Bengaluru scientists find way to build space bricks for lunar habitation

The cost of sending a single pound of material into outer space comes to about Rs 7.5 lakh. How then, can future space explorers afford to build structures on the moon? By making bricks on-site on the lunar surface, say city-based researchers who have found a sustainable method to create such blocks from moon soil.

The research team made up of scientists at the Indian Institute of Science (IISc) and the Indian Space Research Organisation (ISRO) worked from the problem standpoint of making cost-effective human habitation on the moon.

The process developed by the IISc and ISRO team uses urea — which can be sourced from human urine. It exploits lunar soil, and uses bacteria and guar beans to consolidate the soil into possible load-bearing structures. These “space bricks” could eventually be used to assemble structures for habitation on the moon’s surface, the researchers suggest.

IIsc said that: “This decreases the overall expenditure considerably. The process also has a lower carbon footprint because it uses guar gum instead of cement for support. This could also be exploited to make sustainable bricks on Earth. “

Aloke Kumar, Assistant Professor in the Department of Mechanical Engineering, IISc, one of the authors of two studies recently published in Ceramics International and PLOS One, added: “It is really exciting because it brings two different fields — biology and mechanical engineering — together.”

Scientists said that their research was driven by the knowledge that some micro-organisms can produce minerals through metabolic pathways. One such bacterium, Sporosarcina pasteurii, produces calcium carbonate crystals through a metabolic pathway called the ureolytic cycle: it uses urea and calcium to form these crystals as byproducts of the pathway. “Living organisms have been involved in such mineral precipitation since the dawn of the Cambrian period, and modern science has now found a use for them,” Kumar said.

To exploit this ability, Kumar and colleagues at IISc teamed up with ISRO scientists Arjun Dey and I Venugopal. They first mixed the bacteria with a simulant of lunar soil. Then, they added the required urea and calcium sources along with gum extracted from locally-sourced guar beans. The guar gum was added to increase the strength of the material by serving as a scaffold for carbonate precipitation. The final product obtained after a few days of incubation was found to possess significant strength and machinability.

“Our material could be fabricated into any freeform shape using a simple lathe. This is advantageous because this completely circumvents the need for specialized moulds – a common problem when trying to make a variety of shapes by casting. This capability could also be exploited to make intricate interlocking structures for construction on the moon, without the need for additional fastening mechanisms,” said Koushik Viswanathan, Assistant Professor in the Department of Mechanical Engineering, IISc, another author.

While future astronauts and terra-engineers could potentially lug around vials of S. pasteurii to help them set up structures on the moon in a more cost-effective manner, the problem is that S. pasteurii by itself is not cheap. According to IISc, one vial of the bacteria can cost Rs 50,000.

Consequently, the PLOS One study, conceived by Rashmi Dikshit, a DBT-BioCARe Fellow at IISc, also investigated the use of other locally available soil bacteria in the place of S. pasteurii.

After testing different soil samples in Bengaluru, the researchers found an ideal candidate with similar properties: Bacillus velezensis, which is about ten times less expensive, researchers say.

The authors said they believe that this is the first significant step towards constructing buildings in space. “We have quite a distance to go before we look at extra-terrestrial habitats. Our next step is to make larger bricks with a more automated and parallel production process,” Kumar said.

“Simultaneously, we would also like to further enhance the strength of these bricks and test them under varied loading conditions like impacts and possibly moonquakes," he added.