Experiments dealing with impact of large structures, like ships and buses, are cost prohibitive. One possibility is to test scaled models, which unfortunately do not obey the scaling laws due to material strain rate sensitivity. A set of scaling numbers is here presented that allow perfect similarity between model and strain rate sensitive prototypes. It is shown how nonscaled models can be used to predict the prototype behavior. As a complement, it is commented on recent developments of new scaling laws that allow model and prototype with different densities to be directly compared.