At 0502 hours on April 20, 2022, the Tianzhou III cargo spacecraft separated from the rearward-facing port of the core module, flew around to the forward-facing port, and completed automatic rendezvous and docking at 0906 hours. It took about four hours for Tianzhou III to complete the separation and fly around docking, in other words to change positions.
This is the first of the more important actions performed by the space station after the return of the Shenzhou XIII astronauts, so why the Tianzhou III position adjustment? As a cargo spacecraft, where will it end up? Here we come together to talk about this topic.
From April 29, 2021, the sky and the core module to date, the space station project has completed the launch of Tianzhou II and Tianzhou III two cargo spacecraft launch mission, this year will also be launched to ask the sky, Mengtian two experimental module, as well as the Shenzhou XIV, Shenzhou XV manned spacecraft.
After the space station is built and put into operation, it will involve the maintenance and control of the state under multiple modes of operation, several resupply and astronaut visits per year, maintenance and repair of a large number of assembled parts or equipment, and the management of hundreds of types of payloads and their operational planning, etc.
The space station will also have the ability to support a large number of spacecraft.
The Tianzhou series of cargo spacecraft, on the other hand, is seen as part of the tactical-level operational planning for the space station, taking care of the resupply of propellants and living supplies, the replenishment of medical equipment and medicines, maintenance and repair items, and the uplinking of space experiment equipment.
The Tianzhou cargo spacecraft is based on the idea of type spectrum and modularization design, and carries out the platform configuration and layout design. Currently, there are three types of spectrum, namely, fully sealed, semi-open and fully open, and adopts the two-compartment design of cargo compartment and propulsion module, with the cargo compartment used for transporting various kinds of materials and the propulsion module providing energy and power.
The total length of the Tianzhou cargo spacecraft is 10.6 meters, the maximum diameter of the cabin is 3.35 meters, and the maximum width of the solar cell wing is nearly 15 meters after unfolding. Among them, the cargo compartment consists of the front cone section, column section and rear cone section. The maximum upward cargo capacity of the airship is 6.5 tons, and the total weight is 13.5 tons under full load, with a propellant replenishment capacity of 2.1 tons.
Compared with similar foreign active cargo spacecraft, it has a strong uplink capacity and a high cargo ratio (i.e., the ratio of the maximum cargo capacity to the total weight of the cargo spacecraft when fully loaded).
In short, the Tianzhou cargo spacecraft is a newly developed manned spacecraft for the construction and operation of the space station and the supply of material transportation tasks, the uplink cargo ratio, cargo transportation, propellant replenishment, and other comprehensive capabilities are comparable to or even better than the international active cargo spacecraft.
The fourth day after Shenzhou XIII returned, Tianzhou III was under the control of the ground control center, completed the independent separation, fly around and docking, from the core module backward port transfer to the forward port, which is to say, a change of location. So what is the purpose of this? The main points are as follows:
1, to make room for Tianzhou IV
According to the planning of the manned space station project, the return of Shenzhou XIII means the end of the key technology validation phase, and the next step will be to move into the construction phase.
On the afternoon of April 17, the State Press Office held a conference on the progress of China's space station construction, and Hao Chun, director of the China Manned Spaceflight Office, said that the construction of China's space station is divided into two phases: the verification of the key technology and the construction phase, and that through the implementation of the six missions, the relevant key technology has been a comprehensive breakthrough.
In the next construction phase, the space station project will implement six launch tasks: the launch of Tianzhou IV cargo spacecraft in May, the launch of Shenzhou XIV manned spacecraft in June, the launch of the space station in July to ask the sky experimental module, the launch of the Mengtian experimental module in October, and then have to implement the launch of the Tianzhou V and Shenzhou XV tasks.
Then this time the Tianzhou III conversion position, the primary purpose is to make room for the launch of Tianzhou IV. You may ask, the current space station is only the core module and Tianzhou three two parts, there are several interfaces for Tianzhou four intersection docking, why must Tianzhou three previously where the backward port?
In fact, this question is very well understood, the cargo spacecraft docking to the rearward port is to facilitate the astronauts to transfer supplies. This is because the rearward port is on the large column segment of the core module, while the forward port is on the node module.
