This book was written to students and engineers that like the Computational Fluid Dynamics (CFD) area; in other words, that like of programming algorithms to the resolution of physical problems. Some familiarity with code programming is required. The applications of this book aim aerospace problems. This book presents the chemical and thermochemical non-equilibrium conditions applied to Earth reentry and Mars entry flows. The five and seven species chemical models for the Earth reentry are implemented according to the law of mass action and Arrehnius formula. Moreover, vibrational contribution is also taken into account. The transport properties are calculated by the use of collision integral techniques. The nine species chemical model for the Mars entry uses the Wilke formula to obtain the transport properties. Vibrational contribution also takes into account Millikhan and White formula and Park’s correction above 8,000 K. Two and three-dimensional spaces are considered. The Van Leer and Liou and Steffen Jr. schemes are employed. Good results are obtained in both studies. A finite volume formulation and structured and unstructured spatial discretizations are employed.