Lasers for fighting space debris
Humanity has set up a dump in near-Earth orbit. Millions of fragments of old satellites and other particles of industrial origin are orbiting the Earth, threatening the ISS and other spacecraft. Scientists are developing ways to solve this problem before it's too late.
Because of people, the space around the Earth is filled with garbage. Decades of space exploration, which began with the launch of the satellite in 1957, caused the appearance in orbit of fragments of upper stages, fragments of skin and thousands of satellites, many of which have not been functioning for a long time. At high speeds, all this is carried right above the Earth's atmosphere. And as the space industry is booming, more and more objects are being launched into orbit, their accumulation constantly increases the likelihood of catastrophic collisions in orbit. Scientists are concerned that the uncontrolled chain reaction of these collisions, with the concomitant fragmentation of drifting fragments, may one day fill Earth's orbit with so much debris that space will literally become unusable by humans.
That is why the world's leading space agencies and some commercial companies have taken up the problem of space waste, starting with a space garbage collector armed with harpoons and nets and ending with a giant cloud of metal dust. One solution has been offered for many years, and that is lasers. Because if you get creative and start solving the problem right now, you can still make it before it's too late.
Most of the objects of industrial origin surrounding the Earth are located here, in the so-called low Earth orbit. All communication satellites and spacecraft, including the ISS, are located here. There is also a huge amount of space debris flying here. The more objects there are in space, the more likely they are to collide with each other, fall apart and their debris will multiply the amount of space debris. Just a few such events and the total number of objects orbiting the Earth will increase dramatically. This was the case in 2009, when an abandoned Russian satellite accidentally collided with a commercial one and shattered into thousands of fragments. And in 2007, China deliberately destroyed one of its satellites as part of a weapons test, which also resulted in tens of thousands of debris of various sizes.
The theoretical cascade effect, called "Kessler syndrome", a concept introduced in the 1970s, warns that in the case of a sufficient number of such incidents, fragments can provoke an uncontrollable number of catastrophic collisions, increasing the debris field around the Earth exponentially. However, it is still not too late to fix the case, and there are several ways to do this.
To get rid of the bulk of space debris, you need to slow down its movement so that it can fall from orbit into the atmosphere, where it will safely burn up and disappear. But fragments of different sizes require a different approach. The largest of them have a diameter of more than 10 cm and include spacecraft and their large debris. They are large enough to be tracked from the Ground. Scientists are already busy developing tiny spacecraft that can reach these fragments and slow them down, sending them towards the atmosphere for subsequent combustion.
Commercial companies like the European ClearSpace and the Japanese Astroscale are working on this technology together with world space agencies. According to them, the technology of "cleaning up" large space debris may be available to us in the next decade.
The other two categories of fragments arise mainly as a result of explosions and collisions. Their number can only be estimated, since we still do not have reliable technologies for tracking pieces with a diameter of less than 10 cm. The smallest particles include pieces of paint and metal, which, despite their size in fractions of a millimeter, regularly cause minor damage to the skin of spacecraft.
At the moment, scientists have two options for their elimination. The first is an orbital harvesting device for catching or slowing down debris particles with subsequent descent from orbit. But such an approach—at least from NASA's point of view—would be too expensive. Another, more cost-effective solution would be to release a cloud of tungsten dust over the debris so that it would weigh them down and carry them towards the atmosphere, where they would burn up. However, on the other hand, dumping a 20-ton cloud of heavy metal dust into Earth's orbit may eventually contribute to space pollution. In general, no one has tried anything yet.
To date, the ideas with a harvesting machine and tungsten dust can probably not be called practical. But there is another solution for the second class of debris. They generally pose a unique problem because debris ranging in size from 1 to 10 cm is too small to be tracked, but large enough to cause serious damage. Just one fragment of one centimeter, moving at an average speed of 7 km/s, has enough power to disable an entire satellite. NASA conducted an analysis and found that focusing on this range of debris particles would bring maximum benefit in the process of solving a common problem. And this is where lasers come to the rescue.
Lasers can direct an energy beam and affect an object without coming into physical contact with it. They can be used to push a fast-moving piece of small debris out of its orbit, throwing it either to higher and less crowded levels, or down towards the Earth's atmosphere. This method is sometimes called a "laser broom".
A ground-based laser installation was proposed back in 1996 as part of NASA's Orion project. The agency's analysis of the cost-benefit ratio of space debris removal methods in 2023 showed that the most cost-effective way to solve the problem of fragments from 1 to 10 cm in size would be a ground-based or space-based laser system.
But garbage disposal is not the only way to deal with the problem. The charter of the European Space Agency, called "ZeroDebris" ("Zero debris"), proposed in June 2023, focuses on preventing the formation of new debris in the future. In particular, we are talking about designing such satellites that, after completing the mission, will independently enter the Earth's atmosphere, and will not remain drifting around it. In September 2022, the US Federal Communications Commission introduced a new five-year rule according to which American spacecraft launched into low Earth orbit must independently leave it within five years after the end of the mission.
This kind of effort is just the beginning, but it is predicted that the combination of recovery and mitigation efforts will lead to serious progress in combating the problem of space debris.