Another big Chinese rocket launched into space at 2:22 p.m. Beijing time on Sunday, and again, no one knows where or when it will land.
It will be a replay of two previous launches of the same rocket, the Long March 5B, which is one of the largest currently in use. For about a week after launch, global space debris watchers will follow the 10-story, 23-ton rocket booster as dragging drags of air slowly drag it down.
The likelihood of it hitting anyone on Earth is low but significantly higher than many space experts consider acceptable.
The powerful rocket was specially designed to launch parts from China’s Tiangong space station. The latest mission raised Wentian, a laboratory module that will expand the station’s scientific research capabilities. It will also add three additional spaces for astronauts to sleep in and another airlock for performing spacewalks.
The completion and operation of the space station is portrayed in state media broadcasts as important to China’s national prestige. But the country somewhat tarnished its reputation during the first flights of the rocket.
After the Long March 5B’s first launch in 2020, the booster re-entered over West Africa, with debris causing damage but no injuries in villages across the nation of Ivory Coast.
The booster from the second launch, in 2021, splashed harmlessly in the Indian Ocean near the Maldives. Yet Bill Nelson, the NASA administrator, issued a statement criticizing the Chinese. “It is clear that China is failing to meet responsible standards regarding its space debris,” he said.
China dismissed this criticism with great fanfare. Hua Chunying, a senior Foreign Ministry spokeswoman, accused the United States of “hype”.
“The United States and a few other countries have been highlighting the landing of Chinese rocket debris in the past few days,” Hua said. “To date, no damage from landing debris has been reported. I’ve seen reports that since the launch of the first artificial satellite over 60 years ago, not a single incident has occurred where debris has hit anyone. American experts put the odds of that happening at less than one in a billion.
Chinese space agencies did not respond to a request for an interview about the upcoming launch.
Space has immense prestige for the Chinese government, which views each major launch as an addition to its buildup of space power, said Namrata Goswani, author of “Scramble for the Skies: The Great Power Competition to Control the Resources of Outer Space.” space”.
China has overtaken Russia in the sophistication of its space program, Dr Goswani said. “China is ahead of the Russian space program in terms of the lunar and Mars program as well as the military space organization,” she said.
On a sunny, warm morning, crowds of Chinese space fans spilled onto the beach near the rocket launch pad on the country’s southern island of Hainan. Others crowded onto the rooftops of hotels along the seafront.
Zhang Jingyi, 26, set up his camera on the roof of a hotel with around 30 other people on Sunday morning.
It was her 19th trip to “hunting rockets”, she said. She made her hotel reservation four months ago.
“There are more people than ever,” she said.
Seconds before the rocket took off, “Everyone started counting. Then the crowd erupted in 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 study, and landed and operated a rover on Mars. The United States is the only other country to have accomplished this latest feat.
“China hasn’t done anything and hasn’t done anything the United States hasn’t already done in space,” said Joan Johnson-Freese, a professor at the US Naval War College and former chairman of the business department. of national security. “But it is reaching technical parity, which is of great concern to the United States”
She likened the Chinese space program to a tortoise versus the American hare, “although the tortoise has accelerated considerably in recent years.”
As of last April, China had completed a total of six assignments for the construction of the space station. Three crews of astronauts have lived aboard the station, including the trio that will receive the Wentian module this week.
About 15 minutes after launch, the rocket booster successfully placed the Wentian spacecraft on its planned orbital path. It rendezvoused with the Tianhe space station module about 13 hours after liftoff. The Chinese space agency gave no indication that it had made any changes to the booster.
“It will be the same story,” said Jonathan McDowell, an astrophysicist at the Center for Astrophysics in Cambridge, Mass., who tracks the comings and goings of objects in space. “It is possible that the rocket designers made some minor modifications to the rocket that would then allow them to propulsively deorbit the stage. But I don’t expect it.
