A new reference dataset accounts for different engine cycles, propellants and fuel-cooling practices when estimating emissions at the nozzle exit.
The dataset uses a consistent 2200-kilonewton thrust baseline to describe emissions from major cryogenic propellants, a hypergolic propellant combination and a solid rocket motor. For liquid-fueled engines, it compares closed-cycle engines, which burn turbine-driving gases in the main chamber, with open-cycle engines that release those gases separately.
The study also examines fuel film cooling, an approach in which part of the fuel flow is used to cool the engine and modeled at a fuel-rich mixture. The resulting datasets are compared with existing inventories and are intended to give atmospheric and climate models more detailed information about rocket exhaust.
How engine choices affect emissions
The researchers modeled primary rocket emissions up to the nozzle exit plane using equilibrium combustion calculations at realistic oxidizer-to-fuel ratios. They included major cryogenic propellants, one hypergolic combination and a solid rocket motor, all referenced to a 2200-kilonewton thrust class.
For liquid-propellant engines, the study evaluated both closed-cycle, or staged-combustion, designs and open-cycle, or gas-generator, designs. It found that the engine cycle affects predicted exhaust composition and that fuel film cooling also changes the estimated black carbon fraction. The researchers compared these new reference datasets with existing emissions inventories.
Why better inventories matter
Global launch inventories are used as inputs for studies of how spaceflight emissions may affect the atmosphere and climate. The abstract identifies simplified exhaust data as a major limitation because they do not represent the different chemical products and mass flows produced by different turbopump cycles.
By separating these engine designs and accounting for fuel film cooling, the dataset is intended to give future atmospheric and climate models a more consistent representation of rocket exhaust. It does not itself establish the overall climate effect of the space transportation sector.
What the modeling shows
This is a modeling study, not a report of direct exhaust measurements. The researchers used zero-dimensional equilibrium combustion calculations and modeled emissions only through the nozzle exit plane. The dataset covers selected propellant and engine categories around a common 2200-kilonewton thrust baseline, rather than every launch vehicle or operating condition.
Fuel film cooling was assessed with an exploratory method that models part of the total flow at a distinctly fuel-rich mixture. The abstract does not report direct experimental validation or a completed estimate of radiative forcing or climate impact; those questions remain for later atmospheric and climate modeling.
