Reference datasets of primary rocket engine emissions for global launch inventories

Abstract

Abstract Research on the radiative forcing and climate impact of emissions from the space transportation sector remains in its early stages. A critical component of advancing this field is the development of accurate global emission inventories, which depend fundamentally on the precise characterization of rocket engine exhaust products. One major current limitation is the reliance on simplified exhaust datasets that fail to capture the chemical and mass flow complexities introduced by different engine turbopump cycles. To address this gap, this study establishes a comprehensive new reference dataset of primary rocket engine emissions (modeled up to the nozzle exit plane). The dataset is anchored by a consistent 2200 kN thrust-class baseline, encompassing major cryogenic propellants, a hypergolic combination, and a solid rocket motor. For liquid propellant systems, both closed cycle (staged combustion) and open-cycle (gas generator) architectures are evaluated. Additionally, an exploratory methodology is introduced to assess the impacts of fuel film cooling by modeling a fraction of the total mass flow at a distinctly fuel-rich oxidizer-to-fuel ratio. Both the specific engine cycle and the implementation of film cooling are demonstrated to be critical factors in predicting black carbon exhaust fractions. Finally, these newly established reference datasets are compared against existing inventories. By employing 0D equilibrium combustion calculations at realistic oxidizer-to-fuel ratios and explicitly accounting for the distinct mass flows of different turbopump cycles, this study provides a highly consistent exhaust dataset to improve the fidelity of future atmospheric and climate models.