Written by António Vale with Adam Furman.
Space technologies are playing an increasingly critical role in communications, defence and research. As more satellites are launched, there is a growing risk of collision, and of satellites becoming military targets. Satellite-debris collisions have the potential to destroy not just one or two but many satellites, preventing the use of those orbits for years. Although de-orbiting satellites at a faster pace may be a solution, orbital debris falling back to Earth can cause environmental harm. Europe needs to better understand the risks and take regulatory and diplomatic steps to ensure continued access to space while protecting domestic and global interests.
Outer space is vast and empty – or, it used to be. The orbits around Earth are utilised by spacecraft, and not every orbit is fit for every purpose, concentrating satellites in the most useful ones. The number of launches has increased dramatically: in 2023, some 2 600 launches took place, five times more than in 2018, and 10 times more than in 2010. Simultaneously, the cost per kilogram has decreased with the introduction of private reusable vehicles. New projects to form large constellations of satellites such as Starlink, which already numbers in the thousands, are popping up because space, as pointed out in the Draghi Report, is seen as a key strategic sector.
The European Space Agency (ESA) counts around 20 000 objects currently in orbit. Most of those are space debris – everything from non-functioning satellites, to spent rocket boosters, to tiny screws – and this debris accumulates for years before entering the atmosphere. NASA notes that low-altitude (under 600 km) satellites will de-orbit after a few years, and those above 1 000 km can remain as orbiting junk for millennia.
Each piece of debris risks damaging or destroying other spacecraft severely, since they move at speeds that turn bolts into bullets. Even worse, the problem compounds, creating a cascade referred to as Kessler Syndrome. Colliding satellites can disintegrate, generating thousands of new projectiles on unpredictable trajectories. Recently, a failed rocket launch gave rise to 700 new hazards in this way. From a defence perspective, the destruction of a single satellite carries planet-wide consequences. In 2007, the Chinese FengYun-1C mission demonstrated an anti-satellite system: the successful destruction of a single high-altitude satellite created enough debris to increase the number of known space objects by 25 % at that time.
The concern over space debris has caused manufacturers, space launch providers, space agencies and other stakeholders to begin considering ‘end-of-life’ plans for their satellites. SpaceX’s Starlink has stated that it intends to de-orbit its satellites proactively, and that they are designed to burn up fully when re-entering the atmosphere. ESA and NASA both have offices and policies to address orbital debris, and the United States (UN) Federal Communications Commission has recently required communications satellite launch applicants to submit debris mitigation plans. The UN has non-binding guidelines on the topic.
Potential impacts and developments
The risk of widespread destruction of satellites is being studied. Computer models show that the probability of a ‘cascade’ (where one collision creates debris that destroys other satellites, which create more debris, etc.) depends strongly on the de-orbit policy. Without removing additional debris, only short-lifespan satellites can keep the likelihood of a catastrophic accident relatively low, according to these simulations. The same study also notes the adverse effects of ‘debris injection events’ such as the (targeted) destruction of a satellite. Even one such event can permanently increase the risk of a cascade of collisions.
Further analysis suggests that the risk is greatest at high altitudes (where debris decays slowly), and that even a destructive event would not, for example, render human space exploration impossible, but rather that an increasing probability of collision would make using satellites much more expensive; losing a large fraction of them would become the norm. This is leading to a market for collision avoidance.
European and US policy is now to de-orbit satellites after 5 years. The models of satellite collision probabilities suggest this prevents orbital crisis, but now the title of this section becomes literal: there is a potential for actual impacts from orbital objects that fail to burn up completely in the atmosphere. Although rare, impacts have happened (along with other accidents), and have been a focal point of controversy around private space industry regulation in the US. International law on space is also generally weak, not only in the context of harm.
The environmental impact is much more salient. When a satellite ‘burns up’, it is disintegrated at a molecular level by the force of hitting the atmosphere. Metal particles remain in the atmosphere, and researchers are analysing the potential consequences and raising awareness about the issue, noting that early action could completely prevent adverse effects. Particles from re-entering spacecraft are a significant contributor to stratospheric pollution, and requiring faster de-orbiting would increase this. Polluting the atmosphere this way may also carry legal responsibilities under the Montreal Protocol, given the potential to create a new ozone hole crisis. Possible solutions include using alternative materials for satellite construction.
Many methods for actively removing orbital debris have been proposed. The European Science Media Hub interviewed the CEO of a start-up developing a ‘debris removal service’, to be tested by ESA, and NASA has patented its own removal technology. While various other technologies are being explored, as well, an industry consensus on which solutions fit which debris removal needs has yet to be found, and there is no market for these solutions without international consensus on debris removal policy.
Anticipatory policy-making
Space is a commons, posing the problems usually associated with such. This means resolving challenges such as orbital debris requires an international approach, particularly at a time when space is no longer the domain of just a few governmental actors. Ideally, this would involve new agreements at the level of the United Nations, although for now it may still be possible to regulate activity through actions undertaken together by key countries. Such regulation could help encourage innovation and boost space industry by forming a market for debris mitigation and active removal. However, in its absence, imposing EU-only regulation may only disadvantage the European space sector without actually addressing such risks.
The EU is well aware of the growing importance of space, including from a strategic autonomy perspective, as demonstrated by the novel appointment of an EU Commissioner in charge of a space portfolio. Indeed, a space traffic management programme already exists to track debris and satellites. As a follow-up to this, a cohesive response similar to the EU civil protection mechanism could help Member States address any loss of satellites due to collisions or space debris. Furthermore, and building on the 5-year rule, the EU could look for a fine-tuned expansion of existing regulations and environmental impact assessments dealing with the debris issue, to include all stages of a spacecraft’s lifecycle. While a fully fledged approach would need international consensus, such limited regulation could let the EU lead by example, and provide the necessary context to promote research into satellite materials and debris mitigation strategies, together with a head start on future developments in space industry. It would be relevant to and potentially supported by the scientific community, as satellites complicate astronomical observations, and collisions endanger science instruments.
One area where immediate progress might be possible is active debris removal. Technology that can be used to move debris in orbit can also be used to move satellites, as China has demonstrated. Much space technology is intrinsically dual-use, to the point that civilian systems can be repurposed for military ends, as can be seen in the war in Ukraine. This can be leveraged in reverse to encourage further research and development of active debris removal methods as a strategic goal, all while waiting for the development of a market for civilian applications.
Read this ‘at a glance’ note on ‘What if orbital debris destroyed satellites?‘ in the Think Tank pages of the European Parliament.
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