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.
3D printing with moondust
Purpose 
 
 
 
 
The purpose of this paper is to investigate the effect of the main process parameters of laser melting (LM) type additive manufacturing (AM) on multi-layered structures manufactured from JSC-1A Lunar regolith (Moondust) simulant powder. 
 
 
 
 
Design/methodology/approach 
 
 
 
 
Laser diffraction technology was used to analyse and confirm the simulant powder material particle sizes and distribution. Geometrical shapes were then manufactured on a Realizer SLM™ 100 using the simulant powder. The laser-processed samples were analysed via scanning electron microscopy to evaluate surface and internal morphologies, X-ray fluorescence spectroscopy to analyse the chemical composition after processing, and the samples were mechanically investigated via Vickers micro-hardness testing. 
 
 
 
 
Findings 
 
 
 
 
A combination of process parameters resulting in an energy density value of 1.011 J/mm2 allowed the successful production of components directly from Lunar regolith simulant. An internal relative porosity of 40.8 per cent, material hardness of 670 ± 11 HV and a dimensional accuracy of 99.8 per cent were observed in the fabricated samples. 
 
 
 
 
Originality/value 
 
 
 
 
This research paper is investigating the novel application of a powder bed fusion AM process category as a potential on-site manufacturing approach for manufacturing structures/components out of Lunar regolith (Moondust). It was shown that this AM process category has the capability to directly manufacture multi-layered parts out of Lunar regolith, which has potential applicability to future moon colonization.
Active profiling and polishing for efficient control of material removal from large precision surfaces with moderate asphericity
We present the development of an active fabrication technology for controlling material removal on large precision surfaces of moderate departure from a sphere. The underlying philosophy was established as an efficient solution to the challenging problem of fabricating secondary mirrors of up to nominally 2.5 m in diameter for modern 8 m class telescopes and beyond. The facility described comprises a CNC profiler, two contact profilometers, and a full size active polisher. The trial work-piece was a convex surface of 830 mm in diameter on a zero-expansion ceramic (`Cervit') blank – a 1/3 scale hyperbolic mirror for a proposed 2.5 m diameter f/7 secondary mirror for the 8 m Gemini telescope. Using software error-correction from profilometric metrology data, a factor of 2 improvement in generating the convex aspheric profile was achieved. An active loose-abrasive polishing process is also described, in which a full-size tool is configured to deliver variable, edgeless, sub-diameter removal-footprints. Real-time monitoring of process variables is described, and approximately 10% convergence in each polishing pass is reported.