Early Plume Development and NOx Chemistry in LOx/H₂ and LOx/CH₄ Liquid Rocket Engines

Abstract

Projected rocket launch demand in the next 10 years predicts an order-of-magnitude increase in CO₂-equivalent gasses. Despite this expected increase in launch frequency, the on-Earth environmental impacts of off-Earth missions is still understudied, partially due to the lack of combustion and emissions data for these vehicles.

Existing rocket combustion and emission models do not account for altitude dependence on the formation of anthropogenic NOₓ from rocket engines, and has not been adequately evaluated. I accurately model rocket emissions’ altitude dependent chemical composition from 10 km to 40 km. Reaction chemistry in the combustion chamber, nozzle, and plume is modeled with a focus on the implications of NOₓ formation. Analysis of the combustion chamber, nozzle, and post-exhaust chemistry for the Space Shuttle Main Engine (SSME) and SpaceX Raptor Engine (SRE) is performed.

The resulting estimation of altitude dependent NOₓ formation in multiple vehicles can be used in global atmospheric models. In the future, results of this work will inform environmental harm reduction strategies and guidelines.