According to European and American regulations, whenever a company is capable of bringing something into space, it has to provide data about the collective risk bounded to the operations. The total risk shall cover the entire mission, from launch to disposal, and the accepted value of risk is usually stated in a set of regulations and requirements according to multiple criteria (casualty risk, risk to critical assets, toxic risk). With this aim, the objective of the present thesis work is to develop and introduce a dedicated tool, called ORCA (On-ground Risk Casualty Assessment), capable of propagating the trajectory and evaluating the casualty risk at launch and at reentry, with a low computational cost.