What is Kessler Syndrome? SpaceX's Starlink satellites increase the risk of orbital chaos
The space debris problem could cascade dramatically due to a phenomenon known as the Kessler Syndrome, or the Kessler Effect.
There are already more than 27,000 pieces of space debris in orbit, according to NASA, and the number will only continue to rise. The space agency points out that, as space debris travels at about 15,700 mph (25,266 km/h) in low Earth orbit, an impact of "even a tiny piece of orbital debris with a spacecraft could create big problems."
Perhaps the worst-case scenario is Kessler Syndrome. But what is it and how might it pan out?
In an August interview with IE, University of Regina astronomer Dr. Samantha Lawler said we are "right on the edge" of the risk of Kessler Syndrome. If it does happen, it would feel like we were "inside a snow globe within a couple of hours of sunrise or sunset," she explained, and any efforts to fix the problem would be akin to "collecting bullets."
What is Kessler Syndrome?
Kessler Syndrome is a phenomenon that was first proposed by NASA scientist Donald Kessler in a 1978 scientific paper. In the study, titled "Collision Frequency of Artificial Satellites: The Creation of a Debris Belt," Kessler and co-author Burton Cour-Palais highlighted the fact that the likelihood of satellite collision increases with every satellite lifted into orbit.
They went a step further though. What if a collision did take place?
The colliding satellites, or spacecraft, would break into many small pieces, further increasing the likelihood of collisions in a dramatic snowball effect. Essentially, each breakup of a satellite would lead to further breakups and the likely outcome would be an orbital space full of tiny pieces of space shrapnel from destroyed machinery.
In their paper, Kessler and Cour-Palais wrote that "satellite collisions would produce orbiting fragments, each of which would increase the probability of further collisions, leading to the growth of a belt of debris around the Earth."
They also highlighted the difficulties this would cause for future space travel, stating that "the debris flux in such an Earth-orbiting belt could exceed the natural meteoroid flux, affecting future spacecraft designs."
How likely is Kessler Syndrome to happen?
It's difficult to gauge the exact probability of Kessler Syndrome, though the likelihood increases with every satellite launch. In our interview earlier this year, astronomer Samantha Lawler argued that SpaceX's Starlink satellite constellation is dramatically increasing the likelihood of Kessler Syndrome.
"For Starlink, their strategy is to put many, many, many satellites into these very dense orbital shells," Lawler told IE. "Obviously, they have a lot of vested interest in not letting the satellites crash into each other. But if they make a mistake, two Starlinks crash into each other, or a Starlink satellite crashes into a piece of space junk, and that makes a whole bunch more debris."
SpaceX regularly launches batches of about 50 Starlink satellites at a time and CEO Elon Musk recently claimed the company will have "over 4,200 Starlink satellites in operation within 18 months," constituting two-thirds of all active satellites. Other companies, such as Amazon, with its Kuiper Project, also aim to launch their own mega-constellations, meaning the sky will be even more crowded and the Kessler Effect will be more likely.
There's another way of looking at the problem though.
Spacecraft have already collided and crashed in orbit and potentially hazardous debris is already whizzing around the Earth at speeds of a few miles per second. Earlier this year, in fact, the International Space Station was forced into an unscheduled maneuver to avoid Russian space debris from an anti-satellite weapon test. Back in 2009, Russia's retired Kosmos 2251 satellite crashed into the operational communications satellite Iridium 33, creating around 2,000 pieces of space debris.
So, maybe Kessler Syndrome has already started? Donald Kessler himself corroborated this notion in a 2012 interview with Space Safety Magazine, in which he said "the cascade process can be more accurately thought of as continuous and has already started, where each collision or explosion in orbit slowly results in an increase in the frequency of future collisions."
Measures to keep orbit clean
As Lawler pointed out in our interview, she doesn't believe we have the technology required to fix things if Kessler Syndrome did reach a critical threshold. She also argued the private sector is not currently incentivized to create solutions as there is no real profit to be had in collecting space debris.
Space agencies and private space firms obviously want to avoid the Kessler Syndrome, though it's a risk that comes with the territory — and one that many will argue is worth taking. Elon Musk, for example, has stated that the proceeds from the company's Starlink satellites will go towards building its Mars-bound Starship rocket.
NASA's mode of operation when it comes to orbital debris is to take an incredibly cautious preventative approach with its largest spacecraft. The space agency says it will most likely perform an avoidance maneuver even if there is a one in 100,000 chance of a small piece of space debris colliding with the International Space Station. NASA and the U.S. Department of Defense track and classify space debris with its global Space Surveillance Network (SSN) sensors
Several space agencies, including the European Space Agency (ESA), are also working on debris removal technologies. Most of these — like the ESA's e.Deorbit concept shown in the video above — involve capturing debris before sending it downwards to burn up in the Earth's atmosphere.
Arguably, the group most invested in preventing Kessler Syndrome is the global astronomical community, as countless shiny particles in the night sky would greatly impede their ability to do their work. In fact, the adverse effect of satellite mega-constellations on astronomical work is already well documented.
One group, the newly-formed International Astronomical Union Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference (IAU CPS) is campaigning for more regulation that takes into account the risk of Kessler Syndrome as well as the largely undocumented environmental impact of countless satellites burning up on re-entry into the atmosphere.
Even NASA warns that the growing number of satellites in the night sky could impede our ability to "detect and possibly redirect a potentially catastrophic [asteroid] impact" with Earth. The stakes couldn't really get much higher than the potential destruction of human civilization.
Verena Mohaupt, logistics coordinator of MOSAiC, Multidisciplinary drifting Observatory for the Study of Arctic Climate, talks about the perilous journey.