#1490 What is the Kessler syndrome?

What is the Kessler syndrome? The Kessler syndrome is a situation where there is so much space debris in low Earth orbit that pieces start to collide, breaking them into smaller pieces, and causing the collisions to increase.

The Kessler syndrome was named after a study written by Donald Kessler and Burton Cour-Palais in 1978 called “Collision Frequency of Artificial Satellites: The Creation of a Debris Belt”. It became known as the Kessler syndrome, perhaps slightly unfairly to the co-author Cour-Palais. The Kessler syndrome is a basic study of probability. The more things you put into orbit around Earth, the more chance that they will collide with each other. The theory is that two objects orbiting Earth might collide with each other and break up into smaller pieces. That then increases the amount of debris in orbit and therefore increases the chance of another collision.

There are currently estimated to be over 131 million pieces of space debris. 130 million of those are smaller than 1 cm. A million are 1 to 10 cm, and the rest are larger than 10 cm. They range from decommissioned satellites to tiny flecks of paint that have chipped off something. You might think that the smaller pieces would be harmless, but they can be travelling at over 15 kilometers per second, and they can cause significant damage. Clouds of dust at this speed can basically sandblast the surface off a satellite, and a small piece of metal could easily go straight through something. To avoid such damage, the International Space Station has a Whipple shield, which can withstand collisions with debris up to 0.5 cm. Larger debris is tracked, and if any was on a collision course with the space station, they can perform a maneuver called a Debris Avoidance Maneuver, where they fire their thrusters to move out of its way. The larger debris can be dead spacecraft and satellites, ejected boosters, lost equipment, and even parts of weapons.

The main problem, and the reason behind the Kessler syndrome, is that the amount of space debris increases year by year. The first satellite was launched in 1957. In 2024, 2,900 satellites were launched. There were 300 operational satellites in 1978, 1,000 in 2009, and over 11,700 today. Along with that, the number of flights into space has also increased, and, even though reusable spacecraft are improving, there are always pieces left behind. Then, in 2007, the Chinese used a missile to destroy one of their own weather satellites. Just a test, they said. The US followed up by destroying one of their own satellites the year after. Whatever the reason for all of this, it increased the amount of space debris. In 2009, a decommissioned Russian military satellite collided with a mobile phone satellite, increasing the amount of space debris even more.

The Kessler syndrome is not something that will happen suddenly. It will happen over many years, but as the number of things and the amount of debris increases, the number of collisions will also increase. Currently, there is one major collision every 13 years or so, but that is only going to increase. When Kessler and Cour-Palais came up with this idea in 1978, the increase in space junk wasn’t exponential, as it is today. One of the problems is that each major impact produces millions more pieces of debris, rapidly increasing the chance of more impacts.

One of the advantages of orbit is that different things orbit at different altitudes. Just because there is more space debris doesn’t necessarily mean that it is all at the same altitude. However, it is all increasing, so there may come a point where certain altitudes are closed to us because of the space debris there. And those inaccessible altitudes would logically only increase. It is unlikely that there would be a domino effect where this would all happen at the same time, but it will gradually worsen. There may even be a point where we can no longer put satellites up, or leave orbit. Because of low atmospheric drag, debris often accumulates in the 700 km to 1,000 km altitude band. 800 – 900 km may be the first altitude band that is closed off.

There are a lot of plans for ways to remove space debris, but none have been successful yet. There have been a few demos, but nothing on a commercial level. These have ranged from a remotely controlled vehicle to gather up debris to giant nets. The problem is that space exploration is rapidly becoming privatized ,and no single private company has any interest in cleaning up all of space when the value would be for all companies, and not just that one company. A similar problem exists with all of the plastic in the ocean. And this is what I learned today.

Sources

https://en.wikipedia.org/wiki/Space_debris

https://en.wikipedia.org/wiki/2007_Chinese_anti-satellite_missile_test

https://en.wikipedia.org/wiki/2009_satellite_collision

https://en.wikipedia.org/wiki/Whipple_shield

https://en.wikipedia.org/wiki/Kessler_syndrome

https://aquarid.physics.uwo.ca/kessler/Burt%20Cour_Palais.pdf

https://en.wikipedia.org/wiki/Donald_J._Kessler