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Sintering Regolith with Solar Light

Periodic Reporting for period 1 - RegoLight (Sintering Regolith with Solar Light)

Reporting period: 2015-11-01 to 2018-04-30

The project RegoLight is concerned with the development of technologies for producing interlocking building elements with only solar radiation and lunar dust to be used in scenarios for constructions on the Moon. To this end a concurrent engineering approach is pursued: Samples produced
by the irradiation from both natural and artificial solar irradiation on regolith simulants provide the data for mechanical properties to be used for civil engineering calculations allowing for realistic architectural designs. Also, requirements from the designs are used for the optimisation of the building elements.

The project's output shall be a technology handbook detailing the fundamental properties necessary for understanding the additive manufacturing on lunar surfaces as well as many interconnected solutions from the iteration of the designs with the properties achievable in hardware. The outputs are important inputs for enabling further mission-related projects where in-situ resource utilisation also concerns construction with local means. That concept shall free such mission from bringing all materials from Earth.

Regarding the use on Earth of the technologies developed for space, the project brings novel insights into 3D-printing in rather unconventional situations which may be relevant in remote or poor areas as well as in exceptional situations such as disaster relief. Also, another spin-off may proof to be utilisation of similar techniques in order to change the properties of sand for special use cases.

The overall objectives cover the development and refinement of technologies that allow the use of local resources for future space mission as described above.
The work was divided in two approaches: one focusing on the development of hardware for solar additive manufacturing of lunar soil, and another regarding the design of the lunar base, from the shape of the interlockable elements to the scenario or big picture.

Regarding the hardware development, the project main objectives covered the following:
− Utilisation of the Additive Manufacturing (AM) approach for automated fabrication of building elements. A regolith simulant feeder was developed to drop off a thin layer of lunar regolith on top of the sintered layer
− Production of a building element with a fine structure (resolution ≤ 1.4 cm) from lunar regolith simulant without bonding agent, using a solar light source under ambient conditions
− Automated fabrication of larger structures through a mobile printing head outside the solar furnace and in ambient conditions
− Demonstration of producing a building element block from lunar regolith simulant by applying the solar sintering AM approach, using a solar furnace automated setup, under vacuum conditions.

As for the building element design and mission scenario:
− Design and validation of an interlocking building element, which when combined could be used for a variety of space architecture and mission requirements in a modular fashion
− Characterization of the building elements produced (mechanical properties, microscopical observations)
− Study the application of solar sintering element manufacturing in the frame of the larger picture of a lunar base architecture; also by considering concepts such as the ESA Moon Village.

The ultimate goal of the project is to help pave the way for future long duration, sustainable, crewed exploration to the Moon. Projects such as RegoLight use local resources to create ecological solutions using only lunar sand and the sun to build protective shelters for humans.
Our work developed the solar 3D printing technology beyond the current state of the art, mainly regarding two aspects:
• Solar 3D printing of lunar regolith with a mobile printing head,
• Solar 3D printing of lunar regolith under vacuum.
The use of a mobile head brought us one step closer to the lunar application. On the Moon, it is likely that a concentrated solar beam will sweep the surface for sintering the in-situ lunar soil. Using a focusing Fresnel lens attached to a 3-axis Gantry system, we demonstrated in the RegoLight project the feasibility of solar sintering of lunar regolith with a mobile printing head. The process was fully automated, the Fresnel lens was oriented according to the position of the sun to the horizon and a pre-defined computer sintering pattern. After the solar sintering of a layer, a device was dispensing automatically a new layer of lunar regolith that could be sintered. The process was then being repeated until the part was manufactured or that the solar intensity was too low to sinter lunar regolith.
Raising the Technology Readiness Level (TRL) was then the second objective of the RegoLight project. The current state of the art was limited to solar sintering in air. Solar sintering under vacuum was therefore an important objective of the RegoLight project. Fitting a regolith dispenser and a 3-axis table inside a vacuum chamber, few layers of lunar regolith simulant were sintered by the high-flux Xenon lamps of DLR-Cologne, that have a light spectrum close to the sunlight. Important challenges linked to the out-gassing of the material at sintering temperature were highlighted during the experiment campaign. The current TRL of solar sintering is now assessed to be TRL 5.
Developing solar sintering does not only have an impact for further space exploration but has also terrestrial applications. Replacing the lunar regolith with desert sand, it would be possible to build roads and houses in arid areas where bringing concrete material could represent a geographical or cost issue.
Design of lunar habitat shielding
3D-printed brick from moondust using focused sunlight
Moon Base concept
Solar 3D printer with a mobile Fresnel lens