Development of a thermodynamic model to calculate the plume of launchers and other transport vehicles

This personal work has taken place in the context of recent ESA’s studies which have focused the attention on the launchers plume trying to quantify the environmental effect of a launcher’s rise to orbit. For several years the assumption was made that European launchers are too small to really impact on the atmosphere but no results can confirm that hypothesis [18]. The main effect that a conventional rocket can have on the atmosphere is the ozone depletion and for that reason recent studies have focused the attention on the layer of the atmosphere where the concentration of ozone is maximal: the range of 15-50 Km of altitude. As a result of the many problems associated with highly under-expanded nozzles, the main intention of this thesis was to write a fast computer program as an alternative to the high computational costs of the CFD, able to model as accurately as possible the exhausted jet properties and estimate the effect of the afterburning that characterize the main launchers vehicles in the range of a specified altitude. The model of reference used to determine the thermodynamic properties of the plume is the “Method of Characteristics” already used in the 70’s years to describe the flow expansion of spacecrafts and implemented by Allen R. Vick, Earl H. Andrews, John S. Dennard, Charlotte B. Craidon in their work “Comparison of experimental free-jet boundaries with theoretical results obtained with the method of characteristics”. The chemical reactions which develop outside the nozzle have instead been evaluated by C.E.A. “chemica equilibrium with applications”, a software which is executed with the help of Matlab and receives as input some parameters previously evaluated with the method of characteristics To validate the engineering model, a series of comparison have been made with the CFD results obtained with the Athena II rocket at the altitude of 18.7 km when the castor 120 second stage is operating.