In this article, we are going to discuss the hypothesis raised by an astrophysicist and NASA consultant. The Kessler effect suggests that when the amount of space debris in Low Earth Orbit (LEO) reaches a certain level, it will trigger a cascade effect in which this debris will be constantly colliding and breaking up to multiply the amount of debris, creating a permanent danger for any satellite of spacecraft in orbit. It is a kind of space debris domino effect that worries the aerospace sector and all the major space agencies around the world, and is one of the problems they have to solve.
What is the Kessler effect?
The Kessler effect or syndrome is the hypothesis raised by the astrophysicist Donald J. Kessler in 1991, which claims that the volume of space debris in Low Earth Orbit (LEO) will be so great in the near future that it will become increasingly likely that these objects will bump into each other, thereby creating even more debris in space. It is a kind of chain reaction in which this debris will crash into each other more and more frequently, creating an exponentially growing field of debris and endangering other satellites and spacecraft that are still operative.
Although this astrophysicist and NASA consultant was the first to shape this hypothesis, there have been many other scientists who have raised the alarm about the hazard that this domino effect of space debris represents. Even so, there are many uncertainties to analyse and data to consider for the future.
The sheer number of pieces of space debris is astounding, at Solar MEMS we have already mentioned this problem: NASA estimates that there are around 23,000 chunks of debris larger than a baseball orbiting the Earth, half a million pieces around the size of a marble and roughly 100 million fragments that are around a millimetre or more. We can picture all these uncontrolled fragments racing around at speeds of 27,000 kilometres per hour and slamming into each other, and the thousands of working satellites and spacecraft floating in the middle of all this junk, hoping to dodge them.
What are the dangers of the Kessler effect?
What makes the Kessler effect so potentially dangerous is the domino effect of this debris colliding with each other, which can quickly multiply the amount of space debris and endanger active missions, contaminating the LEO space.
Fortunately for science and space exploration, it has become easier and cheaper to put satellites in orbit, which means that many thousands of devices have been launched into space in recent decades. However, both these and out future spacecraft and satellites will be in danger if they are surrounded by debris. We should bear in mind that any tiny fragment of space debris can cause serious damage to a spacecraft or working satellite, and this has already happened, as we see in this article about space debris, which explains that a sliver of paint damaged several windows on the space shuttle.
Dormant satellites and spacecraft are especially worrying because they do not have fuel left to change their route when we detect that a dangerous collision is imminent. These larger items of debris will in turn generate even more junk than the smaller pieces, should they collide, and they are becoming more common because this problem was not foreseen in the past when space missions were being planned.
In the worst of these scenarios such as a collision between two large spacecraft, accompanied by the large volume of fragments that are out of control, the low earth orbit may be practically unusable.
Possible solutions to the Kessler effect
This problem is a concern for space agencies around the world and many companies in the aerospace sector are looking for solutions, such as optimizing their satellites and spacecraft to avoid adding to the debris inundating the low earth orbit.
Recent advances in science and technology and awareness of this problem mean that the objects designed for space missions now take every precaution to prevent them from damaging other spacecraft.
At Solar MEMS we have also discussed responsible space missions on our website, where we mention some of the measures that the international community are taking when designing missions to counteract the effect of space debris in Low Earth Orbit.
One of the most important solutions is to ensure that the satellites are safely disposed of when they are no longer operative, for example sending them back into the atmosphere in a controlled fall when their working life in a low orbit is over, or sending them to a “graveyard orbit” if they are further from the Earth.
Another approach is to ensure that resources like batteries or fuel are fully exhausted when their working life is over, to prevent explosions that can also create space debris.
The small size of most of this debris, and the speed it travels at, make the collection of this material very difficult. However the ESA plans to launch the first mission to collect space debris in 2025, ClearSpace One.
This is an experimental satellite that will test a technology capable of finding, capturing and removing old satellites and space debris from their orbit It does this by deploying a net to trap the debris and satellites that have finished their working life, and take them back into the atmosphere where they, and the satellite itself, will break up.
The ESA has other experimental projects to deal with the problem of space debris, such as a laser telescope that can be installed on Mount Teide (Spain) to monitor the fragments of waste and can be used in the future as a cannon to knock objects back into the atmosphere where they will disintegrate.
Image: Artist`s impression of ESA.