Evaluation of the interest of a New Propulsion Concept for an Upper Stage of Future Launchers

The Inner Arch developed several softwares: One dedicated to solid propulsion projects APSOL One dedicated to liquid propulsion projects ELlS A third one, PERFOL, is used to optimize the trajectory and the propulsion parameters The paper will describe the main software used for this study and illustrate the interest of these tools to make the first design of a new version of a launch vehicle with optimization both of intrinsic propulsion parameters and of the trajectory The project, illustrating this approach, will be to replace the 3rd and the 4th stage of the European Launcher VEGA (replacement of Z9 and Avum) by an unique re-ignitable LOX/Methane Upper Stage A pressure-fed system is leading to a stage easy to operate, reliable, needing no costly solutions (Expander engine, Boost pumps) On another hand, many R&D programs are going on all ceramic liquid engines, engines cooled by effusion (DLR), Transpiration ( PT AH-SOCAR from MBDA), Film or Trim (Astrium, Snecma), so very light engine may be offered on the market in a close future Operating to relatively low pressure the specific impulse is slightly lower than a conventional one with a turbomachine (expander type or other) and the structural index lightly less interesting: a concept with the LOX tank nested inside the fuel tank with a scrolling common bulkhead appears easily usable for LOX Methane stage due to the fact that the 2 propellants are liquids in the same range of temperature and may lead to an interesting mass saving Even if such an upper stage may lead to a dramatic increase of the performance of a small launch vehicle such as Vega, the aim of this presentation is mainly to show the interest of special tools to make the very first evaluation of the interest of a new solution