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Chinese rocket booster falls back to Earth uncontrollably

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The central module of the Chinese Space Station (CSS) took off successfully this Thursday, April 29 aboard a Long March 5 B rocket. The launcher’s booster is about to re-enter the Earth’s atmosphere, but we does not yet know exactly where or when this debris will hit our planet.

The first stage of the Chinese Long March 5B launcher falls “unpredictably” to Earth after its successful launch on Thursday April 29 from the Wenchang base, reports News. His return to Earth could happen any day. The odds suggest that this debris will burn in the atmosphere and that the “survivors” will fall back into one of the oceans, which cover just over 70% of the planet. However, it is not excluded that the booster threatens an inhabited area.

An uncontrolled re-entry

Most rocket boosters do not reach orbital speed and reenter the atmosphere, ending up in a predefined area. Some, larger, go a little higher, but operate deorbitation maneuvers in order to reduce the time in orbit to avoid the risk of collision with other spacecraft and immediately enter the atmosphere.

Regarding the launch that interests us, everything suggested that the Long March 5B would perform an active maneuver to de-orbit. Obviously, that was not the case. Hence the uncontrolled fallout.

It is now very difficult, if not impossible, to anticipate the trajectory of this falling rocket stage, as there are so many uncertainties in the calculation of the effect of atmospheric drag on the central module (the atmosphere terrestrial can expand or contract with solar activity). The size and density of the object are also a factor.

A Chinese Long March 5 heavy launcher, June 26, 2017. Credits: 篁 竹 水 声 / Wikipedia

Timing is essential

According to ground radars used by the US military, the main stage of the launcher, about thirty meters long and five meters wide, is currently flying at an altitude of between 170 and 372 kilometers, traveling through space. over seven kilometers per second. Given its speed, the booster revolves around the Earth approximately every 90 minutes.

The more time passes, the more the object slows down, before being “grabbed” by the gravity of our planet. Its orbital inclination is 41.5 degrees, which means that it sometimes passes a little further north of New York, Madrid and Beijing, sometimes through southern Chile or through Wellington, New Zealand.

As Spacenews points out, “The thrower could therefore re-enter at any time in this zone”. Timing will be essential. At these speeds, a shift of a few minutes in atmospheric reentry can shift this reentry point by several thousand kilometers.

Spaceflight observer Jonathan McDowell ruled “unacceptable”, according to current standards, to let such a massive object enter uncontrollably into the atmosphere. “Since 1990, nothing more than ten tons has been deliberately left in orbit to enter in an uncontrolled manner”, he explains. “However, it is believed that the central stage Longue Marche 5B, without its four side boosters, has a dry mass (thruster vacuum) of about 21 tonnes of mass”.

For the specialist, it is likely that a large part of this booster will end up burning in the atmosphere a few minutes after its re-entry. On the other hand, it is possible that components made of heat-resistant materials, such as tanks and thrusters made of stainless steel or titanium, can reach the ground.


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