his body to get ready for reaching the operating point.
Tianhe-1 core module is considered to be the largest single spacecraft launched by human beings in recent ten years, so how big is it?
As the saying goes, seeing is believing. Since the orbit, few pictures from the third perspective can show its size. At this time, Liu Boming's extravehicular spacesuit camera provides us with a glimpse of the size of the core cabin.
In the camera picture of extravehicular spacesuit A, we can see the four-quadrant core module solar wing as thin as cicada, as well as the small cylindrical section and the large cylindrical section.
The pillar part is the rest area for astronauts to sleep, as well as the space toilet and space treadmill. There are relay communication antennas, measurement and control antennas and other facilities outside the cabin. The large column section shown in the picture is the main place for astronauts to work in orbit.
When Liu Boming arrived at the job site, the panoramic camera A was also powered off, ready to remove the support.
During the transfer of the mechanical arm, the wrist camera recorded another magnificent scene. On the broad solar wing of the core module, the thick sky and mechanical arms hold up Liu Boming, and further away, it is deep space.
Tianhe's mechanical arm supports astronauts' extravehicular operation, and the weight of astronauts plus extravehicular operation equipment will not exceed 0.5 tons. The mechanical arm can carry a spacecraft weighing up to 25 tons, and it is at the world's leading level in moving speed and accuracy. At the same time, it has the functions of monitoring extravehicular conditions, transferring experimental cabin, capturing hovering aircraft, transferring cargo spacecraft load, assisting astronauts' activities, checking cabin surface conditions, assisting astronauts to transfer core cabin solar wings, and cascading with experimental cabin manipulator.
All the above functions are inseparable from the core function of "deck crawling and transferring" realized by the manipulator in the process of docking and separating from the target adapters distributed on the deck through the front and rear end effectors.
The docking and separation mechanism of the mechanical arm is the same as that of the spacecraft. Although the sparrow is small and complete, its docking process is as follows:
At close range, the target of the target adapter is measured by high-precision vision through a binocular camera installed on the side of the end effector. Then, under the guidance of visual posture, the manipulator slowly approaches the target adapter. After grasping, there is a drag mechanism in the end effector to tighten the two devices, and at the same time, there is a positioning pin to limit the position. The whole docking process is divided into coarse positioning and fine positioning. Through these two processes, the mechanical, information and power interfaces are gradually tightened, and finally the four locking mechanisms are completely locked.
In this extravehicular mission, Tianhe manipulator, which assisted Liu Boming, an astronaut in 02, to make a large-scale transfer, crawled from the large column section to the small column section target adapter.
Due to the greater cargo carrying capacity of the mechanical arm, most of the maintenance tools and equipment for this extravehicular operation were carried and operated by the 02 astronaut Liu Boming.
After the two astronauts arrived at the job site, they immediately began to lift the panoramic camera A. The specific operation method was to install a universal handle outside the cabin and lift the base of the panoramic camera A. In this process, the only electric tool used by the astronauts was the "electric screwdriver".
The electric screwdriver is used to remove the mounting screws of extravehicular equipment, which can adapt to the vacuum, cold and dark environment outside the cabin. It has the functions of constant torque and positive and negative rotation, and is equipped with extension rod to adapt to the maintenance of equipment with different heights.
In order to adapt to the grasping ability of extravehicular spacesuit, the electric screwdriver is relatively large, weighing about 10 kg, and its weight is not a problem in space.
Astronauts put forward many constructive suggestions in the development of extravehicular tools, such as the knob design of electric screwdriver. The astronaut suggested that the knob should have a protruding structure, so that the rotation of the knob can be sensed during the tightening process, and the designer finally adopted the astronaut's suggestion.
In addition, if the electric screwdriver fails, there is a spare tool "extra wrench" to replace.
After a series of screwing operations, panorama camera A was lifted, and the gestures of the two extravehicular astronauts were perfectly displayed in the camera lens.
There are still a few questions about extravehicular panorama camera A:
1. Why is the panoramic camera an elevator? Because the camera is installed on the outer side of the four-quadrant control moment gyro in the core cabin, it needs to be lifted to expand the field of vision due to the size and installation height of the fairing of the Long March 5B rocket.
