Solid rocket motor consists of a rigid steel or fibre casing and rubber insulation is bonded to the inner surface. The propellant grain is bonded to the rubber insulation by an adhesive liner. Tangential radiography is used to detect debonds in case/insulation/propellent interfaces. Grain radiography is used to reveal the flaws like voids, cracks, porosity in propellant grain. This is similar to metal radiography, but application in the field of SRM's is complicated because of their large web thickness, low densities and non-uniformity of density of materials. Absence of acceptance standards further makes evaluation complicated.

Radiography of all the motors is carried out following an established exposure plan and a typical SRM of 2800 mm dia and 3200 mm length requires around 250 exposures. Modified triangulation technique is employed to find out voids zones. Microdensitometer is sometimes used to estimate the effective reduction in propellent due to presence of voids. These will give vital inputs for decision making. Above techniques form a part of defect evaluation process. In addition, real time radiography is also used with linac to get 100% coverage and to cut down expenditure by doing away with films.