The thermal management of air-breathing vehicles presents formidable challenges. The high dynamic pressure flight trajectories, the necessity of reducing the aerodynamic drag, the extended flight duration time and the need for a reusable Thermal Protection System (TPS) are stringent requirements. The work presented in this paper is focused on transpiration cooling and investigates the effects of fluid injection into the hypersonic laminar boundary layers. In particular, a simulation model, which is composed of a coupled solution of Self-Similar Method (SSM) and a Difference-Differential Method (DDM), is introduced to study the transpiration cooling along a flat plate. The reduced order code is intended to assess the boundary layer characteristics and will serve as a research tool for the design and analysis of future experimental investigations in the UTA's 2MW arc-heated facility that has been modified and is currently in use for TPS studies. The DDM solves a system of coupled algebraic and Partial Differential Equations (PDE) for the case of Pr=1 and Le=1. Self-Similar solutions are considered in order to compare the code results for the case without transpiration.