WHAT IS SPACE JUNK?

 

  

Humans have covered the entire Earth with so much garbage that now there’s no space left to pollute. No wonders the same thing is happening in outer space, especially in the lower orbits of the Earth.

 

Jokes aside, space junk is an expression mostly used to refer about the debris orbiting around the Earth: dead satellites, non-functional vehicles, abandoned stages of rockets, materials expelled from rocket engines and many other particles. Moreover, when two satellites collide, they split into thousands of small pieces, creating new debris.

The very first satellite, the Sputnik, was launched by the Russians in 1957. That opened the so called “space race” which is in a certain way still on going. Nowadays, there are around 6.000 satellites around the Earth, but only the 40% of them is operational. Like it’s not enough, there are more than 34.000 space debris and millions of smaller pieces that could cause huge disasters if they hit something.

So how does space junk get into space?

From the 1960s on, humans have been launching into space anything, starting from rockets and satellites to gloves lost by astronauts and even cars! Did you know there’s a Tesla orbing the Earth?

Never mind, all these launched objects remain in orbit until they re-enter the atmosphere. Some of them, the ones placed in the lower orbits, can “fall” back to the Earth within a few years. During the re-entry phase, most of them burns because of their high speed, so they don’t reach the ground. Their speed while re-entering is so high that the air gets compressed and really hot: it can reach 3,000 degrees. In other words, they burn because of the friction of the air on the object.

The debris or satellites left at a higher altitude of 36,000 km are the most difficult to remove. They can orbit around the Earth for hundreds of years.

 

                                                           

 

 

But why are space debris so dangerous and what are they dangerous for?

Well, first of all even the smallest piece of space debris, if it hit something, could cause huge damages that can be compared to an exploding hand grenade. Fortunately, at the moment, space junk isn’t representing a huge risk to space exploration. The ones that are more in danger are the satellites already in orbit.  The more satellites are around the Earth, the more the risk of collision is high. A single collision can cause a chain of crashes, filling the orbits with so much debris that we wouldn’t be able to escape the planet. This is called the Kessler syndrome.

Therefore, these satellites have to move out of the way of all this space junk in order to make sure they don't get hit. The International Space Station has to do hundreds of collision avoidance manoeuvres every year. The ISS is more important to protect rather than dead satellites because there are six astronauts living on board.

 

So the question is: how do we clean space debris?

Well, since it’s a global issue, every nation has to collaborate so as to reduce and remove the space debris.  NASA, the European Space Agency and many other  agencies are currently looking for a way to clean up the space. But the European Space Agency took a step further: by 2025 ESA will launch a mission called ClearSpace-1 that will catch a piece of the Vega rocket. The ClearSpace-1, once it’s completed its mission, will burn in the atmosphere.

 

The university of Surrey has also developed a spacecraft capable to remove debris called RemoveDebris. It was launched into space in April 2018 and docked to the ISS. Once there, it released a ten centimetres cube and then re-captured it with a giant net. It also fired a small harpoon, a sort of a spear with a rope attached, to grab debris. This experiment was a whole success and it’s become part of the RemoveDebris Satellite Project.

Unfortunately, this method only works for large satellites and we still don’t know how to catch the smaller ones.

 

But the issue of debris seems to be destined to increase in the future. SpaceX is planning to form a mega constellation made of satellites in order to send the Internet down to the Earth, even in the hidden places. Several companies, including SpaceX and Amazon, are planning to launch thousands of satellites to achieve a global Internet coverage. If successful, there would be an additional 50,000 satellites in orbit! This means higher risk of collision, more avoidance manoeuvres and more space junk to clean.

 

Also, the most important satellites are parked in the lower orbit: these satellites provide us with Internet connection and any kind of communication. So it's important that we use the lower orbit sustainably, allowing the future generations to enjoy its benefits, too.

                                                            

Maria, 3scB