China News Service, Beijing, March 31 (Zhang Yafeng and Ma Shuaisha) The Tianzhou-2 cargo spacecraft successfully completed the controlled re-entry mission on the 31st. Most of the spacecraft's components were ablated and destroyed, and a small amount of debris fell into the South Pacific for scheduled safety. sea ​​area.

Why did the Tianzhou-2 cargo spacecraft deorbit?

How is controlled re-entry achieved?

How difficult is it?

Yang Sheng, chief designer of the Tianzhou-2 cargo spacecraft of the Fifth Academy of China Aerospace Science and Technology Corporation, revealed the secret.

　　Yang Sheng said that in accordance with international practice, the de-orbit operation of the on-orbit spacecraft after the completion of the mission is an inevitable choice for China Aerospace to fulfill its responsibility as a major country.

　　According to reports, in general, space debris larger than 10 centimeters is a disaster for on-orbit spacecraft once it collides.

These space debris often make the flying spacecraft have to take orbital change measures to avoid collisions to ensure their own safety, and sometimes seriously affect on-orbit missions or even lead to mission failures.

Space debris management is a global challenge. In low-Earth orbit at an altitude of 400 kilometers, it will take several years or even decades for space debris to gradually deorbit and disappear.

　　After the expiry of the Tianzhou-2 mission, the de-orbit operation will be carried out in accordance with international practice, which can not only reduce the amount of space debris and avoid harm to on-orbit spacecraft and the ground, but also play an important role in the governance of the global space debris environment. Occupying orbital resources is an important choice for China Aerospace to fulfill its responsibilities and responsibilities as a major country and establish the image of a responsible major country.

　　How was Tianzhou-2 controlled to deorbit?

Yang Sheng pointed out that at the end of the life of satellites or other spacecraft in low orbits, the orbits gradually decrease under the action of atmospheric resistance or control systems. When they drop to an altitude of about 100 to 120 kilometers, under the action of aerodynamic forces, the orbital altitude decreases rapidly. , the aerodynamic action is intensified, and the spacecraft can be considered to re-enter the atmosphere at this time.

　　When a low-orbit spacecraft re-enters the atmosphere, it will fly at a speed of 8 kilometers per second. At this time, under the dual action of aerothermal and aerodynamic forces, the spacecraft will gradually disintegrate, disintegrate and ablate.

　　In order to reduce the risk to ground personnel, the common practice for deorbiting large spacecraft near the Earth is controlled re-entry. The controlled re-entry method successfully deorbited and fell into a safe area.

The safe area is generally chosen in the uninhabited area of ​​the South Pacific, where few planes and ships pass by, and it is an internationally common low-orbit spacecraft re-entry "grave".

　　It is reported that China also successively implemented the controlled re-entry missions of Tianzhou-1 and Tiangong-2 in 2017 and 2019. In order to reduce ground risks, orbit and attitude maneuvers were adopted to control the re-entry and landing points.

　　The controlled re-entry process of the Tianzhou-2 cargo spacecraft adopts a staged control method to precisely control the fall.

The first time is to change from a circular orbit at an altitude of 400 kilometers to a perigee elliptical orbit of 200 kilometers, and the second time is to change its perigee to an altitude of 90 kilometers below the atmosphere, so that it can enter the atmosphere and burn up, and the entry without burning The scheduled landing area was successfully completed in the end.

　　During its in-orbit period, Tianzhou-2 has successfully completed various technical tests and verifications during the construction phase of the Chinese space station, as well as on-orbit expansion tests. This controlled de-orbit and re-entry into the atmosphere has created a safe and clean space for other spacecraft. environment.

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