Simulation and optimisation of atmospheric re-entry trajectories

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. The mathematical models consist in simulating the environment (i.e. atmosphere and gravity field), implementing the equations of motion and modelling the aerodynamic and aerothermodynamic phenomena that are generated during an atmospheric re-entry. To ensure its validity, the software has been used to simulate two different real missions, i.e. IXV by ESA and AS202 by NASA, and the results have been compared to the mission data. To understand how to implement a study of the re-entry corridor, an optimisation process has been considered; the results deriving from the trajectory optimisation with respect to different optimisation indexes revealed how the parameters of interest, such as structural and thermal stresses on the vehicle, starting orbit and deorbiting manoeuvre, affect the flight. Moreover, sensitivity and visibility analyses have been implemented for completeness, in order to have a single tool which gives as output all the most important information, related to the trajectory analysis, to define the re-entry mission. The results obtained with this thesis are based on assumptions with margin of improvement, first of all the refinement of the mathematical models, but provide a solid basis to develop the competences of flight dynamics needed for planning and operating re-entry missions.