In summer 2005, based upon the DMAs validated experience on the ignition transient of solid propellant rockets simulation and analysis, a brand new solution to control pressure oscillations at ignition was proposed for the solid rocket motors of the new VEGA Launcher of the European Space Agency. This solution, based upon the utilization of Helium instead of Nitrogen as a chamber pressuring gas, was presented and discussed for the first time during the JPC in Tucson (AIAA-2005-4165) and in Sacramento (AIAA-2006-5277); in particular in these articles the Zefiro9 and the Zefiro16 motors have been analysed. In the present article we have studied with details the Zefiro23 and the P80 motors, and extended the analysis of the Zefiro9. Numerical predictions and analysis of internal ballistics, experimental data measured in the firing tests and dynamics analysis are presented, focusing the attention of the pressuring gas effects on the induced pressure oscillations and structures loads. A detailed analysis of the numerical simulations are presented, comparing the calculated results with experimental measurement.