Atmospheric re-entry is related to different aspects of the space sector, such as the return of astronauts to Earth, the exploration of other planets with landers and rovers or the demise of satellites at the end of their life. All these scenarios are characterised by specific requirements for their trajectory, which strongly influences the design of spacecrafts. This thesis describes the development of a tool focused on the preliminary design and analysis of re-entry corridors for manned and unmanned vehicles. The tool has been created with Matlab, adopting an object-oriented programming, implementing different mathematical models and using algorithms already provided by Matlab, such as ode45 and fmincon.