The core stage of a Chinese Long March 5B rocket is set to fall uncontrollably back to Earth next week, in a re-entry that China is closely monitoring and says it poses little risk.
The roughly 25-metric-ton (23-ton) rocket stage launched on July 24 to deliver the Wentian laboratory cabin module to China’s incomplete Tiangong space station is expected to reenter Earth Atmosphere on July 30 at 7:24 p.m. ET, more or less 16 hours, according to Aerospace Corporation researchers Center for Orbital and Reentry Debris Studies (opens in 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 new tab)a US government-funded nonprofit research center based in California.
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The first stage of a rocket, its booster, is usually the bulkiest and most powerful section. Usually, rocket engine trajectories are planned to avoid orbit and harmlessly crash into the ocean, or if they make it into orbit, perform a controlled re-entry with some bursts of their engines. But Long March 5B’s booster engines cannot be restarted once stopped, dooming the booster to spiral around the earth before landing in an unpredictable location.
This is the third time in two years that China has dumped its missiles unchecked. In the second case, the rocket debris landed harmlessly in the Indian Ocean in May 2021. But the first incident, in May 2020, reportedly resulted in metal objects raining down on villages in Ivory Coast, although there were no reported injuries.
Because of their massive size, LongMarch 5B boosters can be particularly vulnerable to uncontrolled re-entry, meaning significant portions of their mass are not safely burned up in the atmosphere.
“The general rule of thumb is that 20 to 40 percent of a large object’s mass reaches the ground, but the exact figure depends on the object’s construction,” says Marlon Sorge, space debris expert at The Aerospace Corporation. said in an online Q&A (opens in new tab). “In this case, we would expect around five to nine tons [6 to 10 tons].
“In general, with an upper stage, we see small and medium tanks surviving more or less intact, and large engine components,” Sorge added. “The large tanks and skin of this core stage will likely fall apart. We’ll also see light items like insulation falling out. The melting point of the materials used will make a difference in what’s left.”
What is the risk?
With more than 88% of the world’s population residing below the rocket’s orbit, according to The Aerospace Corporation, some surviving debris could end up in a populated area. However, Muelhaupt said the chances of that debris injuring someone is between 1 in 1,000 and 1 in 230 and the risk for a single person is much lower — about 1 in 6 trillion to 1 in 10 trillion. For comparison, he added, you’re about 80,000 times more likely to be struck by lightning. The internationally recognized threshold for accident risk from uncontrolled missile reentry is 1 in 10,000, according to a 2019 report issued by the US government’s Orbital Debris Mitigation Standard Practices.
Despite the relatively low risk of injury or property damage, China’s decision to launch rockets with no controlled re-entry options has drawn some stern admonitions from US space experts.
“Space nations must minimize the risks to people and property on Earth from the re-entry of space objects and maximize transparency regarding these operations,” said NASA Administrator Bill Nelson wrote in a statement (opens in new tab) after the Long March 5B crash-landed in 2021. “It is clear that China is not meeting responsible standards regarding its space debris.”
“Why are we worried? Well, it resulted in property damage last time [in 2020], and so people need to prepare,” said Ted Muelhaupt, a space expert and consultant at The Aerospace Corporation, during a news conference. “No need. We have the technology to not have this problem.”
China has dismissed these concerns as “shameless hype”. In 2021, Hua Chunying, then spokesman for China’s foreign ministry, accused Western reporting of bias and “textbook-style double standards” in its coverage of China’s falling missiles. For example, in March 2021, debris from a falling SpaceX rocket slammed into a farm in Washington state, an event she claims western news outlets reported positively and with “romantic language.”
Under Article VII of the 1967 Outer Space Treaty, to which all major space nations – including China – are party, any country that sends an object into space is internationally liable for the damage it may cause to another party if it crashes back to Earth . Should that happen, the incident would be dealt with in a damage commission or dealt with through diplomatic channels—like in 1978 when the malfunctioning Soviet satellite Kosmos 954 crashed in western Canada, leaving a roughly 370-mile (600-kilometer) trail of debris from its defunct nuclear reactor on board.
Christopher Newman, professor of space law and policy at Northumbria University in London, said all major launch nations will have pieces of space objects returning to Earth uncontrolled, but it’s important to create an international consensus on how to deal with them difficult to get around 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. “Nevertheless, we only have to look at countries’ attitudes towards space tracking and situational awareness and the in-orbit debris problem to see that the international community is not yet motivated to try to solve this problem.
“As a lawyer, I realize that change only happens when there is some kind of catastrophe or tragedy – and by then it’s often too late,” he said. “The warnings apply to all users of space; the question is whether they are taking action now to deal with it.”
Originally published on Live Science.