Space above earth is turning into a junkyard

Debris from past launches puts future space exploration at risk

By Andrei Li, Contributing Writer

For satellites and other spacecraft, space around Earth is a perilous freeway of life and death. Orbital junk, commonly known as space debris, turns outer space into a gigantic game of bumper cars, where any collision means the end for the unfortunate satellite(s) involved.

What is space debris?

The last fifty years of human activity have created a trash field around Earth [1]. Up to 170 million pieces of debris could be in orbit above our planet [1]. About 25,000 of these are large, trackable objects (obsolete satellites, rocket stages, etc.) [8]; however, the vast majority of this debris is too small to track, meaning that avoiding it is almost impossible for spacecraft.

To stay in orbit, an object must move at a very high speed relative to the Earth’s surface. As a result, orbital collisions happen at an average speed of 10 km/s [3]. For context, a bullet shot from a rifle moves at about 1 km/s. At such speeds, even seemingly harmless objects, like foam, become destructive projectiles.

The speed of space debris makes avoiding collisions challenging. Most space debris, as well as satellites and space missions, are located in low Earth orbit, a band of space between 160 and 1600 km above Earth’s surface [11]. The concentration of satellites and debris in low Earth orbit increases the chance of such dangerous incidents occurring.

In December 2021, the Chinese space station Tiangong almost collided with a Starlink satellite [20], prompting calls for stricter regulation of outer space usage. Not a year later, last October, the ISS was forced to evade a piece of space debris [6]. These measures are not cheap: an estimated $100 million was spent in 2020 responding to space pollution, a cost that is expected to rise in the coming years [2].

In the worst-case scenario, satellite collisions could snowball in an exponential reaction, with debris from previous impacts fueling new crashes [7]. This would result in a junk field completely enveloping Earth at low orbit, blocking any future launches from reaching outer space.

Kessler syndrome, as such a catastrophic scenario is called, would set back all technological progress from the space age. It would prohibit space travel for centuries, before atmospheric friction sufficiently reduces space pollution back to safe levels [14].

Where does space debris come from?

Most uncontrollable space junk has been traced back to satellite collisions and tests of anti-satellite missiles—weapons developed to destroy enemy satellites in war.

Present-day satellites move into lower orbit before the end of their lifetimes, so that they re-enter the atmosphere within 25 years of being decommissioned [10]. However, older satellite missions were often designed without such contingencies in mind and, consequently, wind up as useless trash orbiting the Earth.

These defunct satellites pose the risk of colliding with other spacecraft in their orbital regions. In 2009, a depowered Russian craft collided with an American communications satellite and released a swarm of high-speed debris. That collision, the first collision between satellites in history, was assessed to pose minimal threat in its immediate aftermath. Nevertheless, Nicholas L. Johnson, then-chief scientist for orbital debris at NASA, cautioned that the most important step “is trying to quantify that risk”, warning that the debris swarm may wear down and destroy other satellites in the long run [18].

Tests of anti-satellite weapons, known as ASATs, are attributed to a large portion of orbital junk [17]. ASAT tests have been conducted by China, the U.S., Russia, and India as contingency weapons to knock out enemy satellite networks. A kinetic, non-explosive warhead is fired at a target satellite, using its high speed to slam into the satellite and destroy it.

Debris from such tests has been linked to satellite failures [4], posed a threat to the ISS [15], and led to international calls for prohibiting such weapons [16]. That said, regulating ASATS remains difficult, as tests are often conducted in absolute secrecy [19].

The launch of large satellite constellations, such as SpaceX’s Starlink project, has also come under scrutiny for increasing the risk of orbital collisions. Defunct minisatellites, which are  small and operate at the same altitude as many other commercial satellites, have a much higher chance of slipping past detection and crashing into another spacecraft.

The Starlink network is designed so that individual satellites deorbit within five years [12]. Nonetheless, as satellite constellations are built at higher altitudes and longer deorbit times, there remains a critical lack of international regulation regarding the overcrowding of space.

How can we combat space pollution?

Removing space debris can be done in one of two ways. We could either deorbit the debris and allow it to burn up in the atmosphere, or relocating it to a “graveyard orbit” where it cannot collide with any other space objects [10].

As of now, there is no commercially viable method for removing space junk. The 2018 RemoveDEBRIS mission, deployed from the ISS, tested two physical methods of debris removal with mixed results. In the first method, a net was used to capture a simulated piece of space debris—a balloon—and launch it into a re-entry trajectory. In the second method, a harpoon latched onto a test plate. A dragsail was then supposed to slow the satellite enough to enter the atmosphere, but it ultimately failed to deploy [9].

Space tugs, similar to the RemoveDEBRIS mission, are designed to move satellites into different orbits. NASA’s Space Shuttle program, before its retirement in 2011, often performed orbital maintenance on satellites. In 2021, China launched its own orbital tug, the Shijian-21, moving a defunct navigation satellite into a graveyard orbit [13].

