The Space Shuttle Columbia's catastrophic failure is thought to have been caused by a dislodged piece of external tank spray on foam insulation (SOFI) striking the left wing of the orbiter causing significant damage to some of the reinforced carbon/carbon leading edge wing panels. Microwave and millimeter wave nondestructive evaluation methods have shown great potential for inspecting SOFI for the purpose of detecting anomalies such as small air voids that may cause separation of the SOFI from the external tank during a launch. These methods are capable of producing relatively high-resolution images of the interior of SOFI particularly when advanced imaging algorithms are incorporated into the overall system. To this end, synthetic aperture focusing techniques (SAFT) are being developed. This paper presents some of the preliminary results of this investigation using SAFT-based methods and microwave holography at relatively low frequencies illustrating their potential capabilities for operation at millimeter wave frequencies.
J. T. Case et al., "Microwave and Millimeter Wave Imaging of the Space Shuttle External Fuel Tank Spray on Foam Insulation (SOFI) using Synthetic Aperture Focusing Techniques (SAFT)," Proceedings of the Review of Progress in Quantitative Nondestructive Evaluation (2005, Brunswick, ME), vol. 820, pp. 1546-1553, American Institute of Physics (AIP), Aug 2005.
The definitive version is available at https://doi.org/10.1063/1.2184706
Review of Progress in Quantitative Nondestructive Evaluation (2005: Jul. 31-Aug. 5, Brunswick, ME)
Electrical and Computer Engineering
Keywords and Phrases
Focusing; Insulation Testing; Microwave Holography; Millimetre Waves; Nondestructive Testing; Microwave And Millimeter Wave Imaging
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