Development and assessment of space launch and re-entry emission inventories for atmospheric modelling

The space sector has experienced significant growth in recent years, with rocket launch rates increasing by over 20% since 2019. In its 2022 Scientific Assessment of Ozone Depletion the World Meteorological Organization cautions that future increases in launch rates, the adoption of new propellants like hydrogen and methane, and emissions from reentering objects could significantly influence future ozone levels . Therefore, the creation and evaluation of emission inventories of space activities, which can be used in atmospheric chemistry modelling, is of particular importance. Here we present two open-source tools developed at the University of Stuttgart. 1) Launch Emission Assessment Tool (LEAT), and 2) Re-entry Emission Assessment Tool (REAT), and discuss the underlying models and assumptions. Furthermore, we compare results obtained with LEAT to previously published emission inventories.

LEAT enables the calculation of a launch trajectory based on basic launcher data and calculates emissions such as CO, H2O and NO either using emission indices or by calculating the engine and afterburning emissions. The model accounts for the different flight states and environmental conditions based on a chemical equilibrium model. This makes it possible to distinguish between emissions stemming from different fuel systems and those from different flight paths.

REAT enables the calculation of emissions from re-entering objects. The interaction with the atmosphere is simulated using emission indices or a chemical equilibrium model depending on atmospheric conditions.

Both tools enable us to create detailed high-resolution 3-D emission inventories, which can readily be used in chemistry-climate models in order to assess the atmospheric and climatic effects of launcher and re-entry emissions. Furthermore, by using existing emission inventories a comparison can be made with literature. We also assess and discuss underlying model assumptions and parameter and model uncertainties as well as measures required to reduce uncertainties related to the emission inventories.