Quantifying the atmospheric and climatic effects of reusable, hydrogen-fueled rocket launches

Rocket launches emit climate-relevant gases and particles in the atmosphere. Although rocket launches are transient and local emission sources, long lifetimes within the upper atmosphere allow the emitted gases and particles to accumulate. This potentially causes a significant climate impact in the future with an expected increasing frequency of launches, e.g. for installation of mega-constellations. The German Aerospace Center (DLR) has launched the S3D-BETTER project in 2026. One of the aims of the project is to assess the potential atmospheric and climatic effects caused by gases and particles emitted from future rocket launches or created in its aftermath via reaction with ambient gases. An exhaust inventory based on hydrogen-fueled reusable launch vehicles from the European Next Reusable Ariane (ENTRAIN) study is used as a case study. The inventory has been developed by DLR and includes eight exhaust species. The atmospheric and radiative effects are calculated for the ENTRAIN rocket launches by using the European Center HAMburg general circulation model (ECHAM) and Modular Earth Submodel System (MESSy) Atmospheric Chemistry (EMAC) model. Our simulations provide initial results on atmospheric effects of those rocket launches, particularly focusing on stratospheric ozone changes, and examine the radiative forcing caused by those rocket launches. Remaining challenges for climate-modelling and for future research is also discussed.