Digital radiography-based 3D-CT imaging for the NDE of solid rocket propellant systems

The application of digital radiography for the non-destructive evaluation (NDE) of space vehicle components is a recent development. A flat-panel detector-based real-time digital radiography system has been established for the NDE of solid rocket motors and space vehicle components. This system is upgraded for CT imaging by integrating a computerised object manipulator and suitable software to capture the two-dimensional projection data in real-time mode and reconstruction of CT images. The system consists of a Flat Panel Detector (FPD), mini-focus X-ray machine, computerised four-axis object manipulator and data retrieval and processing software. The two-dimensional image recording capability of FPD is utilised in this work for multiple CT reconstruction using the cone beam X-ray set-up. Studies are also carried out to generate a 3D-CT image from a set of adjacent CT images. The capability of revealing the spatial location and characterisation of defects is demonstrated by the CT and 3D-CT images generated for a solid propellant grain and rocket motor. The analysis carried out with CT and 3D-CT images of the solid propellant grain revealed the presence of more defects than are detected by digital radiography. The CT analysis exposed the criticality of defects in the propellant grain with respect to location, dimension and nature of defect.