Artwork showing two of the potential dangers of low-Earth orbit. MARK GARLICK/SCIENCE PHOTO LIBRARY/Getty
In 1978, astrophysicist Donald J. Kessler revealed his troubling hypothesis to the world. Dubbed Kessler syndrome, the theory proposes that the density of objects in low Earth orbit (LEO) will eventually be great enough to set off a cascade of collisions. Each collision will create more space debris than the last, increasing the likelihood of future collisions. This cosmic domino effect would render space services and satellites in specific orbital ranges largely inoperable for generations.
In 1978, Kessler syndrome may have been thought of as being an extreme, nearly dystopian scenario, however the current threat posed by space debris is tangible and pressing. In April 2024, The Center for Strategic and International Studies released its 7th Annual Space Threat Assessment Report. The report analyzes various space-based national security concerns and cites space debris, also known as orbital debris and space junk, as a prevalent risk.
Due to increased space activity over the last several decades, space debris is becoming a serious issue that indiscriminately affects satellites and human-crewed systems. With over 2,800 satellites launched into orbit in 2023, a 23% increase from 2022, the issue of space debris is growing.
As such, the space industry must work together to address the increasing threat of space debris and ensure that future launches are safe and effective. Fortunately, modern data and modeling tools can illuminate critical information about space debris.
Once understood, a clearly defined, collaborative protocol for space debris clean-up should be implemented to support the long-term vitality of space missions for nation-states worldwide and their commercial partners.
Space Debris: A Universal Issue
NASA defines space debris as “human-generated objects, such as pieces of spacecraft, tiny flecks of paint from a spacecraft, parts of rockets, satellites that are no longer working, or explosions of objects in orbit flying around in space at high speeds.”
According to NASA, millions of pieces of space debris are flying in LEO. As commercial space activity continues to boom, with a 50% increase in commercial launch activity from 2022 to 2023, space debris will undoubtedly continue to pile up.
Troublingly, depending on its altitude, debris can remain in orbit for decades, if not centuries. Most space debris travel at speeds of around 18,000 miles per hour, which poses serious collision risks to current and future spacecraft.
Orbital collisions can damage critical assets, such as Global Positioning Systems (GPS) and satellite communications systems, disrupting space-based operations. For instance, in 2009, two communications satellites accidentally collided at 26,000 mph, destroying both satellites and creating thousands of pieces of space debris.
Most significantly, space debris presents a safety hazard to astronauts working on space stations. The life-threatening implications of space debris are depicted in the 2013 film Gravity, and while the film is a work of fiction, it portrays a possibility that is all too real.
Notably, no organizations are explicitly responsible for managing space debris, and there are no international space laws governing debris in LEO. It's unlikely that any one nation or organization would take on this challenge alone, as close to 6,000 tons of materials are currently in LEO.
The International Organization for Standardization (ISO), a worldwide federation of national standards bodies, published the fourth edition of its space debris mitigation requirements in 2023 (ISO 24113:2023). These standards are widely accepted as best practices in the space community, however, adherence to the requirements is entirely voluntary, with no ramifications for those who disregard these safety guidelines.
Space debris is a problem for all nations and corporations with space aspirations. As such, this universal issue presents an unprecedented opportunity for global collaboration.
Proactive and Reactive Approaches to Cleaning Up LEO
Removing space debris from orbit is a daunting and costly task. U.S. agencies are striving to design equipment to reduce the debris already in space with initiatives such as the NASA Orbital Debris Program. However, U.S. government agencies cannot overcome this issue alone.
To that end, NASA is also incentivizing private-sector organizations to assist with these galactic clean-up efforts with competitions such as "Detect, Track and Remediate: The Challenge of Small Space Debris." NASA's initiative outlines three primary approaches to correcting the space debris problem.
Detecting and characterizing small space debris involves using radar systems, optical telescopes and data fusion algorithms to deliver real-time data on debris orbits, properties, positions and velocities. Currently, the U.S. Space Force tracks any debris larger than 10 cm, but small particles still pose a risk.
Tracking small space debris particles requires even more advanced sensor capabilities and predictive models of orbital drag to project trajectory accurately. This information is essential for successful clean-up efforts because capturing and removing space debris is impossible if its location is unknown.
Various debris removal methods have been debated by leading scientists, from giant nets to targeted laser beams. While the ideal approach for debris removal for each type of debris is still up in the air, regardless of the strategy, the removal process will be extremely expensive. That's why many nations and commercial entities are currently focused on managing the risk posed by space debris instead of spending considerable time and resources to eliminate the threat altogether. For example, according to a December 2022 NASA report, the International Space Station (ISS) has course-corrected itself 32 times to avoid satellites and trackable space debris since 1999.
Given the increasing density of space debris in LEO, remediation is perhaps the most important objective to avoid a Kessler syndrome scenario. To ensure a sustainable future of space activity and exploration, it's imperative not only to remove current debris but also to limit additional debris as much as possible.
Future missions can limit the volume of debris they produce by following the ISO 24113:2023 standards. Additionally, engineers may consider designing future satellites and spacecraft with some sort of propellant or device that can remove the asset from orbit and direct it back to Earth once its mission is complete. Admittedly, with debris ranging from paint flecks to rocket bodies, removal and remediation techniques will vary significantly depending on the size and velocity of the debris in question.
In addition to technical innovation, cross-sector collaboration between commercial organizations, academia and government agencies is paramount to provide critical insights about space debris for engineers and policymakers alike. Organizations such as the United Nations Committee on the Peaceful Uses of Outer Space provide a critical venue for international discussions about space debris. Continued research efforts will ensure all relevant stakeholders are well-informed on this evolving challenge and empower them to coordinate their efforts.
As society becomes increasingly dependent on space-based services, the threat of space debris becomes greater. To ensure the longevity of humankind's space exploration and activity, the universal issue of space debris must be addressed with a coordinated, international strategy. In doing so, future missions can proceed with confidence.