Future of lunar habitats: Designing for life on the Moon
The next step in Moon exploration will go beyond rovers and focus on building sustainable and safe lunar habitats
In 2024, US space agency Nasa’s Artemis programme will see astronauts return to the Moon for the first time since December 1972. Recent news reports suggest China too is developing a plan for an international lunar research station for crewed missions in the near future.
Over the decades, there have been multiple moon landing missions—be it India’s Chandrayaan programme or the Chinese Lunar Exploration Programme, Chang’e. But clearly, the next big step in exploring the Moon will go beyond lunar landers, rovers, orbiters and robots. The next milestone is figuring out how to build Moon habitats that will not only allow astronauts to survive on the lunar surface but eventually enable human settlements on the astronomical body closest to us.
And scientists around the world are already working on the building blocks. Earlier this month, a team of researchers at the Indian Institute of Science (IISc) in Bengaluru published the results of a sustainable process for making brick-like structures that could be used to assemble habitats on the Moon.
This process uses a lunar soil simulant, bacteria and guar beans to consolidate the soil into load-bearing structures. Aloke Kumar, assistant professor at the department of mechanical engineering, IISc, explains how these bricks are made in special bio-reactors through a process called bio-mineralization or bio-cementation. “The bacteria (Sporosarcina pasteurii) turns to stone. It recreates calcium carbonate crystals around itself under certain conditions," says Kumar over the phone. “We literally have to grow the bricks. Apart from the bacteria and lunar soil simulant, the third key element is the food you supply to the bacteria. Once we put all these elements into the bio-reactor, the brick grows in about 7-10 days," he explains. Every bacteria takes a different pathway for the bio-cementation process. “There are multiple pathways. The one we used for this particular case was urea, which we supplied as an artificial additive," adds Kumar.
The lunar soil simulant—a recently patented, artificial lab copy of lunar soil—was supplied by the Indian Space Research Organisation (Isro). Why the guar beans and gum though? Kumar says the initial results were not satisfactory. The bricks were brittle and would break easily. In an official statement, the IISc explains that guar gum increased the strength of the material by serving as a scaffold for carbonate precipitation. “Guar is a popular additive in the chemical and oil industry," says Kumar. “It’s a natural biopolymer, which helps the bacteria in the binding process. The final cohesiveness in the binding process was lacking. That’s why we added guar and it gave us some fantastic results."
The next step in the development of these “lunar space bricks" is to test their use in interlocking structures and see whether they can hold. The IISc team is also analysing the material’s “compressive strength"—testing the stress it can take. “At the moment, we have gone till 2.5 MPa (megapascal), which is still at the lower limit of where we would want to be. Ice, for example, has a compressive strength of around 3-4 MPa," says Kumar.
Every element of a lunar habitat will need to take into account a host of factors—the Moon’s gravity, for instance. In June, Nasa announced a “lunar loo" challenge, seeking design ideas for toilets that are “capable of working in both microgravity and lunar gravity".
Danish space architects Karl-Johan Sørensen and Sebastian Aristotelis are working on the “Lunark Habitat", which seeks to combine origami—the ancient Japanese art of paper folding—with biomimicry to design a lightweight and strong foldable structure that will feel like a tank from the outside but will have enough features inside to support long-term stay in space. As the official website goes on to explain, this would include a dynamic light system to create an artificial circadian rhythm for its inhabitants, solar panels, 3D-printed interiors, a vertical farm and an algae-based life support system, among other things.
Testing the structural resilience, among other factors, of any possible habitat is also crucial. At Purdue University’s RETH (Resilient ExtraTerrestrial Habitats) Institute, Prof. Shirley Dyke is working on testing three such characteristics: resilience, intelligence and autonomy. Prof. Dyke, a professor of mechanical and civil engineering and head of the RETH Institute, uses a method known as “cyber-physical" testing.
According to a news release on the university’s website, this combines computer models with physical test specimens. For the research, RETH will build realistic, quarter-scale habitats in Purdue University’s Herrick Labs. Prof. Dyke explains how different scenarios could affect future habitats. “Meteoroid impacts, quakes and issues with moon dust (which is very sharp and abrasive) are just some of the many hazards that can impact the performance of the space habitat, causing a risk to humans," she notes in the statement.
But while she expects “lunar dwellings to begin emerging in a decade", she adds that the ultimate goal is a habitat that does not require constant human oversight.