The International Space Station (ISS) is serving as a test bed for technologies that will supply crews on deep space missions with vital resources we may take for granted: oxygen and water. NASA researchers are seeking improvements to the environmental control and life support system (ECLSS).
This system currently recycles about 90 percent of the water and about 42 percent of the oxygen in the spacecraft, while disposing of the crew’s solid waste and the briny liquid waste left over from recycling. Regular resupply missions to the orbiting outpost supplement the unrecovered water and oxygen and replacement components for those that fail on the system.
However, deep space missions will not have the space station’s resupply capability, pointing to the need for recycling process advancements.
Engineers aim to reach the goal of 75 percent recycled oxygen for deep space missions using methods that involve the reaction of hydrogen and carbon dioxide to produce solid carbon and water, or acetylene and water. These candidate technologies go beyond the current system on the station that reacts carbon dioxide and hydrogen to produce methane and water, and would increase the current recovery to between 75 and 100 percent. The resulting water is split into breathable oxygen for the crew by the oxygen generation system, and the hydrogen is recycled back to react with more carbon dioxide.
The robustness of the system itself is also crucial, and teams must know what parts can be printed using 3-D printing technology during the mission and what spares have to be sent along from Earth. Many of the improvements in development will also extend the life of components and reduce failure rates.
The enhanced ECLSS will be tested on the ISS for at least two to three years to prove reliability before building the system for deep space. The greater efficiency and increased reliability from improvements to the life support system will strengthen systems in low-Earth orbit and enable continued presence in space, both near and far.
Schematic of the flow of recyclable resources in the ISS. (Source: NASA)As shown in the schematic at left, the regenerative ECLSS, whose main components are the water recovery system and the oxygen generation system, reclaims and recycles water and oxygen. The ECLSS maintains a pressurized habitation environment, provides water recovery and storage, maintains and provides fire detection and suppression and provides breathable air, and a comfortable atmosphere in which to live and work within the ISS. Improvements to the system will be key to sending humans to Mars and returning them safely to Earth.
