Sintering of micro-trusses created by extrusion-3D-printing of lunar regolith inks
Abstract The development of in situ fabrication methods for the infrastructure required to support human life on the Moon is necessary due to the prohibitive cost of transporting large quantities of materials from the Earth. Cellular structures, consisting of a regular network (truss) of micro-struts with ∼500 μm diameters, suitable for bricks, blocks, panels, and other load-bearing structural elements for habitats and other infrastructure are created by direct-extrusion 3D-printing of liquid inks containing JSC-1A lunar regolith simulant powders, followed by sintering. The effects of sintering time, temperature, and atmosphere (air or hydrogen) on the microstructures, mechanical properties, and magnetic properties of the sintered lunar regolith micro-trusses are investigated. The air-sintered micro-trusses have higher relative densities, linear shrinkages, and peak compressive strengths, due to the improved sintering of the struts within the micro-trusses achieved by a liquid or glassy phase. Whereas the hydrogen-sintered micro-trusses show no liquid-phase sintering or glassy phase, they contain metallic iron 0.1–2 μm particles from the reduction of ilmenite, which allows them to be lifted with magnets.
Selective Separation Sintering ( SSS ) A New Layer Based Additive Manufacturing Approach for Metals and Ceramics
Selective Separation Sintering (SSS) is a powder layer based Additive Manufacturing approach. SSS can fabricate high temperature ceramic and metallic parts at comparatively lower cost with high quality. In the printing process a dry powder of higher sintering temperature is deposited into the base material which makes up the part. The inserted powder defines the boundary of the part and separates the part from its surroundings. When printing of all layers is completed the deposited dry powder serves as a separation coating which defines the shape of the part. In the sintering process the base material is sintered into a solid part while the separation coating remains as loose powder. The part is then separated from the surrounding area at the separation coating surfaces, and is post processed if necessary. Preliminary results have proven the capability of SSS in successfully printing ceramic and metallic parts. Future experiments are planned for improving the process resolution.
Lunar In Situ Materials-Based Habitat Technology Development Efforts at NASA/MSFC
For long duration missions on other planetary bodies, the use of in situ materials will become increasingly critical. As man's presence on these bodies expands, so must the structures to accommodate them including habitats, laboratories, berms, garages, solar storm shelters, greenhouses, etc. The use of in situ materials will significantly offset required launch upmass and volume issues. Under the auspices of the In Situ Fabrication & Repair (ISFR) Program at NASA/Marshall Space Flight Center (MSFC), the Habitat Structures project has been developing materials and construction technologies to support development of these in situ structures. This paper will report on the development of several of these technologies at MSFC's Prototype Development Laboratory (PDL). These technologies include, but are not limited to, development of extruded concrete and inflatable concrete dome technologies based on waterless and water-based concretes, development of regolith-based blocks with potential radiation shielding binders including polyurethane and polyethylene, pressure regulation systems for inflatable structures, production of glass fibers and rebar derived from molten lunar regolith simulant, development of regolithbag structures, and others, including automation design issues. Results to date and planned efforts for FY06 will also be presented.