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  • Software Bugs in Space Environment

    Paper number

    IAC-04-IAA.4.9.P.01

    Author

    Mr. Fabio Sebastiano, Italy

    Year

    2004

    Abstract

    The aim of this paper is to present the numerical rebuilding results and procedure of the in-flight experiment of the CIRA Unmanned Space Vehicle USV carried out during the first mission DTFT (Dropped Transonic Flight Test). USV is a multi-mission, re-usable vehicle developed at CIRA, the Italian Aerospace Research Centre, and it is funded by the Italian National Aerospace Research Program (PRORA). It is basically a slender, not-propelled, winged vehicle able to perform experiments on Aerodynamics, Structure and Materials, Autonomous Guidance Navigation and Control. The first mission was performed at the end of February 2007, and it was aimed at experimenting the transonic flight of a re-entry vehicle. The aerodynamic characterization of the transonic segment of a re-entry space vehicle trajectory is made difficult by the strong variability of the aerodynamic coefficients mainly due to non linearity of the flow field. In this framework it is really important to correctly predict the aerodynamic performance of the vehicle by means of suitably developed numerical/theoretical tools. One of the aims of the aerodynamic experiment is the validation and improvement of the prediction tools (CFD, extrapolation to flight) through the comparison between pre-flight predictions and in-flight measured data. Both global aerodynamic coefficients (inertial measurements) and local quantities (pressure measurements) have been acquired during the flight. In order to compare local pressure distributions some selected flight conditions occurred during the DTFT mission will be numerically rebuilt aimed at reproducing the most relevant fluid dynamic phenomena characterizing the USV vehicle aerodynamics. The numerical methodology is based on both eulerian and viscous CFD computations, carried out by means of the CIRA code H3NS, a RANS multiblock finite volume solver, implementing a Flux Difference Splitting second order numerical scheme. The k-ε Myong-Kasagi turbulence modeling has been used for the turbulent simulations. CFD simulations can allow the computation of both global coefficients and local pressure distributions, and therefore the comparison with the in-flight acquired pressure measurements. The analysis of numerically rebuilt flight conditions will allow the assessment of local non linear phenomenologies, such as separation induced by shock waves and flap deflection and the high sensitivity of shock position with the Mach number, as well as a better understanding of the global aerodynamic coefficients trends in function of both Mach number and angle of attack. Moreover, depending on the analysis of the numerical results and the comparison with the flight data, an assessment of the entire CFD methodology (grid generation, turbulence and transition modelling, etc.) will be carried out. The analysis of the local measurements of pressure at different altitude (high and low branch of the trajectory), and the comparison with the CFD data, will allow for a deeper understanding of the Reynolds number effects with the aim at improving the extrapolation-to-flight procedure.

    Abstract document

    IAC-04-IAA.4.9.P.01.pdf