Taking the Trash Out of Orbit

Walt Whitman once wrote that “every cubic inch of space is a miracle”. Yet it seems that every cubic inch of space is becoming increasingly inhospitable, clogged with garbage from Earth. As the amount of debris in space proliferates, space debris looks set to be one of the biggest challenges facing space sustainability efforts. Questions remain, however, over the best way to solve these problems in a way that is cost-effective and does not hamper further development in space. Examining the issue of space debris in more depth highlights some of the difficulties in ensuring sustainable growth of the industry and provides insight into what is likely to be a key area of focus in the coming years, as people try to limit space debris’ destructive potential.

Anyone familiar with movies like Salyut-7 or Gravity will be aware of the potential damage debris can cause in space. As the name suggests, space debris is essentially stuff in space that is no longer used for anything. These objects can stay in orbit for years or even decades before falling and burning up in the atmosphere (or sometimes even hitting Earth). Much of the attention has been focused on large objects, like satellites, which hold greater risk of collision. With an average speed of almost 22,500 miles per hour, these collisions can be catastrophic. In 2009, for instance, a privately-owned American satellite collided with an inactive Russian military satellite, resulting in the destruction of both. That then led to the creation of almost 2,500 trackable fragments, each of which has destructive potential due to its speed. Even something as small as a fleck of paint has been recorded as having caused serious damage to equipment, and a 4-inch object could shatter a satellite or spacecraft.

Unfortunately, these small pieces are abundant. There are over 91,000 tonnes of space objects in orbit, with around 28,000 debris objects currently regularly tracked. Moreover, there are about 3,500 defunct satellites and an estimated 750,000 fragments. The number of objects in space is expected to increase in the future; SpaceX, for example, is planning to send up to 40,000 satellites into space to provide internet access through their Starlink project. If a single project from a single company might send that many objects to space, more ventures from other actors could potentially lead to a situation in the near future where there are millions of pieces of debris, any one of which could cause significant damage.

One particularly chilling scenario is the possibility of what is called the “Kessler Syndrome”, where, past a certain critical mass, there will be an irreversible chain reaction where one collision creates debris, and that debris goes on to cause more collisions, which creates more debris, and so on. The result of this would be that most satellites and spacecraft could be incapacitated, thereby greatly limiting space travel and preventing any service that uses satellites from operating, such as GPS or television. While this worst-case scenario does not appear to have played out yet, space debris levels have increased 50% in the past five years alone in the low orbit region. This region is the most likely to experience an accident, with some at NASA suggesting we are already at critical mass there. Similarly, a report 10 years ago from the US National Research Council suggested the amount of debris had reached a “tipping point, with enough [debris] currently in orbit to continually collide”.

These problems are compounded by the lack of regulation surrounding space debris and sending objects into space more generally. In 1995 NASA became the first space agency to issue guidelines for mitigation of debris, and various other space agencies have followed suit, as well as international organizations like the Inter-Agency Space Debris Coordination Committee and the United Nations' Committee on the Peaceful Uses of Outer Space. However, these are only guidelines, meaning they are voluntary and non-binding, and have not stemmed the increase in space debris. Additional issues also exist with space law, such as problems of liability: it can often be difficult to establish who is responsible and at fault when damage is caused by a piece of debris. Efforts to have stricter criteria for debris have frequently been opposed by the industry. For example, last year the Federal Communications Commission withdrew requirements for stricter orbital debris standards after experiencing pressure from industry trade groups and companies, who cited the increased cost of such requirements. These factors mean there are comparatively few legal barriers to increasing space debris.

The overall problem of space debris needs to be addressed with a two-pronged approach: there has to be an effort to both prevent the accumulation of more space debris and remove current debris. Reduction in debris increases can be solved through regulation and the establishment of stringent disposal guidelines, provided these guidelines are complied with. This can be accomplished either in the form of an international treaty, or through a system where there is a financial incentive to use space more sustainably, such as clearer regulations about liability. In the words of the European Space Agency (ESA), “strong compliance with post-mission disposal guidelines is the most effective long-­term means of stabilising the space debris environment at a safe level”. In the short term, there must be an effort to reduce the quantity of debris created by limiting the number of inorbital explosions and collisions that create higher numbers of debris. Due to a lack of public, legal, or financial pressure, previously few organizations focused on how to do this. This has changed recently, however, with the introduction of the ESA’s Space Safety program, where a team monitors possible collisions every day and informs satellite operators when they need to move their equipment. There likely needs to be an increase in this sort of monitoring to keep debris numbers from increasing drastically.

Removing debris is a more difficult (and expensive) task, but there are multiple projects which aim to solve this problem. Numerous ideas have been mooted, ranging from electrodynamic tethers to robotic tentacles and space slingshots. One of the most promising is the ESA’s ClearSpace-1 mission, set to be launched in 2025. At the cost of €120m, a robot junk collector with four arms will be sent into space to grab a piece of space debris around the size of a small satellite and drag out of orbit. While this represents an exciting example as to how space debris could be reduced in the future, the high costs and long time horizon required to remove just one piece of debris illustrates the difficulties in reducing space debris. Regardless of the difficulties, progress continues to be made, as space junk was removed for the first time in 2018, and new debris removal projects are being launched on a regular basis.

Space debris is undeniably a serious problem. Hoping that the proliferation of space debris will not lead to problems soon is playing with fire, as a lack of regulation and increase in the use of space seems set to exacerbate the problem. Left unchecked, a serious collision could significantly impact several services used on a daily basis and leave our whole species earthbound for generations. However, the problem is one that can be solved through a combination of oversight and technological advance, and there have been several promising signs of change recently. If the space and science industries properly react to this problem, we could finally start seeing space debris becoming a less threatening issue in the near future