Cosmox Blogs

Nov 02, 2024

Space Debris: Tackling the Orbital Threat

The world is currently facing significant challenges related to climate change and various forms of pollution. As part of Sustainable Development Goal #13 (SDG #13), addressing climate change is crucial for building a sustainable future. One issue that often goes overlooked is space debris—essentially, trash in outer space. Charity Weeden, who leads NASA’s OTPS (Office of Technology, Policy and Strategy) said that “growing activity in Earth’s orbit has brought us everything from faster terrestrial communications to a better understanding of our changing climate. These blossoming opportunities are resulting in a more crowded space environment". In this article, we will define what constitutes space debris, reveal that the most hazardous type might not be what you expect, and discuss global efforts to mitigate this problem

What exactly is space debris?

The official definition of space debris, according to the Inter-agency space debris coordination committee (IADC), is as follows: “Space debris are all human made objects, including fragments and elements thereof, in Earth orbit or re-entering the atmosphere, that are non-functional.” In simple words, just like trash on Earth, space debris or orbital debris is just junk in space. This mainly consists of non-functional spacecrafts, abandoned vehicle launch vehicle stages, and mission related debris. Of course, there are also natural ejecta from Earth and micrometeoroids, but for the purpose of this article, our focus will be on the space debris caused by humans.

Space debris by numbers

You might be imagining space debris as several big rocket parts or satellites just orbiting the Earth with no purpose, posing a major threat to functional satellites and astronauts in the International Space Station (ISS), but the truth is far from that. Let us take a look at the types of space debris to know exactly what is floating out there.

As of September 2024, there have been around 6700 successful rocket launches since the start of the space age in 1957. These missions have placed nearly 20,000 satellites into orbit, with 13,000 of them still in space and about 10,000 still functioning. The space age started 47 years ago, and we have already placed a multitude of civil, commercial, and defense satellites in Earth orbit. However, this also means that there is an increased risk of collisions in the space environment. And indeed, there have been collisions in space. The number of breakups, explosions, collisions, or anomalous events resulting in fragmentation is estimated to be more than 650. These events cause even more space debris to form this chain has its own name, ‘Kessler Syndrome’ which we will talk about later.

By size, the estimated numbers are as follows: Greater than 10 cm: 40500 space debris objects ⁠Greater than 1 cm to 10 cm: 1100000 space debris objects Greater than 1 mm to 1 cm: 130 million space debris objects

The numbers might be daunting, but keep in mind that these are just estimates based on statistical models, and space is HUGE, it is difficult to spot space debris just floating around. The images of space debris around the Earth's orbit are not to scale and are only meant to show how much space debris we have and where. But this cannot keep going because everything has a tipping point. Let us look at the risks associated with space debris.

Space debris as a risk

The risk of collisions is a real concern among spacecraft operators, which is why space debris is tracked by radar and optical detectors such as lidar, which basically targets an object with a laser and measures the time taken by reflected light to reach the receiver to determine its range. Various organizations track and measure space debris.

Even the International Space Station has needed tens of maneuvres to avoid debris collisions, usually performed when the risk is determined to be greater than one-in-10,000. Small pieces of debris have still impacted the solar panels, and some returned hardware. According to a paper on observations of MMOD (micrometeoroids and orbital debris), over 1,400 impact records have been recorded on the ISS. Collision threats: In space, even the tiniest objects like paint flecks can cause real damage to spacecrafts. This is because these objects can travel at insane speeds of more than 25,000 kilometers (15,500 miles) per second, circling the planet in under 90 minutes! To show you how much damage something as small as this can do, this image, captured by ESA astronaut Tim Peake, shows a 7-mm-diameter circular chip gouged out by the impact from a tiny space junk fleck only a few thousandths of a millimeter across. To put it in perspective, that is no larger than a tiny bacterium.

This is just to show that even a tiny speck of space junk can cause substantial damage because of the high velocity. Energy is related not just to mass but also to velocity. Now, what would happen if two large bodies hurtling towards each other collide? This is exactly what happened with two satellites, Kosmos 2251—a derelict Russian military communications satellite—and Iridium 33, another communications satellite launched by Russia for an American company. The relative speed of the impact was about 42,000 kilometers per hour (26,000 miles). The collision created thousands of new pieces of small space debris.

Kessler’s syndrome: 

Chances are, if you have watched the movie ‘Gravity’ or the Japanese animated show ‘Planetes’, you might have heard this term before. In a 1987 paper titled “Collision Frequency of Artificial Satellites: The Creation of a Debris Belt,” NASA scientist Donald J. Kessler states that with the number of increasing satellites in orbit, the probability of collisions also increases. Satellite collisions, he says, would increase the probability of further collisions leading to the growth of a belt of debris around the Earth. Thus, the debris flux will increase exponentially even if no further launches take place. This collisional cascading effect is loosely termed ‘Kessler’s syndrome’. In another paper about ‘critical density’, Kessler talks about how some parts of the low earth orbit may be rendered unstable due to the density of larger debris confined to these parts. In another paper, clarifying Kessler’s syndrome, Kessler says that the 1987 paper may have exaggerated and distorted conclusions, but according to current research, we might as well be in a time where we must completely follow the guidelines that were formed to reduce space debris after these papers. Let us take a look at these and ways to mitigate space debris.

Efforts to mitigate and deal with space debris

After the alarming calls from research done by scientists, a few organisations and departments were formed to address the issues of space debris. The United Nations Committee on the Peaceful Uses of Outer Space (COPUOS) published voluntary guidelines for developing standards for debris mitigation. Similarly, space agencies of various countries have followed suit in creating their own guidelines and practices to ensure the mitigation and minimal creation of space debris. In brief, some of them include:

-> An upper limit of 25 years to de-orbit satellites in low earth orbit (LEO) after their mission has ended.

-> Launching satellites above low earth orbit into elliptical orbits with perigees inside Earth’s atmosphere to allow for quick orbit decay, ensuring they burn up in the atmosphere.

-> Designing the mission architecture to leave the rocket second-stage in anelliptical geocentric orbit with a low perigee.

-> Moving geostationary satellites to a graveyard orbit after the end of their mission.

-> Active removal of space debris using innovative technologies.

Progress has been made in developing technologies to address this issue. Out of the ideas proposed, external removal of debris seems useful. Using a remotely controlled vehicle to rendezvous with, capture, and return debris to a central station, this method is going to prove itself with ESA’s upcoming ClearSpace-1 mission.

Conclusion

Space debris can prove to be a challenge, especially because it does not generate profit and requires funding. A NASA study suggests cost-effective solutions by comparing them. If these solutions are implemented by tagging private players in, it might prove to be a fix for this issue of space debris. In the 80s and 90s, acid rain and damage to the ozone layer were seen as major problems that, similar to space debris, might cause irreparable damage to the Earth and thus, humanity. However, these issues were dealt with due to global cooperation. We are now working together on climate change across the globe. This sense of cooperation and perseverance is what makes us human. I am certain that we will deal with space debris too and begin our journey to new horizons!