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Space debate -

If you have ever watched a scientific debate on the topic of space congestion, you may well have heard the term "Kessler effect" bandied about.

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Namesake -

Named after the retired astrophysicist and NASA scientist who first described it, Donald Kessler, this phenomenon has quite a muddy definition.

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General meaning -

In broad terms, however, it refers to a scenario in which the debris floating around in space sets off a chain reaction of collisions.

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Chain reaction -

In this chain reaction, a single collision sends out a cloud of fragments of debris, and those fragments in turn collide with other spaceborne objects, creating further debris.

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End result -

In this nightmare scenario, the chain reaction would continue until space becomes so clogged with debris that satellites are no longer able to operate, and mankind has to fully withdraw from space.

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Lack of consensus -

Experts disagree as to the likelihood that a Kessler event could occur. There is a widespread consensus, however, that space congestion is a problem.

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Why congestion occurs -

Congestion in space occurs due to the fragmentation of objects in orbit. It is a problem that has only been getting worse since the dawn of space flight in 1957.

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Reasons for fragmentation -

Fragmentation can occur for various reasons, including satellites colliding with one another, or even spacecrafts spontaneously exploding.

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Example -

In 2021, for example, Russia launched a missile at one of its own satellites as part of a weapons test. This created more than 1,500 traceable pieces of debris.

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Why congestion is a problem -

Debris floating around in space is a problem for various reasons. On the one hand, it endangers the lives of astronauts living on space stations.

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Recent event -

In November 2024, for example, astronauts living on the International Space Station (ISS) prepared for the worst as a piece of spaceborne garbage hurtled towards them.

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Outcome -

Thankfully, they were able to tweak the trajectory of the ISS and avoid a collision. If the debris had made contact with the station, however, it could have caused sections of the station to depressurize, which would have put the astronauts' lives at risk.

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Other risks -

On the other hand, debris floating around in space poses a risk to satellites and to the space-based technologies that power our everyday lives, such as GPS tools.

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To complicate things further -

To make matters worse, difficulties in tracking spaceborne debris means that the problem of space congestion may be much worse than it first seemed.

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Tracking objects -

In general, objects floating around in space must be at least the size of a tennis ball in order to be tracked. Any objects smaller than this are unable to reflect light.

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NASA's opinion -

Objects smaller than tennis balls can still cause significant damage, however. In fact, according to NASA, even an object the size of a fleck of paint is capable of smashing through metal.

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The importance of speed -

This is due to the fact that when orbiting in space, these objects move around very fast. The speed at which they move means that even the tiniest piece of junk left in space is worrying.

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No general consensus -

As previously mentioned, experts currently disagree as to when, where, and how a ripple effect of collisions, as described by Kessler, may play out.

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Difficulties in modeling -

The effect is very difficult to model, not least because space experts do not have a fully accurate picture of where objects are in orbit.

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Tricky to make predictions -

Couple this with the fact that space weather can change orbital trajectories, and the fact that no one really knows about the size and shape of airborne debris, and it becomes very difficult to make predictions.

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To illustrate -

Indeed, in order to model a single Kessler syndrome effect, scientists would have to guess exactly how a given satellite would break apart, how each piece of debris would look, where each piece of debris would go, and what it would collide with next.

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Minority opinion -

Given that the Kessler syndrome is a continuous event, there are some scientists who believe that the phenomenon is already in motion. They are in the minority, however.

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Prevention -

When it comes to preventing the Kessler effect, there are two proposed solutions that receive the most attention.

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Cleanup technology -

The first is investing in cleanup technology. Companies and governments have already started looking at ways that technology can drag pieces of debris out of orbit.

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Example technology -

One example of such technology is the Drag Augmentation Deorbiting Subsystem (ADEO), developed by the European Space Agency and tech company High Performance Space Structure Systems (HPS GmbH).

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Successful deployment -

According to the European Space Agency, the prototype braking sail was successfully deployed from the ION satellite in December 2022.

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The caveat -

The problem with breakup technologies, however, is that they are extremely expensive, and it is not clear who would foot the bill to roll them out at scale.

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Regulation -

The other proposed solution is to increase regulation and adopt international and/or national laws aimed at preventing companies and individuals from acting irresponsibly in space.

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UN efforts -

There are already some efforts underway. In September 2024, the United Nations adopted the Pact for the Future, which includes a section on the topic of space congestion.

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Going forward -

Time will tell whether this problem can be controlled by regulation. Some experts believe that such laws are much more likely to be enforceable if introduced at a national level. 

Sources: (CNN) (Aerospace America)

See also: Astronauts who have been in space the longest

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