Description: To address NASA's need for evaluation of bondline and in-depth integrity for lightweight rigid and/or flexible ablative materials, Physical Optics Corporation (POC) proposes to develop a novel Thermal Protection System Nondestructive Evaluation Tool (TERRET) providing accurate in situ detection, identification, and spatial localization of internal and surface defects (cracks, voids, delaminations, porosity, and inclusions), and evaluation of bondlines and in-depth integrity of lightweight, rigid, and/or flexible ablative materials and large-area multilayer thermal protection system (TPS) structures with complex geometries. TERRET is based on the POC-patented innovative X-ray Compton imaging tomography technique and POC-patented apodized aperture X-ray imaging optics with high spatial resolution and a wide field of view, substantially modified and optimized to meet NASA's requirements for operation on a wide range of lightweight TPS materials, noncontact operation, portability, and ease of use. TERRET will provide detection and spatial localization of defects and damage in TPS material and structures, with spatial resolution of ~1 mm and sensitivity of 1% in material density difference. In Phase I POC will demonstrate the feasibility of TERRET for NDE of TPS by fabricating and testing a TRL-4 prototype, with the goal of achieving TRL-6 by the end of Phase II.

Benefits: The primary NASA application of the proposed TERRET is a compact NDE system that can be used for in situ evaluation of structural integrity of TPS spacecraft material and structures, with the capabilities of accurate detection, identification, and spatial localization of internal and surface defects (cracks, voids, delaminations, porosity, and inclusions), and evaluation of bondlines and in-depth integrity of lightweight, rigid, and/or flexible ablative materials and large-area multilayer TPS structures with complex geometries. Additional NASA applications include in situ NDE/NDT of large-area nonuniform multilayer aluminum/titanium/composite structures with complicated geometry used in the development of advanced aircraft and spacecraft, providing accurate identification, localization, and measurements of all types of internal and surface defects.

Military applications of TERRET will include in situ NDE/NDT of U.S. Air Force, Navy, and Army military aircraft large-area, nonuniform, multilayer, aluminum/titanium/composite structures with complex geometry, and also combined polymeric, ceramic, and metal matrix composite structures. TERRET-based systems (with minimum modifications of TERRET) will also be used for NDE/NDT of airplane, helicopter, and missile parts containing electronics, mechanical components, propellants, explosives, etc., to detect defects and integrity. TERRET-based systems can be incorporated by the U.S. Air Force, Navy, and Army as a reliable, rapid, robotic, easy-to-use NDE/NDT system. Potential DHS applications include the detection of vehicle-borne contraband, drugs, and explosives. The commercial applicability of TERRET includes its use for in situ NDE/NDT of large-area nonuniform multilayer aluminum/titanium/composite structures with complex geometry in aging and modern commercial aircraft, spacecraft, light marine vessels, and any application requiring defect detection for multilayer ceramic, composite, metallic, and plastic nonuniform structures.