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1. Space Environment
Lecture 56 – Space Sustainability
Kessler Syndrome misconceptions
Professor Hugh Lewis
SESA3038 Space Environment

2. Overview of lecture 56
• In the previous lecture, we saw that Kessler had recognised some
difficulties understanding the concept of a “critical density”
• Now we will see how misunderstandings have led to substantial
misconceptions and misrepresentations – not just in the media but also in
published research
– Is it really a “collision chain reaction”?
– Is it something that would happen quickly?
– Once it starts, is there no way to stop it?
– Does it mean the end to all space travel?
– Is there a tipping point and, if so, when will we (did we) reach it?
• In the next lectures we will see why the ideas above are likely incorrect
Space Environment – Space Sustainability

3. 3
Space Environment – Space Sustainability
Misconceptions

4. Space Environment – Space Sustainability
Misconceptions
“Elon Musk’s Starlink satellites
could ruin space travel forever –
terrifying ‘Kessler Syndrome’
explained
Kessler Syndrome is a concept
thought up by the Nasa scientist
Donald J. Kessler. It refers to the idea
that a chain reaction of exploding
space debris could create so much
space junk in the Low Earth Orbit
that we'd be trapped on Earth…
Once a space debris explosion
reaction starts it could take tens of
years before it ends.”
https://www.thesun.ie/tech/5350537/starlink-satellite-space-junk-kessler-syndrome-explained/

5. Space Environment – Space Sustainability
Misconceptions
“NASA space debris expert Don
Kessler observed that, once past a
certain critical mass, the total
amount of space debris will keep on
increasing: collisions give rise to
more debris and lead to more
collisions, in a chain reaction.”
http://www.esa.int/Enabling_Support/Space_Engineering_Technology/The_Kessler_Effect_and_how_to_stop_it

6. Space Environment – Space Sustainability
Misconceptions
“That runaway debris generation
scenario, often called the Kessler
syndrome, may seem far off. But in
fact, the sheer density of derelict
objects in orbit has already exceeded
what many consider to be the
mathematical point of no return.
In some of the most congested
regions of low earth orbit, this point
was actually passed more than 10
years ago, although the onslaught of
chain-reaction collisions will likely
take decades to pick up steam.”
https://spectrum.ieee.org/aerospace/satellites/weve-already-passed-the-tipping-point-for-orbital-debris/

7. What happens if…
…the top 50 statistically most-concerning
derelicts in LEO were to breakup?
https://www.sciencedirect.com/science/article/pii/S0094576521000217
Space Environment – Space Sustainability

8. Results: population growth Space Environment – Space Sustainability

9. Results: collisions Space Environment – Space Sustainability

10. Recap of lecture 56
• In the previous lecture, we saw that Kessler had recognised some
difficulties understanding the concept of a “critical density”
• In this lecture we have seen how these misunderstanding have led to
substantial misconceptions and misrepresentations
– Is it really a “collision chain reaction”?
– Is it something that would happen quickly?
– Once it starts, is there no way to stop it?
– Does it mean the end to all space travel?
– Is there a tipping point and, if so, when will we (did we) reach it?
• In the next lectures we will see why the ideas above are likely incorrect
Space Environment – Space Sustainability