Duration: 18 months
Current on-orbit inspections of structures rely heavily on visual or video checks [1], which reveal only major visible issues. As structures grow, risks from micrometeoroids, orbital debris, and failed joints increase, and common problems like cracks and disbonds remain. After the Columbia incident, non-destructive testing (NDT) received a significant boost. Space structures are inspected during manufacturing on the ground, while on-orbit NDT lags behind. Engineers have handbooks [2,3] with extensively evaluated NDT techniques, where shearography (a full-field speckle pattern shearing interferometry) is shortlisted for its non-contact, high-productive inspection [4-6]. Shearography directly assesses microstrain-level surface irregularities using an external excitation, e.g. heat or vibration, which is captured with cameras in laser light. This high strain sensitivity enables the detection of small but critical defects like closed cracks and kissing bonds, which often remain hidden. In this project, ShearScope, we will explore the feasibility of a passive shearography inspection and develop a concept prototype for ground laboratory tests. We aim at passive inspection to eliminate the power-demanding excitation by leveraging natural excitations, e.g. orbital sunrises or internal pressure changes. ShearScope is the first step towards our long-term goal of a shearography instrument capable of autonomously inspecting space structures, integrated into a robotic manipulator alongside other NDT solutions, such as thermography [7-8]. The value of shearography is in the mechanically interpretable results that can support predictive assessments like residual life estimation. At TU Delft, we have pushed the application boundaries of shearography to enable detection of submillimeter or deep defects, inspection of curved objects [9-11] – developments often beyond the scope of commercial instrumentation. ShearScope can contribute to reliable and energy-efficient on-orbit inspection