This means that the astronauts can transfer supplies directly from the cargo ship to the core module through the rearward port, whereas with the forward port, the astronauts would have to go through two more doors, which is a more cumbersome process.
In fact, Tianzhou-2 had previously performed the same operation, and it was separated from the rearward port before the launch of Tianzhou-3, and flew around to the forward port to rendezvous and dock, moving position for Tianzhou-3.
So, Tianzhou 3 is also flying around and docking to make room for Tianzhou 4, which will make it easier for Shenzhou 14 to transfer supplies in the future.
2. Docking of the experimental module will be convenient
After the launch of Shenzhou XIV in June, the space station will be formed into a "one-cabin, three-boat" configuration, which means that the three docking ports on the core module will be fully occupied.
Then the implementation of the evacuation mission can only be Tianzhou III cargo spacecraft, by then it has completed its mission, is about to reach the life of the flight in orbit. After Tianzhou III evacuation, the empty docking port happens to be the core module forward port, which is exactly the docking interface for the experimental module segment program.
After flying in orbit for a period of time, the QSEM will complete a horizontal transposition with the assistance of a robotic arm, and transpose from the forward port of the core module to the horizontal radial docking port, after which it will stay for a long time. Similarly, the Dream Sky Experiment Module will be docked to the forward port of the core module before translocating to the radial mooring port. At this point, construction of the station assembly is complete.
So Tianzhou 3 is docking around the flight at this time, translocating from the core module backward port to the forward port, mainly to make room for the subsequent launch mission and to facilitate the subsequent docking of the experimental module.
In fact, about the end of Tianzhou III, Tianzhou II has already made clear where to go. As a non-reusable cargo spacecraft, after completing its mission, Tianzhou III will evacuate the space station and re-enter the atmosphere in a controlled state, and ultimately disintegrate completely over the South Pacific Ocean under the violent friction of the air and burn up.
Shenzhou XIII in the operation of the six-month period, life work produced a variety of garbage will be transferred to the Tianzhou III cargo spacecraft, these wastes will be disintegrated with the Tianzhou III incineration, together with the smoke.
Some people may ask why Tianzhou III is not recycled. This is actually due to two considerations:
The first is that the Tianzhou series of cargo spacecraft itself is not a recyclable structure, it has no high-temperature resistant paint on the surface, and there is no propulsion module. The purpose of this design is actually to maximize the carrying capacity.
The cargo capacity of China's Tianzhou series of cargo spacecraft is three times that of Russia's Progress M cargo spacecraft, and two times that of SpaceX's Dragon spacecraft, so it can be said that the Tianzhou cargo spacecraft is the strongest cargo spacecraft in the world in active service.
The Dragon is currently the only cargo ship in the world that can be recycled and used again. However, in order to meet the recovery capacity, the Dragon uses a large amount of load on the return component, which makes its uplink cargo capacity only about 3.3 tons, only about half of the Tianzhou series of cargo spacecraft.
Second, the recovery of cargo spacecraft need to invest a lot of manpower and material resources, such as manned spacecraft return capsule return, the need for search and rescue teams to practice many times, and put a variety of transportation, search and rescue equipment, etc., the staff of all parties to cooperate with each other, in order to complete the recovery task.
The design life of the Tianzhou III cargo spacecraft is one year in orbit, and it is close to its design life when it returns, even if it is recovered and can not be used again. For a cargo spacecraft that has reached the end of its useful life, it is clearly inappropriate to invest a large amount of cost for recycling.
All in all, after Tianzhou 3 completes its mission, it will end up the same as Tianzhou 2, re-entering the atmosphere and burning over the Pacific Ocean, illuminating the future of the space station project with the light of the fire that burned itself.
Shenzhou XIII has returned, the three astronauts are undergoing rehabilitation training, the next space station will be transferred to the stage of full-scale construction, Tianzhou III at this time to fly around the docking, will be for the next Tianzhou IV cargo spacecraft launch to vacate the location.
As a cargo spacecraft, Tianzhou III's mission is about to be accomplished, and before the launch of the Ask the Sky Experiment Module, it will be evacuated from the space station and re-entered into the atmosphere, completely disintegrated and ablated over the South Pacific Ocean. With the light of the flame, it will light the way for future rocket launches.
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