What Is Space Debris?

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Our planet’s surface—including oceans, rivers, and other water bodies—is riddled with human-made waste, and most of it is toxic and non-biodegradable. What’s worse, humans are not particularly good at managing waste. This is especially troubling since the scale and impact of human activity on the environment continues to increase. In fact, even space, which not too long ago was the final frontier, is home to human-made waste in the form of space debris.

How Did Orbital Debris Get There?

Remarkable technical and technological developments made space exploration a reality. We can send people and spacecraft into space.  After years of launching satellites, Earth’s orbit is now home to a large volume of space junk, or “space debris.”

Originally, the term referred to natural debris found in our solar system, including stray asteroids, comets, and meteors. However, the term now refers solely to non-functional human-made objects in the immediate vicinity of our planet. In fact, “orbital debris” is a more accurate term in this context: it refers to defunct human-made objects found in Earth orbit.

Space Debris in Earth Orbit

Currently, most space debris is scattered in Low Earth Orbit (LEO)—that is, within 1,250 miles (2,000 kilometers) from our planet’s surface. The concentration of orbital debris is highest between 500-530 miles (800-850 kilometers) from Earth’s surface. The variety of space junk orbiting our planet is truly astonishing: space waste ranges from extremely small chips of paint to launch canisters and even abandoned or destroyed spacecraft.

Debris particles in Earth orbit are affected by Earth’s gravity, and, as a result, travel at very high speeds. According to Aerospace.org, this estimate, space junk has an average impact velocity of 21,600 mph. Due to their high speed, even small debris particles can be hazardous. Moreover, it is almost impossible to spot untracked space junk coming your way. Indeed, not all debris particles in Earth orbit are trackable. Nonetheless, according to a NASA quarterly news report this report released by the United States Strategic Command on July 2016, there are as many as 17,852 trackable objects in LEO. Staggeringly, this includes 1,419 functioning satellites.

On the other hand, the estimated number of debris particles between 0.4 and 4 inches in diameter is upward of 500,000. More notably, scientists estimate the number of smaller debris particles—that is, particles with a diameter of less than 1 inch— to be more than 10 million. Therefore, the possibility of a collision involving debris particles and functioning satellites is exceptionally high.

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Preventing Dangers Posed by Orbital Debris

Particles greater than 0.4 inches in diameter can destroy functioning satellites. In fact, even millimeter-sized particles can cause severe damage to satellites. What’s more, collisions involving space junk in Earth orbit create more debris, as bigger objects disintegrate into smaller, fast-moving particles—more about this shortly. Evidently, orbital debris is difficult to manage.

To prevent collisions, scientists make frequent but minor adjustments to satellites’ positions. Another way to alleviate space pollution is to produce stronger, more sustainable satellites and spacecraft. Unfortunately,  we can’t do much about the orbital debris already created. Prevention may be the most feasible option currently available to us.

Nonetheless, the European Union (EU) has funded a collaborative satellite research project called RemoveDEBRIS, which aims to test the efficacy of active debris removal techniques. In its current form, RemoveDEBRIS remains an experimental undertaking—a rather expensive experiment, in fact. It has been that the experiment costs  upward of 18.7 million USD.

Surrey Satellite Technology designed the satellite platform used to test debris removal techniques. RemoveDEBRIS features a net, a harpoon, and a dragsail. In addition, the platform is also equipped with a laser ranging instrument and two miniature research satellites called “CubeSats.”

Testing RemoveDEBRIS

RemoveDEBRIS launched on April 2, 2018, and four months later—on September 16, 2018—the spacecraft recorded its first capture. The spacecraft demonstrated its ability to actively remove orbital debris by using its net to snap up a deployed target. The target was designed to simulate debris particles in Earth orbit. Although this is quite a remarkable achievement, we are still quite a long way from ascertaining the feasibility of active orbital debris removal techniques.

Moreover, these efforts are not only highly expensive but are also subject to the risk of collision, which may, in turn, precipitate a succession of collisions, thereby possibly increasing the amount of orbital debris beyond critical density. This possibility is known as The Kessler Syndrome.

However, not all scientists consider this a possibility. This is not because they find this scenario improbable. On the contrary, some scientists argue that the syndrome is already underway. Nonetheless, scientists now recognize orbital debris as a serious threat. This recognition significantly informs contemporary astronomy, as well as space science. It’s noteworthy since the traditional definition of astronomy dictates that the scientific study of celestial objects and phenomena that originate outside the Earth’s atmosphere. It’s noteworthy since the traditional definition of astronomy is the scientific study of celestial objects and phenomena that originate outside the Earth’s atmosphere.

Orbital Debris: A Threat to Life on Earth?

Debris particles that return to our planet do not cause much damage to human life or property. This is remarkable since nearly 75 percent of all human-made objects launched into space have plummeted back to Earth. However, objects almost always burn up when they enter Earth’s atmosphere. Those that do make it to the surface typically tend to land in water bodies, especially oceans, or thinly populated regions.

Space junk, therefore, is not a direct threat to life on Earth. Nonetheless, it is essential to alleviate space pollution, mainly because collisions in Earth orbit produce more and more debris.

Where Do We Go from Here?

As one can infer, prevention alone will not suffice. It is equally important to identify the most congested orbits and the most hazardous particles in these orbits. This, no doubt, will require extensive research. Although the RemoveDEBRIS project is a big step toward achieving this end, it is only a stepping stone. In sum, researchers must simultaneously aim to manufacture more sustainable satellites and thoroughly test active debris removal techniques.

Editor’s Note: Dennis Wesley contributed this article. Dennis Wesley is an independent educational researcher and budding blogger, whose interests include STEM and Humanities education, especially interdisciplinary practices and methods. You can follow his personal blog here.

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Article by: Megan Ray Nichols

Megan Ray Nichols is a freelance science writer and science enthusiast. Her favorite subjects include astronomy and the environment. Megan is also a regular contributor to The Naked Scientists, Thomas Insights, and Real Clear Science. When she isn't writing, Megan loves watching movies, hiking, and stargazing.