Fragmentation models for bombs, hand grenades and projectile perforation of target plates are considered. Previous models are normally, but not always, designed so that mass conservation is achieved, whereas energy conservation appears not to be accounted for. Simple energy considerations indicate that the number of fragments may be expressed via "understandable" parameters, old as well as new. The new parameters are non-dimensional, whereas established parameters, such as the elastic modulus, account for the dimensions in the relations that are suggested. It remains to investigate if the suggested theoretical model describes experimental results in an acceptable manner. The goal is to obtain a simple and reliable model for use in large computer programs for assessment of effects and vulnerability of complex targets. In this particular connection the focus is on BAD (Behind Armour Debris), which is detached from the rear surface of a target plate that is perforated by a projectile or a Shaped Charge jet.