Space debris

DEFINITION: Human-made nonfunctional objects that are in orbit around Earth

Space debris—which consists of nonfunctioning spacecraft, rocket bodies, refuse from missions, and fragments thereof—poses a hazard for space missions, satellite-based services, and people both in space and on Earth. As space-faring nations have become more aware of the dangers of this debris, they have worked to minimize its generation during operations in space.

Since 1957, human beings have launched thousands of satellites and other spacecraft. Most of the spacecraft launched successfully achieve orbit. Those that explode after attaining orbit altitude and those that fail after achieving orbit become space debris (also known as orbital debris or space junk). Anything that reaches orbit altitude—about 300 kilometers (186 miles) above Earth’s surface—becomes a satellite. Once in orbit, objects are constantly under the pull of Earth’s gravity, and, in time, they slowly fall from orbit. The greater the distance from Earth, the longer an object will remain in orbit. Above 1,000 kilometers (621 miles), objects can remain in orbit for at least a century. Objects orbiting at an altitude of 800 kilometers (497 miles) are likely to fall to Earth within decades, and those at altitudes between 200 and 600 kilometers (124 and 373 miles) tend to remain in orbit for several years at best.

In 2024, the the European Space Agency (ESA) had estimated roughly 40,500 debris objects larger than 10 centimeters (4 inches) in diameter. An estimated 1,100,000 orbiting particles were between 1 and 10 centimeters (0.4 and 4 inches) in diameter. Particles measuring less than 1 centimeter in diameter probably number in the hundreds of millions. Most of the debris orbits within 2,000 kilometers (1,243 miles) of Earth’s surface, with the greatest concentrations accumulating at altitudes between 800 and 850 kilometers (497 and 528 miles).

Each object in orbit runs the risk of running into another object. The volume of space surrounding Earth is immense, and the chances of a collision between two objects are relatively low; however, the likelihood of collision increases when the objects occupy the same orbit. Because certain orbits are particularly desirable for satellites used for communications and surveillance purposes, various nations and commercial interests place their satellites into these positions, thereby increasing the chances of collision.

Many different kinds of space debris orbit Earth. From the 1960s through the mid-1980s, nations deliberately destroyed orbiting satellites while testing weapons for antisatellite warfare. Other forms of space debris have less dramatic origins, such as astronaut Ed White’s glove, which slowly drifted away from his Gemini spacecraft in 1965. Each item adds to the ever-increasing number of human-made objects orbiting Earth. Collisions between objects, and explosions of residual fuels in abandoned rocket engines, break existing debris into many smaller pieces.

Objects ranging in size from spent rocket boosters and nonfunctional satellites to small chips of paint, solid-fuel fragments, and coolant droplets have the potential to damage spacecraft. It is not merely the mass of an object that poses a danger but also its high velocity. At orbits below 2,000 kilometers, debris travels at speeds of 7 to 8 kilometers (4.3 to 5 miles) per second so that even tiny particles can pit space shuttle cockpit windows and damage unshielded satellite components. In 2017 alone, commercial companies, military departments, and amateurs launched over four hundred new satellites into orbit, and by 2018, there were about twenty thousand human-made objects in orbit. In 2021, the National Aeronautics and Space Administration (NASA) estimated that the number had risen to 27,000. Over subsequent years, reports continued to highlight that satellite launches had only further increased on a yearly basis as technology advancements and affordability had made commercial networking ventures for companies such as SpaceX more accessible. In 2024, the ESA estimated that there were over 10,200 active satellites in orbit by that point.

Hazards

The amount of space debris has grown great enough that it has become standard practice to shift uncrewed satellites out of harm’s way when large debris (objects larger than 10 centimeters) is detected. Space shuttle flights have to adjust course to avoid debris reported by the Space Surveillance Network. The International Space Station is heavily shielded against objects smaller than 1 centimeter, but it has the capability to maneuver away from larger tracked objects.

Only one collision between large, intact satellites has ever occurred. In February 2009, an operational US Iridium 33 communications satellite accidentally struck a deactivated Russian Kosmos-2251 communications satellite. Both spacecraft were destroyed, and more than 1,500 large fragments were generated. The amount of large debris had already been dramatically increased two years earlier, when in January 2007, China conducted an anti weapons test in which it used its aging Fengyun-1C weather satellite as a target. The resulting destruction created roughly 2,600 large debris fragments and hundreds of thousands of smaller particles. In March 2021, a Chinese satellite broke up after a collision, though the event was far less severe.

Efforts to minimize the problems associated with space debris include the boosting of geostationary satellites that have ended their missions out of their orbits (nearly 36,000 kilometers, or 22,369 miles, above Earth’s surface) into a higher “disposal orbit.” Similarly, deactivated satellites that operate at lower altitudes may be moved to even lower orbits that will decay more quickly, hastening the satellites’ fall to Earth. If a satellite fails to burn up in the atmosphere, however, it can present a threat to people and property on Earth’s surface.

In 1978 a Soviet satellite with a nuclear power source survived reentry and strewed small amounts of radioactive material across Canada. The following year, large pieces of the Skylab space station withstood a fiery plunge through the atmosphere and scattered debris across western Australia. In 2001, a rocket upper stage that had been part of a 1993 global positioning satellite launch fell to Earth in the Saudi Arabian desert. All of these incidents would have caused considerable damage if the debris had not landed in sparsely populated areas. Only one instance has been recorded of a person being struck by space debris: In 1997, a bit of woven metallic material from a Delta II rocket fuel tank hit an Oklahoma woman on the shoulder but did not injure her. In 2018, the Chinese space station Tiangong-1 fell to Earth above the southern Pacific Ocean after a highly publicized following of its descent from space. On average, one piece of cataloged space debris falls out of orbit every day, usually burning up in the atmosphere. In 2023, a large, cylindrical piece of debris was found on an Australian beach; the nation's space agency ultimately deduced that the piece had belonged to a rocket recently launched by the Indian Space Research Organization. The year prior, the agency had also determined that a piece of debris found on a farm had come from a SpaceX craft.

