Space junk from the Long March 5B booster, used to launch the first module of China‘s new space station last month, is expected to reenter the Earth’s atmosphere in the coming hours, with authorities unsure exactly where debris will land. The 18 tonnes booster it is one of the largest items in decades to have an undirected dive into the atmosphere, causing alarm among some.
Where is the danger zone?
Projections are difficult and uncertain given the speed and volatile nature of the object.
Originally injected into an elliptical orbit approximately 160km by 375km above Earth’s surface on 29 April, the Long March-5b core stage has been losing height ever since.
Just how quickly the core’s orbit will continue to decay will depend on the density of air it encounters at altitude and the amount of drag this produces.
Experts have said that, based on the trajectory, it shouldn’t fall further north than approximately 41.5 degrees North latitude or further south than 41.5 degrees South latitude, but the rest is impossible to determine.
That still leaves a large portion of the Earth still in the danger zone.
Most of the debris should burn up when it reenters Earth’s atmosphere, but experts are saying there is a real chance of resistant materials surviving to the surface.
However, the chances of anyone being hit by space junk are very small.
The majority of the Earth’s surface is covered by ocean, and much of the surface covered by land is uninhabited.
Authorities said they are hopeful the rocket will land in the ocean.
The US said it was watching the path of the object closely but have no immediate plans to shoot it down.
US Defense Secretary Lloyd Austin said: “We’re hopeful that it will land in a place where it won’t harm anyone.
“Hopefully in the ocean, or someplace like that.”
The Chinese government has downplayed the severity of the incident, saying it is unlikely to land on populated areas or a plane in the sky.
Foreign ministry spokesman, Wang Wenbin, said on Friday: “The probability of causing harm to aviation activities or on the ground is extremely low.”
Commentary in the country’s media has described Western reports about the potential hazards involved as “hype” and predicted the debris will likely fall somewhere in international waters.
The Global Times quoted aerospace expert Song Zhongping who added that China’s space monitoring network would keep a close watch and take necessary measures should damage occur.
However, Jonathan McDowell from the Harvard-Smithsonian Center for Astrophysics in the US said it was seen as “negligence” on behalf of the Chinese.
He said: “This is the second launch of this rocket; the debris in Ivory Coast last year was from the previous launch, ie a basically identical rocket.
“These two incidents [the one now and the Ivory Coast one] are the two largest objects deliberately left to re-enter uncontrolled since Skylab in 1979.”