Science & Technology

What Is the Sabatier Reaction? Learn How Astronauts Create Water and Oxygen in Space

Written by MasterClass

Aug 31, 2019 • 3 min read

Access to a drinkable, clean water supply is perhaps the most essential resource for human survival during space missions. Since room is limited on space shuttles, the International Space Station (ISS) and other spacecraft, it’s important to have a life support system that can maximize water production without taking up too much space. That’s why NASA and other space agencies use something called the Sabatier reaction, which was developed by the French chemist Paul Sabatier.



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What Is the Sabatier Reaction?

The Sabatier reaction is a process that produces water (hydrogen and oxygen) and methane through a reaction of hydrogen with carbon dioxide. The beauty of the Sabatier reaction is that it’s nearly a closed loop: the water generated can be split again and pumped back into the reaction to continue generating more oxygen and fuel through CO2 methanation.

How Does the Sabatier Reaction Work?

The Sabatier reaction relies on electrolysis to separate water into hydrogen and oxygen.

  1. The first step of the Sabatier process is to decompose the water through water electrolysis: essentially, run an electric current through water to separate the H20 into hydrogen and oxygen gases, collecting them separately.
  2. Then, by mixing that hydrogen gas with the carbon dioxide in the atmosphere (or from human exhalation) at a high temperature across a nickel catalyst brought from Earth, the Sabatier process generates drinkable water and methane to be used for heating and rocket propellant.
  3. The exothermic reaction looks like this: CO2+4H2 →CH4 +2H2O
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How Does NASA Use the Sabatier Reaction Aboard the ISS?

As the oxygen generators aboard the ISS produce oxygen, they leave behind a hydrogen byproduct that used to be discarded into outer space. When the astronauts consume oxygen, they produce carbon dioxide that additionally must be removed and jettisoned. This overall process required water to be transported regularly to the ISS.

For many years, NASA used shuttles to provide water to crew members aboard the ISS, which was created as a byproduct of the fuel cells the shuttles used for electricity generation.

Now, the Sabatier reactor works as a high-efficiency recycling system, recovering water through its hydrogen and CO2 conversion system.

Why Is the Sabatier Reaction Important to Humanity’s Future?

The Sabatier reaction may provide solutions to essential questions both on Earth and in space.

  • Future space travel. As future missions of space exploration take us deeper into our solar system, the Sabatier reaction may be a key component in making missions to Mars and beyond feasible through in-situ resource utilization. The Sabatier methanation reaction can theoretically be tweaked to produce methane from the raw materials in the Martian atmosphere. Tests have shown that using a reverse water gas shift reaction to reduce carbon dioxide to carbon monoxide, the Sabatier methanation process can be used for methane rocket propellant production at nearly 100% conversion rate. The process of such conversion efficiency functionally creates a renewable energy system that could be used to help propel a Mars spacecraft back home.
  • Synthetic natural gas. The methanation of carbon dioxide is a key stepping stone to the production of synthetic natural gas. The Sabatier process can supplement a power-to-gas method to help create a renewable energy system, alongside wind energy, solar panels that create solar energy, and water energy. The methane created by the Sabatier reaction can be injected directly into a country’s existing gas network. As climate change impacts the planet further, the need for an energy system that is less reliant on fossil fuels will be essential.

Whether you’re a budding astronautical engineer or simply want to become more informed about the science of space travel, knowing the rich and detailed history of human space flight is key to understanding how space exploration has advanced. In his MasterClass, Chris Hadfield, the former commander of the International Space Station, provides invaluable insight into what it takes to explore space and what the future holds for humans in the final frontier. Chris also talks about the science of space travel, life as an astronaut, and how flying in space will forever change the way you think about living on Earth.

Want to become better engaged with science and technology? The MasterClass All-Access Pass provides exclusive video lessons from master scientists and astronauts, including Chris Hadfield.


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