An Onera figure created using Cedre

What about ozone?

1. Why is it important to assess the impact of launchers on the atmosphere?

The interesting thing about launchers plumes is that they are the only man-made direct  emission at high altitudes. No other anthropogenic activities can directly emit chlorine or alumina directly into the ozone layer. To understand better the implications of these emissions we must conduct a thorough investigation of the chemical and radiative interaction of these plume emissions with the equilibrium atmosphere.

2. Has a study to understand the impact of launchers on the atmosphere ever been done before?

Yes and No. There have been many ground breaking studies by the Americans looking at the impact of plumes on the area immediately around the plume using numerical simulations and also they have undertaken flight campaigns where they flew through the plume and measured important data such as alumina size and chemical composition. All these studies have been invaluable contributions to our understanding of plume impact but thus-far nobody has conducted a study that incorporates the near plume region into a global climate model to see the far-ranging and long-term effects. This is unique to the ESA Clean Space studies.

3. How do you plan to assess the impacts of launchers on ozone?

We will use a number of computational codes to assess the creation and development of the plume. This involves computing the combustion process in the engine followed by the spatial development and propagation of the plume in the atmosphere. Once this is completed we must insert the plume into climate models to assess the final impact at a global scale. The major complication in this process is due to the fact that the plumes are relatively small and the computational grid of climate models are relatively large. We need to introduce the plume into the climate models carefully if we are to accurately capture the non-linear chemical reactions that take place. 

The 'ozone hole' is shown in dark blue, measured on November 1, 2011

4. Do you already know some of the impacts?

It is generally assumed that although plumes destroy all ozone in the immediate area where the plume is emitted, the impact of plumes on global ozone levels is negligible. The objective of these studies currently being funded by ESA is to evaluate this assumption.

CERFACS model simulations

5. What are plumes composed of?

Plumes are composed of the products of combustion. The plumes of the Ariane 5 and Vega solid rocket motors contain almost one-third alumina particulate and substantial amounts of hydrogen chloride and Carbon Monoxide. Chlorine and Carbon Dioxide exist in smaller quantities initially but processes that occur when the plume interacts with the external atmosphere such as afterburning can convert HCl to Chlorine.  The liquid main stage of Ariane 5 on the other hand has a plume that is almost entirely composed of water.

Last update: 29 January 2014

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