This paper deals with a problem of trajectory optimization of the flight phases of a three-stage launcher. The aim of this optimization problem is to minimize the consumption of ergols that is need to steer the launcher from the Earth to the GEO. Here we use a global optimization procedure based on Hamilton-Jacobi-Bellman approach and consider a complete model including the transfer from the GTO to the GEO orbit. The Hamilton-Jacobi approach proposed here takes also into account parametric optimisation that appears in the flight phases. The work presented in this paper has been performed in the frame of CNES Launchers' Research and Technology program