Printing the future of space telescopes

Space telescopes, for either Earth, Solar System, or astronomical observations, are vital for mapping the effects of climate change and understanding the origins and evolution of the Universe. The telescope mirrors that collect light and relay it to the detectors are one of the most critical components - only if these are of the highest quality can we obtain the best possible observations.

Due to the time and expertise required to create a bespoke piece of precision hardware, mirrors in space telescopes are often the single most expensive item of the system. The mirror shape typically needs to be accurate to less than the width of a human hair and smooth on the scale of DNA (i.e. nanometre scale). Moreover, to reduce launch costs, mirrors often need to be lightweight structures, leading to a further increase in time and cost. The fabrication of the mirror is just the first challenge, even if optically perfect, poor mounting of a mirror can render it unusable by creating distortions in its shape.

My proposed research focusses on a possible disruptive technology for future fabrication of space optics. Additive manufacture (AM; 3D printing) is the creation of a 3D object layer-by-layer, where each layer is added on the previous. This manufacturing process is `additive' in comparison to traditional methods where material is removed from a solid (mill, drill or lathe), or where material is set within a mould (casting, forging).

A huge advantage of AM is the increase in potential geometries available to design engineers. Traditional methods constrain the possible geometries via the tools and access needed to remove material from the object/mould. In contrast, AM requires no extra tooling to create intricate structures beyond the laser (or nozzle) that prints each layer. The freedom of building a part via a layered approach significantly increases the possible geometries and design options - essentially, the designer gains structural complexity for free!

AM has the potential to revolutionise the production of lightweight, bespoke mirrors. The increase in the design space allows lightweight structures to be optimised for their specific functions, creating geometries that are impossible via traditional methods. This promises lighter and more rigid mirrors than those currently available. Even more powerful could be the ability to print a mirror and its mount as one structure, thus reducing deformations caused by interfaces and fasteners. In addition, the cost and time required to fabricate such lightweight mirrors would also decrease, promoting the affordability of imaging from space.

Despite the advantages of AM in mirror fabrication, there are two key research challenges that are the focus of one strand of my research. First, with the increase in design space, how is the ideal lightweight structure best determined? Options include regular and non-regular lattices, computer optimisations, and adapting structures from nature - identifying the best approach for a given mirror is a difficult design problem. Second, can suitable materials and structural properties for mirror fabrication be adapted for use by AM? Mirror fabrication requires a unique set of material properties and characteristics to generate the best surfaces. AM has not been optimised for this application to date, and the optimal parameters and materials require detailed research.

The second element of my research focusses on establishing AM as a go-to technique for the future fabrication of flight hardware. This is arguably the biggest challenge facing AM components designed for space. Due to expensive launch costs, all space hardware needs to be qualified (i.e. approved for operation) prior to launch and this process of qualification is expensive, time consuming and nurtures a resistance for change. Therefore, I will work towards space qualification of AM components, to demonstrate experimentally the benefit of AM for future flight hardware.

Industry, particularly small- to medium-enterprises (SMEs), are a prime beneficiary of this research. For SMEs across all industry disciplines the ability to optimise the additive manufacture (AM) process for application is typically out of scope due to accessibility and/or cost. My project will develop strategies for AM adoption that utilise the design freedom and showcase how AM can be tailored to a given application. More specifically, my research is directly transferable into industries involved in space hardware, optics fabrication and AM, and has the objective to provide public domain fundamental research to enable innovation across these disciplines. In optics manufacture, AM has potential to provide a new product line, where the benefits of lightweighting and structural optimisation are prioritised over optical performance. In a broader view, this research has the potential to drive innovation in other fields, for example in dimensional metrology, where optimised AM structures, often organic in shape, pose a challenge for measurement.

Within academic disciplines that have yet to embrace AM for component manufacture, my research will provide a foundation upon which to build capacity. Specifically, my project targets space research, astronomical instrumentation and optical fabrication and has the potential to disrupt the status quo within these disciplines. Astronomical instrumentation in particular often poses structural challenges, either in confining an instrument within a small volume, or in minimising the weight without compromising strength. With future ground- and space-based increasing in size, these structural challenges require a new methodology. One of the key objectives of my project is to output accessible paths for space qualification of AM components. Qualification can be limiting factor in the development of proof-of-concept hardware due to time and cost; however, with a path to follow, some of the burden associated with incorporating a new technique is removed and thereby increasing the potential for workforce upskill.

One work package in my project is dedicated to public outreach with the goal of both familiarising the public with benefits of AM and how it should be considered on a par with traditional manufacturing methods, and developing outreach material to increase accessibility to astronomical images. This latter point is particularly beneficial for the visually impaired (VI) community, where visual data cannot be experienced. However, the majority of visual data is digital, which is the ideal format to be built via AM and by tailoring outreach material for a minority, it has the potential to be impactful with the majority as well.

Internationally, developing countries can benefit from this research. The competiveness of this project within the field is the focus on accessibility within the public domain. AM has the potential to uplift research and development across many disciplines, with the benefit of reduced cost and waste. However, these benefits are not necessarily quick-wins and require foreknowledge to enable them, which can be a challenge in developing countries. By creating AM strategies in design and parameter optimisation for the common AM metal, this alleviates some of the burdens preventing innovation via AM.