CFD simulations on aerodynamic descent phase of reusable vehicles with aerospike engines

Researchers and engineers active in the space industry operate not only with the aim of constantly improving the performance of the space vehicles, but they also strive to reduce the carbon footprint which has huge impact on the environment. Furthermore, the high level of quality should be guaranteed while keeping the total expenditure under control. A possible strategy that can be adopted to achieve the two previously mentioned objectives, reducing the carbon footprint and costs, is the transition from the expendable transportation systems to Reusable Launch Vehicles (RLVs). Nevertheless, the so far developed and fully operational RLVs are powered by bell nozzles which may not guarantee the best operating conditions neither during the ascent trajectory nor during the reentry maneuvers. The aerospike nozzle however may represent an alternative propulsion system able to overcome the potential limitations of the conventional engine, especially in the Supersonic Retro Propulsion (SRP) phase. Bearing this aspect in mind, a truncated annular aerospike nozzle with clustered chambers was designed with the aim of starting a research project to evaluate the possibility of deploying this technology in a future class of RLVs. This engine with its renewed baseplate has been integrated in the preexisting European launcher RETALT1, which represents the case study of this dissertation. The original RETALT1 vehicle, whose CAD was provided by the partners of the RETALT consortium, is equipped with nine conventional bell nozzles placed in an Octaweb layout. A comparative study of the two configurations (original and aerospike) focused on the unpowered atmospheric descent phase has been carried out through CFD simulations in Ansys Fluent and using the High Performance Computing (HPC) resources made available by Technische Universität Dresden. In particular, three trajectory points, in supersonic, transonic and subsonic regime, have been analyzed in order to achieve a complete aerodynamic characterisation of the two launchers versions. This paper will present and compare the simulated flow fields and the results in terms of aerodynamic and ballistic coefficients.