2. Why not design it to lift automatically? First, the space near the control moment gyro is limited, and then a camera equipped with a lifting motor alone is not worth the loss.
3. Why are there stitching marks in the pictures given by panorama camera? Because this is a panorama camera with four lens combinations to achieve a 360-degree viewing angle;
4. Why can't panorama camera be designed so that a single lens can be rotated by a motor? The fewer moving parts outside the cabin, the more reliable it is, and the rapid response ability of a single lens is not as good as that of four lenses working at the same time.
After the completion of the operation, the ground expressed its gratitude to the astronauts who carried out the extravehicular walking mission: the work of Shenzhou 12 was completed very well, and the ground also thanked you.
Liu Boming, astronaut of Shenzhou XII, responded with high EQ: Thank you for your hard work, thank you.
Panorama camera A has a better view after lifting. At this time, Liu Boming, who has completed the lifting work, also has free time to enjoy the beauty of space. He reported to the ground that there were white clouds, patches like the ocean, and ice. You can fly freely with the panoramic view of my extravehicular service camera and follow my steps.
While everyone is enjoying the beauty of space, 03 astronaut Tang Hongbo is drifting away from the camera. Next, he will perform another extravehicular task-the emergency return of the astronauts.
Tang Hongbo, who performed the emergency return mission, first climbed from the operating point of panorama camera A to the big column position near the resource cabin, and started the emergency return process from there. The whole crawling speed is 1 times faster than the normal crawling speed, so as to verify the emergency return ability of astronauts in case of sudden danger outside the cabin.
Before the emergency return, the three astronauts had a brief conversation:
Liu Boming: At 03, my mechanical arm began to swing.
Nie Haisheng: See you at the hatch.
Tang Hongbo: See you at the hatch.
At this time, the space station component is running in the shadow area. In the dark and deep space, 03 astronaut Tang Hongbo seems so lonely. However, with the full cooperation of his teammates, the full support of the ground crew and the expectations of hundreds of millions of people behind him, he would not have the word "loneliness" in his heart.
Soon, under the skillful crawling operation of Tang Hongbo, he passed through the large column section and the small column section in a shorter time than the mechanical arm transfer, and came to the hatch of the node cabin.
At this time, Liu Boming also arrived at "Intermediate Point 2" by mechanical arm, where he could see Tang Hongbo enter the cabin through his own extravehicular service camera. At the same time, the side berth of the second quadrant of the node module is also presented to the Chinese for the first time. Next year, another 22-ton large-scale module "Meng Tian Experimental Module No.2" will be permanently parked here, and the berth in the fourth quadrant corresponding to the second quadrant is the berth position of "Experimental Module No.1".
Astronaut Tang Hongbo began to enter the cabin after confirming that there were no unnecessary objects. Before entering the cabin, he reported to the ground: 03 thanks to all the scientific and technological workers, I wish the motherland's space industry will become stronger and stronger, and enter the cabin at 03.
At this time, the mechanical arm moved to the middle point of 1, and moved to the equipment receiving point after astronaut Tang Hongbo finished entering the cabin in 2003, where Liu Boming transferred the maintenance tools from Tang Hongbo to the node cabin.
After the maintenance equipment is transferred, the mechanical arm is transferred to the lower arm point, where Liu Boming gets off the mechanical arm.
Liu Boming can't directly return to the node cabin after completing the lower arm. Instead, he has to dismantle the foot stop and the extravehicular operation platform docked on the manipulator end effector. This part of the extravehicular activity equipment was initially transferred from the node cabin to the extravehicular activity, but they will not return to the node cabin during the return procedure.
After the manipulator moved to the "foot unloading limit point", Liu Boming unloaded it and installed it on the outer wall interface of the node module, which provided convenience for the next spacewalk mission.
Just as Liu Boming was preparing to install the foot limiter to the external interface of the node cabin, the command suddenly came from the ground: 02, please enter the cabin now, please temporarily put the foot limiter at the door of the cabin, please enter the cabin now, over.
