How the Long March 5B, the uncontrollable Chinese rocket approaches Earth

For several days, a Chinese rocket has returned to Earth without knowing where or when it will strike. But if their remains could reach an inhabited area, the risk is extremely limited, experts say.

On April 29, China launched the first module of its future space station, Tianhe (“Heavenly Harmony”), with the Long-range carrier rocket 5B. The first phase of this powerful shuttle is what is now returning to Earth.

The rocket took off from the Wenchang Space Launch Center on Hainan Island in southern China with a central stage, four side thrusters and a height equivalent to an 18-storey building, which makes it one of the largest debris that would enter the atmosphere, hence its continued vigilance.

Now, its trajectory is uncontrollable because its creators envisaged that it disintegrates naturally in the atmosphere. The problem is that because of its enormous mass, between 17 and 21 tons, the rocket is unlikely to be completely consumed.

The lighter parts will surely vanish but “Considering the size of the object, some parts will remain strong”, according to Florent Delefie, astronomer at the Paris-PSL Observatory. In addition, “if the rocket is made of materials that do not disintegrate on entry into the atmosphere, which appears to be the case, the risk is greater,” according to Delefie.

China “should have anticipated a controlled return with a retro-rocket, as the Russians did in particular during the de-orbit of the Mir station”, Nicolas Brobrinsky, head of the Engineering and Innovation department at the European Space Agency (ESA ), told AFP.

What can happen?

Given the altitude at which the object is located, between 150 km and 250 km, is difficult to predict because the lower layers of the atmosphere are more vulnerable to variations in density. In fact, “we cannot know when it will fall,” according to Brobrinsky.

The only certainty is that the object is in an orbit inclined 41 degrees from the Earth’s equatorIt can therefore only fall in the band between latitudes 41 of the northern and southern hemisphere, which includes, for example, a good part of Latin America, southern Europe and Africa.

But, as Beijing claims, the most likely is that the rocket’s remains fall into the sea, which occupies 70% of the planet, or in a desert area.

The probability of an impact in an inhabited area is “negligible, undoubtedly less than a million”, specifies the head of ESA.

Even if the debris fell on the houses, the speed of the impact would be relatively low (around 200 km / h). Well below the expected impact of a meteorite (36,000 km / h). Instead, for one person, the impact could be fatal, according to Delefie.

Is there a background?

In 2020, the remains of another Longue Marche rocket struck several villages in Côte d’Ivoire, causing damage but no injuries.

According to NASA figures from January 2020, There are approximately 20,000 objects in Earth’s orbit with sizes greater than 10 cm, which are monitored by radar and telescopes.

In 60 years of space flight, some 6,000 uncontrolled entries into Earth of large man-made objects have been recorded and only one has reached a person, without injuring him, according to ESA expert Stijn Lemmens.

With information from AFP and EuropaPress

KEEP READING: