As government agencies and commercial entities around the world set their sights on Mars and further destinations in space, they are looking to the Moon as a kind of base camp for space exploration.
NASA and its commercial partners envision a space station orbiting near the Moon to facilitate new discoveries. The first step is to design and manufacture the power and propulsion system element. This element is necessary to maintain and adjust the gateway’s position in lunar orbit. NASA selected five companies to come up with propulsion technology solutions. They will need to develop a system that is three-times more powerful than existing systems. They have also solicited proposals for space habitats.
While NASA has its eye on the sky, the European Space Agency (ESA) is digging deep. The ESA is considering all options for the lunar base, from a modular system to subterranean. The most appealing plan is to create a lunar base by turning lunar regolith into construction material. Instead of manufacturing a lunar base and shipping it to the Moon, which comes with numerous logistical challenges and points of failure, 3D printing robots could do the job onsite.
Turning the lunar soil into building material is attractive because it requires the least amount of resources from Earth. Excavating machines or heavy payloads would be unnecessary, saving time and money. Repairs to the structure could be completed quickly without shipping in supplies.
The preliminary design uses an inflatable structure to secure a pressurized internal environment. The lunar regolith would then be printed and placed over the inflatable. The blocks need to be 800 mm thick to protect from radiation, meteorites and thermal gradients. The side facing the sun will need 1500 mm of regolith to protect from solar flares, solar winds and galactic cosmic rays. It is easier to estimate the direction of these forces with plans to place the base at one of the poles. The poles offer better access to frozen water that can be used to create breathable air in the inflatable.
The original study used a saline solution and metal oxides as additives to bind the regolith together, an expensive solution since the additives need to be shipped from Earth. A more recent study used concentrated sun light to bind the dust particles together. The proof of concept was completed using volcanic rock to simulate the moon dust.
Whether floating in space or creating lunar hobbit holes, returning to the Moon appears to be the next stop on our journey through the solar system.