If the design of the rocket has not changed, no thruster will guide its descent and the thruster motors cannot be restarted. The final rain of debris, with a few tonnes of metal expected to survive to the surface, could occur anywhere along the booster’s path, which travels as far north as 41.5 degrees north latitude and as far south as 41.5 degrees south latitude.
This means there will be no danger for Chicago or Rome, both of which are a little north of the orbital trajectories, but Los Angeles, New York, Cairo and Sydney, Australia are among the cities the booster will cross.
The science of predicting where a free-falling rocket stage will fall is tricky. Earth’s atmosphere inflates and deflates depending on how hard the sun shines on a particular day, and this phenomenon speeds up or slows down the rate of fall. If a calculation is wrong by half an hour, the falling debris has already traveled a third of the way around the world.
By design, the Long March 5B core booster stage will push the Wentian module, which is over 50 feet long, into orbit. This means that the booster will also reach orbit.
This differs from most rockets, where the lower stages typically fall back to Earth immediately after launch. Upper stages that reach orbit typically re-ignite the engine after releasing their payloads, guiding them to re-entry above an unoccupied area, such as the middle of an ocean.
Malfunctions sometimes cause involuntary and uncontrolled re-entry, such as the second stage of a SpaceX rocket that hit Washington State in 2021. But the Falcon 9 stage was smaller, about four tons, and less likely to cause damage or injury.
The United States and NASA have not always been as careful as they are now when bringing large objects back into the atmosphere.
Skylab, the first US space station, crashed to Earth in 1979, with large chunks hitting Western Australia. (NASA never paid a $400 fine for waste.)
Nor did NASA plan to phase out its Upper Atmosphere Research Satellite, or UARS, after that mission ended in 2005. Six years later, when the dead satellite, which was the size of city bus, headed for an uncontrolled re-entrance, NASA calculated a one in 3,200 chance that someone could be injured. It ended up falling into the Pacific Ocean.
Typically, 20 to 40 percent of a rocket or satellite will survive reentry, said Ted Muelhaupt, a debris expert at Aerospace Corporation, a largely federally funded nonprofit that conducts reentry. research and analysis.
This would suggest that 10,000 to 20,000 pounds of the Long March 5B booster could hit the Earth’s surface.
Muelhaupt said the United States and some other countries avoid uncontrolled re-entries of space debris if the risk of injury to someone on the ground is greater than 1 in 10,000.
To date, there have been no known cases where anyone has been injured by falling man-made space debris.
“That number of 1 in 10,000 is somewhat arbitrary,” Muelhaupt said. “It’s been widely accepted, and recently there’s been concern that a lot of objects are going in, they’re adding up to the point where someone is going to get hurt.”
If the risk is higher, “it’s quite common to throw them into the ocean,” said Marlon Sorge, executive director of Aerospace Corporation’s Center for Orbital and Re-entry Debris Studies. “That way you know you’re not going to hit anyone.”
Mr Muelhaupt said that without details of the Chinese rocket’s design, it would not be possible to calculate an estimate of the risk. But “I am very confident that it exceeds the threshold” of risk of 1 in 10,000, he added. “Well above the threshold.”
The Long March 5B booster is about three times more massive than the UARS. A rough estimate would be that it poses three times the 1 in 3,200 risk that NASA had estimated for the UARS, possibly higher.
“It’s three UARS in a sense,” said Dr. McDowell. The chance of this booster hurting someone, he said, “could be as high as one in a few hundred.”
During a pre-launch broadcast on CGTN, a Chinese state media, Xu Yansong, a former official of the National Space Administration of China, discussed the 2020 incident in Ivory Coast. Since then, he says, “we have improved our technologies” bring down the rocket stage in an uninhabited area, but he gave no details.
The same series of events could soon happen again.
In October, China will launch a second laboratory module named Mengtian into orbit to complete the assembly of Tiangong. He too will fly on another Long March 5B rocket.
Li You contributed to the research.
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