My question is about the rocket aerodynamics. I'm getting in a course of CFD (computational fluid dynamics) in my university. We have to do a project for this quarter. And I thought in modelling (with Matlab) the supersonic aerodynamics of the Soyuz/ST rocket. I'm only going to test the leading fairing. I have made yet the mesh generation in Matlab (it took me a lot of time) with an elliptic generator. But now I'm analysing the on flight conditions of the free stream, at a height of 100km. I'm not sure if Navier Stokes equations are valid at such heights, where density is too small. If anybody has coursed aerospace studies, have you ever made something similar and with which equations?. I have read N-S equations are not valid for the re-entry of space vehicles due to the low density. If they are not valid, which equations are used?. I need some advice before proceeding further.