There are many challenges for in-situ resource utilization off-Earth. However, as human space exploration plans draw near, there is a pressing need to come up with creative solutions that will give space crew access to critical supplies and life-sustaining elements. NASA’s human lunar exploration plans under the Artemis program could send astronauts to the surface of the Moon as early as 2024 and anticipates sustainable exploration by the end of the decade.
However, living and working in space for months or years means generating products with localized materials to avoid extremely high transportation costs – estimated at $100,000 per ton to Mars by space entrepreneur Elon Musk. Although several processes have been proposed that use native minerals and rocks as feedstock for 3D printing on-site, experts have pointed out that it is still unclear to what extent any of these materials can be economically converted and used for additive manufacturing (AM).
Now, a new study by a team of scientists at the Singapore University of Technology and Design (SUTD) proposed using a common organic biopolymer and working with simple chemistry to produce a material that could be used to 3D print objects, like tools and shelters, on Mars. The result, a bioinspired regolith composite called Martian biolith that can be made with minimal energy and no need for transporting specialized equipment or dedicated feedstock.
The scientists described their experiments in a recent paper published in the journal PLOS ONE. Co-author and founding Academic Member at SUTD Javier Fernandez and his colleagues explained that their simple manufacturing technology is based on chitin, one of the most ubiquitous organic polymers on Earth. It is produced and metabolized by organisms across most biological kingdoms, and will likely be part of any artificial ecosystem as it is biology’s recurrent solution to forming structural components. Chitin can be found in cell walls in fungi; the exoskeletons of arthropods, such as crustaceans and insects, and the scales of fish and amphibians.
For this study, the researchers used chitosan derived from shrimp, which they then dissolved in a low concentration of acetic acid (a common byproduct in both aerobic and anaerobic fermentation). They then combined the chitosan with a mineral designed to mimic the properties of Martian soil to create the final biolith solution.
To test the suitability of the biolith as feedstock for 3D printing, they created a scaled habitat model inspired by the design of NASA 3D printed habitat winner MARS HAbitat (MARSHA) by AI SpaceFactory. The biolith was robotically extruded in three segments, using a pneumatic ram extruder mounted onto a KUKA KR 60 HA, six-axis robotic arm. It took the team less than two hours to print the structure. One of the advantages of the printer setup is the ability to tune the process to balance speed and definition, as well as the ability to scale printed artifacts to several orders of magnitude using the same material and manufacturing technology.
They also used the versatile biolith to cast different geometries, including a functional wrench that was later tested, used to repair a broken pipe. Through the study, the authors were able to demonstrate that this material enables the rapid manufacturing of objects that could support humans in a Martian environment. Describing that the initial products of biolith could be consumable tools and equipment mass fabricated by hand or casting.
Scarce resources in an extraterrestrial environment pose extreme challenges to the establishment of a closed ecological cycle that supports human activities, similar to the problem of sustainable development on Earth. Fernandez suggested that the technology was originally developed to create circular ecosystems in urban environments, but due to its efficiency, it is also the most suitable and scalable method to produce materials in a closed artificial ecosystem in the extremely scarce environment of a lifeless planet or satellite. It was by looking at nature’s successful strategies to adapt to harsh environments, that they could create the versatile Martian biolith.
“Against the general perception, bioinspired manufacturing and sustainable materials are not a substituting technology for synthetic polymers, but an enabling technology defining a new paradigm in manufacturing and allowing to do things that are unachievable by the synthetic counterparts,” said Fernandez. “Here we have demonstrated that they are key not only for our sustainability on Earth but also for one of the next biggest achievements of humanity: our transformation into an interplanetary species.”
The research community is currently assessing opportunities to use existing rocks and minerals for space manufacture that will not require an extreme or high level of processing. Many manufacturing methods currently being considered for off-Earth developments are based on technologies for the bountiful paradigm of Earth and are commonly characterized by processes involving high temperatures and pressure or polymers with complex and dedicated biosynthesis.
Nonetheless, future space exploration missions to Mars will require a sustainable extraterrestrial settlement that must be resource-efficient with closed ecological systems in place, that call for less energy to process, phasing into something that can be used for AM. Through this new study, the team has demonstrated an innovative way to create a composite with low manufacturing requirements, ecological integration, and versatile utility that could become the basis of future Martian environments.
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