Another large Chinese rocket blasted off at 2:22 p.m. Beijing time on Sunday, and again, no one knows when or where it will land.
This will be a replay of two earlier launches of the same rocket, the Long March 5B, one of the largest currently in use. For about a week after launch, the world’s space debris watchers will track the 10-story, 23-ton rocket booster as air friction slowly pulls it back.
The probability of it hitting anyone on Earth is low, but well above what many space experts consider acceptable.
The powerful rocket was specially designed to launch debris from China’s Tiangong space station. The latest mission boosts “Ask the Sky,” a laboratory module that will expand the station’s scientific research capabilities. It will also add three more spaces for astronauts to sleep and an airlock for their spacewalks.
State media broadcasts that completing and operating the space station is important to China’s national prestige. But the country did some damage to its reputation in the early rocket flights.
After the first Long March 5B launch in 2020, the booster re-entered the skies over West Africa, with debris causing damage to villages in the Ivorian country, but no casualties.
A second booster launch in 2021 splashes harmlessly in the Indian Ocean near the Maldives. Still, NASA Administrator Bill Nelson issued a statement critical of the Chinese. “It’s clear that China is not meeting responsible standards when it comes to space debris,” he said.
China has rejected the criticism with great fanfare. Hua Chunying, a senior foreign ministry spokeswoman, accused the US of “hyping up.”
“The US and some other countries have been hyping up the landing of Chinese rocket fragments over the past few days,” Ms Hua said. “To date, no damage from landing debris has been reported. I have seen reports that since the launch of the first artificial satellite more than 60 years ago, there has not been a single incident of debris hitting a person. U.S. experts believe this possibility is not to one in a billion.”
The China Space Administration did not respond to interview requests about the upcoming launch.
Space has enormous prestige for the Chinese government, which believes that every major launch will Increase its accumulation of space power.
Dr Goswani said China had surpassed Russia in the sophistication of its space program. “Compared with Russia’s space program, China has a leading position in the Moon and Mars program and military space organization,” she said.
On a sunny, warm morning, throngs of Chinese space fans scattered on the beach near the rocket launch site on Hainan Island in southern China. Others huddled on the rooftops of beachfront hotels.
Zhang Jingyi, 26, and about 30 people set up cameras on the hotel roof on Sunday morning.
She said it was her 19th “chasing a rocket”. She booked the hotel four months ago.
“There are more people than ever before,” she said.
Seconds before the rocket took off, “the countdown started. Then the crowd erupted into cheers and exclamations,” she said in a later interview.
China has landed a rover on the far side of the moon, collected lunar material and brought it back to Earth for scientific research, and landed and operated a rover on Mars. The US was the only other country to accomplish the last feat.
“China has not and has not done what the United States has not done in space,” said Joan Johnson-Fries, a professor at the U.S. Naval War College and former chairman of the Department of National Security Affairs. Concerns”
She likened China’s space program to a tortoise, compared to a hare in the United States, “although the tortoise has accelerated considerably in recent years.”
As of April this year, China has completed six space station construction tasks. Three astronauts live on the space station, including the trio that will receive the SkyQuest module this week.
About 15 minutes after the launch, the rocket booster successfully sent the Wentian spacecraft into the predetermined orbit. About 13 hours after launch, it will rendezvous with the Tianhe space station. The Chinese space agency has given no indication that it has made any changes to the booster.
“It’s going to be the same story,” said Jonathan McDowell, an astrophysicist at the Center for Astrophysics in Cambridge, Massachusetts, who tracks the comings and goings of objects in space. “It’s possible that the rocket designers would make some small changes to the rocket that would then propel them off-orbit. But I don’t want that.”
If the rocket design hasn’t changed, the booster’s engines can’t be restarted without the thrusters to guide its descent. The final shower of debris, with several tons of metal expected to survive all the way to the surface, could occur anywhere in the booster’s path, moving north to 41.5 degrees north latitude and south to 41.5 degrees south latitude.
That means there’s no danger in Chicago or Rome, which are both north of the orbital orbit, but Los Angeles, New York, Cairo and Sydney, Australia, are among the cities the booster will pass.
The science of predicting where a tumbling rocket stage will land is tricky. Earth’s atmosphere expands and contracts depending on how strongly the sun shines on a given day, a phenomenon that speeds up or slows down the descent. If the calculations were off by half an hour, the falling debris would have traveled a third of the way around the Earth.
According to the design, the central booster stage of the Long March 5B will propel the 50-foot-long capsule into orbit. That means the booster will also go into orbit.
This is unlike most rockets, whose lower stages usually return to Earth immediately after launch. Upper stages reaching orbit typically start their engines again after releasing their payloads, guiding them to re-entry over uninhabited areas such as the middle of the ocean.
Failures occasionally lead to unexpected runaway re-entry, such as the fall of the second stage of a SpaceX rocket in Washington state in 2021. But the Falcon 9 is smaller, about 4 tons, and less likely to cause damage or injury.
The United States and NASA haven’t always been as careful as they are now when it comes to bringing large objects back into the atmosphere.
America’s first space station, Skylab, crashed into Earth in 1979, and a chunk of debris hit Western Australia. (NASA has never paid a $400 fine for littering.)
NASA also has no plans to dispose of its Upper Atmosphere Research Satellite, or UARS, after the mission ends in 2005. Six years later, with the dead satellite the size of a city bus heading for a runaway-entry, NASA calculated the chance of someone being injured at 1 in 3,200. It ended up in the Pacific Ocean.
Typically 20 to 40 percent of a rocket or satellite survives re-entry, said Ted Muelhaupt, a debris expert at Aerospace Corporation, a largely federally funded nonprofit that does research and analysis.
That means the 10,000 to 20,000-pound Long March 5B booster could hit the Earth’s surface.
Mr. Mulhaupt said the United States and some other countries would avoid the uncontrolled re-entry of space debris if the chance of someone on the ground being injured was higher than one in 10,000.
To date, there have been no known cases of anyone being injured by falling man-made space debris.
“The one in 10,000 figure is a bit arbitrary,” Mr Moorehaupt said. “It’s been widely accepted, and recently there’s been concern that when a lot of objects re-enter, they add up to cause someone to get hurt.”
If the stakes are higher, “dumping them in the ocean is fairly common practice,” said Marlon Sorgue, executive director of the Aerospace Corporation’s Center for Orbital and Reentry Debris Research. “That way, you know you’re not going to hit anyone.”
Mr Mulhaupt said risk estimates could not be calculated without details on the Chinese rocket’s design. But he added, “I’m pretty confident it’s above” the 1 in 10,000 risk threshold. “Well above the threshold.”
The mass of the Long March 5B booster is about three times that of the UARS. A rough guess is that it poses a risk three times as high as the 1 in 3,200 risk NASA estimates for UARS, and perhaps more.
“In a sense, it’s three UARS,” Dr. McDowell said. He said the chance of the booster harming someone “could be as high as a few percent”.
In a preview broadcast on Chinese state media CGTN, Xu Yansong, a former official of the China National Space Administration, mentioned the 2020 incident in Côte d’Ivoire. Since then, “we have improved the technology” to land the rocket stage in an uninhabited area, he said, without giving details.
The same series of events could soon be repeated.
In October, China launched a second laboratory module called “Mengtian” into orbit to complete the assembly of the Tiangong. It will also carry another Long March 5B rocket.
Li You contributed research.