There is more space junk in Earth’s orbit now than ever before. And this growing problem is creating an increasingly hazardous environment for operational spacecraft and satellites.

Space junk consists of nonfunctional satellites, spent rocket stages, and fragments resulting from satellite collisions and explosions.

With thousands more satellites scheduled to launch in the coming years, the potential for collisions is set to increase, which threatens to exacerbate the space debris issue and creates challenges for future space activities. The issue has also sparked discussion of a phenomenon known as Kessler syndrome.

What Is Kessler Syndrome?

Kessler syndrome is a hypothetical scenario proposed by NASA scientist Donald J. Kessler in 1978, predicting what might happen when the density of objects in low Earth orbit (LEO)—roughly 100-1,200 miles above our planet—reaches a certain critical level.

“This syndrome predicts an escalating space debris population that leads to an increased likelihood of collisions and further debris creation, resulting in a cascade of detrimental impacts,” wrote the authors of a 2023 study about the phenomenon, published in the journal Frontiers.

“Such collisions, even minor ones, can set off a catastrophic chain reaction, jeopardizing all existing satellites and filling orbits with high-velocity debris. Accessing space orbits would become immensely challenging, and the prospect of exploring outer space might be compromised.”

Kessler syndrome is a process that could unfold over varying timescales, potentially from decades to centuries, depending on factors like the density of satellites in orbit, compliance with debris mitigation and removal efforts and any future collisions that may occur. But such a scenario could potentially make space exploration and the use of satellites dangerous, or even unfeasible—as well as more expensive—for many generations.

Experts debate the potential severity and timelines of Kessler syndrome, with opinions differing on how quickly it could escalate and how damaging it could be to space operations.

What Technology Could Be Threatened?

Kessler syndrome poses a significant threat to an array of technologies that rely on satellites. For example, the phenomenon could potentially result in widespread service outages affecting telecommunication and internet services.

Navigation systems, fundamentally reliant on the satellite-based Global Positioning System (GPS), would also face serious challenges in such a scenario. This could have an impact on everything from personal navigation to aviation logistics. The domino effect would extend to other areas as well, such as weather forecasting, given that meteorological satellites would be at risk.

If Kessler syndrome becomes severe enough, the phenomenon could potentially limit space exploration activities to some extent by making the launch and safe navigation of spacecraft through the debris field challenging.

The heightened risk of navigating through a debris-laden orbit could imperil voyages to the International Space Station, as well as future endeavors to the moon, Mars or more distant destinations, among other missions.

The burgeoning commercial space sector, which includes satellite internet initiatives and space tourism, would face roadblocks to development.

How Can We Prevent the Kessler Syndrome?

Measures have been introduced in an effort to prevent Kessler syndrome from occurring.

One example is the recent decision by the Federal Communications Commission (FCC)—adopted in 2022—to require satellites in LEO to de-orbit within five years of their mission, rather than the previous 25 years.

The goal of the rule, which applies to satellites licensed by the FCC or seeking access to the U.S. market, is to reduce the amount of debris above the Earth by shortening the time objects spend in orbit.

The European Space Agency (ESA) has also reduced the maximum time spent in LEO for its new missions from 25 to five years, while NASA is reassessing its mitigation policies.

The implementation of detailed end-of-life strategies for satellites is critical, encompassing controlled reentry procedures or relocation to graveyard orbits that avoid active satellite paths.

An artist’s illustration of space debris in orbit above the Earth. There is more space junk in Earth’s orbit now than ever before. An artist’s illustration of space debris in orbit above the Earth. There is more space junk in Earth’s orbit now than ever before. SiberianArt/iStock/Getty Images Plus

The incorporation of collision avoidance technologies and the enhancement of space situational awareness (SSA) are equally pivotal. These efforts involve tracking space debris more precisely and deploying predictive systems to foresee and circumvent potential in-orbit collisions. Advancements in spacecraft design are also aiming to minimize the generation of debris.

Internationally, efforts such as the ESA’s Clean Space initiative and the Inter-Agency Space Debris Coordination Committee (IADC) are focused on advocating and facilitating global cooperation on space debris issues.

Technologies are also being developed to actively remove existing large debris from orbit using innovative solutions like capture nets and harpoons. Other strategies include “drag sails,” which accelerate the de-orbit process of spacecraft, with the ultimate aim of reducing space debris.

How Many Satellites Has SpaceX’s Starlink Launched?

Several large satellite constellation projects are underway or in planning stages with the goal of providing global broadband internet coverage, among other services. There are concerns that these massive constellations increase the risk of space debris.

Among these projects is Starlink, a satellite internet constellation being developed by SpaceX to provide high-speed, low-latency broadband internet globally, particularly with the aim of serving remote and rural areas where access is unreliable or unavailable. It consists of a planned network of thousands of small satellites in LEO, working in conjunction with ground transceivers.

Starlink has launched almost 7,000 satellites, making up a majority of the total number of satellites that are in LEO.

SpaceX has implemented several measures to mitigate space debris risks with its Starlink satellites, including designing the spacecraft to autonomously avoid collisions using onboard propulsion and tracking data.

Additionally, Starlink satellites are placed in relatively low Earth orbits, which naturally decay over time, ensuring that they reenter the Earth’s atmosphere and burn up at the end of their operational life. This inherently lowers the long-term risk of debris compared to satellites in higher orbits, which remain for much longer time periods.

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