The number of objects in low Earth orbit could be hundreds of thousands. These are typically satellites no longer in use, fragments detached from space stations and spacecraft, more commonly known as space debris. Space debris around the Earth can cause enormous damage, so efforts should be made to minimise its quantity as much as possible. Let's look at where cosmic debris comes from and how to reduce "space debris"!
What is space debris?
Space debris - for many people, the term comes to mind when they think of the waste produced by astronauts, the various types of packaging, used items and clothing. Although space debris is man-made, it is very different.
Space debris, or cosmic debris, is a collective name that covers all man-made objects that orbit in space but have no useful function, that is no longer serve any purpose. Thus, satellites in use are not space debris, but those that are no longer used for anything but orbiting in space are.
We might think that space debris around the Earth doesn't cause problems because there's plenty of room in space for a bit of space technology “waste”. Indeed, the vastness of space is difficult for the human mind to process, but that has nothing to do with the dangers that space debris poses.
Where does space debris come from?
Therefore, space debris is any object that is floating in space but is out of order. Space debris can be produced in many ways: it can come from space as a detached stage of a launch vehicle, or it can be found in space debris from defunct satellites, space stations and various objects left behind during space missions. In 1965, for example, Ed White, the first American who made a spacewalk, lost his glove when he forgot to fix it in the Gemini-4 spacecraft and was released into space through the open doorway.
Another example was when landing on the Moon, astronauts were instructed to leave all their equipment on the Moon's surface, thus reducing the mass they had to lift from the Moon. Consequently, the lander unit was left on the surface of the Moon, which is now considered as space debris as well. But there is no doubt that the biggest sources of space debris are satellites, which sometimes explode accidentally or deliberately and fall apart into a multitude of pieces.
Space debris has been growing in volume since 1960 and now constitutes a measurable threat. In the last 60 years or so, there have been nearly 5.500 rocket launches, resulting in 23.000 pieces of debris larger than 10 cm in 2019, weighing more than 8.400 tonnes. The number of 1-10 cm debris is estimated at 900.000 pieces, and 128 million pieces of 1-10 mm debris are orbiting in space. Most of the debris is in LEO orbits between 800-1.000 km and 1.400 km.
The question may arise about how these unused objects can remain up there and why they are not removed. The answer is simple: to make a satellite disappear that has been switched off or has malfunctioned, it would have to return to the atmosphere to the point where it would burn to tiny pieces. But that is a lot of additional expense that no one wanted so far.
Why is space debris dangerous?
The amount of space debris is constantly increasing, thanks to the growth of the space industry and the fact that smaller and larger pieces occasionally collide or explode due to fuel residues or electrical faults. Understandably, the more space debris there is, the greater the chance of such a collision.
Objects orbiting the Earth without propulsion are constantly being thrown into lower orbits. The reason is that, although, in a very small amount, atmospheric braking has an effect, reducing their angular momentum, which causes them to move into a lower but higher speed orbit. The lower they are, the faster they lose altitude, meaning they burn up in the atmosphere over time. This would be fine, but in practice, it could take years or even decades.
As the amount of space debris increases, so does the chance of collisions. These are dangerous for spacecraft, satellites and space stations, endangering the lives of people on board and causing serious material damage to the equipment in use. The International Space Station is in low Earth orbit too. To remain in orbit, it needs a speed of 27.000 km/h. So it's easy to see that even a few centimetres wide object can cause huge damage and destruction, and the risks of unwanted encounters.
Theories and various simulations have shown that the more debris there is, the greater the chance of a collision. And if two satellites collide and fall apart, these fragments could trigger another collision and start a chain reaction that would cause massive destruction among satellites and space instruments and threaten the very existence of the space station.
The movement of space debris is constantly monitored by researchers and global space agencies. The first such monitoring system was NORAD, but the list includes ORDEM2000 too, launched by NASA in 2002.
What could be the solution to remove space debris?
The space industry is increasingly active, and with the democratisation of the sector, there are now market players working hard to overtake each other in the space race. Therefore, it is certain that space activity will not decline in the coming decades, on the contrary. And if nothing changes, this will increase the amount of space debris and the chances of collisions.
Space pollution is a real problem, and there are two ways to answer it: in a technological way and in a regulatory way. We can see both attempts in the history of cosmic environmentalism!
In 2018, the European Space Agency experimented with a device that could capture space debris using a 'grappling lasso' and then tow it into the atmosphere to burn. However, the usefulness of the space debris transporter would be rather limited, as it would only be used on fully depleted satellites to avoid accidents and when there is no doubt about the accuracy of the targeting. This is only one of the possible ways of collecting rubbish, but whatever the solution, it is certainly a very expensive procedure that companies and governments would be reluctant to finance.
A change in regulation may be more advisable, which would at least prevent the amount of space debris from increasing in the future. It would aim to ensure that satellite manufacturers and other space industry players design the devices they send up in a way that they can return to Earth, or at least to the atmosphere, where they burn up. An example of this is the Artemis Convention, signed in 2020, which states that future lunar landings must leave no debris behind in space.
Space debris is already a real problem, but the situation will become even more critical as the number of space industry players grows. We can only hope that as a result of the regulations, companies and organisations going into space in the future will not only focus on how to get to the stars but also on how to remove the equipment that is no longer in use, i.e. how to collect their space debris.