This order emphasizes the high risk of the spacewalk mission. The reason why the command to enter the cabin came suddenly was because the ground monitored that the space station had encountered abnormal radiation, and the purpose of emergency entry was to avoid abnormal radiation.
Where does the abnormal radiation come from? I can't give a final conclusion until there is more public information.
Most of the radiation from the space protected by the earth's magnetic field will be shielded, but some radiation will pass through the magnetic field protection zone.
In addition, there is an abnormal radiation belt in the South Atlantic region of the earth, which is called the "South Atlantic abnormal belt". This belt covers the entire Brazilian coastline and is formed by the inclination of the axis of rotation of the earth's magnetic dipole to North America11,which causes the center of the earth's magnetic dipole to shift to the western Pacific Ocean by 500 kilometers and the radiation belt to extend downward by 200 kilometers.
In view of these radiation risk factors, it is necessary to take necessary evasive and protective measures. The cabin of Tiangong Space Station has a multi-layer protective structure, which can shield most dangerous radiation, so it should be returned to the cabin as soon as possible when encountering abnormal radiation.
After the radiation was abnormal, Liu Boming left the cabin again and installed the foot limiter on the equipment interface on the outer surface of the node cabin.
Then, after confirming that there was nothing unnecessary, he began to enter the cabin for the second time. Before entering the cabin, he reported to the ground: 02 As the astronaut who left the cabin for the first time, he thanked all the scientific researchers who participated in the research and experiment, and thanked the people of the whole country for their strong support. I will continue to leave the cabin and fly higher. The space station will be built even bigger. Thank you.
Liu Boming's report revealed that he would continue to take part in the second extravehicular mission of the Shenzhou 12 crew. According to the operating specifications, two astronauts should participate in each outbound mission of the space station. Who will be another astronaut on the next extravehicular mission?
Nie Haisheng has previously disclosed that any combination of the three astronauts of Shenzhou XII can accomplish any task that requires the cooperation of two people, which means that he can also perform the task of walking out of the cabin. As the second astronaut in China, if he can realize his dream of going out of space this time, his career as an astronaut can be described as a great success.
After entering the cabin, Liu Boming and Tang Hongbo successively completed the operations of removing the protective cover of the hatch, closing the hatch and checking the tightness of the hatch, followed by the recompression of the node airlock.
When the pressure of the airlock cabin reaches the rated working pressure of the extravehicular service, the extravehicular service is connected by umbilical cord, and the extravehicular service independently guarantees the transfer section.
When the pressure of the airlock cabin is the same as that of the extravehicular spacesuit, astronauts can take off the extravehicular spacesuit.
When the pressure of the airlock cabin is the same as that of the core cabin, the two-way pressure-bearing door connected with the airlock cabin is opened, and the mission of leaving the cabin is successfully completed.
After the two astronauts took off their extravehicular spacesuits in the airlock cabin, Nie Haisheng, who was sitting in the console of the large column section of the core cabin, got up in a hurry and then jumped to the door of the two-way pressure-bearing cabin to welcome the two comrades home.
At this time, the ground flight control center also sent a new message: congratulations on the successful completion of the first extravehicular activity of the space station on Shenzhou 12, and I wish the follow-up work smooth. Nie Haisheng replied: Shenzhou 12 understands, thanks to the support of scientific and technical personnel, and will work hard in the future.
Since last year, more than half of the six missions in the key technology verification stage of Tiangong Space Station have been completed, and the Long March 5 first flight test, Long March 5 second launch day and No.1 core module, Long March 7 third launch Tianzhou No.2 cargo spacecraft and Long March 2F second launch Shenzhou 12 manned spacecraft have been successfully implemented. At present, the three-cabin assembly has been running stably in orbit for more than a month.
A thousand miles without accumulation. The implementation of the above tasks has fully tested a series of core technical capabilities such as space rendezvous and docking, on-orbit propellant replenishment, and astronauts' mid-term stay obtained in the first two steps of the three-step planning of manned spaceflight project. There is more development with inheritance, especially the improvement and perfection of Shenzhou VII's extravehicular walking mission by the space station for the first time, which further proves the scientific planning and arrangement of the three-step manned spaceflight project in China.