High Fidelity CT Imaging of High-Z Materials for Rocket Motor Aging Detection

Propellant aging in solid rocket motors can result in various defects such as micro-cracks, fissuring, and abnormal density variations. These defects can lead to abnormal burn rates and unsafe operations of the motor. Nondestructive inspection of solid rocket motors is critical in monitoring solid rocket motors integrity. High energy gamma-ray CT is a nondestructive inspection method to evaluate structural integrity of a rocket motor. Various artifacts in the reconstructed image due to high-Z beam hardening and scattering can hinder the detection of defects and subtle changes over time due to aging. In Phase I high fidelity Monte Carlo simulation of gamma-ray interaction and transport through solid rocket motors was proposed to characterize such artifacts. New high-Z beam hardening and scatter mitigation algorithms based on the simulation were formulated and applied to projected CT data. In Phase II, this research will be extended to realistic imaging instrumentation and rocket motor models. Required calibration measurements will be performed to specify Monte Carlo inputs. Model-independent and dependent beam hardening and scattering corrections will be derived and verified with real data reconstructions. The fidelity of high resolution artifact corrected image reconstruction will be verified with full Monte Carlo simulation.