Additive Manufacturing as an Enabling Technology for smaller, lighter, cheaper, and faster access to
RUAG Space, Morf3D and Altair team to demonstrate Additive Manufacturing (3D Printing of metallic parts) as an enabling technology for smaller, lighter, cheaper and faster access to space. In a current project for Surrey Satellite Technology LTD, SSTL, the partnership triad validated an aggressive six-month end-to-end timeline that includes concept development, design, optimization, 3D printing, testing and verification of the SSTL technology mission.
The dovetailing of Additive Manufacturing with an economically sustainable approach to spaceflight is a natural coupling. The benefits realized by the use of Additive Manufacturing, AM, in high-speed, low-cost space programs are numerous and include: the ability to implement rapid designs and design revisions; eliminate molds, tooling and the time and cost associated with their fabrication and warehousing; create lighter weight structures thereby reducing the fuel requirements (current payload costs reported by NASA are $20,000/kg); (Drachlis 2016) consolidate system parts thereby providing volumetric efficiency and reducing engineering design, manufacturing, inventorying and assembly time and cost.
Moreover, AM lends itself to topology optimization, in which the optimum distribution of mass for prescribed loading conditions results in an efficient lightweight design that may be customized for performance such as frequency response. Depending on design constraints, organically shaped, bionic designs often result that find natural coupling with Additive Manufacturing processes.
To illustrate the benefits achieved with topology optimization and Additive Manufacturing,three components fabricated for the SSTL technology mission in a rapid timeframe are presented and illustrated in the figure below.
Each of the topologically optimized components were printed in AlSi10Mg on an EOSM290 at Morf3D in El Segundo, and include a StarTracker camera bracket (top artifact in figure below), satellite panel edge inserts (two long rectangular components on the right), and a monopole antenna bracket (on the lower left). These components were optimized with Inspire and OptiStruct structural analysis solver, which is based on finite-element analysis for structural design and optimization. All components possess the same attachment point geometry and are designed to withstand the same loading conditions as their unoptimized counterparts, the topologically optimized parts were significantly lighter in weight (e.g., 85% reduction for the StarTracker camera bracket). What is not visually evident is that the AM part shown was also optimized for frequency performance.
The illustrated component redesigns highlights some, but not all, of the benefits associated with AM as an enabling technology for space development programs. Other benefits of AM include the use of internal lattice structures for significant lightweighting of components, and the ability to add embedded internal functionality such as cooling channels in ways that are impossible with traditional subtractive methods. With AM, structures can be designed and fabricated with shapes and contours not normally associated with its usage, requiring design engineers to rethink how they envision engineering components as well as the entire system into which it fits. In short, it is necessary for design engineers to erase their previously conceived notions of what an engineering component should look like.
In order to insure that the optimized AM fabricated components are suitable for flight, the partnership triad followed a holistic process flow that includes: the design, topology optimization, FEM validation, 3D printing, and testing of alloy components and test coupons that were printed simultaneously. The entire holistic process flow was completed in a one-month time-frame.
It should be noted that several features of the components presented cannot be obtained with traditional methods. For example, the edge inserts, which were required to maintain the initial orthogonal geometry, were significantly lightweighted by incorporating a 'macro-lattice' of branch-like members as shown in the cross-section in the figure. Additionally, the monopole bracket that was originally solid, was optimized to incorporate a hollow annulus of revolution around each attachment point.
It can be summarized that Additive Manufacturing, under carefully controlled and validated conditions, is an enabling technology for rapid end-to-end satellite production. Because of its layer-wise material build properties, Additive Manufacturing allows structural components to be optimized and customized in ways that are not possible with traditional methods. Hence, optimized satellite components can be designed and fabricated in a rapid timeframe with properties and functionality superior to those conventionally fabricated.
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