The roughly 25-ton (23 metric tons) rocket stage, which launched on July 24 to deliver the Wentian Cabin Laboratory Module to China’s unfinished Tiangong space station, is scheduled to re-enter. land 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 and Re-Entry Debris Studies (opens in a new tab). Exactly where it will land is unknown, but the likely debris field includes the US, India, Australia, Africa, Brazil and Southeast Asia, according to The Aerospace Corporation (opens in new tab), a non-profit, US government-funded research center based in California. A rocket’s first stage, its booster, is usually the bulkiest and most powerful part. Typically, booster rocket trajectories are designed to veer off course and fall harmlessly into the ocean or, if they reach orbit, to perform a controlled reentry with a few bursts of their engines. But the Long March 5B booster engines cannot restart after stalling, dooming the booster to orbit Earth before landing in an unpredictable location. This is the third time in two years that China has fired its missiles in an uncontrolled manner. On a second occasion, in May 2021, the wreckage of the missile landed safely in the Indian Ocean. But the first incident, in May 2020, caused metal objects to rain down on villages in Ivory Coast, although no injuries were reported. Because of their enormous size, Long March 5B boosters can be particularly vulnerable to danger 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% of the mass of a large object will reach the ground, but the exact number depends on the design of the object,” said Marlon Sorge, a 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 about five to nine metric tons [6 to 10 tons].” “Generally, for 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 base stage are likely to separate. We’ll also see lightweight items like insulation fall off. The melting point of the materials used will make a difference to what’s left.”
What is the risk?
According to The Aerospace Corporation, since over 88% of the world’s population is under the missile’s orbital footprint, some surviving debris could land in a populated area. But Muelhaupt said the odds of that debris harming someone range from 1 in 1,000 to 1 in 230, and the risk to a person is much lower — about 1 in 6 trillion to 1 in 10 trillion. For comparison, he added, the chance of being struck by lightning is about 80,000 times greater. The internationally accepted accident risk threshold for uncontrolled missile re-entry is 1 in 10,000, according to a 2019 report issued by the US Government. Orbital Debris Mitigation Standard Practices. Despite the relatively low risk of harm to people or property, China’s decision to launch missiles without controlled re-entry options has prompted some stern warnings from US space experts. “Spacefaring nations must minimize risks to people and property on Earth from the reentry of space objects and maximize transparency about these operations,” NASA Administrator Bill Nelson he wrote in a statement (opens in new tab) after the 2021 Long March 5B landing. “It is clear that China is failing to meet responsible standards regarding its space junk.” “Why are we worried? Well, he caused property damage last time [in 2020], and people need to prepare as a result,” said Ted Muelhaupt, a space expert and consultant to The Aerospace Corporation, during a press conference. “That’s not necessary. We have the technology to avoid this problem.” China has dismissed these concerns as “shameless hype”. In 2021, Hua Chunying, then a spokeswoman for the Chinese Foreign Ministry, accused Western reports of bias and “textbook-style double standards” in coverage of rockets fired from China. For example, in March 2021, debris from a falling SpaceX rocket smashed into a farm in Washington state, an event he claims Western news outlets covered positively and using “romantic words.” 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 to another part when it crashes back to earth. If that happened, the incident would be handled in a claims commission or handled through diplomatic channels — as in 1978, when the malfunctioning Soviet Kosmos 954 satellite crashed in western Canada, spewing about 370 miles (600 kilometers) of spray. debris path from its broken nuclear reactor. Christopher Newman, professor of space law and policy at Northumbria University in London, said all major launch nations will have pieces of space objects that return to Earth in an uncontrolled manner, but building an international consensus on how to deal with them is difficult given the of current geopolitical tensions. “This is a problem that needs an international solution, especially since objects like missile bodies are three times more likely to affect cities in the ‘Global South,’” Newman told Live Science. “However, we only have to look at countries’ attitudes to space monitoring and space situational awareness, as well as the problem of debris in Earth orbit, to see that the international community is not yet motivated to try to solve this matter. “As a lawyer, it’s clear to me that the impetus for change only comes when there’s some form of disaster or tragedy — and by then it’s often too late,” he said. “The warnings are there for all space users; the question is whether they will take action now to address them.” Originally published in Live Science.
