EVALUATING SOME AERODYNAMIC PARAMETERS OF THE FLIGHT TEST BED (FTB-X) IN HIGH ALTITUDE FLIGHT

Some aerodynamic parameters of the FTB (Flight Test Bed) vehicle, designed at CIRA in the frame of the program named PRORA, have been evaluated in the intervals of altitude from 100 to 120 km and angle of attack from –10 to 40 deg., in symmetric flow and clean configuration. Due to the failure of the Navier-Stokes equations to solve the flow field in rarefied regimes, the computation relied on a Direct Simulation Monte Carlo (DSMC) code. As the aim of the work is providing useful information for planning the mission tagged SRT (Sub-orbital Reentry Test), the analysis focused on global aerodynamic coefficients (lift, drag and moment) and local quantities (heat flux and stress) on the most exposed surfaces (i.e. nose and leading edges of the wing and of the rudder). These parts will be made of Ultra High Temperature Ceramic (UHTC) material, thus the combined effect of heat flux and stress could be critical for their integrity and therefore for the safety of the vehicle. The present results showed that: the maximum value of the lift to drag ratio, meet at an altitude of 100 km and at an angle of attack of 30 deg. is 0.6, the maximum values of heat flux and stress on the nose are 2656 W/m2 and 3.3 N/m2, on the leading edges of the wing are 1891 W/m2 and 2.4 N/m2, of the rudder are 1600 W/m2 and 2.1 N/m2. The lift to drag ratio is much lower than the one predicted by means of Euler calculation (2.5), putting in evidence the unacceptability of Euler calculation at these altitudes. Also the heat flux is considerably far from the target value of 650 kW/m2, expected from continuum calculation, at an altitude of about 25 km. Furthermore as the nose is the most loaded part of the vehicle, from a thermal and a mechanical point of view, detailed profiles of the heat flux and of the stress are provided along the windward surface in the range of angle of attack from 0 to 40 deg.