How Does the International Space Station Produce Oxygen and Water?

Astronauts aboard the international space station do not need spacesuits to access breakable air. This implies that the space station is specially designed to provide humans with breathable and suitable living conditions outside Earth. But how does the International Space Station produce oxygen and water? Will it ever run out of oxygen? What is the science behind the sustainability of the international space station? Continue reading to find out.

How Does the International Space Station Produce Oxygen and water?

Since the first crew arrived at the International Space Station on November 2, 2000, humans have continued to remain aboard the station until this day. The space station is designed to provide astronauts and cosmonauts with their basic needs for life including food water and air. Space agencies often deliver food to the astronauts on frequent resupply missions.

But the space station is made to be self-sufficient to generate and recycle its water and air. Unlike Earth where we get our oxygen from the ocean and plants, astronauts aboard the station depend on the technological capabilities of the ISS to stay alive. During the construction of the ISS, NASA (United States), ESA (Europe), ROSCOSMOS (Russia), JAXA (Japan), and CSA (Canada) collaborated and came up with plans to make the station to be self-sustaining for astronauts conducting scientific experiments in low earth orbit.

Hence, before launching the International Space Station in 1998, the engineers successfully perfected the methods of creating oxygen within a vacuum for a longer duration. We used our knowledge of providing oxygen inside submarines operating below the surface of the ocean to generate oxygen aboard the space station. Keep in mind that submarines stay under the water for an extended period of time, exploring the vastness of the ocean. Since they often move under the ice, moving the submarines above the surface will complicate the mission even more.

The first submarine was built in the 17th century by Cornelius Drebbel. Hence, we have operated this technology for centuries before embracing the era of the international space station. During these years of operation, scientists discovered how to recycle oxygen to create long-term supplies of internal oxygen for people aboard the submarines. Engineers that designed the space station used similar primary systems found mostly on the submarines to supply astronauts with breathable air.

What Primary Systems are used to Generate Oxygen and Water Aboard the International Space Station

The international space station is designed with an oxygen and water system that consist of two major elements including the Water Reclamation System (WRS) and the Oxygen Generation System (OGS). These two systems basically rely on each other to operate actively without failure. The WRS helps in collecting condensation, humidity, and urine before purifying them to a usable standard. The WRS recycles the water and provides part of the water used aboard the space station. However, the space station also gets an additional supply of water from Earth to ensure that the astronauts never run out of fresh water. Combining the recycled water and the one coming from the earth, humans aboard the station will have enough water for usage.

Water aboard the station provides astronauts with their basic needs, while the remaining water serves the purpose of creating oxygen for them. NASA’s OGS system alongside the Russian Elektron system deploys the process of electrolysis to divide water into hydrogen and oxygen, which are its elemental components. Keep in mind that Electrolysis is a process of moving an electric current via water from an anode to a cathode to create enough energy that can separate the atoms. The outcome of this electrolysis process is the formation of hydrogen gas, H2, and oxygen gas, 02.

But before the space station can complete the electrolysis process, electricity is highly needed. The ISS has continued to obtain most of its electricity from solar arrays added to its exterior. These solar panels capture solar energy from the sun and provide the required electricity to facilitate the chemical reaction of the electrolysis. After NASA’s OGS system alongside the Russian Elektron system establishes the electrolysis process, the hydrogen gas generated during the water splitting process is fed into the Sabatier System aboard the station. The system then proceeds to mix waste hydrogen with waste obtained from carbon dioxide gotten from the respiration of the astronauts to produce water and methane via a process known as an exothermic reaction.

CO2 + 4H2 → CH4 + 2H2O + heat

After the entire process is completed, the methane is allowed into space while the heat is managed via heat exchangers. Generating oxygen in the international space station actually requires a lot of sophisticated technologies. Despite the advanced technology of the ISS, the generated oxygen can only accommodate the maximum number of 7 astronauts. But next-generation space stations that are currently under development will be designed to accommodate more astronauts and possibly space tourists.

Are there backup methods for Generating Oxygen Aboard the International Space Station?

Space agencies have realized that relying on a single means to provide astronauts aboard the station with oxygen and water is not sustainable. Agencies operating the space station often consider backup plans for their systems in case of system failure. To ensure that humans are not exposed to complicated dangers aboard the station, many backups of high-tech space systems are installed in the ISS.

Space agencies often send a cargo of oxygen to the ISS from the earth. These shipments of oxygen are stored in pressurized tanks which are often mounted outside the airlock of the space station. These oxygen shipments from earth serve as additional top off to supplement the regular leaks of oxygen in the ISS.

The Russian Space Agency also designed the Solid Fuel Oxygen Generator (SFOG) for its Mir Space station. But since the Mir space station is no longer active, ROSCOSMOS decided to use the SFOG as an additional backup system for oxygen generation in the International Space Station. Since Mir was decommissioned, the SFOG or Vika System has remained part of the ISS as a backup system. However, the crew aboard the station have avoided using it since implemented.

The system uses canisters of powdered sodium chlorate and powered iron for its full operation. The Vika system operations begin when canisters are ignited and they can reach up to 600 degrees Celsius (1,112 degrees Fahrenheit). At this hot temperature, the sodium chlorate can break down into sodium chloride and oxygen gas.

The high temperature of the system caused one of the canisters to ignite fire aboard the Mir station in 1997. The system does not generate enough oxygen that can sustain the crew for a longer term. Hence, the use of the Vika System is not actually put into consideration by the crew members. However, it will remain as a backup system in case of any failure.


Space agencies operating the international space station are working tirelessly to ensure that astronauts aboard the station never run out of water and oxygen. Advanced space technologies are designed to ensure that astronauts and cosmonauts aboard the space station experience water or oxygen shortage throughout their stay in the station. As we are working towards the future, we should be expecting more sophisticated space technologies to revolutionize the comfort of our astronauts in low earth orbit. What do you think about this technology?

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