Sustainability has gathered momentum in recent years. The aim is to reduce our impact on the environment so that it can usefully be preserved for generations to come. To this end we try to reduce rainforest destruction, greenhouse gas emissions and plastics in the ocean. But what about outer space? Are there sustainability concerns there, too?
In short, the answer is 'yes'. As on Earth, parts of outer space face serious issues of overcrowding and rising levels of debris. Ignoring these issues could be a major threat to future space operations and to current critical technologies on Earth.
Space traffic
The vastness of space might suggest that it is unlikely to become congested. However, the most important layer of space, in terms of satellite support for everyday life on Earth, is the low Earth orbit. This is the layer of space reaching to about 2,000 kilometres above the Earth's surface. Most satellites orbit the Earth in this band.
Today's highly interconnected world requires a great number of satellites in space to support it. Satellites are needed for navigation, financial transactions, television, internet, time keeping, weather forecasting and climate change monitoring, amongst other things. There are currently around 8,400 satellites in orbit. That number is increasing rapidly: almost 30% of all satellites launched since 1957 were launched in the last two and a half years. Of the 8,400 satellites in orbit, around 2,600 are no longer functioning.
At present, there is no global space traffic management system governing who has access to which orbits, or who should give way to whom. As the number of satellites continues to grow, this lack of coordination may lead to collisions.
Space debris: millions of bullets
In addition to these 8,400 functional (or once-functional) satellites, Space Surveillance Networks track almost four times as many pieces of space debris, such as broken pieces of old satellites, that are also in orbit. That is a total of almost 40,000 sizeable objects circling the planet according to the European Space Agency (ESA).
That might still not seem like a lot, given the size of the low Earth orbit. However, this is just the number of objects that can be tracked. The numbers increase massively when you include smaller objects that cannot be tracked. Based on statistical models, the ESA estimates that there are 1 million objects of space debris of between 1cm and 10cm. Space debris objects of between 1mm and 1cm are estimated to number 130 million.
The problem is that these pieces of space debris are travelling at extremely high speeds: approximately 15,700mph according to NASA. That's around 30 times the speed of a jet; or almost ten times the speed of a bullet. At these speeds, even the smallest objects can cause significant damage.
In 2016, astronaut Tim Peake took a photo of a 7mm chip on the glass window of the International Space Station (ISS). While the damage was relatively minor, it is thought to have been caused by something as small as a flake of paint. Scaling up, the ESA has said that an object up to 1cm in size could disable an instrument or a critical flight system on a satellite. Anything above 1cm could penetrate the shields of the ISS's crew modules. Anything larger than 10cm could shatter a satellite or spacecraft into pieces.
Bullets creating more bullets
When objects collide in space, they tend to fragment and create more objects in orbit. NASA scientist Donald Kessler observed that each collision creates more space debris, increasing the likelihood of further collisions, which in turn creates even more debris. When the amount of space debris reaches a critical mass, this creates a chain reaction, or cascade effect, where the amount of space debris increases exponentially. The result might be that space operations and use of satellites become much more difficult if not impossible for generations to come.
An inaccessible space?
With every new piece of debris, the low Earth orbit steadily becomes a more difficult place to navigate. While satellites can generally be steered around larger objects that are identifiable, smaller objects often cannot be tracked so avoiding collisions with these items is left to chance.
The risks posed by space debris are current and future. These items already pose a risk to the lives of astronauts and the integrity of high value assets. A significant amount of the global economy, military operations and climate change monitoring rely on satellites in space. It is in our general interests to ensure that they can continue to exist and provide services without risk of collision.
If space debris continues unchecked, the Kessler effect predicts that space operations will become much more difficult and expensive if not impossible in the future. This raises an issue at the heart of sustainability: how do we oblige the small number of actors who are currently able to make use of space technology to ensure that space remains open and accessible for all.
There is also a risk that a burgeoning economy and industry in space may be cut short. Morgan Stanley has projected revenues in the space industry could reach over USD 1trillion dollars by 2040, in areas including security, telecoms and combating climate change. Whether these opportunities can be exploited will depend in part on whether the conditions in space remain viable.
Solutions
Guidance on managing space debris has been published by several international organisations including the UN Committee on the Peaceful Uses of Outer Space (UN COPUOS), the Inter-Agency Space Debris Coordination Committee (IADC) and the International Organization for Standardization (ISO). The guidance is mainly aimed at:
- reducing the amount of debris that is created, and
- monitoring debris and communicating with other spacecraft operators to help avoid collisions.
UN COPUOS has also published wider-ranging guidance on the long-term sustainability of outer space generally.
Methods of reducing the amount of space debris include extending the operational lifetime of satellites (after which time they are more likely to become debris), depleting fuel reserves when no longer needed to reduce the risk of "dead" satellites exploding, and removing satellites from the low earth orbit at the end of their life. However, these guidelines are all voluntary with no agreed enforcement mechanism.
These guidelines don't deal with the removal of existing space debris. This is an area of opportunity for technology and engineering companies. Some ingenious methods have already been developed and tested, including nets and harpoons to capture space debris and take it out of orbit. Mitigating orbital debris is one of the five growth areas identified in the Morgan Stanley report on the space industry.
The fact that space debris is a risk for those currently operating in space might be sufficient incentive for them to find ways of solving the problem. This contrasts with the position on Earth, where, in general, those who cause harm to the environment are unlikely to be the ones who suffer most from environmental degradation.
A number of space industry stakeholders grouped together in 2019 to form the Space Safety Coalition (SCC). The SCC publishes best practices for sustainability of space operations. These incorporate the voluntary guidance of the IADC, UN COPUOS and ISO mentioned above, and are endorsed by the SCC's members. However, more regulation and enforcement mechanisms are likely to be necessary to achieve sustainability in space. This will require cooperation from all actors in space, countries and companies alike.
