The main stage of a Chinese Long March 5B rocket is due to fall uncontrollably back to Earth today in a re-entry that China is tracking closely and says 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 unfinished Tiangong space station, is expected to re-enter on the ground atmosphere on July 30 at 12:15 a.m. ET, plus or minus 1 hour, according to researchers at The Aerospace Corporation Orbital and Re-Entry Debris Research Center (opens in new tab).
Exactly where it will land is unknown, but the possible debris field includes the United States, India, Australia, Africa, Brazil and Southeast Asia. according to The Aerospace Corporation (opens in new tab), a US government-funded non-profit research center based in California.
Related: Largest spacecraft to fall out of control from space
A rocket’s first stage, its booster, is usually the bulkiest and most powerful section. Typically, booster rocket trajectories are planned to avoid orbit and land harmlessly in the ocean or, if they do achieve orbit, to perform a controlled re-entry with a few shots from their engines. But Long March 5B’s booster engines cannot be restarted after stalling, dooming the booster to spiral around Earth before landing in an unpredictable location.
This is the third time in two years that China has decommissioned its missiles in an uncontrolled manner. In the second case, in May 2021, debris from a missile landed harmlessly in the Indian Ocean. But the first incident in May 2020 caused metal objects to rain down on villages in Côte d’Ivoire, although no injuries were reported.
Because of their enormous size, the Long March 5B boosters may be particularly at risk during uncontrolled re-entry, meaning that significant portions of their mass do not burn up safely in the atmosphere.
“A general rule of thumb is that 20% to 40% of the mass of a large object will reach the ground, but the exact number depends on the design of the object,” Marlon Sorge, space debris expert at The Aerospace Corporation, said in an online Q&A (opens in new tab). “In that case, we would expect about five to nine metric tons [6 to 10 tons].”
“In general, for an upper stage, we see small and medium tanks survive more or less intact, and the large engine components,” Sorge added. “The large tanks and shell of this main stage are likely to disintegrate. We’ll also see lightweight items like insulation fall out. The melting point of the materials used will make a difference to what remains.”
What is the risk?
According to The Aerospace Corporation, since more than 88% of the world’s population lies below the rocket’s orbital footprint, some surviving debris may land in a populated area. But Muehlhaupt said the chances of that debris harming someone ranged from 1 in 1,000 to 1 in 230, and the risk for an individual was much smaller, about 1 in 6 trillion to 1 in 10 trillion. By comparison, he added, you’re roughly 80,000 times more likely to be struck by lightning. The internationally accepted accident risk threshold for uncontrolled rocket re-entry is 1 in 10,000, according to a 2019 report issued by the US government on Standard Practices for Orbital Debris Reduction.
Despite the relatively low risk of harm to people or property, China’s decision to launch missiles without controlled return options has prompted some stern warnings from US space experts.
“Space nations must minimize risks to people and property on Earth from re-entry of space objects and maximize transparency regarding these operations,” NASA Administrator Bill Nelson said in a statement (opens in new section) after the Long March 5B crash landing in 2021 “It is clear that China is failing to meet responsible standards regarding their space debris.”
“Why do we bother? Well, last time it caused property damage [in 2020], and as a result, people need to prepare,” said Ted Muelhaupt, a space expert and consultant at The Aerospace Corporation, during a press conference. “It’s not necessary. We have the technology to not have that problem.”
China dismissed these concerns as “shameless noise”. In 2021, Hua Chunying, then a spokeswoman for China’s Ministry of Foreign Affairs, accused Western reporting of bias and “textbook-style double standards” in its coverage of China’s missile downing. For example, in March 2021, debris from a falling SpaceX rocket crashed into a farm in Washington state, an event she claims Western news outlets covered positively and with the use of “romantic words”.
Under Article VII of the 1967 Outer Space Treaty, to which all major space nations, including China, are parties, any country that sends an object into space bears international responsibility for the damage it may cause to another country when it crash back to Earth. If that happens, the incident will be handled in a claims commission or handled through diplomatic channels — such as in 1978, when the defunct Soviet satellite Kosmos 954 crashed in western Canada, scattering about 370 miles (600 kilometers) of debris debris from the broken shipboard nuclear reactor.
Christopher Newman, professor of space law and policy at Northumbria University in London, said that all major launch nations would have parts of space objects that return to Earth in an uncontrolled manner, but establishing an international consensus on how to deal with it is difficult for them given the current geopolitical tension.
“This is a problem that needs an international solution, especially since objects like missile bodies are three times more likely to impact cities in the ‘Global South,'” Newman told Live Science. “Yet we only have to look at countries’ attitudes 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 is clear to me that the impetus for change only comes when there is some form of disaster or tragedy – and then it is often too late,” he said. “The warnings are there for all users of space; the question is whether they will act now to address them.”
Originally published on Live Science.
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