Why is it important to limit the amount of debris in the sky?

An anti-satellite test shot by Russia on Monday caused thousands of pieces of debris and threatened the safety of the International Space Station, inside which astronauts had to make an emergency exit. Such strategies are only likely to increase as the number of satellites launched increases – and with them the amount of debris. So much so that ten space players have signed a petition to limit their expansion. Here’s why.

Where does debris come from?

About 10,000 tons of debris orbit the Earth today. The number of objects larger than 1 mm is estimated at 330 million, including more than a million larger than 1 cm and about 30,000 debris larger than 10 cm. The latter is mainly followed by the United States, accounting for 95% of them.

There are several sources of this debris. The first is the launcher that puts the satellite into orbit and creates the debris. Then the last stage of the rocket, which finds itself in orbit, will itself become a large piece of debris. “Since then, actors have thought about it and are bringing the stages back into the atmosphere so that they disintegrate. But the old launchers are in orbit”, noted Stephanie Lizzi-Destrez, teacher-researcher at ISAE-SUPAERO. our newspaper

Then there are satellites at the end of their lives, cluttering up space without being used. Aging is also a factor: when a satellite decays, it can lose solar cells, cables, equipment or even water blocks, resulting in combustion. Finally, come to the explosion or crash debris – this is the debris that threatened the ISS. The European Space Agency estimates that “ruptures, explosions, collisions or unusual events resulting in fragmentation” number around 630.

Ruins whose numbers will only increase

As the researchers noted, there are several reasons for the increase in the number of debris. First, increasingly frequent satellite launches. SpaceX, Elon Musk’s company, for example, plans more than 40,000 launches into the “constellation” with the first arrival of 12,000 satellites by 2025. Amazon also has a similar project, albeit a bit more modest, with about 3200 satellites With another start-up, SpaceX plans to launch advertising panels in space… In 2020, more than 1,300 satellites were sent into orbit, compared to ten times less five years ago.

But that’s not all: Romain Luken, co-founder of the startup Share My Space, which aims to map the largest possible number of debris, recalls a process of exponential increase in the number of debris by “debris syndrome”. Kessler”. From a certain threshold, the more satellites or large debris collide with each other, the more new debris is created. “At a certain altitude, this critical threshold is already reached”, assures Romain Lueken. This is the case for low orbits, where There are more observation and network satellites.Geostationary orbit is used more for telecommunication and defense.

Why debris is dangerous

The risk is reaching full saturation of Earth’s orbit. “Space is huge. The amount of debris is increasing, but there is still a great distance between objects. However, at speeds of 7 to 8 km/s, in low orbits, the shock effect is very violent”. Stephanie Lizzi-Destrez analyzes. “This debris will disperse and prevent the satellites from functioning properly. This can range from a simple breakdown to breaking a component, for example cutting a cable, or even exploding. This creates new debris in addition to disabling the satellite.”

However, we all rely on satellites in our daily lives: geolocation, telecommunications, weather, emergency or health services… everything goes through it.

Apart from the shocks that can cause damage, we don’t know all the debris. Below a certain size, they are not well mapped. “Some are visible, but others are too small to observe. So we have to model the propagation”, explains Stephanie Lizi-Destrez.

“Today, we know the location of about 3% of the debris that could destroy satellites,” adds Romain Luken. “We have a catalog of about 30,000 objects measuring 10 cm and a million objects larger than one centimeter, which endangers satellites. Only anything larger than 10 centimeters has been tracked”. So his start-up aims to develop tracking tools to obtain a catalog of 150,000 objects up to 2cm by 2024 through observing stations.

Faced with this proliferation of debris, the ISS, for example, was forced to employ evasive tactics. In total, between 1999 and 2017, the station recorded 25 maneuvers to avoid debris. In 2020, the ISS also had to maneuver three times, as former NASA administrator Jim Bridenstine recalled in September. In May this year, debris hit one of the station’s robotic arms, leaving a hole in it, but luckily it didn’t stop working.

What can we do?

Much of the debris eventually enters the atmosphere and disintegrates. But it takes time, about twenty years, when the number of satellites accelerates much faster. CNS notes for example the relaunch of small satellites without propulsion, which prevents them from orbiting collisions and deorbiting (re-entering the atmosphere) at the end of the mission.

“I also see an ethical problem there. Starlink will place its satellites 550 kilometers above the Earth, so no one would dare go that high to avoid a collision. We will either go down or up. So Starlink is indirectly appropriating an area in space, which is not allowed!” , Lament Stephanie Lizzi-Destrez

Faced with this phenomenon, a dozen players in the space sector signed a petition on Friday called “Net Zero Space”, which aims to reduce space pollution and better regulate its use. “This involves de-orbiting end-of-life satellites, for example, to provide resources for debris removal missions, deterrence systems … and to detect and accurately track objects to avoid collisions”, noted Romain Luken in a text signed by Share My Place. Among other signatories, Arianespace, Cnes, Eutelstat or the Chinese CGSTL.

The United Nations has also issued guidelines on “good behavior” in outer space to limit the spread of debris. For example, satellites should not be more than 25 years old, but this is not a mandatory rule. “An update of the law on space activities is underway at the French level”, Romain Luken also recalls.

The ISAE-SUPAERO researcher also works with his unit on the circular economy: “How to extend the life of satellites, either by refueling them or by repairing them. Instead of bringing back new objects, we use the ones we already have. This requires a lot of adaptation work. Because the satellites are not standardized – you can’t just get a piece from one for the other,” he says

“No Space Constable”

“We are also working on more economic issues, because until then, even if there are rules of good behavior, there is no space police. What can motivate large companies? To come into deorbiting, space cleaning services? For example, a Swiss company, Clearspace, is a prototype “boarding” satellite. is working on allowing satellites to detach and re-enter the atmosphere.

“It’s already late but it’s better than nothing. Perhaps this event will push this issue and the discussion forward. Governments must support space agencies that have programs. This is a real geopolitical problem”, concluded the teacher-researcher. . And if nothing is done, could we reach this saturation of space that leads to massive breakdowns for our satellites? “Before last year, we were on a deadline for the next century. But I’m afraid that’s going to decrease with the acceleration we’re seeing. And the time scale isn’t going to be shorter, 2040 or 2050.”

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