China News Agency, Beijing, April 1 (Ma Shuisha) The Tianzhou-2 cargo spacecraft completed its mission a few days ago, deorbited and re-entered the atmosphere and burned up, causing widespread concern.

　　After the Tianzhou-2 mission expires, the de-orbit operation will be implemented, which provides an important reference for the global space debris environmental governance.

At present, tens of thousands of space debris has become a "stumbling block" for human exploration of space.

Are abandoned spacecraft going to fall and burn up?

How to clean up the "space road"?

Who will pay for this?

Yang Yuguang, vice chairman of the International Astronautical Union Space Transportation Committee, was interviewed by a reporter from China News Agency to make an interpretation.

　　Do all abandoned spacecraft need to fall and burn?

　　According to reports, the main source of space debris is human spaceflight activities, such as the last stage of rockets, the disintegration or explosion of abandoned satellites, and the collision of spacecraft.

These space debris often make speeding spacecraft have to take measures to avoid collisions.

"Because the relative speed is very high, space debris of 1 cm may break down the outer shell of the spacecraft, let alone fragments of more than 10 cm." Yang Yuguang said.

　　In order to reduce the generation of space debris, the Tianzhou-2 cargo spacecraft has been controlled to deorbit and re-enter the atmosphere.

Yang Sheng, chief designer of the Tianzhou-2 cargo spacecraft of the Fifth Academy of China Aerospace Science and Technology Corporation, said that this is an inevitable choice for China Aerospace to fulfill its responsibility as a major country.

　　In fact, not all spacecraft enter the atmosphere, fall and burn up.

Yang Yuguang pointed out that there are two types of spacecraft de-orbiting. Large-scale spacecraft like Tianzhou-2 need to lower their orbital altitude and re-enter the atmosphere in a controlled manner so that they will not pose a threat to outer space or ground objects.

　　Another situation is that the spacecraft will not return to the earth after deorbiting. The most typical example is a satellite in geosynchronous orbit.

As we all know, there is only one geosynchronous orbit, which shows that the orbit is congested. However, its height is about 36,000 kilometers. It is too expensive for satellites at the end of their lives to return to the ground from this orbit. It requires a lot of energy, and it is still difficult for humans to achieve.

　　Yang Yuguang pointed out that responsible spaceflight countries will raise the orbit of abandoned satellites by about 200 kilometers and enter the "grave orbit". The atmospheric density of this orbit is extremely thin, and the satellite will basically not fall to the earth again, thereby avoiding and working spacecraft. produce an intersection.

　　How to solve large and small fragments?

　　In addition to active deorbiting, debris mitigation is also a common measure taken by major aerospace powers, such as passivating the final stage of the rocket, eliminating the risk of explosion and reducing the amount of space junk by exhausting propellant, gas in high-pressure gas cylinders, and battery power .

　　For low-orbit small satellites, some countries also use reverse thrust rockets to lower the perigee of the satellite, and use off-orbit sails to increase the windward area of ​​the satellite, enhance resistance, shorten the satellite's stay in orbit, and reduce the probability of spacecraft collision.

　　Regarding debris mitigation technology, Yang Yuguang believes that space debris of different sizes needs to be handled differently.

"Large" debris requires active capture technology, but this consumes a lot of fuel, requires high technical equipment, and costs a lot, so it is obviously not suitable for "small" debris.

　　"One of the most promising methods at present is to use lasers to remove them." Yang Yuguang said that irradiating space debris with lasers for many years can vaporize the surface materials of the debris, and the resulting force can slow down the speed of the debris, reduce its orbital height, and reach The effect of reducing the time spent in orbit by debris.

　　Should debris removal be co-paid?

　　How to deal with the accelerating amount of space debris has become the focus of space powers in recent years.

Yang Yuguang believes that data sharing between countries is very important.

At present, all countries in the world, especially the major aerospace powers, have certain observation capabilities for space debris. While observing and determining the orbit of debris, sharing relevant data is an important aspect of international cooperation in the space field.

　　Then there's debris removal.

Wu Weiren, chief designer of China's lunar exploration project, said that space debris removal technology experiments are also being carried out internationally, but this task is very heavy, because there are more and more debris, and there are about tens of thousands of space debris above 10 cm that have been catalogued , With more and more subsequent launches and more space vehicles, the total number of space debris will also increase, and the difficulty of removal will also increase.

　　Yang Yuguang also pointed out that although there are many ways to remove debris, it lacks direct economic returns. "Who will do such a public welfare thing? There is no clear answer yet, and it is necessary to carry out international consultations and establish relevant mechanisms, such as whether to jointly pay the bill. etc.” In addition, measures to mitigate debris, such as passivation, de-orbit, etc., are measures that all spacefaring nations should take.

　　"International cooperation should be carried out at multiple levels to jointly safeguard the precious resource of outer space." Yang Yuguang said.

(over)