Despite the established role of additive manufacturing (AM) in aerospace and medical fields, its adoption in astronomy remains low. Encouraging AM integration in a risk-averse community necessitates documentation and dissemination of previous case studies. The objective of this study is to create the first review of AM in astronomy hardware, answering: where is AM currently being used in astronomy, what is the status of its adoption, and what challenges are preventing its widespread use? The review starts with an introduction to astronomical instruments size/cost challenges, alongside the role of manufacturing innovation. This is followed by highlighting the benefits/challenges of AM and used materials/processes in both space-based and groundbased applications. The review case studies include mirrors, optomechanical structures, compliant mechanisms, brackets and tooling applications that are either in research phase or are implemented.
Additive manufacturing (AM; 3D printing), which builds a structure layer-by-layer, has clear benefits in the production of lightweight mirrors for astronomy, as it can create optimised lightweight structures and combine multiple components into one. AM aluminium mirrors have been reported that demonstrate a 44% reduction in mass from an equivalent solid and the consolidation of nine parts into one. However, there is a limit on the micro-roughness that can be achieved using AM aluminium at ∼5nm RMS (root mean square; Sq), therefore, to target applications at shorter wavelengths alternative AM materials are required. New capabilities in AM ceramics, silicon carbide infiltrated with silicon (SiC + Si) and fused silica, offer the possibility to combine the design benefits of AM with a material suitable for visible, ultraviolet and x-ray applications.
This paper will introduce the different printing methods and post-processing steps to convert AM ceramic samples into reflective mirrors. The samples are flat disks, 50mm diameter and 5mm in height, with three samples printed in SiC + Si and three printed in fused silica. Early results in polishing the SiC + Si material demonstrated that a micro-roughness of ∼2nm Sq could be achieved. To build on this study, the 50mm SiC + Si samples had three different AM finishing steps to explore the best approach for abrasive lapping and polishing, the reflective surfaces achieved demonstrated micro-roughness values varied between 2nm and 5nm Sq for the different AM finishing steps. To date, the printed fused silica material has heritage in lens applications; however, its suitability for mirror fabrication was to be determined. Abrasive lapping and polishing was used to process the fused silica to reflective surface and an average micro-roughness of <1nm Sq achieved on the samples.
A-DOT (Active Deployable Optical Telescope) is a payload prototype of a 6U deployable telescope operating in the visible from 400 to 800 nm with an aperture diameter of 300 mm. It aims to deliver diffraction-limited performance using on-board wavefront sensing (WFS) and active control (WFC). A-DOT is currently in the design phase. This paper presents the development of a deployable, single-segment, mechanical prototype. The deployable mirror segment is kinematically mounted to a monolithic flexure using three spherical contacts in a cup-grooveflat arrangement. Tip, tilt and piston (PTT) are controlled using linear, piezoelectric actuators at each contact and the mirror position measured using capacitive sensors. The prototype is packaged within the allowable CubeSat volume and uses space-compatible hardware in a non-magnetic design.
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