Researchers Chart Course for Sustainable Water Systems in Space

United Kingdom - Ekhbary News Agency

Researchers Chart Course for Sustainable Water Systems in Space

As humanity's ambitions stretch towards establishing a permanent presence in space, the provision of clean, reliable drinking water emerges as a fundamental prerequisite. Whether for habitats on the Moon, bases on Mars, or distant space stations, water is not merely a comfort but the very essence of survival. This necessity is compounded by the harsh realities of space exploration, where resources are scarce and resupply missions are prohibitively expensive, time-consuming, or both. Relying on Earth for a continuous water supply is an unsustainable model for long-duration extraterrestrial endeavors.

The human body's absolute dependence on water, with survival limited to a mere three days without it, underscores its critical role. Beyond personal hydration, water is indispensable for generating breathable oxygen through electrolysis, cultivating edible plants in controlled environments, and maintaining essential hygiene standards within closed habitats. To meet these multifaceted demands, the development of sophisticated closed-loop systems is paramount – systems capable of providing clean water consistently for months, even years, without external replenishment.

A significant contribution to this field comes from a recent study published in *Water Resources Research*. The paper examines the progress made, citing the Environmental Control and Life Support System (ECLSS) aboard the International Space Station (ISS) as a prime example. The ECLSS has demonstrated remarkable efficiency, recovering approximately 93% of the water lost by astronauts through urine, sweat, and respiration. However, the study's authors emphasize that despite this progress, substantial challenges persist. They advocate for exploring multiple innovative approaches to realize truly sustainable water systems (SWS) that are not only highly energy-efficient and durable but also capable of delivering a steady, reliable supply of potable water in extraterrestrial settings.

The comprehensive review was spearheaded by David Bamidele Olawade, a public health researcher affiliated with the University of East London, the Medway NHS Foundation Trust, and York St John University. He collaborated with James O. Ijiwade, an environmental science and nanotechnology researcher from the University of Ibadan, Nigeria, and Ojima Zechariah Wada, a postdoctoral researcher specializing in water management and environmental biotechnology at Hamad Bin Khalifa University, Qatar. Their collective expertise provides a multi-disciplinary perspective on the complexities of space water sustainability.

While the ISS's ECLSS serves as a valuable blueprint for closed-loop water reclamation, its limitations for future deep-space missions are evident. The ISS benefits from relatively rapid resupply capabilities from Earth, but the logistical and financial burdens are immense. Official estimates suggest that transporting just one kilogram of water can cost tens of thousands of dollars, with costs escalating exponentially for missions to more distant celestial bodies. This financial barrier, coupled with the limited payload capacity of spacecraft, severely restricts the amount of cargo, including water, that can be transported.

Furthermore, current systems like the ECLSS are notably power-intensive, rendering them impractical for use beyond Low Earth Orbit (LEO). Their efficiency levels are also insufficient for indefinite sustainability. The extraction of resources in off-world locations presents a unique set of obstacles, including microgravity, vacuum conditions, extreme temperature fluctuations, weight constraints, and difficulties in data analysis and communication. In remote environments, such as the lunar poles or deep space, where solar power availability is intermittent due to long periods of darkness, the development of alternative and reliable energy sources is crucial.

Maintenance is another critical consideration. Conventional water recycling systems are susceptible to corrosion and wear and tear over time. For long-duration missions, the ability to perform regular maintenance is severely limited, making system durability and longevity paramount. To overcome these hurdles, Olawade and his colleagues investigated recent advancements in filtration technologies, novel disinfection methods, and autonomous system management. The ISS's ECLSS provides a foundation, but future systems must be engineered for greater energy efficiency and enhanced resistance to degradation in harsh space environments.

The researchers strongly emphasize the importance of In-Situ Resource Utilization (ISRU) – the practice of sourcing and utilizing materials found on-site. ISRU is a cornerstone of plans for future lunar and Martian exploration. NASA's Artemis Program, for instance, aims to establish a lunar base in the resource-rich South Pole-Aitken Basin, an area characterized by numerous craters. China's International Lunar Research Station (ILRS) and the European Space Agency's vision for an International Moon Village also target this region, primarily due to the confirmed presence of abundant water ice within permanently shadowed regions (PSRs).

Similar strategic considerations guide planning for Mars missions. Robotic explorers have spent years identifying potential water sources across the Martian surface, particularly in mid-latitude regions. However, the extraction and purification of extraterrestrial water present significant technical and logistical challenges. This includes developing specialized equipment capable of accessing and processing water reserves potentially buried beneath the Martian regolith. Moreover, the quality of subsurface water on Mars is a concern, with high concentrations of perchlorates and other potentially harmful organic compounds requiring advanced purification techniques to render it safe for human consumption and life support.

Consequently, advanced extraction and purification systems are essential, alongside power systems that are equally sustainable, durable, and adapted to extreme extraterrestrial conditions. In essence, space-based water systems must be closed-loop, highly efficient, robust, and minimally power-dependent. To address the substantial energy demands of extraction and purification, the study examines various solar and solar-thermal energy applications. These could power critical processes such as water pumping, desalination (using methods like reverse osmosis or electrodialysis), and purification (via photocatalysis or advanced filtration). Such decentralized systems are ideal for extraterrestrial habitats where large-scale power plants are infeasible.

Photothermal systems, which convert solar radiation into heat, offer versatile applications from solar distillation to desalination. Hybrid photovoltaic-thermal (PV-T) solutions can enhance efficiency further by simultaneously generating electricity for pumps and filters while also producing heat for water treatment. Nevertheless, the reliance on solar power faces limitations, especially in lunar polar regions with extended darkness and on Mars, which receives significantly less solar radiation than Earth (approximately 43% to 60%). To mitigate these energy challenges, the researchers also explore the potential of small modular nuclear reactors. These are currently under consideration for future lunar and Martian bases, exemplified by NASA's Kilopower Reactor Using Stirling Technology (KRUSTY) program.

The study further considers recent advancements in bioreactors and genetic engineering, which could offer novel solutions for water processing and waste management in space. Progress in these interconnected fields is crucial for enabling sustainable human habitation beyond Earth and ensuring the well-being of future space explorers.

Ekhbary News Agency