A 25-ton Chinese rocket booster will crash into Earth today. What is the risk?

The main stage of a Chinese Long March 5B rocket is scheduled to return to Earth in an uncontrolled manner today in a reentry that China is closely monitoring and has said poses little risk.

The roughly 25-ton (23 metric tons) rocket stage, which launched on July 24 to deliver the Wentian Laboratory cabin module to China’s incomplete Tiangong space station, is expected to return to enter of the Earth atmosphere on July 30 at 12:15 p.m. ET, give or take 1 hour, according to researchers at The Aerospace Corporation Center for Orbital Studies and Debris Reentry (opens in a new tab).

Exactly where it will land is unknown, but the possible debris field includes the US, India, Australia, Africa, Brazil and Southeast Asia. according to The Aerospace Corporation (opens in a new tab), a non-profit research center funded by the US government based in California.

Related: The Largest Spacecraft to Fall Out of Space Uncontrolled

A rocket’s first stage, its booster, is usually the bulkiest and most powerful section. Typically, the trajectories of rocket boosters are planned so that they avoid orbit and sink harmlessly into the ocean or, if they reach orbit, perform a controlled re-entry with a few bursts of their engines. But Long March 5B’s booster engines can’t restart once they’ve stalled, dooming the booster to spiral around Earth before landing in an unpredictable location.

This is the third time in two years that China has removed its rockets in an uncontrolled manner. In the second instance, in May 2021, the remains of the rocket landed harmlessly in the Indian Ocean. But the first incident, in May 2020, caused metal objects to rain down on villages in Ivory Coast, although there were no injuries.

Because of their massive size, Long March 5B’s boosters may be particularly prone to hazards during uncontrolled reentry, meaning that significant portions of their mass do not burn up safely in the atmosphere.

“The general rule of thumb is that 20 to 40 percent of the mass of a large object will make it to Earth, but the exact number depends on the design of the object,” explains Marlon Sorge, space debris expert at The Aerospace Corporation. he said in an online Q&A (opens in a new tab). “In this case, we would expect between five and nine metric tons [6 to 10 tons].”

“Typically, for an upper stage, we see small and medium tanks survive more or less intact and large engine components,” Sorge added. “Large tanks and the skin of this core stage are likely to break. We’ll also see lightweight items like insulation fall off. The melting point of the materials used will make a difference in what’s left.”

What is the risk?

According to The Aerospace Corporation, since more than 88% of the world’s population is under the rocket’s orbital footprint, some surviving debris could land in a populated area. But Muelhaupt said the odds of such debris harming someone range from 1 in 1,000 to 1 in 230, and the risk for a single individual is much smaller: about 1 in 6 trillion to 1 in 10 trillion By comparison, he added, the likelihood of being struck by lightning is about 80,000 times greater. The internationally accepted casualty risk threshold for uncontrolled rocket reentry is 1 in 10,000, according to a 2019 report issued by the US government’s Standard Practices for Orbital Debris Mitigation.

Despite the relatively low risk of harm to people or property, China’s decision to launch rockets without controlled re-entry options has drawn some stern warnings from US space experts.

“Space nations must minimize risks to people and property on Earth from re-entries of space objects and maximize transparency regarding these operations,” said NASA Administrator Bill Nelson. he wrote in a statement (opens in a new tab) after the crash landing of 2021 Long March 5B. “It is clear that China is not meeting responsible standards for its space debris.”

“Why are we worried? Well, last time it caused property damage [in 2020], and people need to prepare as a result,” said Ted Muelhaupt, a space expert and consultant for The Aerospace Corporation, during a news conference. “This is not necessary. We have the technology to not have this problem.”

China has dismissed these concerns as “blatant exaggeration”. In 2021, Hua Chunying, then a spokeswoman for the Chinese Foreign Ministry, accused Western reports of bias and “textbook-style double standards” in their coverage of China’s rocket downing. For example, in March 2021, debris from a falling SpaceX rocket crashed into a farm in Washington state, an event she says the Western media covered positively and with the use of “words romantic”.

Under Article VII of the 1967 Outer Space Treaty, to which all major space-faring nations, including China, are parties, any country that sends an object into space is internationally responsible for the damage it may cause elsewhere when it crashes. on earth. If that happened, the incident would either be processed in a claims commission or dealt with through diplomatic channels, as in 1978, when the malfunctioning Soviet satellite Kosmos 954 crashed in western Canada, scattering about 600 kilometers (370 miles) long. way with the remains of its broken nuclear reactor on board.

Christopher Newman, professor of space law and policy at Northumbria University in London, said that all major launch nations will have parts of space objects that return to Earth in an uncontrolled manner, but establishing an international consensus on how to deal with los is necessary. difficult given the current geopolitical tensions.

“This is a problem that needs an international solution, especially since objects like rocket bodies are three times more likely to hit cities in the ‘Global South,'” Newman told Live Science. “However, we only have to look at the attitude of countries towards space tracking and space situational awareness, as well as the issue of debris in Earth’s orbit, to see that the international community is still not motivated to try to solve this problem.

“As a lawyer, it’s clear to me that the impetus for change only comes when there’s some kind of disaster or tragedy, and by then it’s often too late,” he said. “The warnings are there for all users of space; the question is whether they will take action now to deal with them.”

Originally published in Live Science.

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