The Magneto-Fluid Dynamics has many aerospace applications when the gas is an ionized mixture. Typically, this happens when the temperature of the mixture is very high. Indeed, we need to consider new degrees of freedom of the molecules, the presence of the chemical reactions, and the possibility to have free electrons that can move from one point to another. This is the typical situation during a normal atmospheric entry problem. In this context, all the physical properties cannot be computed with the classical approximation laws. The Chapman-Enskong method gives us the possibility to perturb the Boltzman Transport Equation and to understand which are the different contributions (of electrons and heavy particles) to take into account.