Description: GOALIE is investigating a process to indirectly infer the as-manufactured shape and mechanical performance of composite booms under microgravity (i.e., flight-like) conditions by developing experimental methods to validate computational models of booms under the influence of Earth’s gravity. Deployable space structures, such as booms, enable efficiencies of scale and reduce the number of rocket launches required for a complete structure compared to conventional rigid structures that are launched in their intended-use configuration. For example, support structures for deployable solar arrays have enabled much larger areas of solar capture, and therefore larger power generation, than would otherwise fit into a single launch vehicle payload. As new concepts, materials, and structures are developed, deployable space structures are becoming more flexible. Structures with higher flexibility are correspondingly more difficult to accurately characterize for as-manufactured geometrical shape and structural performance in mimicked microgravity using traditional horizontal gravity offloading techniques such as whippletrees. Triangular, Rollable, and Collapsible (or TRAC) booms are proposed for the solar sailing mission called Solar Cruiser. The TRAC boom design is extremely sensitive to torsional disturbances – so much so that structural testing experts are not confident that conventional horizontal whippletrees are good enough at supporting TRAC booms without influencing the shape of the boom even when mechanically unloaded. As a result, it is difficult to have confidence in computational predictions of the response of the booms under flight conditions because any realistic shape in microgravity is unknown. GOALIE is investigating TRAC boom shape and performance characterization while vertically hanging the booms from one end. In the vertical orientation, torsional disturbances are less likely to result in a collapse of the structure (often seen in horizontally offloaded configurations) while imparting minimal shape-changing effects due to gravity. Once the vertically oriented shape and performance of the boom, while under the influence of Earth's gravity, are able to be captured by numerical analyses, the GOALIE project will attempt to infer the true shape of the TRAC boom under microgravity-like conditions by removing gravity from the analysis and letting the structure resume an unloaded, stress-free state.

Benefits: When complete, missions using high-strain composite deployable space structures such as the booms studied in the GOALIE project will have higher confidence in numerical predictions of their response under flight-like microgravity conditions. Higher confidence in numerical predictions for deployable space structures can lead to 1) higher rates of mission success, 2) risk reduction through use of computational tools to inform flight-test-like performance without requiring to conduct physical flight tests, and 3) increased technology adaptation for concepts such as solar sails or other types of structures proposed for use with deployable booms. Higher confidence in numerical predictions result from achieving a better understanding of fundamental performance of deployable space structures such as the Triangular, Rollable, and Collapsible (or TRAC) boom investigated in the GOALIE project. The GOALIE project is investigating TRAC booms specifically because a future solar sailing science mission, Solar Cruiser, proposed to use TRAC booms to support the orders-of-magnitude-larger solar sail than what has previously flown (1,653 m2 compared to the few dozen m2 currently). However, there are some challenges in developing such large, flexible structures. Technology Readiness Level (TRL) 6 requirements state a demonstration of a system in “flight-like" conditions is needed before advancing to higher levels. On Earth's surface, flight-like conditions such as microgravity do not exist for highly flexible TRAC booms supporting a solar sail. Instead of physical demonstration of flight-like conditions, GOALIE aims to demonstrate one methodology to computationally infer the response of TRAC booms under microgravity conditions by developing validated models of booms under the influence of Earth's gravity.