A hybrid system to simulate the atmospheric dispersion of rocket exhaust clouds

Abstract

Rocket exhaust clouds are composed by hazardous pollutants, e.g. alumina, carbon monoxide and dioxide, and hydrogen chloride, which are generated during the burning of rocket engines. In the case of vehicle launching, huge and hot clouds are generated near the ground level and are composed by the buoyant exhaust products, which will rise, expand, stabilize, entrain the ambient air, and they will start to be dispersed according to the atmospheric conditions. This process takes a couple of minutes to occur, and generally human receptors located in populated areas nearby the launching center may be exposed to high levels of concentrations within a few to tens of minutes, up to less than one hour. Also, these pollutants may be carried farther due atmospheric dispersion, and chemically interact with other atmospheric compounds, forming new pollutants, impacting other populated areas located in farther distances. The launch centers around the globe, like spaceports, need to operationally assess the impact of rocket launchings events in the environment, requiring to evaluate both short and long range impacts prior to launchings through meteorological and air quality modeling. In general, however, air quality models do not account for calculating peak and average concentration for a short time scale, i.e. ranging from minutes to one hour. In addition, there is the fact that modeling rocket exhaust clouds formed due rocket/vehicle launching is quite a unique air quality problem. For this purpose, this work chose to use a modern air quality model which targets this problem, named MSDEF. For long range assessment, it has been chosen the CMAQ modeling system, since it represents the state-ofthe- art in regional and chemical transport air quality modeling, and due to its capability to deal with chlorine gases – which is a considerable part of rocket exhaust clouds. In order to couple both models, the MSDEF code has been rewritten using the I/O API library, making it possible for MSDEF to generate the initial conditions as input to CMAQ model. Thus, it forms the basis for a hybrid, modern and multidisciplinary system which, in conjunction with the WRF model, can be operationally used in different launching missions for a complete environmental assessment.