Beijing: US fears for unprecedented damage as 18-tonne main segment of a Chinese rocket is in freefall and is expected to make an uncontrolled re-entry into the Earth’s atmosphere around 2300 GMT on Saturday. However, Beijing has downplayed fears, saying there is a very low risk of any damage.
“We’re hopeful that it will land in a place where it won’t harm anyone,” US Defense Secretary Lloyd Austin said. “Hopefully in the ocean, or someplace like that.”
Notably, the main segment from the Long March-5b vehicle was 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. At 18 tonnes, is one of the largest items in decades to have an undirected dive into the atmosphere.
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. These details are poorly known.
Our latest prediction for #LongMarch5B CZ-5B rocket body reentry is 🚀 09 May 2021 04:19 UTC ± 8 hours along the ground track shown here. Follow this page for updates: https://t.co/p2AU9zVEpA pic.twitter.com/rsE6yzcnHb
— The Aerospace Corporation (@AerospaceCorp) May 7, 2021
Meanwhile, the US on Thursday said it was watching the path of the object but currently had no plans to shoot it down.
A Long March-5B rocket launched the first module of China’s new space station into Earth’s orbit on April 29. Its is now in freefall and experts have said it is difficult to say precisely where and when it will re-enter the atmosphere.
Re-entry is expected to be around 2300 GMT on Saturday, according to the Pentagon, with a window of nine hours either side.
Chinese authorities have said most of the rocket components would likely be destroyed on re-entry.
“The probability of causing harm… on the ground is extremely low,” Chinese foreign ministry spokesman Wang Wenbin told reporters on Friday.
Although there has been fevered speculation over exactly where the rocket — or parts of it — will land, there is a good chance any debris that does not burn up will just splash down into the ocean, given that the planet is 70 percent water.
“We’re hopeful that it will land in a place where it won’t harm anyone,” said Pentagon spokesman Mike Howard.
The chances of anyone actually being hit by a piece of space junk are very small, not least because so much of the Earth’s surface is covered by ocean, and because that part which is land includes huge areas that are uninhabited.
Latest TIP (as of 2021-05-08 0222Z) for CZ-5B (#LongMarch5B) (48275 / 2021-035B) shows projected re-entry at 2021-05-09 0252(UTC) +/- 360 minutes at latitude -39.4 longitude 180.5.
NOTE: Still not a reliable time or location, given the large window; both will still vary wildly
— Space-Track (@SpaceTrackOrg) May 8, 2021
Howard said the United States was tracking the rocket segment but “its exact entry point into the Earth’s atmosphere cannot be pinpointed until within hours of its re-entry”.
Defense Secretary Lloyd Austin earlier said that the US military had no plans to shoot it down, and suggested that China had been negligent in letting it fall out of orbit.
“Given the size of the object, there will necessarily be big pieces left over,” said Florent Delefie, an astronomer at the Paris-PSL Observatory.
“The chances of debris landing on an inhabited zone are tiny, probably one in a million.”
In 2020, debris from another Long March rocket fell on villages in the Ivory Coast, causing structural damage but no injuries or deaths.
Jonathan McDowell, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics, said that although there was no need to worry “too much”, the rocket’s design needed a re-think to stop such a scenario happening again.
“There is a real chance of damage to whatever it hits and the outside chance of a casualty,” he said.
“Having a ton of metal shards flying into the Earth at hundreds of kilometres per hour is not good practice, and China should redesign the Long-March 5B missions to avoid this.”
In 1979, US space station Skylab had attracted worldwide attention after its fragments were scattered across Western Australia.