The Wentian experimental cabin has been relocated, and here come the hard-core knowledge points!

At 12:44 on September 30, after about an hour of coordination between the ground and the spacecraft, the Wentian experimental module completed its transfer. This is the first time that my country has used a transfer mechanism to carry out a large-scale module transfer operation in orbit. After the transfer of the Wentian experimental module was completed, the space station complex changed from a two-module "I" configuration to a two-module "L" configuration. Today, let's take a look at the hard-core knowledge points about the transfer of the Wentian experimental module.

Why should we implement transposition?

According to my country's space station construction plan, during the space station construction phase, the two experimental modules launched successively will be symmetrically distributed at the two lateral berthing ports of the core module node module, thus completing the construction task of the basic "T" configuration of the space station.

The Wentian Experimental Module is currently China's largest single spacecraft. If it is directly docked sideways with the space station assembly, the deviation of the center of mass will have a greater impact on the attitude of the space station, and there will even be a risk of rolling out of control. It's like when we push the bottom of a wooden stick with our hands. If we push it straight in its direction, the stick will go straight forward; if we hit it from the side, the stick will deflect greatly. In the microgravity state of space, the force that deviates from the center of mass is enough to "move a thousand pounds with a little effort" and make the attitude of the space station unstable. Therefore, both of China's experimental modules will first be docked axially at the forward port, and then moved to the lateral parking port through rotation. The rotation action has played an important role in the construction of China's space station and the implementation of subsequent tasks.

Why use planar indexing?

In order to make the transfer process of the Wentian Experimental Module more stable and smooth, the research and development team has conducted several demonstrations and compared the transfer schemes of the International Space Station, and creatively proposed a "planar transfer scheme". This is the first time in the world that a spacecraft transfer action has been completed with a planar transfer scheme. The Russian "Mir" space station uses a flip assembly scheme, but this scheme will cause the cabin to flip 90° after the cabin is transferred into place. The scheme adopted by my country is to transfer the Wentian Experimental Module in the same plane. At this time, since the motion trajectory of the center of mass is also in a plane, the transfer action has less disturbance to the attitude of the space station assembly, making it easier for the space station to control its attitude.

However, compared with the flip-type transfer scheme, the planar transfer scheme is more difficult to design and the ground test system is more complicated. In order to complete the transfer task in one go and succeed at one time, the development team carefully analyzed and demonstrated the planar transfer scheme, and developed a corresponding test system to conduct on-orbit workload and transfer full-time test verification, ensuring the orderly, safe and reliable transfer task of the experimental cabin.

Do I need to do a “physical examination” before transfer?

There is no fulcrum during the operation of spacecraft in orbit. Every time the space station assembly receives a new module for berthing, and performs transfer and docking movements, the space station assembly will be disturbed. At the same time, with the addition of new modules, the system center of mass position, system inertia, configuration and other parameters of the space station assembly are constantly changing, resulting in constant changes in the dynamic characteristics of the space station, such as modal frequency and vibration mode. Therefore, every time the space station is "transformed" in orbit, it becomes a "new self". In order to ensure that the model is accurate enough in each attitude, after the simulation model is established, it must be continuously corrected through modal tests to provide accurate dynamic characteristic parameters for the design of the space station attitude control system, so that the model is more accurate, the transfer is more stable, and the various operations in orbit are smoother.

After working day and night, the "Physical Examination Master" - a high-precision modal parameter identification system was born. This system can realize the high-precision modal parameter identification of the world's largest single spacecraft , and accurately identify the modal parameters of the entire space station and large subsystems , providing essential input for the on-orbit assembly and attitude adjustment of the space station. Every successful "change of costume" of the space station is inseparable from this test system. After the Mengtian experimental module docks with the node module, it will also dock with another lateral berthing port of the node module through transfer, forming the basic "T" configuration of China's space station. Based on subsequent needs, this system will also be continuously upgraded to contribute to the long-term stable operation of the space station in orbit.