The Kessler Effect
Detailing the Current State of Space Debris
Aug 28, 2024
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Thank you for reading the Brainwaves newsletter. I’m Drew Jackson, your content curator, and today I’m writing about space objects and space debris. Let’s dive in.
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Credit Interesting Engineering
Thesis: As space continues to be commercialized, an increasing amount of items will be put into space, dramatically increasing the possibility of collisions. Donald Kessler predicted this effect in 1978, and the problem has only increased since then.
If you haven’t read my Space Primer, I’d highly recommend it before reading this article as some of the terminology associated with this subject may be difficult to understand.
The Kessler Effect
Donald J. Kessler was born in Texas in 1940. After serving in the Army for a couple of years, he decided to study physics at the University of Houston in 1962. Before graduating college, Kessler began working with NASA.
His career at NASA began with modeling the interplanetary meteoroid environment. Later, he applied these techniques to model artificial satellites in Earth’s orbit. This helped him predict, with supporting data, that man-made orbital debris would soon exceed the natural meteoroid environment.
Credit Cosmos Magazine
This discovery led to the founding of NASA’s Orbital Debris Program at the Johnson Space Center in 1979. There, Kessler continued to develop his models of orbital debris. Inter-agency collaboration with national and international entities led to the establishment of the Inter-Agency Space Debris Coordination Committee (IADC).
This work on space debris led to Kessler receiving the NASA Medal for Exceptional Scientific Achievement in 1989. Eventually, Kessler retired from NASA in 1996. Throughout his career, Kessler published more than 100 technical papers on meteoroids and orbital debris.
What is the Kessler Effect?
Kessler’s crowning achievement, the coining of the Kessler Effect, was published in 1978 in a paper titled “Collision Frequency of Artificial Satellites: The Creation of a Debris Belt”.
To explain his conclusions simply, Kessler started with the idea that there is debris in space (the sources of which I’ll explain below, but at this point, you’ll have to take my word for it). This debris is also orbiting the Earth, like other things in space (satellites, spaceships, etc.). The Kessler effect says that when this debris hits other things in space that aren’t debris, it will create more debris from these collisions. Ultimately, this creates a cascading effect where debris will hit things, creating more debris, which will hit more things, creating more debris, and so on, until everything in the Earth’s orbit is just debris.
To rephrase, Solar MEMS states the Kessler Effect as the following:
Kessler’s research culminated in 2009 when he concluded that the current space debris levels were already unstable. Any attempt to remove existing debris will likely fail because fragments from future collisions will be generated faster than they can be removed.
However, there is good news in all of this. If Kessler is right, even a catastrophic scenario would pose minimal risks for launches continuing past the Low Earth Orbit into the Medium Earth Orbit or further. The catastrophic scenarios predict an increase in the number of collisions per year, not a physically impassable barrier.
Credit The Market for Ideas
What type of debris is in space?
The European Space Agency estimated that there are around 11,500 satellites currently in space, of which around 9,000 are still functioning. Since 1957, more than 640 break-ups, explosions, or collisions have resulted in fragmentation. The total number of space debris is largely unknown, but there are estimates.
One source, the MASTER-8 statistical model, estimates the following:
- 36,500 pieces of space debris larger than 10 cm
- 1 million pieces of space debris between 1 cm to 10 cm
- 130 million pieces of space debris between 1 mm to 1 cm
NASA estimates the following:
- 25,000 pieces of space debris larger than 10 cm
- 500,000 pieces of space debris between 1 cm to 10 cm
- 100 million pieces of space debris between 1 mm to 2 cm
Credit Statista
Where does space debris come from?
It may seem self-explanatory, but space debris comes from things being put into space. The central idea behind Kessler’s theory is that more things in space will only continue to compound the amount of debris in space.
But what are we putting into space? Well, if you think about most of the things being put into space, they either go outside the Earth’s orbit or inside of it. The things going outside Earth’s orbit aren’t of consequence here, but they are usually more exploratory. The items staying inside of the Earth’s orbit are usually satellites, orbiting voyages, or science vessels.
Yet, this isn’t a description of space debris. For example, NASA cites the following list of space debris examples, “Derelict spacecraft and upper stages of launch vehicles, carriers for multiple payloads, debris intentionally released during spacecraft separation from its launch vehicle or during mission operations, debris created as a result of spacecraft or upper stage explosions or collisions, solid rocket motor effluents, and tiny flecks of paint released by thermal stress or small particle impacts.”
So, you can see that space debris comes from a wide variety of sources. However, the number of potential sources of space debris is expected to increase exponentially. Multiple companies are expecting to put large satellite constellations into orbit in the next couple of years. For instance, SpaceX expects to launch up to 40,000 satellites, OneWeb is projected to launch up to 648, Amazon is projected to launch up to 3,200 satellites, and Astra is projected to launch up to 13,600.
Credit Research Gate
What are the different methods proposed for reducing space debris?
The first step in reducing space debris is to cut off the source, hopefully preventing further space debris from entering the Low Earth Orbit. In many countries, designers of new satellites and spacecraft are required to demonstrate the vehicle can be safely disposed of at the end of its life. This generally means one of two scenarios: using a controlled atmospheric reentry system where the space vehicle is relanded on Earth’s surface or boosting into a graveyard orbit.
The basic solution is to rely on atmospheric drag. Around 500 kilometers altitude and lower, atmospheric drag plays a major role. Dead satellites and debris slow and burn up in the atmosphere within a few years. This is the Earth’s natural cleansing process. By the time you get to 600 km, it takes decades for things to drag down. At 800 or 900 km, it takes centuries for things to drag down, and once you get past 1000 km, it takes millennia to drag down.
Besides this, two major solutions have been proposed, firstly, reducing new junk, and secondly, removing large pieces of debris. Reducing new junk refers to the point made above where we aren’t putting anything into orbit that shouldn’t be there and that will stay there forever. This means adhering to space treaties that say satellites must not stay in orbit longer than 5 years after their mission is completed.
Removing large existing debris helps mitigate potential sources of the cascading debris events cited by the Kessler Effect. In principle, by removing enough existing space junk, the space debris curve could begin to flatten out significantly.
While these solutions, and many others, have been proposed, it’s unclear what will work. For instance, who would pay for orbital debris removal? What are the penalties for creating more space debris?
Credit IBSS Corp
Conclusions
Governments and companies continue to put things into Low Earth Orbit. The graph below from the Australian Space Academy shows the progression of space density by orbital altitude over time.
Space continues to be filled with more and more objects. This means the Kessler Effect continually becomes more and more likely to happen.
One conclusion to be taken from the Kessler Effect is the idea that the current distribution of debris in orbit could make it difficult for space activities and satellites to be employed in the future.
Credit Space Debris User Portal
As you can see, the amount of debris in space has only increased over time. Since 1960, the amount of space debris has exponentially increased.
Yet experts estimate that the Kessler Effect will happen over the course of decades if not centuries. This isn’t an immediate effect that’s astronomically affecting our world currently.
Even though the Kessler Effect is not an immediate problem, it, like other problems plaguing society today (e.g., climate change, water scarcity, etc.) will only continue to compound upon itself unless action is taken to mitigate damaging collisions.
See you Saturday for The Saturday Morning Newsletter,
Drew Jackson
Twitter: @brainwavesdotme
Email: brainwaves.me@gmail.com
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