Experts: No need to worry about falling space...

Edited and Translated by Yao Chun, People's Daily Online

As more and more satellites are being launched into the space, will the debris of the failed satellites bring disaster to earth? The experts from the Center for Space Science and Applied Research (CSSAR) under the Chinese Academy of Sciences say: "Don't panic, space junk will not fall on your head."

"Recently some reports may have caused certain panic in the public, who are worried that space debris will threaten people's survival. But, in fact we can rest assured that space debris will not hit people because the probability is minimal," said Gong Jiancun, deputy director of CSSAR. 

Space debris will not pose a threat to humans, he said. However, the real reason why scientists are concerned about space debris is because of its potential to harm or hinder spacecraft.

Since 1957, when the first artificial satellite was launched into space, the amount of space debris has increased year by year. As of this week, there are more than 16,000 pieces of debris with a diameter of more than 10 centimeters in space, according to observation data from the United States. 

This debris is distributed in different earth orbits: low orbit, hundreds of kilometers away from the earth; moderate-altitude orbit, thousands of kilometers away, and high orbit, tens of thousands of kilometers away. Because of this, the debris is not concentrated in a dense region of space.

Generally speaking, space debris is divided in three categories: large space debris, with a diameter of more than 10 centimeters; small space debris, with a diameter of less than 1 millimeter, and dangerous debris, with a diameter between large and small debris.

"If the debris falls to the earth, most of it will be burned away by the high temperature of thousands of degrees produced by the high-speed friction with the atmosphere. Even if a large chunk of space debris penetrated the atmosphere and posed a threat to the earth, mankind should be capable of defending against it," Gong said.

First, we can roughly estimate its orbit. With the estimation of its orbit, we can intercept it. Gong said that the U.S. has successfully intercepted a failed satellite using a missile. That satellite contained highly toxic substances. In order to prevent it from falling into the sea, the U.S. destroyed the satellite by a missile launched from a warship. China also has similar technologies and can disintegrate it in the space before it causes harm."

"Scientists also have come up with many other methods to clear the space debris. For example, we can leave some fuel in satellites and control the satellite to fly out of the original track," Gong said. "Some countries have developed passive technologies, such as launching a spacecraft to catch space debris and take it away. Other countries are developing satellites with mechanical arms, which not only can repair satellites but also can pull the failed satellites out of the orbit."

However, these technologies are not very mature. It is still uncertain when they will come into use, he said.