Investigating Mass Reduction Capabilities of Additive Manufacturing through the Re-Design of a Space-Based Mirror

TL;DR

This study explores the use of additive manufacturing to create lightweight, high-precision space-based mirrors by redesigning them with internal lattices and topology optimization, aiming for significant mass reduction and assessing their optical performance.

Contribution

It demonstrates the application of AM for space optics, integrating lattice and topology optimization to achieve substantial mass savings while maintaining surface accuracy.

Findings

Achieved 50% and 70% mass reduction in mirror designs.

Successfully manufactured mirrors using laser powder bed fusion.

Quantified optical surface accuracy via interferometry.

Abstract

Additive manufacture (AM) involves creating a part layer by layer and is a rapidly evolving manufacturing process. It has multiple strengths that apply to space-based optics, such as the ability to consolidate multiple parts into one, reducing the number of interfaces. The process also allows for greater mass reduction, making parts more cost-effective to launch, achieved by optimising the shape for intended use or creating intricate geometries like lattices. However, previous studies have highlighted issues associated with the AM process. For example, when trying to achieve high-precision optical surfaces on AM parts, the latticing on the underside of mirrors can provide insufficient support during machining, resulting in the quilting effect. This paper builds on previous work and explores such challenges further. This will be implemented by investigating ways to apply AM to a deployable mirror from a CubeSat project called A-DOT. The reflective surface has a spherical radius of curvature of 682 mm and approximate external dimensions of 106 mm x 83 mm. The aim is to produce two mirrors that will take full advantage of AM design benefits and account for the challenges in printing and machining a near-net shape. The designs will have reduced mass by using selected internal lattice designs and topology-optimised connection points, resulting in two mirrors with mass reduction targets of 50% and 70%. Once printed in aluminium using laser powder bed fusion, the reflective surface will be created using single point diamond turning. Finally, an evaluation of the dimensional accuracy will be conducted, using interferometry, to quantify the performance of the reflective surface.