Spacecraft sometimes fall to Earth. Sometimes on purpose, sometimes by accident. So, there is a worry that somehow a satellite may fall on your head. In order to understand how real the danger is, it is worth understanding what’s going on.
1. Why are spacecraft being taken out of orbit?
There is no friction in space. Therefore, theoretically, a spacecraft can orbit forever, even when it has already completely failed. However, there is nothing good in this, because then it turns into debris that needs to be tracked using radars so that it does not crash into a working satellite or station.
In fact, a certain number of atmospheric molecules around the Earth are present. And in the end, most of the satellites will eventually fall by themselves. However, most often they are helped by engineers using the last remnants of fuel to slow them down.
2. Do satellites fall anywhere?
If a satellite, or, for example, a rocket stage, falls into the atmosphere uncontrollably, then this can happen anywhere and where its orbit allows it. At higher latitudes (that is, closer to the poles), the possibility of this is lower since fewer vehicles are brought into polar orbits.
But when a satellite or station is deorbited as planned, the trajectory is usually adjusted so that even the debris reaching the surface ends up in the ocean, where it cannot harm anyone. Therefore, most spacecraft do not fall in random places.
3. What happens to the spacecraft when it enters the atmosphere?
When a spacecraft enters the dense layers of the atmosphere, it encounters a frictional force. It is proportional to its speed, which can be several kilometers per second. The kinetic energy of the spacecraft begins to be converted into mechanical and thermal energy. The first is trying to break it, and the second is trying to heat it.
As a result, the satellite begins to burn and fall apart, the surface area of the debris increases, and the friction force grows. Simultaneously, the fall slows down. As a result, most of the material burns up in the atmosphere, and mostly small fragments reach the Earth.
4. Is there a danger to people from the fall of the spacecraft?
The chance of being injured or killed by falling space debris is usually defined as extremely low. The Earth is big, and not so much debris falls on it. Therefore, it’s not worth worrying about it.
At the same time, this chance is growing. The number of commercial launches is constantly increasing, and developers do not always think about what will happen to the satellites after they have served their time. Therefore, experts have calculated that over the next 10 years, there is a 10% probability that somewhere on Earth, one or more people will die from falling space debris.
5. Does the fall of satellites pollute the atmosphere?
For a very long time, people have not thought about the question of what happens to the matter of satellites that burns up when entering the atmosphere. But after all, it does not disappear as a result of this, it just turns into other forms. And recently, NASA research planes have found traces of it in the stratosphere.
It continues to exist there in the form of very fine dust consisting of lithium, copper, lead and aluminum. The latter is especially dangerous because it can destroy the ozone layer. It protects us from cosmic radiation, that is, the fall of satellites can harm you even so.
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