Debris from a massive Chinese booster rocket could rain down in the coming days

Definitely look up.

Scientists say there’s an outside chance that debris from a massive, spent Chinese booster rocket will not entirely burn up on reentering Earth’s atmosphere and could rain down on populated areas in the coming days.

And it’s not the first time Chinese space junk has raised public safety concerns.

Here’s the news: China delivered a second module to its manned but still under construction Tiangong space station over the weekend. But, while the mission was considered a success and smaller parts of the cargo spacecraft have already largely burned up in the atmosphere, a 25-ton booster rocket is currently in a decaying, uncontrolled orbit, and scientists expect it to fall back to Earth in a matter of days.

The Aerospace Corporation, which tracks space junk through its Center for Orbital and Reentry Debris Studies, tweeted its estimate that the rocket body would reenter Earth’s atmosphere on or about July 31 and included a chart showing the used rocket’s orbital path.

In a statement, the Aerospace Corp. noted that while the chances of debris coming down in a populated area are very small, they are not nonexistent.

“Due to the uncontrolled nature of its descent, there is a non-zero probability of the surviving debris landing in a populated area — over 88% of the world’s population lives under the reentry’s potential debris footprint,” the Aerospace Corp. statement reads. “A reentry of this size will not burn up in the Earth’s atmosphere, and the general rule of thumb is that 20%–40%of the mass of a large object will reach the ground, though it depends on the design of the object.”

A rocket reentry re-run: There are at least two other instances of spent Chinese rockets falling back to Earth in uncontrolled reentries, noted in an academic paper from a group of University of British Columbia scientists published earlier this month by the Nature Communications journal.

According to the research, in May 2020, an 18-metric-ton core stage of another Chinese rocket reentered the atmosphere from orbit in an uncontrolled manner after being used to launch an unmanned experimental crew capsule. Debris from the rocket body, including a 12-meter-long pipe, struck two villages in the Ivory Coast, causing damage to several buildings. One year later, another similar piece of rocket debris made an uncontrolled reentry after being used to launch another part of the Tiangong space station into low Earth orbit. This time, the debris crashed into the Indian Ocean. Researchers said the two rocket stages were the heaviest objects to reenter in an uncontrolled manner since the Soviet Union’s Salyut-7 space station in 1991.

And, while the technology exists to bring large, ejected sections of spacecraft back through the atmosphere in a controlled manner, the University of British Columbia scientists suggest there is an increasing risk of harm — 10% of one or more casualties in the next decade — from falling space debris coming to those on the ground. And, the extra cost of utilizing those control systems is worth it, from a safety standpoint.

“We argue that recent improvements in technology and mission design make most of these uncontrolled reentries unnecessary, but that launching states and companies are reluctant to take on the increased costs involved,” the paper reads. “Those national governments whose populations are being put at risk should demand that major spacefaring states act, together, to mandate controlled rocket reentries, create meaningful consequences for non-compliance and thus eliminate the risks for everyone.”

Chinese authorities, however, claim the risks are minimal and on Wednesday, China Foreign Ministry spokesperson Zhao Lijian rejected concerns about potential harm to those on the ground.

“Since the development stage of the space engineering program, China has taken into consideration the debris mitigation and return from orbit into atmosphere of missions involving rocket carriers and satellite sent into orbit,” Zhao said at a daily briefing Wednesday, according to The Associated Press.

“It is understood that this type of rocket adopts a special technical design that most of the components will be burnt up and destroyed during the reentry process,” Zhao said. “The possibility of causing damage to aviation activities or on the ground is extremely low.”