"99.5% Safe"?... The Real Reason China Is Criticized for Space Debris [Reading Science]

Experts: "Irresponsibility and Lack of Transparency Are Bigger Issues"

[Image source=Yonhap News]

[Asia Economy Reporter Kim Bong-su] A large piece of Chinese space debris is expected to fall to the surface on the 31st (Korean time). Although experts generally analyze that the probability of damage is low, criticism of the Chinese authorities responsible for the problem remains. They are accused of acting irresponsibly and opaquely by leaving it so that no one can accurately predict when and where it will fall, unnecessarily causing anxiety in other countries.

According to space news outlet Space.com, the upper stage of the Long March 5B rocket used by China to launch a space station module on the 24th is expected to re-enter the atmosphere around 3 a.m. on the 31st. It is a large piece of space debris estimated to weigh 20 tons, 31 meters long, and 5 meters in diameter.

In South Korea, the Korea Astronomy and Space Science Institute, a space hazard monitoring agency, is tracking the trajectory of this object. Since the 26th, the Ministry of Science and ICT has been conducting space monitoring activities in cooperation with the institute to prepare for the risk of rocket debris falling on the Korean Peninsula.

The Chinese authorities claim that the rocket debris is designed to burn up upon atmospheric re-entry and that there will be no damage. Zhao Lijian, spokesperson for the Chinese Ministry of Foreign Affairs, said at a briefing on the 27th, "This rocket booster is specially designed to mostly burn up and disintegrate during re-entry," adding, "The possibility of causing damage on the ground is extremely low."

However, experts point out that for large space debris, 20-40% does not burn up after atmospheric re-entry, so it is highly likely that at least 5 to 9 tons of fragments will remain and fall to the surface this time as well. In fact, in May 2020, debris from the same Long March 5B rocket fell into the Atlantic Ocean without completely burning up and was found on the beach in C?te d'Ivoire, Africa. In April and May of this year, space debris presumed to be Chinese rocket fragments fell in rural areas of western India, frightening residents.

The problem is that no one can accurately predict when and where the debris of this Long March 5B rocket will fall. Based on current orbital tracking results, only an approximate time and a location somewhere between 41 degrees north and 41 degrees south latitude on Earth can be estimated. The rocket is currently orbiting the Earth at an incredible speed of 27,400 km/h. The density of the upper atmosphere changes constantly, and weather can also be a major variable.

Jonathan McDowell, a researcher at the Harvard-Smithsonian Center for Astrophysics, explained, "Because atmospheric density and weather change moment by moment, it is impossible to accurately predict when and how the rocket debris will re-enter the atmosphere."

The movement of the upper stage of this Long March 5B rocket is also irregular. Matthew Schaefer, senior director at LeoLabs, said, "The rocket debris appears to be continuously subjected to various forces, causing it to rotate sideways," adding, "Because we do not know exactly how it is spinning, we cannot accurately model the expected trajectory."

It is certain that the rocket debris will fall to the surface, but the probability of damage is low. Since 70% of the Earth's surface is ocean, and even if it falls on land, many areas are uninhabited. Ted Mulholland, a researcher at the U.S. Aerospace Research Institute, stated, "The probability that nothing will happen (no damage) is 99.5%."

However, criticism of the Chinese authorities remains because these incidents could have been avoided. Most orbital rocket launch authorities design launches so that rocket debris falls immediately after liftoff into the ocean or unpopulated safe areas to avoid such problems. SpaceX’s Falcon 9 rocket, for example, uses advanced technology to control thrust and safely land at a designated location for reuse. However, China’s Long March 5B rocket leaves the upper stage drifting uncontrolled in the atmosphere after placing payloads such as satellites and space station modules into orbit, allowing it to fall under gravity without any control.

Other countries also criticize the Chinese authorities for this irresponsibility and the lack of transparency that causes anxiety in other nations by not disclosing specific information. In fact, Bill Nelson, NASA Administrator, said in May last year, "Countries that launch space vehicles should strive to minimize and transparently manage the risks that debris poses to life and property during atmospheric re-entry," adding, "It is clear that China is not meeting responsible standards regarding their space debris."