3D printing is potentially of great use to lunar exploration. Weight is a key constraint in space travel and the ability to create structures in situ, using lunar materials and solar power could bring lunar colonisation one step closer. Transporting the infrastructure needed by lunar colonists from Earth is technically challenging. Far more desirable would be the ability to use 3D printing to build structures in place.
But this raises questions including the nature of the material to use and how to harness the solar power needed. While the idea of 3D printing structures in space using lunar soil and solar energy seems like science fiction, the technology of tomorrow is swiftly becoming the technology of today thanks to the EU-funded REGOLIGHT project.
The project has developed techniques to take a ground-breaking proof of concept, established by the European Space Agency, one step further.
Work done by the European Space Agency, using facilities at the DLR German Aerospace Centre in Cologne, has shown it is possible to create bricks from simulated moondust and solar energy.
A 3D printer table was attached to a solar furnace, baking successive 0.1 mm layers of moondust at a temperature of 1000°C. The test has shown a 20 x 10 x 3 cm brick for building can be completed in around five hours.
The centre’s solar furnace uses 147 curved mirror facets, which can focus sunlight into a high temperature beam and this was employed to fuse grains of regolith. As this technique is weather dependent, a solar simulator was used as well.
This took the form of an array of xenon lamps more frequently found in cinema projectors. The result shows that this method of creating building material, potentially for lunar construction, is feasible.
The REGOLIGHT (Sintering Regolith with Solar Light) project will now recreate the experiment through trials to see how the well the technology works under representative lunar conditions: vacuum and high-temperature extremes.
The idea of replicating the result in a vacuum seems to be particularly challenging, however a paper the project recently published in ‘The Journal of Aerospace Engineering’ reports their finding that a vacuum environment has a positive effect on sintering.
Grains bond at lower temperature than in air, which prevents the formation of additional porosity and increases the compression strength by up to 152 MPa compared with only 98 MPa for sintering in air. The study also considers the influence of changes in glass content, main plagioclase series and ilmenite content on a defined sintering process.
Various techniques have been developed by the project to lay the ground for the trials to build on the ESA’s results. The team recently announced the development of regolith feeds which stock the raw material in a sealed tank and then spread it at the right density and rate on the printing area.
Because of the abrasive property of the regolith, proper deposition of the powder can be difficult to control. But the new device REGOLIGHT has created allows the thickness of each layer to be regulated through the number of auger screws. Material leak (which occurs when the feeder is idle), flow, and adequate thickness and spread of the deposited material were each verified.