Mitigation Measures

Careful design and operational measures can keep new space missions from contributing unnecessarily to the proliferation of space debris. For example, upper stages of launch vehicles can be placed at lower altitudes so that their orbits decay sooner. Since 1988, the United States has had an official policy of minimizing debris from governmental and nongovernmental operations in space, and the US government approved a set of standard practices for the mitigation of space debris in 2001. The governments of France, the European Union, Japan, and Russia also have issued guidelines pertaining to space debris. Additional guidelines have been published by the United Nations Committee on the Peaceful Uses of Outer Space (COPUOS) and the Inter-Agency Space Debris Coordination Committee (IADC), a group established by the world’s leading space agencies in 1993.

Cleaning up existing space debris remains an expensive and technologically challenging prospect. Proposed solutions have included hastening objects’ fall to Earth by using lasers to slow their orbits and conducting special robotic space missions to grab and haul debris. Solutions that are both technically feasible and economically viable have yet to be developed. In addition, the development of technologies for the cleanup of space debris is controversial because any methods capable of moving spacecraft have potential weapons applications.

A 2006 study sponsored by the US National Aeronautics and Space Administration (NASA) Orbital Debris Program concluded that, if no new launches were conducted and no new objects introduced to Earth’s orbit, the number of objects falling out of orbit over the next half century would balance the number of new objects created through collisions. After 2055, however, the increasing number of collision-generated fragments—which would go on to create their own catastrophic collisions—would overtake the number lost through decaying orbits.

The international space community’s concern in the wake of the 2006 NASA study, China’s 2007 weapons test, and the 2009 satellite collision led to the first International Conference on Orbital Debris Removal, convened in December 2009. Participants examined the many technical, economic, legal, and policy issues surrounding near-Earth space cleanup, but they reached no conclusions regarding exactly how humankind might best address the worsening problem of space debris. While surveillance systems to track debris had advanced, allowing some active satellites to be remotely controlled to avoid collisions with incoming debris, creating a solution to remove space debris was an increasingly important task in the 2020s. In addition, plans were suggested to command satellites to reenter Earth's atmosphere within twenty-five years of mission completion. The second International Conference on Orbital Debris, 2023, focused on promoting additional collaboration and cooperation regarding orbital debris research between the United States and the international community.

Bibliography

"Active Debris Removal." The European Space Agency, www.esa.int/Space‗Safety/Space‗Debris/Active‗debris‗removal. Accessed 13 Nov. 2024.

Inter-Agency Space Debris Coordination Committee. IADC Space Debris Mitigation Guidelines. United Nations, 2002.

Johnson, Nicholas L., and Darren S. McKnight. Artificial Space Debris. Updated ed., Krieger, 1991.

Klinkrad, Heiner. Space Debris: Models and Risk Analysis. Springer, 2006.

“Mitigating Space Debris Generation.” The European Space Agency, www.esa.int/Our‗Activities/Operations/Space‗Debris/Mitigating‗space‗debris‗generation. Accessed 13 Nov. 2024.

Moses, Claire. “Object Found on Australian Beach Is a Mystery No More.” The New York Times, 31 July 2023, www.nytimes.com/2023/07/31/world/australia/australia-mystery-object-indian-rocket.html. Accessed 13 Nov. 2024.

National Research Council. Orbital Debris: A Technical Assessment. National Academy Press, 1995.

O’Callaghan, Jonathan. “What Is Space Junk and Why Is It a Problem?” Natural History Museum, www.nhm.ac.uk/discover/what-is-space-junk-and-why-is-it-a-problem.html. Accessed 13 Nov. 2024.

Simpson, John A., editor. Preservation of Near-Earth Space for Future Generations. 1994. Reprint, Cambridge University Press, 2006.

Smirnov, Nickolay N., editor. Space Debris: Hazard Evaluation and Mitigation. Taylor & Francis, 2002.

“Space Debris and Human Spacecraft.” NASA, 21 July 2022, www.nasa.gov/mission‗pages/station/news/orbital‗debris.html. Accessed 13 Nov. 2024.

“Space Safety: Frequently Asked Questions.” European Space Agency, Apr. 2021, www.esa.int/Our‗Activities/Operations/Space‗Debris/FAQ‗Frequently‗asked‗questions. Accessed 13 Nov. 2024.

“Space Safety: Space Debris by the Numbers.” European Space Agency, 20 Sept. 2024, www.esa.int/Space‗Safety/Space‗Debris/Space‗debris‗by‗the‗numbers. Accessed 13 Nov. 2024.

United Nations Committee on the Peaceful Uses of Outer Space. Technical Report on Space Debris. United Nations, 1999.

Williamson, Mark. Space: The Fragile Frontier. American Institute of Aeronautics and Astronautics, 2006.

Witze, Alexandra. “The Quest to Conquer Earth’s Space Junk Problem.” Nature, 5 Sept. 2018, www.nature.com/articles/d41586-018-06170-1. Accessed 13 Nov. 2024.

Young, Stephen. “How Many Satellites Are in Space? The Spike in Numbers Continues.” The Equation, Union of Concerned Scientists, 11 July 2023, blog.ucsusa.org/syoung/how-many-satellites-are-in-space-the-spike-in-numbers-continues/. Accessed 13 Nov. 2024.