Swarms of robots could dig underground cities on Mars
Subterranean habitats have recently become a focal point of off-planet colonization efforts. Protection from micrometeorites, radiation, and other potential hazards makes underground sites more desirable than surface dwellings. Building such underground structures presents a plethora of challenges, not the least of which is how to actually build them. A team of researchers at Delft University of Technology (TUD) works on a blueprint to extract materials and then use them to print habitats. It would all be done with a group of swarming robots.
The idea stems from a grant opportunity posted by the European Space Agency. Students of the Robotic construction laboratory (RB) at TU Delft, led by Dr Henriette Bier, were excited to participate in the challenge which focuses on the use of in situ resources for above-ground construction. The RB team, working with experts in materials science, robotics and aerospace engineering, submitted an idea that received € 100,000 to develop a preliminary proof of concept.
The proposed approach focuses on the specialty of the laboratory – robotic construction – and has four main components – digging out the regolith, printing a new habitat using an additive manufacturing process, coordinating the work between all the robots that would be necessary to accomplish the tasks, and to feed them as well as the habitat.
The excavation of the regolith with robots was previously explored, but usually against the backdrop of the moon. Different excavation models are useful for building different structures, and the model the RB team focused on was a downward spiral. Such a structure could create a stable and secure structure in a relatively small footprint on the surface.
The modeling of stresses and strains on this structure is a key element of the current study project. The team developed a 1m x 1m scale prototype of a fragment with patterns that would allow them to effectively create safe and stable areas. Some of these areas have been designed with habitation in mind, including detachable plant areas that can house plants grown in hydroponics.
Tons and tons of regolith would have to be removed from any full scale excavation site. This regolith is used as a material to 3D print a stable habitat. Originally, the team planned to combine regolith with Liquid sulfur produce concrete. But after involving materials scientists and an industrial partner specializing in robotic printing with cement, they decided to use cement-based concrete by tapping into some of Mars’ water resources. However, the creation of the cement itself requires infrastructure, so such a plan for using the regolith would have to wait until this infrastructure is already in place on the planet.
The structuring of the habitat itself is also a key consideration when designing the shape that should be 3d printed. The team focused on relatively porous structures, which allowed them to use less materials in its construction. However, the structures still had remarkably high strength and durability and also offered good insulation against radiation and micrometeorite impacts that the underground colony seeks to avoid.
Some of the benefits of this approach are due to one of the main drivers of innovation: collaboration. The project is coordinated by the RB laboratory but involves partners both at TUD and external business partners. These collaborators bring expertise in civil engineering, aerospace and robotics, as well as additive manufacturing technologies to develop the robotic swarm construction approach.
These collaborators will have to continue working together for a long time to see this project eventually implemented on Mars. As a technology demonstrator, it still has a long way to go to be accepted as a mission concept. Dr. Bier and her team hope to continue advancing the concept and seek future funding opportunities as part of this development path.
With luck, swarming robots and 3D-printed cement-based habitats will play a key role in the further development of what so far is just science fiction – an underground city on Mars.
arXiv – From design to robotic production of underground habitats on Mars
ESA – Implementing OSIP Ideas – December 2020
UT – This Martian lava tube skylight is 50 meters in diameter. The largest lava tube on Earth is only 15 meters in diameter
UT – Underground liquid water found on Mars!
Concept of underground habitat and the robots and energy sources that will build and power it.
Credit – Bier et al.