A more fantastical alternative to physical tugs consists of moving large pieces of junk into higher orbit with a “tractor beam”. The tug works by shooting a stream of electrons at the object, imbuing it with a negative charge, while the tug itself acquires a positive charge. As a result, both junk and tug will attract each other, allowing the tug to drag the piece of debris with it. This method poses a lower risk of damaging the object and/or the tug via direct physical contact [5]

All of the above methods are designed to move large individual objects and thus remain insufficient to deal with the sheer quantity of trash in orbit. Moreover, the second method can only move a single large object over the course of weeks, making it impractical in the long run.

It is imperative to continue researching ways to remove space debris from orbit. Furthermore, a comprehensive international framework is needed to reduce junk left by missions, to mitigate the risk of space collisions, and to prohibit the development and testing of ASATs.

To allow the space missions of tomorrow, we must protect Earth’s space today.

References

1. About space debris. (n.d.). https://www.esa.int/Space_Safety/Space_Debris/About_space_debris. 
2. Adilov, N., Braun, V., Alexander, P. J., & Cunningham, B. M. (2023). An estimate of expected economic losses from satellite collisions with orbital debris. Journal of Space Safety Engineering, 10(1), 66–69. https://doi.org/10.1016/j.jsse.2023.01.002. 
3. ARES | Orbital Debris Program Office | Frequently asked Questions. (n.d.). https://orbitaldebris.jsc.nasa.gov/faq/. 
4. Atkinson, N. (2013, March 11). Chinese space debris collides with Russian satellite. Phys.org. https://phys.org/news/2013-03-chinese-space-debris-collides-russian.html. 
5. Baker, H. (2023, October 29). Sci-fi inspired tractor beams are real, and could solve a major space junk problem. livescience.com. https://www.livescience.com/space/space-exploration/sci-fi-inspired-tractor-beams-are-real-and-could-solve-the-major-problem-of-space-junk. 
6. Doubek, J. (2022, October 26). The International Space Station had to move to dodge space junk. NPR. https://www.npr.org/2022/10/26/1131374307/international-space-station-junk-debris-problem-satellite. 
7. Drmola, J., & Hubík, T. (2018). Kessler Syndrome: System Dynamics model. Space Policy, 44–45, 29–39. https://doi.org/10.1016/j.spacepol.2018.03.003. 
8. Editorial Board. (2023, November 2). A convention to clean up space debris threatening Earth’s orbits. Washington Post. https://www.washingtonpost.com/opinions/interactive/2023/space-junk-debris-removal/. 
9. Forshaw, J., Aglietti, G. S., Navarathinam, N., Kadhem, H., Salmon, T., Pisseloup, A., Joffre, É., Chabot, T., Retat, I., Axthelm, R., Barraclough, S., Ratcliffe, A., Bernal, C., Chaumette, F., Pollini, A., & Steyn, W. J. (2016). RemoveDEBRIS: An in-orbit active debris removal demonstration mission. Acta Astronautica, 127, 448–463. https://doi.org/10.1016/j.actaastro.2016.06.018. 
10. Graveyard orbits and the satellite afterlife. (2023, November 8). National Environmental Satellite, Data, and Information Service. https://www.nesdis.noaa.gov/news/graveyard-orbits-and-the-satellite-afterlife. 
11. Gregersen, E. (2023, November 7). Low Earth orbit (LEO) | Definition, Distance, & Facts. Encyclopedia Britannica. https://www.britannica.com/technology/low-Earth-orbit. 
12. Howell, E., Pultarova, T., Dobrijevic, D., & Mann, A. (2023, August 2). Starlink satellites: Everything you need to know about the controversial internet megaconstellation. Space.com. https://www.space.com/spacex-starlink-satellites.html. 
13. Jones, A. (2022, January 27). China’s Shijian-21 towed dead satellite to a high graveyard orbit. SpaceNews. https://spacenews.com/chinas-shijian-21-spacecraft-docked-with-and-towed-a-dead-satellite/. 
14. Kelvey, J. (2022, January 3). Kessler Syndrome: How runaway space junk could trap humans on Earth. Inverse. https://www.inverse.com/science/what-is-kessler-syndrome. 
15. NASA Administrator Statement on Russian ASAT test – NASA. (2021, November 15). NASA. https://www.nasa.gov/news-release/nasa-administrator-statement-on-russian-asat-test/. 
16. Russia proposes treaty to ban space weapons. (2008, February 12). New Scientist. https://www.newscientist.com/article/dn13312-russia-proposes-treaty-to-ban-space-weapons/. 
17. Smith, M. (2022, August 10). Anti-satellite weapons: History, types and purpose. Space.com. https://www.space.com/anti-satellite-weapons-asats. 
18. U.S.-Russian satellite collision sends debris flying – NYTimes.com. (2009, February 12). https://archive.nytimes.com/www.nytimes.com/2009/02/12/science/space/12satellite.html. 
19. Wall, M. (2023, February 7). Mysterious Russian satellite breaks up in orbit, generating cloud of debris. Space.com. https://www.space.com/russian-satellite-kosmos-2499-breakup-earth-orbit
20. Zhen, L. (2022, January 2). China’s complaints over Elon Musk’s satellites ‘highlight need for better communications to prevent accidents in space.’ South China Morning Post. https://www.scmp.com/news/china/military/article/3161854/chinas-complaints-over-elon-musks-satellites-highlight-need.

Image source: The European Space Agency, “The Kessler Effect and how to stop it”