Alert, an out of control rocket is about to crash into Earth! On November 4, Beijing warned that its Long March-5B was going to fall from the sky, without being able to specify the place. A few days later, it was on a beach on Busuanga Island, in the Philippines, that metal debris several meters long, some marked with the Chinese flag, were found. History repeats itself because, in July, the stage of another Chinese rocket, of the same model, had caused concern. A few hours before the crash, it was impossible to determine its location. Finally, the 22 tons of the machine had plunged into the Indian Ocean.
“There is no way to accurately predict the point of impact, recognizes Christophe Bonnal, from the strategy department at the National Center for Space Studies (CNES), in Toulouse. Ten days earlier, the area concerned is 1.2 million kilometers, the day before 120,000 kilometers, and an hour before more or less 2,700 kilometers. » Under these conditions, it was impossible to evacuate the populations. However, every day, an object of more than 10 centimeters returns to the Earth, and this is the case every four days for a satellite or an entire stage. All largely burn up upon entering the atmosphere, but 10% to 40% of their mass remains intact.
“We can tell where they won’t fall, but not where they will crash”, sums up this expert, who is also chairman of the orbital debris committee of the International Academy of Astronautics. If the risk of making victims is limited – only 3% of the surface of the globe being really inhabited, the seas and the deserts covering more than three quarters – the danger exists. In August, an Australian sheep farmer found a piece of metal more than 2 meters high in his field, coming from one of the missions of SpaceX, Elon Musk’s firm. Other space debris was found in nearby properties.
Severe impact regardless of size
These data illustrate one of the dangers inherent in the proliferation of debris, the other being the risk of collision in space, where satellites are increasingly numerous. In ten years, their number in activity has increased from 900 to 6,750. With the development of constellations (Starlink, Kuiper and that of the Chinese program), it could reach 40,000 by 2030.
As for the debris, to date, the European Space Agency has identified 36,000 more than 10 centimeters, including 5,000 inactive satellites. The smallest objects, smaller than a centimeter or even a millimeter, are estimated at around a hundred million. Regardless of their size, the impact is severe. “An aluminum scrap of 1 millimeter in radius is the equivalent of a bowling ball launched at 100 kilometers per hour. [km/h]at one centimeter, it’s a Renault Laguna traveling at 130 km/h and, at 10 centimeters, it’s a load of 240 kilos of TNT, emphasizes Christophe Bonnal. Hence the importance of constantly monitoring their development. »
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