Base flow predictions for a lightsat launcher at supersonic speeds

A numerical investigation of the base flowfield past a lightsat launcher un der development in Italy is presented. The analysis regards different point s along the flight path in the supersonic regime under axisymmetric conditi ons and has been focused on the base region of the missile with the aim to investigate the influence of different motor nozzle exit conditions (motor- on and motor-off) and different motor fluid properties (air/combustion prod ucts) on the base drag. This activity has been performed using both a Centr o Italiano Ricerche Aerospaziali code and the RAMPANT commercial code. A ge neral satisfactory agreement between the two codes is observed in the globa l aerodynamic coefficients; however, predicted local base pressures show so me differences, probably due to the different turbulence models and differe nt numerical methods employed. The numerical results indicate that, in the supersonic flight regime, the base region is only slightly affected by diff erent fluids and motor conditions at the nozzle exit.