Description: In order to mitigate risk to equipment and crew, NASA needs nondestructive evaluation (NDE) techniques and sensors that are capable of detecting holes, pits, cracks, and corrosion of structures that are not visually accessible. The Independent Assessment of Instrument for ISS On-Orbit NDE highlights the challenges and importance of performing NDE of the international space station (ISS) pressure walls. These walls are subject to impacts from space debris and micrometeroids, causing punctures in the walls, which are then patched with pressure wall repair kits (PWRKs). Commercially available NDE tools are unable to meet all the requirements of scanning through PWRK patches to assess the nature of the covered defects. EHT has developed an innovative NDE tool that is able to circumvent the usual limitations of eddy-current based NDE. The EHT NDE tool generates eddy currents by physically moving a permanent magnet over a sample made of a conductive material. The magnetic perturbation caused by passing over non-uniform regions of the sample under test is picked up by an inductive coil. EHT's High Gain Integrator technology is capable of measuring the small signals produced. Using this tool, EHT has demonstrated increased scanning depth compared to other NDE tools, up to 1/4" depth, already thicker than ISS walls. A through hole defect under a PWRK patch has been successfully imaged. Throughout the Phase II, the sensitivity and spatial resolution of the NDE tool will continue to be improved and a standalone system developed. EHT's NDE tool will be specifically engineered to meet NASA's on-orbit NDE needs, including for the ISS application and for other applications of interest such as Composite Overwrapped Pressure Vessels (COPVs).

Benefits: NASA is the primary customer for EHT's NDE tool. The application that has been specifically targeted is on-orbit NDE of ISS pressure walls. Additional applications include the inspection of Composite Overwrapped Pressure Vessels (COPVs). The system also has the potential to be built into structures for in situ evaluation. A handheld version of the NDE tool could be used by ground personnel, spacecraft crew, or automated robots to evaluate structures for subsurface defects.

NDE techniques are used in a range of commercial applications where material quality and adequate structural condition must be ensured. Applications include evaluation of aging commercial and military aircraft. EHT's ability to print small, flexible magnetic probes could enable the NDE tool to be used in hard to access locations like piping and tubing. Another application is pressure vessels.