The International Space Station is now home to a brand new life-support system. This system is capable of recycling breathable air, which promises to drastically reduce the amount of water that needs to be brought to the ISS, to make oxygen.
The new system will mark a pivotal move toward what’s known as a closed-loop life-support system, which could one day sustain space crews indefinitely without the need for supply missions from Earth. These systems will be vital for future long-duration missions to the moon and Mars.
The newly installed Advanced Closed Loop System (ACLS), designed by the European Space Agency (ESA), was sent to the space station in late September aboard the Japanese HTV-7 cargo ship. This system could decrease the amount of water required for the oxygen system by 400 litres (100 gallons).
The 750-kilogram (1,650 lbs.) system, is located inside a payload rack that measures 2 meters by 1 m by 90 centimetres in size (6.5 by 3.3 by 3 feet). It recycles 50 percent of the carbon dioxide (CO2) exhaled by the astronauts back into oxygen. As the air passes through the system, the CO2 is trapped in small beads made of amine, an organic compound much like ammonia.
Daniele Laurini, who was in charge of the ESA team that engineered the system, explained to Space.com that once they remove CO2 from the cabin air, they extract it from these materials and they get almost pure CO2. Then, they react the CO2 with hydrogen and extract water and methane.
Water is then further split into hydrogen and, of course, oxygen, which the astronauts breathe. Before this new system, all water for making oxygen had to be sent from Earth. The new process extracts an equal amount of water and methane, as per Laurini. However, there is currently no use for the methane, which is produced in the form of carbon dust.
Laurini added that processing pure methane in orbit and getting something usable out of it is quite the challenge because dust in microgravity is messy. Thus, they vent the methane into space.
Laurini also explained that his team doesn’t intend to increase the efficiency of the system to recycle more than the present 50 percent of the exhaled CO2. But, in 2019, the team will test the system in collaboration with an algae photo-bioreactor produced by the German aerospace agency, DLR.
Laurini said the extracted CO2 would then be fed to the algae. The algae will grow with the CO2, and via the process of photosynthesis, it will release oxygen. What’s more, in the more distant future, they would have the algae directly pick up the CO2 from the cabin atmosphere.
The ACLS was installed inside the US Destiny module this month and will give half of the oxygen needed for three astronauts, according to a statement by ESA officials. (Six crewmembers make up a fully-staffed space station but as many as nine can live there.) The agency intends to test the system for one or two years. The station already uses a system that recycles urine back into drinkable water.
A system similar to ACLS might also be used in the future to assist in regenerating breathable air inside the Lunar Gateway. The world’s space agencies are presently considering that proposed moon-orbiting station. However, Laurini stated that having a system like the ACLS aboard any spacecraft would make sense only for longer-duration missions.
Laurini explained that there is a trade-off between launch mass and the number of days you spend in the place. It’s like travelling on Earth, if you only leave for two weeks, you don’t need to bring a whole washing machine with you. Similarly, in space, it would only make sense if you are going for longer-duration missions, at least 90 to 120 days. Then the trade-off between recovery and an open-loop system becomes convenient.
Since a future mission to Mars would take many years, a closed-loop system would be a necessity because resupply missions would not be possible, and carrying resources that would last for the entire mission would be too expensive, as per experts.
The ESA is currently working on a closed-loop system dubbed Melissa that would recycle all the resources the crew would need to survive on Mars including food, water and oxygen. This system would take exhaled air, human waste and wastewater and use bacteria, algae and higher plants to create drinkable water and breathable oxygen. The system would also be capable of growing plants for the astronauts to consume.
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