WENCHANG, CHINA - APRIL 29: A Long March-5B Y2 roc
WENCHANG, CHINA - APRIL 29: A Long March-5B Y2 rocket carrying the core module of Chinas space station, Tianhe, blasts off from the Wenchang Spacecraft Launch Site on April 29, 2021 in Wenchang, Hainan Province of China. (Photo by VCG/VCG via Getty Images)
  • An uncontrolled Chinese rocket reentered Earth's atmosphere and landed in the Indian Ocean Saturday.
  • The rocket had been hurtling towards Earth for a week, with no one knowing when or where it would land.
  • The landing quelled fears that debris from the rocket might have fallen on people or property.
  • See more stories on Business Insider SA's home page.

A Chinese rocket falling toward earth at around 29,000 kilometres an hour reentered Earth's atmosphere late Saturday, landing in the Indian Ocean near the Maldives, China's space agency reported, according to the South China Morning Post.

It was the 22.5-ton core stage of China's Long March 5B rocket, which launched the first module of the country's new space station on 28 April. For the last week, the 10-story-tall cylinder was hurtling around Earth uncontrolled, losing altitude with each lap. No space agency was certain when it would fall or where it would land.

Although the rocket stage ultimately landed in the ocean, there was a small chance it could have rained more than 5 tons of debris onto unsuspecting people or property.

As the rocket stage fell through Earth's atmosphere, friction likely heated the surrounding air to more than 1,600 degrees Celsius. The rocket stage likely fell apart in this heat and most likely burned up. But experts stressed that some parts could come through the heat intact.

The general rule of thumb is that 20% to 40% of a large object's mass will survive its fall through the atmosphere. In this case, that would be 5 to 9 metric tons of debris.

A spokesperson for China's Foreign Ministry, Wang Wenbing, said at a briefing on Friday that the rocket stage posed little threat, the Associated Press reported.

"As far as I understand, this type of rocket adopts a special technical design, and the vast majority of the devices will be burnt up and destructed during the re-entry process, which has a very low probability of causing harm to aviation activities and the ground," Wang said.

Space debris experts agreed that any surviving pieces of the Long March 5B rocket stage were unlikely to hit inhabited areas, much less planes or boats. Most of the Earth consists of water and much of its land is uninhabited by people.

Still, the object's orbit took it as far north as New York and Beijing and as far south as New Zealand and southern Chile.

The possible reentry points of the Long March 5b rocket's core stage. The blue and white lines capture the uncertainty in the model - the range of places where the rocket could fall.

"Its trajectory covers much of the populated world. So if you can't control where it reenters [the atmosphere], then there's a real danger it will reenter someplace with people underneath it," John Logsdon, the founder of George Washington University's Space Policy Institute and a former member of the NASA Advisory Council, told Insider last week.

It's not clear whether this uncontrolled fall was an accident

The US Space Force and Russia's space agency, Roscosmos, both tracked the rocket stage as it lost altitude.

"For those of us who operate in the space domain, there's a requirement, or should be a requirement, to operate in a safe and thoughtful mode," US Defense Secretary Lloyd Austin told reporters on Thursday, according to The Guardian.

Normally, after a launch, rockets push themselves into the atmosphere and fall back to Earth over remote ocean areas like the South Pacific - a process called "controlled reentry." China's older rockets follow this practice. But two days after the Long March 5B launched, observers on Earth realised that its upper stage had fallen into orbit.

Experts aren't sure whether this was an accident or simply how the rocket was designed.

"Rockets get launched all the time, and very seldom is there concern about reentry," Logsdon said. "So yeah, I'm a little confused as to why this is happening. Is it just willful disregard of the international guidelines? Or because it's a new vehicle it wasn't properly designed so it could do a controlled reentry? Whatever. It's unfortunate that it puts a lot of people at risk."

Either way, Logsdon said, "I think at a minimum, China owes the international community an explanation."

China launched a Long March 5b once before, in May 2020, with the same outcome. That launch was a test that put a spaceship prototype into orbit, and the rocket's core stage also fell to Earth uncontrolled, six days after launch. It reentered Earth's atmosphere over the Atlantic Ocean, according to the US Space Force's 18th Space Control Squadron. Some local reports indicated that bits of the rocket fell in Côte d'Ivoire.

China plans to launch 2 more of these rockets to build its space station

A Long March-5B Y2 rocket carrying the core module of China's space station, Tianhe, stands at the launching area of the Wenchang Spacecraft Launch Site on April 23, 2021.

China's plans to build its space station involve 11 launches by the end of 2022, two more of which would use Long March 5B rockets. The vehicle is designed to put space-station modules into orbit, according to Andrew Jones, a journalist covering Chinese space programs.

It's not clear how China's space agencies will dispose of the next two Long March 5B rocket bodies. Designing a rocket stage to ensure it makes a controlled reentry after launch can be more expensive and may reduce how much cargo the rocket can carry.

Still, Logsdon is hopeful that China will change its future launch plans based on the international response to this one.

"China in 2007 did an anti-satellite test that created a lot of debris and created a lot of international criticism. And they have not repeated that kind of test since then," Logsdon said. "So it's conceivable that international pressure could influence the next couple of launches."

Read the original article on Business Insider

Receive a daily news update on your cellphone. Or get the best of our site emailed to you

Go to the Business Insider front page for more stories.