Aerotecnica Missili & Spazio, The Journal of Aerospace Science, Technology and Systems Aerodynamic performance analysis of three different vehicle concepts ∗ A. Viviani a , G. Pezzella b a Second University of Naples via Roma, Aversa. Italy b Italian Aerospace Research Centre via Maiorise, Capua. Italy g.pezzella@cira.it Abstract The paper deals with the aerodynamic performance analysis of three reusable and unmanned flying laboratories designed to perform a return flight from low Earth orbit to provide experimental data in the framework of re-entry technologies. Several design approaches, ranging from low-order methods to computational fluid dynamics analyses, have been ad- dressed in this work. In particular, vehicles aerodynamic performances for a wide range of free stream flow conditions, from subsonic to hypersonic regime, including reacting and non-reacting flow and different angles of attack have been provided and in some cases compared. Computational fluid dynamics results confirm that real gas effects seem to be fundamental for the assessment of the concept aerodynamics, especially concerning pitching moment evaluation. 1. INTRODUCTION This paper deals with the aerodynamic performance analysis of three reusable and unmanned flying lab- oratories designed to perform an experimental flight return from low Earth orbit. Therefore, each vehicle concept belongs to the class of orbital re-entry vehicle (ORV) e.g., re-entry energy of the order of 25 MJ/kg. Indeed, concepts under investigation in the present research effort are conceived as flying test beds (FTB) that will re-enter the Earth’s atmosphere, thus allow- ing to perform a number of experiments on critical re-entry technologies. For example, the FTB may be useful to demonstrate maneuverability in the upper atmosphere, to test advanced thermo-structure con- cepts such as leading edges made of advanced ther- mal protection material (TPM), and to investigate the flowfield features during re-entry in order to vali- date numerical (e.g., CFD) and experimental predic- tion capabilities. In particular, the vehicle may pro- vide aerodynamic and aerothermodynamic flight data to correlate with ground test (e.g., the CIRA Plasma Wind Tunnel “Scirocco”) results, thus providing new insights into the understanding of complex aerother- modynamic phenomena occurring in flight and im- proving prediction methodologies and extrapolation to ∗ Based on paper presented at the XXII AIDAA National Congrex, September 2013 Naples, Italy 1 c AIDAA, Associazione Italiana di Aeronautica e Astronautica flight capabilities. Right now Europe has undertaken the development of three very different FTBs, namely ARD (Atmo- spheric Re-entry Demonstrator), EXPERT (European eXPErimental Re-entry Testbed), and IXV (Interme- diate eXperimental Vehicle). ARD was a scaled-down version of an NASA Apollo capsule. It was launched by ARIANE 5 V503 on Oc- tober 21, 1998. After a fully successful sub-orbital and re-entry flight, it was recovered in the Pacific Ocean [1]. ARD allowed Europe to assess the aero- dynamics of such a kind of capsule that still repre- sents a very attractive design solution for what con- cerns manned high energy re-entry (e.g., return from Mars/Moon missions). EXPERT, not yet flown, is a small sphere-cone FTB designed to perform several in-flight experiments, such as for example advanced thermal protection system (TPS), wall catalyticity, flow transition assessment and so on [2]. Finally, the Intermediate Experimental Vehicle, de- veloped by the European Space Agency (ESA), is a rather blunt FTB which features a lifting-body config- uration. It faced re-entry flight conditions on Febraury the twelfth 2015 at the end of a sub-orbital flight char- acterized by an energy level very close to that of an orbital re-entry (e.g., 25 MJ/kg) [3]. IXV allowed to address several in-flight experiments like GN&C of a flapped aeroshape, TPS catalyticity, and etc. The 16