It has been less than 70 years since humans launched their first artificial satellite, Sputnik 1, into orbit around Earth. That event started not only the Space Race but also the Space Age, our modern age of satellite instruments.
At the beginning of 2019, there were about 2,000 active and dead satellite payloads orbiting the Earth. Today, there are more than 17,000, more than half of which are operated by one company: Starlink. Ten private companies plan to have more than 1,000 satellites in low-Earth orbit (LEO) – a space class of less than 2,000 kilometers (1,240 miles) in height – in the near future, with the total number of planned satellites expected to exceed 700,000 by 2040. orbit as part of its operations for orbital data centers, which exceed the total from all other providers combined.
The worst side effect of having so many satellites in LEO would be the Kessler syndrome: intense collisional activity that makes the environment above our planet an impenetrable danger zone. Scientists have begun to measure those risks – and to explain what might be needed to reduce them.
One collision after another
While the benefits of satellite technology are often at our fingertips – from location and navigation services to messaging, streaming, and gaming devices – the risks are relatively minor.
If LEO was home to only two satellites, and they collided, the impact would destroy them both and create debris that would last for a while, and most of it would fall off after a few centuries. However, if there are too many satellites in the “orbital shell” – that is, within a certain orbital region above the Earth – a single first strike can lead to many substations until all the satellites in the orbital shell are affected. This, in the worst case scenario, could create a debris field that cannot move around the Earth. The LEO environment would be a major collision hazard for any spacecraft, manned or unmanned, attempting to pass through it, perhaps for thousands or even tens of thousands of years.
This phenomenon – Kessler syndrome – was presented as an object of science fiction back in 1978 by Donald Kessler and Burton Cour-Palais, and highlights the dangers of space in general, and in particular LEO: The greater the number of satellites in LEO, the greater the risk of Kessler’s disease.
“The chances of an orbital collision leading to Kessler’s death … scares me a lot,” says astronomer Samantha Lawler of the University of Regina in Saskatchewan.
To help better measure the risks of satellite collisions, Dr. Lawler, in collaboration with other astronomers, developed a new metric known as Collision Realization and Significant Harm (CRASH). By calculating how long it would take for a satellite collision to occur with no collision avoidance mechanisms in place, the CRASH clock informs us of the dangers of our satellite LEO instruments. Furthermore, it helps us measure the risks of succumbing to Kessler’s disease at this time, especially with the complete lack of mitigation measures.
He explains: “Larger satellites produce larger targets, so they have a greater chance of collision, and if they are hit, they will produce more debris than a smaller satellite. “The basic idea of the CRASH clock is: What if all the satellites in orbit failed to collide, how long would it take for them to collide? Right now, the CRASH clock metric says we may crash for 3.8 days.”
Rearranging deck chairs
If a satellite operator knows that trouble is coming, he can take action to prevent it. Dr. “Starlink, which is the largest galaxy at the moment, has made one collision avoidance every two minutes on average between Dec. 2024 and Dec. 2025,” says Dr. Lawler. Lawler. But as more satellites continue to go up, the frequency of collision avoidance will have to increase accordingly – if we get 1.7 million satellites in LEO, collisions will occur too many times each day to prevent successful avoidance techniques.
Since satellites have limited sizes and response times, collision avoidance measures are not sufficient to prevent all accidents, however we do not currently have any other barriers in place. According to experts, we have exceeded the critical mass of satellites to make Kessler’s death a real risk. Dr. “If we stop creating new objects in orbit tomorrow, the rate of orbital collisions will continue to increase,” Lawler says. “That’s the explanation for Kessler’s disease, but now the time scale between collisions is years. As we add more objects into the orbit, the time gets shorter and the chance of collisions increases.”
Each new satellite launch brings us one step closer to the worst kind of disaster: one that is completely avoidable.
Removing every inactive satellite might reduce Kessler’s risk of death, but it wouldn’t solve the problem, and it would have its own serious problems.
Long before humans developed satellites, objects from space already existed on earth. Because the planets are so large, their gravity constantly pulls small objects – asteroids, micrometeoroids, space dust, cometary debris, etc. – to them. This slightly reduces the mass of matter in interplanetary space – the material and space between the planets – while increasing the mass of the planets themselves. It also reduces the number of deviant bodies that may affect them in the future.
Earth absorbs more than 12,000 tons of material per year, and almost all of it evaporates and is added to our atmosphere. However, the composition of that material is very different from the composition of burning satellites in space.
“[Meteoroids] “Mainly satellites are made of aluminum, carbon fiber, batteries, computers, solar devices, plastic, etc.: materials that are not usually added to the surface,” Dr. Lawler repeats. If they are fully operational, and each of the 42,000 satellites has a five-year lifespan, they will be burning about one satellite every hour.
From a legal perspective, outer space is not considered an environment, so no one is assessing the environmental impact of adding these satellite features to our space. Whether we like it or not, we are conducting a random experiment in geoengineering – which is increasing exponentially as we increase the number of LEO satellites.
A recipe for endurance
Another proposal that has been made in the past is that any crew of satellite constellations should be required to create “safe parking routes” as a precaution against any potential adverse weather event in space. Although the party line of the satellite industry is often to point out their security and the unnecessary confidence that their hardware will not have such events (which it seems that they are not), choosing ways that eliminate the risks of conflict is still a sad choice.
Dr. Asked what solutions he would prefer, Lawler says: “The biggest improvements to orbital safety will come from reducing the amount of satellites and debris in LEO.” This can be done by spreading your circles more. But even better would be to reduce the number of satellites in orbit!
However, without any pressure on the satellite operators – save the stakeholders – to comply with these requests, many fear that the requests for responsible planning will continue to fall on deaf ears. Scientists have watched the number and total number of LEO satellites increase without limit, and many expect that it will continue to do so until the inevitable happens: a collision that starts a dangerous chain reaction, causing Kessler syndrome. The peak of the next solar cycle, in the mid-2030s, represents the most dangerous time in history for this completely preventable natural disaster.
We have the knowledge to be resilient against these negative events and prevent them before they happen. But until satellite providers take and implement these necessary mitigation measures, each new satellite launch brings us closer to the worst kind of disaster: one that is entirely avoidable, if only we had acted responsibly in the first place.
This article is part of the monthly issue of Big Think Roots of Perseverance.
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