correction. Propulsion system tankages operate for a mission life of over 10 years; under severe environment of low gravity, extreme temperature variation, leading to pressure cycling and corrosive action of propellant fluids. These tankages are designed based on fracture mechanics principles; so as to provide least inert mass. The quality control techniques must ensure that the tankages are free from defects which may grow during operation leading to catastrophic failure. Non- destructive inspection (NDI) in the form of intermediate checks, standard inspection and specialised inspection are carried out during various stages of manufacture of these tankages.

In this paper the NDI test philosophy, acceptance criteria are discussed. For obvious reasons, a number of NDI techniques namely X-radiography, visual, dye/fluorescent penetrant, ultrasonic, holographic, eddy current and proof pressure tests are employed. Salient features of applications of these techniques and our experiences in standardising them are discussed in brief. Our excitements in the application of X-ray techniques in characterising the defects viz, modified triangulation technique, evaluation of scatter factor for titanium alloy Ti6Al4V and reliability analysis of detection of lack of fusion in electron beam weldment (EBW) inspection are discussed. A new application of X-rays as an alignment tool during blind EBW of buttons is also discussed in this paper.

Defect characterisation based on X-ray techniques and ultrasonic techniques are found to agree validating the characterising techniques.