The Danger of Space Debris

One small change in policy, one giant leap for mankind

Above our heads in Earth’s orbit, there are roughly $170 billion worth of satellites providing commercial services which are critical to our modern world. However, this infrastructural web is under growing threat from space debris, and the response of policymakers has been disappointing so far.

Space debris is defined by NASA as ‘all man-made objects in orbit about the Earth, which no longer serve a useful purpose’. This debris can travel at speeds of 17,500mph, giving even small fragments  tremendous kinetic energy. For instance, a 100 gram bolt could cause a lethal event on the International Space Station if it strikes a crew capsule, while objects wider than 10cm are considered capable of destroying a satellite. As of 2013, there were over 20,000 such pieces of debris in orbit. These objects come from many sources, such as defunct satellites, spent rocket stages, and ejected materials from spacecraft. In an economic sense, space debris can be considered a negative externality of space launches, but there is currently a lack of strong incentives for space launching private firms and governments to fix this market failure.

As we launch more satellites and space missions, Earth’s orbit will be increasingly crowded, jeopardising even more useful space vehicles. Worse still, similar to climate change, space debris also has a positive feedback mechanism. When space debris collides with other objects, it creates more fragments of debris, that can then create yet more pieces of debris in future collisions, and so on. This ‘snowball’ property can lead to what is known as Kessler syndrome, where a cascading series of collisions generate so much debris that all objects that are close by are completely destroyed and the space becomes physically impassable to future vehicles. Not only would this destroy the $170 billion worth of commercial services, this cloud of debris would be extremely expensive and time consuming to clean up. Therefore, rational economic thinking would call for us to fix the issue before it spirals to a Kessler cascade.



Policy responses

As with other forms of pollution, there are two main approaches: actively removing debris and minimising the creation of new space debris.

At first glance, it may appear that removal policies may not seem like the best approach. Active debris removal (ADR) is very costly. Current satellite-based ADR systems can only remove one or two pieces of debris and have a minimum launch cost of $65m. In addition, land-based ADR requires large amounts of power to provide contactless propulsion and are ineffective against large and heavy debris.

Mitigation policies, on the other hand, can internalise the pollution externality whilst incurring little to no cost to governments. One popular mitigation policy used on terrestrial pollution is Pigouvian taxation. This is where a tax is levied per unit of pollution generated, with the idea that agents take into account the cost of their polluting behaviour and so reduce the amount of pollution. For space debris, this type of tax would reduce the number of space launches, encourage firms to destroy their satellites once they have expired, and reduce the amount of object and waste material ejected from their spacecraft.

Another popular terrestrial pollution abatement strategy is pollution permits. These introduce incentives for firms to adopt less polluting technologies while giving them the option to strategically trade their permits on a market. The advantage of this method is that it offers a lot of flexibility; regulators could mitigate debris from different types of space missions by altering their respective pricing structures and issuing different types of permits.

The clock is ticking

However, while the above mitigation policies have been deployed with various degrees of success on terrestrial pollution, space debris pollution requires even stronger international coordination. An international body would be needed to regulate tax taxes and pollution permits. Humanity’s efforts to tackle climate change have revealed the difficulties inherent in international coordination and negotiations. A notable example is President Trump’s decision to withdraw the United States’ from the Paris Agreement in 2017, which he claimed was stifling the American economy. In the era of a new ‘space race’ to colonise Mars and gather resources from asteroids, nations may be unwilling to handicap their lucrative space activities and let their rivals get ahead. Therefore, pulling together an international effort by all space-faring nations to tackle space debris pollution could take a lot of time.

 And time is rapidly running out, as we may be past the threshold at which space debris population will grow by itself even with zero additional space launches. According to estimates from NASA and the European Space Agency, a ‘business-as-usual’ scenario without future space launches could still lead to an eventual Kessler cascade. NASA’s LEGEND model (Figure 1) shows that a minimum of 5 objects with the highest probability of collision must be removed each year, just to keep the population growth linear. This means that mitigation can only help to delay a Kessler cascade, not fix it.  Some form of ADR is essential to prevent the debris situation from spiralling out of control.




To adequately address the space debris pollution problem, governments will have to incur a short-term financial cost to deploy ADR systems. But the fact that space debris remains in the atmosphere could actually be useful. International space law allows nations to retain jurisdiction over their space objects, so governments could sell their debris to private firms. Approximately 1,000 tons of aluminium are in orbit as forms of debris, launching an equivalent amount into orbit now could cost between $5-10 billion. Thus, there is a strong potential market here for firms to profit by buying space debris from governments and either selling it on or using recycled material in future constructions in space.

Further inclusion of market forces, such as supporting insurance premium rises and auctioning debris cleaning contracts, can be used together in conjunction with ADR and mitigation policies to form a cost-effective package of abatement strategy. Nevertheless, the best way of reducing the cost to address this problem is by acting as soon as possible.

Bowen Zhu

The Danger of Space Debris