A 21-tonne rocket is set for an uncontrolled re-entry into Earth following a Chinese space station launch.

The Long March 5B rocket carried the core “Heavenly Harmony” module of China’s new Tianhe Space Station into low Earth orbit last week. The rocket was launched from the Wenchang Space Launch Centre in Hainan province on April 29. It will now become one of the largest ever launchers to make an uncontrolled re-entry with the landing point as yet unknown.

Velocity means rocket’s landing point is impossible to predict

Most expendable rockets do not reach a velocity which would take them into orbit and usually re-enter the atmosphere to land in a known re-entry zone. According to space experts, no rockets or space vehicles weighing more than 10 tonnes have been deliberately left in orbit for an uncontrolled re-entry since 1990. The core is currently orbiting Earth around every 90 minutes at about 27,600km/h at altitude of more than 300km. The rocket has dropped nearly 80km in altitude since the weekend – its current velocity will make it impossible to predict where it will land. The rocket’s re-entry is being tracked, with the US military naming it 2021-035B.

Jonathan McDowell, Astrophysicist at the Astrophysics Center at Harvard University, fears the rocket could re-enter Earth and land on an inhabited area. With 71 per cent of Earth covered by oceans, McDowell has said in media reports that the most likely outcome was that the rocket would fall into the sea. He added: “Last time they launched a Long March 5B rocket they ended up with big long rods of metal flying through the sky and damaging several buildings in the Ivory Coast. Most of it burned up, but there were these enormous pieces of metal that hit the ground. We are very lucky no one was hurt.”

Debris will be “equivalent of a small plane crash”

McDowell said some rocket debris “equivalent of a small plane crash scattered over 100 miles” could survive re-entry into the Earth’s atmosphere.

The rocket is currently passing over Earth as far north as New York, Madrid and Beijing and as far south as southern Chile and Wellington, New Zealand. It could make its re-entry at any point within this area in a time period spanning two days before and after May 10. Once it becomes clear that the rocket will be returning to the Earth’s atmosphere, experts could predict its landing time to a six-hour window.

The launch formed part of 11 planned missions to construct China’s new space station, which is expected to be complete in late 2022. The T-shaped space station, weighing around 60 tonnes, will be smaller than the International Space Station (ISS), which weighs around 408 tonnes. Tianhe Space Station will have a docking port and connection to a Chinese satellite. As with the ISS, the station can be expanded using modules.

The first launch of Long March 5B last year also reached orbit, followed by an uncontrolled re-entry six days later. US military said the rocket re-entered over the Atlantic Ocean but had its re-entry window been 15 to 30 minutes earlier, any debris not burning up would have landed on US soil. Heat resistant materials, such as stainless steel component or titanium tanks are among the items which can survive re-entry to Earth.


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