Environmentally sustainable space transport

We live in an age where human activity is the dominant influence on climate and the environment. Currently, the impact of space activities make up a tiny proportion of humankind’s emissions and environmental impact. But what is the environmental impact and sustainability of space transport – from rockets to transfer and return vehicles?

The environmental impact of space transportation that is quantifiable amounts to a tiny proportion of the total global transport industry, but in some areas – such as the upper atmosphere – there are unknowns. As space activities evolve, and the number of rockets and missions launched each year grows, it is important that we understand this sector’s environmental impact on the planet and beyond.

Rockets are our only way to reach space, to place into orbit essential hardware, to explore our Solar System and beyond, and to seek out past and present signs of life in the Universe to answer the age-old question if we are unique – and if not, why? Rockets propel us to understand the nature and origin of the Universe and are at present our only way to look down at our Pale Blue Dot from the vastness of space and take the pulse of our changing planet.

Rockets or ‘launchers’ developed by ESA, or partners under ESA programmes, must adhere to applicable environmental standards and regulations, such as EU REACH and the EU Green Deal, as well as to ESA guidelines and standards, such as those developed under the ESA Green Agenda and the Zero Debris approach.

Rockets allow us to launch Earth observation satellites and more that provide essential information on the environment for decision-makers to ensure the sustainability of our planet. At the same time ESA is determined to safeguard that these launches have minimal impact on the environment themselves.

What do we know about the impact of space transportation activities on the Earth and space environment, and what is the European Space Agency and its Space Transportation directorate doing to ensure the sustainability of space transportation?

The impact on the ground

Europe’s rockets are launched from Europe’s Spaceport in Kourou, French Guiana, and various programmes and studies are monitoring and reducing the impact of launches on the local environment.

The Ariane 6 launch pad, for example, was built to lessen the site’s carbon footprint and preserve local natural resources. The location was chosen to avoid interfering with protected species.

Find out more about the ways that Ariane 6 was built with sustainability in mind, from the transport of its parts from mainland Europe to Europe’s Spaceport to the conservation of valuable water resources, replacing toxic materials and much more.

To enhance the sustainable production of liquid hydrogen – an essential part of the fuel powering Ariane – the Hyguane (HYdrogène GUyanais A Neutralité Environnementale) project is under development.

Various additional programmes in support of environmental sustainability have been put in place as part of the Ariane 6 programme at Europe’s Spaceport, such as the ‘Improve!’ sensor development campaign to measure real-time carbon dioxide emissions across the site, and the ‘ReUse!’ Initiative to ensure the maximum possible reuse of ESA materials, assets and buildings.

The impact on the atmosphere

The interaction between a rocket and the environment on Earth and our atmosphere, is highly complex and requires a detailed Life Cycle Analysis (LCA), taking into account the full life cycle of the space transportation system, from its development through to its operation and retirement, from the emission of greenhouse gases to soil pollution and the acidification of water.

ESA’s Space Transportation directorate, together with the Agency’s Clean Space Office, has been conducting Life Cycle Assessment for its Ariane 5 and 6 and the Vega and Vega-C rockets. Some of the environmental impacts of these rockets, such as global warming potential, are well understood and limited compared to other means of mass transportation, but there remain some unknowns that make it difficult to fully assess their environmental impact.

In particular, the mixing of rocket fuels with the atmosphere at different altitudes is not yet fully understood and it is possible that certain chemical reactions could have an impact on the global climate. This is of particular importance when we consider that the number of rocket launches will continue to increase.

One complexity here is that different rocket fuels may have a different impact. So while one fuel combination may be “clean” at lower altitudes, it could have a strong environmental impact at higher altitudes and vice versa.

ESA is contributing to worldwide research activities that will conduct measurements during rocket launches and will help assess the environmental compatibility of different propulsion systems.

ESA’s Future Launchers Preparatory Programme is also preparing a tool to assess the Life Cycle Assessment of future launcher missions, including a campaign to take measurements – from exhaust plumes to interactions with the atmosphere – gathering data to understand the impact of a launch vehicle at high atmospheric layers.

The impact on space

Space transport also impacts the space environment and the long-term sustainability of outer space activities. Since 2016, ESA’s Space Debris Office publishes an annual Space Environment Report to provide an overview of global space activities and determine how well these and other international debris-reduction measures are improving the long-term sustainability of spaceflight.

ESA only procures launch services on launch systems that will adhere to ESA’s own strict space debris mitigation requirements, from design to operation and end of life.

ESA has also set itself the goal to avoid the creation of any space debris by 2030 through its Zero Debris approach and kicked off a Zero Debris Charter that brings together the diverse international space community to collaborate and co-create a sustainable future. ESA and over 100 organisations and international space agencies have signed the Charter.

As rockets and their stages are the largest structures we send to space and have historically been responsible for the creation of large amounts of debris, their sustainable demise is of utmost importance.

Ariane 6 and Vega-C, with their restartable upper stages, are able to launch a wide variety of missions in adherence with the ESA space debris mitigation standard and to subsequently conduct a final ‘disposal’ burn to safely reenter Earth's atmosphere or move to a ‘graveyard orbit’ - out of the way of potential collisions. ESA is conducting research and supporting the development of new technologies for its existing and future launchers to ensure the sustainability of space transportation activities and to be ready to meet updated stricter environmental standards as they may evolve in the future.

Reusability

The decision to develop Ariane 6 was taken at the end of 2014. The aim was to provide a versatile heavy-lift launch vehicle that would not only meet Europe's institutional needs and be able to launch a wider variety of missions than Ariane 5, but also to significantly reduce production costs. ESA and its partners are taking various steps to reduce the climate impact of Ariane 6 but versatility, power and cost were the main considerations. 

In parallel to Ariane 6 development, ESA and its partners are working towards the first reusable European rockets. ESA’s Prometheus rocket engine is a reusable rocket engine – fuelled by liquid oxygen and liquid bio-methane – with a thrust able to lift 100 tonnes. Prometheus will initially power Themis, a reusable first stage prototype to demonstrate rocket recovery and reuse technologies and later future European rockets.

Conclusion

Without rockets, there’s no space transport. Europe’s rockets are vital for our independent access to space, for the launch missions that ensure the prosperity of Europe’s citizens and the world, for creating new knowledge through science and exploration and for our ability to care for our own planet.

ESA is working hard to understand the impact of space transport on our environment, develop new technologies to minimise it, and ensure the long-term sustainability of space activities.

Rockets enable us to launch Earth Observation and other satellites that provide essential information on the state of the environment and for decision-making to ensure the sustainability of Planet Earth. At the same time ESA is determined to safeguard that these launches have minimal impact on the environment themselves.