Bend-Forming: A Deformation Process for In-Space Manufacturing of Truss Structures

Abstract

In-space manufacturing (ISM) is a candidate approach for constructing next-generation space structures with larger dimensions than modern deployable systems. While many ISM approaches have been proposed, analysis of their performance for building precision structures on orbit, such as large-diameter reflectors, is scarce. In this thesis, we present a quantitative comparison of materials and processes for ISM, using performance metrics for suitable feedstock materials and a fast and accurate manufacturing method. Our analysis finds that deformation processes are a promising ISM approach due to their low specific energy consumption, almost an order of magnitude lower than melt-based and extrusion processes which rely on heating of the feedstock. This low specific energy consumption potentially enables deformation processes to fabricate 100-meter diameter structures on orbit in less than a day, whereas melt-based processes may take more than a month and be limited to inferior feedstock materials.

Motivated by this comparison of ISM processes, we present an exemplar deformation process, termed Bend-Forming, for fabricating truss structures in space. The method relies on the combination of CNC wire bending with mechanical joints to form trusses from raw feedstock via plastic deformation. We demonstrate the method with exemplar structures on the order of 1 meter and provide a framework for fabricating arbitrary geometries with Bend-Forming, including reticulated columns, shells, and trusses. To guide the design of Bend-Formed structures for space applications, we next investigate the compressive behavior of Bend-Formed isogrid columns through experiments, finding that the structures undergo a smooth formation of buckling deformations. Finite element analyses accurately predict the maximum loads observed experimentally, highlighting the imperfection-insensitive nature of the Bend-Formed columns. Finally, we present a potential space application of Bend-Forming, namely the fabrication of support structure for an electrostatically-actuated reflector antenna. To demonstrate the concept, we design and fabricate a 1-meter diameter antenna prototype with Bend-Forming.

Overall, this research adds to the growing field of ISM by 1) providing a framework for assessing materials and processes suitable for ISM; and 2) introducing a novel approach for constructing truss structures, called Bend-Forming, with potential application to ISM.