Technology and Applications of Terahertz Imaging Non-Destructive Examination: Inspection of Space Shuttle Sprayed On Foam Insulation

The implementation of terahertz (THz) imaging for non‐destructive evaluation shows great promise in 2 and 3 dimensional non‐contact inspection of non‐conductive materials such as plastics, foam, composites, ceramics, paper, wood and glass. THz imaging employs safe low power non‐ionizing electromagnetic pulses, which produce images with lateral resolution <200 microns, and depth resolution <50 microns. We demonstrate the detection of voids and disbonds intentionally incorporated within the sprayed on foam insulation of a space shuttle external tank mock‐up segment using time domain THz imaging. Recently, highly integrated turn‐key THz imaging systems have been introduced commercially. An industrially hardened THz scanning system which has been deployed to scan the space shuttle tank with small remote THz transceiver on a 30 meter fiber optic umbilical, is described.