Another large Chinese rocket launched into space on Sunday at 14:22 Beijing time, and once again, no one knows where or when it will land.
It will be a repeat of two previous launches of the same rocket, the Long March 5B, which is one of the largest in use today. For about a week after launch, observers in the space debris world will follow the 10-story, 23-ton rocket booster as air friction slowly pulls it down.
The probability of it reaching anyone on Earth is low, but significantly higher than many space experts consider acceptable.
The powerful rocket was specifically designed to launch parts of 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 more spaces for astronauts to sleep in and another airlock for spacewalks.
Completing and operating the space station is described in state media broadcasts as important to China’s national prestige. But the country has damaged its reputation during the rocket’s first flights.
After Long March 5B’s first launch in 2020, the propellant reentered West Africa, with debris causing damage but no injuries to villages in the nation of Ivory Coast.
The booster from the second launch, in 2021, splashed harmlessly into the Indian Ocean near the Maldives. Still, Bill Nelson, NASA’s administrator, issued a statement criticizing the Chinese. “It is clear that China is not meeting responsible standards for its space debris,” he said.
China rejected these criticisms with considerable force. Hua Chunying, a senior spokeswoman for the Ministry of Foreign Affairs, accused the United States of “exaggeration.”
“The United States and some other countries have been promoting the landing of Chinese rocket remnants for the past few days,” Ms. Huh “So far, no damage has been reported from the landing debris. I have seen reports that since the launch of the first man-made satellite over 60 years ago, there has been no incident in that a piece of debris hit someone. US experts put the chances of that at less than one in a billion.”
China’s space agencies did not respond to a request for an interview about the upcoming launch.
Space holds immense prestige for the Chinese government, which sees each major launch as adding 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”.
China has surpassed Russia in the sophistication of its space program, Dr Goswani said. “China is ahead compared to the Russian space program in terms of its lunar and Mars program as well as military space organization,” he said.
On a sunny and warm morning, crowds of China’s space enthusiasts lined the beach near the rocket launch site on Hainan Island in the country’s south. Others crowded onto the rooftops of beachside hotels.
Zhang Jingyi, 26, set up his camera on the roof of a hotel along with 30 others on Sunday morning.
It was his 19th trip to “chasing rockets,” he said. He made his hotel reservation four months ago.
“There are more people than ever before,” he said.
Seconds before the rocket lifted off, “Everybody started counting down. Then the crowd erupted in cheers and exclamations,” he 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 has landed and operated a rover on Mars. The United States is the only other country to have achieved the latter feat.
“China is not and has not done anything that the United States has not done in space,” said Joan Johnson-Freese, a professor at the US Naval War College and former chair of the department of security affairs. national “But technical parity is being reached, which is of great concern to the US”
He compared the Chinese space program to a tortoise compared to the American hare, “although the tortoise has accelerated considerably in recent years.”
As of this April, China had completed a total of six missions for the construction of the space station. Three teams 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 into its intended orbital path. It is to rendezvous with the Tianhe Space Station module about 13 hours after liftoff. 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, Mass., who tracks the comings and goings of objects in space. “It’s possible that the rocket designers could have made some minor change to the rocket that would have allowed them to propulsively deorbit the stage. But I don’t expect it.”
If the rocket design has not changed, no propellant will guide its descent and the propellant engines cannot be restarted. The final shower of debris, with a few tons of metal expected to survive to the surface, could occur anywhere along the path of the booster, which travels up to 41.5 degrees north latitude and up to 41.5 degrees of south latitude.
This means there will be no danger to Chicago or Rome, which are slightly north of the orbital paths, but Los Angeles, New York, Cairo and Sydney, Australia, are among the cities the booster will travel through .
The science of predicting where a falling rocket stage will land is complicated. The Earth’s atmosphere inflates and deflates depending on how hard the sun is shining on a particular day, and this phenomenon speeds up or slows down the rate of fall. If a calculation is off by half an hour, the falling debris has already traveled a third of the way around the world.
By design, Long March 5B’s center booster stage will push the Wentian module, which is more than 50 feet long, into orbit. This means that the booster will also reach orbit.
This differs from most rockets, where the lower stages usually return to Earth immediately after launch. Upper stages that reach orbit typically fire their engines again after releasing their payloads, guiding them toward reentry through an unoccupied area, such as the middle of an ocean.
Sometimes malfunctions lead to unintended inbounds, like the second stage of a SpaceX rocket that fell over Washington state in 2021. But the Falcon 9 stage was smaller, about four tons, and was less likely to cause damage or injury.
The United States and NASA were not always as careful as they are now when it comes to getting large objects into the atmosphere.
Skylab, America’s first space station, plummeted to Earth in 1979, with large pieces impacting Western Australia. (NASA never paid a $400 fine for leaving litter.)
NASA also did not plan for the disposal of its Upper Atmosphere Research Satellite, or UARS, after the end of that mission in 2005. Six years later, when the dead satellite, which was the size of the city bus, headed for an uncontrolled reaction. -entry, NASA calculated a 1 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 survives reentry, said Ted Muelhaupt, a debris expert at the Aerospace Corporation, a nonprofit organization funded largely by the federal government that conducts 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.
Mr. Muelhaupt said the United States and some other countries avoid uncontrolled inflows of space debris if the chance of injuring someone on the ground is greater than 1 in 10,000.
To date, there have been no known cases of anyone being injured by falling man-made space debris.
“That 1 in 10,000 number is a bit arbitrary,” said Mr. Muelhaupt. “It’s been widely accepted, and recently there’s been concern that when a lot of objects come back in, they add up to the point that someone will get hurt.”
If the risk is higher, “it’s pretty common practice to dump them in the ocean,” said Marlon Sorge, executive director of the Aerospace Corporation’s Center for Orbital Debris and Reentry 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 a risk estimate. But “I’m pretty sure it’s above the threshold” of a 1 in 10,000 risk, he added. “Way above the threshold.”
The Long March 5B booster is about three times more massive than the UARS. A rough guess would be three times the 1 in 3,200 risk that NASA had estimated for UARS, perhaps higher.
“These are three UARS in a sense,” Dr. McDowell said. The chance of that reinforcement 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 outlet, Xu Yansong, a former China National Space Administration official, referred to the 2020 incident in Ivory Coast. Since then, he said, “we have improved our technologies” to drop the rocket stage in an uninhabited region, but gave no details.
The same series of events could soon be repeated again.
In October, China will launch a second laboratory module called Mengtian into orbit to complete the assembly of Tiangong. It will also fly on another Long March 5B rocket.
You contributed to the research.