Debris from an uncontrolled Chinese rocket falls on the seas of Southeast Asia

According US Space Command.

In an update posted on social networking site Weibo, China’s manned space agency said most of the debris burned up during re-entry over the Sulu Sea, a body of water between the Borneo Island and the Philippines.

The possibility, however remote, that debris from the rocket could hit a populated area had led people around the world to follow its trajectory for days.

NASA Administrator Bill Nelson issued a reprimand on Saturday, saying China “did not share specific trajectory information as its Long March 5B rocket fell back to Earth.” He added that all countries should “share this type of information in advance to enable reliable predictions of the potential risk of debris impact, especially for heavy vehicles, such as the Long March 5B, which carry a risk significant loss of life and property”.

The rocket Mr Nelson referred to in his statement launched last Sunday, carrying a laboratory module into orbit that was added to China’s space station, Tiangong. Usually, large rocket booster stages immediately fall back to Earth after being released. But the 23-tonne core stage of Long March 5B accompanied the segment of the space station into orbit.

Due to the friction caused by the rocket rubbing against the air at the top of the atmosphere, it quickly began to lose altitude, making what is known as an “uncontrolled reentry” toward Earth. In recent days, space observers had projected potential re-entries over much of the planet. Over the past day, the forecast has become more accurate, but even then forecasters were unsure whether it would fall over the Indian Ocean, off Mexico, or in the Atlantic.

Residents of Sarawak, a Malaysian province on the island of Borneo, have reported sightings of rocket debris on social media, with many initially believing pyrotechnics to be a meteor shower or one comet.

It was the third flight of Long March 5B, China’s largest rocket. The country’s space program needed such a large and powerful vehicle to transport parts into orbit for the assembly of its space station.

On its first test flight in 2020, it orbited a reusable astronaut capsule with no crew on board. This recall fell on villages in Côte d’Ivoire in West Africa, causing material damage but no injuries.

The second flight carried Tianhe, the main module of Tiangong, the new space station, last year and crashed in the Indian Ocean. This launched Wentian added, the lab module.

The Long March 5B contained several parts. Four side thrusters fell shortly after launch, crashing harmlessly into the Pacific Ocean. (Disposal of used and unwanted rocket parts in the ocean is standard practice.) But the main booster stage — a 10-story cylinder weighing 23 tons empty — carried the Wentian module to orbit.

The installation of the laboratory advances the progress of a second outpost in orbit where humanity is able to conduct scientific research in a microgravity environment.

China plans to operate the new Tiangong station for at least a decade, inviting other nations to join. Tiangong is smaller than the aging International Space Station, which is due for retirement in 2030 under current NASA plans, although Russia has given conflicting signs about how long it will be involved.

In recent decades, rocket stages that reach orbit typically re-ignite the engine after releasing their payloads so that they exit orbit, aiming for an unoccupied area like the middle of an ocean.

Typically, 20 to 40 percent of a rocket or satellite survives re-entry, suggesting that 10,000 to 20,000 pounds of Chinese propellant would reach Earth’s surface.

Another laboratory module is to be launched using the same rocket in October, completing construction of the space station. A final rocket mission is scheduled for 2023, carrying an orbiting space telescope.

Experts say the rocket’s designers had alternatives to its approach. They could have stopped the booster before reaching orbit. It would then immediately fall back to Earth in the Pacific. But then they would have had to augment the space station module’s propulsion systems to get it the rest of the way to orbit.

Jonathan McDowell, an astrophysicist at the Center for Astrophysics in Cambridge, Mass., who tracks space debris, suggested the Chinese could have used a trick similar to what NASA engineers did more than 40 years ago with the Saturn 1B rocket. The Saturn 1B second stage was large and, like the Long March 5B booster, had no thrusters to control reentry.

“They actually did something smart in terms of venting the fuel,” Dr. McDowell said. “They didn’t actually have rocket engine ignition, but they did vent the fuel in a way that lowered the perigee in the atmosphere.”

Li You contributed to the research.

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