The interaction of the environment with a moving body is called "e;localized"e; if it has been found or assumed that the force or/and thermal influence of the environment on each body surface point is independent and can be determined by the local geometrical and kinematical characteristics of this point as well as by the parameters of the environment and body-environment interactions which are the same for the whole surface of contact.Such models are widespread in aerodynamics and gas dynamics, covering supersonic and hypersonic flows, and rarefied gas flows. They describe the influence of light on a body, and are used for modelling penetration of solids into metals and soils, etc.Localized Interaction Theory (LIT) studies various theoretical and applied problems using the most general description of the influence of the environment on the body. This makes it possible to integrate results obtained from different models and to create new universal methods that can be used for various conditions, even if the description of the real interaction model is unknown. Such a unified approach to the problems of analysis, calculation and optimization of the integral characteristics of bodies moving in different media is the main content of this book which is the first monograph on this subject. Many applications, chiefly in aerodynamics and space engineering are presented.