Comparison and data analysis of the exhaust plumes of Athena II and Vega

Abstract

The rocket exhaust plume computed with the method of characteristics (MOC) was compared with CFD calculations for Athena II (18.7 km) and Vega (18.7, 30 and 42 km) launchers. The Mach number values obtained with the MOC are lower than the values from the CFD computation with gas only. When compared with CFD data that includes large particles the situation reverses. In the first case, the temperature values produced by the MOC are larger than the values from the CFD while in the second case they are similar. Pressure values fit well in both cases. The influence of the input parameters, ambient and nozzle exit conditions, on the main thermodynamic quantities and the shape of the plume is presented. Afterburning processes occur as the exhaust species mix with the surrounding air. The OH mass fraction can be used as a tracer for this process. Afterburning is less likely to occur with increasing altitude. A study on Vega CFD data revealed other compounds and parameters that have a similar behavior to OH. These are the concentrations of CO2, Cl and O as well as the temperature. The species in the afterburning zones of the CFD computation where compared to CEA calculations. The sum of all species which have the same order of magnitude as in the CFD account for more than 95%.