A huge piece of a Chinese rocket will fall back to Earth "soon", and no one can say for sure where. The component in question is the first stage of the Long March 5B that was used to put the first module in orbit into orbit chinese space station Tiangong, last week. 

After fulfilling its mission, the piece was discarded in an elliptical orbit around our planet, which places it at 375 km of altitude at the most distant point and 170 km at the nearest point.


But the friction with the atmosphere at the lowest point of this trajectory causes it to lose energy and get closer and closer, until the moment when it will perform an uncontrolled reentry.

Launch of Long March 5B with the first module of the Chinese space station. The first stage is where the auxiliary thrusters are.
Launch of Long March 5B with the first module of the Chinese space station. The first stage is where the auxiliary thrusters are. Image: CNSA

Small objects reentering the atmosphere are usually incinerated by the heat generated by the friction, but the first stage of Long March 5B cannot be considered “small”: it is 33 meters long and 5 meters in diameter, weighing 21 tons. This means that a considerable part can reach "somewhere" on Earth.

According to the website SpaceNews, this will be one of the largest uncontrolled reentry of a spacecraft, and the wreckage has the potential to reach an inhabited area.

The 41,5 degree orbital inclination means that the first stage passes a little further north in New York, Madrid and Beijing, and further south in the southern region of Chile and Wellington, in the New Zealand.

Reentry can occur anywhere in this area, which also includes Brazil. But we must not worry: BRAMON, the Brazilian Meteor Monitoring Network, calculated that the probability that it will reach some point in the national territory is only 4%.

But if something hits the ground, anywhere in the world, it won't be the entire first stage. Marcelo Zurita, technical director at BRAMON, recalls that “a large part of the rocket material is completely vaporized on re-entry. Generally, only the fuel tanks that receive thermal protection are left ”.

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Considering that 70% of the surface of our planet is covered by oceans, it is likely that the first stage of Long March 5B will reach one of them. But the possibility that it will reach dry land, or an inhabited region, still exists: in 1979, a miscalculation caused pieces of the first spacial station American company, Skylab, would reach Western Australia.

In early March, part of the French rocket Ariane 44L, which took off in 1992, reentered our atmosphere over northern Brazil, generating a fireball that was seen in the skies of Ceará and Pará, more specifically in the capital region, Belém. There is no record of pieces reaching the ground. 

China intends to complete the construction of the Tiangong space station by 2022. For that purpose, 10 more missions will be necessary: ​​two for the launch of additional modules, four manned missions and four cargo missions. 

Source: SpaceNews