Estimation of location of defects in propellant grain by X-ray radiography

Defects in rocket propellant grain can create catastrophic effects and the purpose of the mission may get defeated. This necessitates the need to locate the defects in the rocket propellant in order to decide its efficacy. In the absence of suitable tomography systems, there is a need to devise a method to estimate the location of the defect through conventional radiography techniques. This paper describes a 2D geometrical method for location of defects. This method has been found very useful for analysis of defects lying near the port of large-size propellant grain/motor. In this method, two radiographic images at two orientations are used to estimate the location of defects in the propellant grain in plane polar co-ordinate with a reference. The experiments were conducted to evaluate (r,θ) of the known points of lead letters, fixed on the propellant grain. The dimensions of the letters were computed from (r,θ) values of the two corners and there is close agreement with respect to the actual dimensions confirming the applicability of the method for estimation of the location of the defect.