Understanding rocket emissions into the atmosphere by modeling the fluid dynamics of rocket exhaust

Reusable space technology has led to an increase in lower-cost space transportation, as popularized by commercial spaceflight from companies like SpaceX and Virgin Galactic. What is misunderstood, however, is the rocket propulsion emissions that create significant heating and compositional changes in the atmosphere.

In Fluid physicsby AIP Publishing, researchers from the University of Nicosia in Cyprus assessed the potential impact of a rocket launch on air pollution by studying heat and mass transfer and the rapid mixing of combustion by-products to altitudes of up to 67 kilometers in the atmosphere.

“A better understanding of rocket emissions requires modeling and simulation of the fluid dynamics of rocket exhaust in the atmosphere,” said co-author Dimitris Drikakis.

The team modeled the exhaust and developing plume at multiple altitudes along a trajectory typical of a current standard rocket. They made it as a prototypical example of a two-stage rocket to transport people and payloads to Earth orbit and beyond.

“We show that rocket pollution should not be underestimated because future frequent rocket launches could have a significant cumulative effect on Earth’s climate,” said co-author Ioannis Kokkinakis.

The researchers found that the production of thermal nitrogen oxides (NOx), components of combustion exhaust gases, can remain high up to altitudes with ambient atmospheric pressure above or even slightly below the pressure of outlet of the nozzles, that is, below an altitude of about 10 km. .

At the same time, the mass of carbon dioxide emitted when the rocket rises 1 kilometer in altitude in the mesosphere is equivalent to that contained in 26 cubic kilometers of atmospheric air at the same altitude.

They found that the impact on the atmosphere locally and momentarily in the mesosphere can be significant. As the air currents will gradually transport and mix the exhaust CO2 throughout the atmosphere, eventually bringing the CO2 drop back down to its natural levels, the time scale over which this occurs is unclear.

Scientists believe a number of rocket launches may still exist above which mesospheric carbon dioxide could build up over time, increasing natural levels and affecting our climate.

Their results suggest that in a worst-case scenario, enough NOx could be produced during the time it takes the rocket to reach an altitude of 10 kilometers to pollute more than 2 cubic kilometers of atmospheric air with a concentration of NOx that , according to the World Health organization, would be at a level dangerous to human health.

“We hope that commercial airlines, such as SpaceX, Virgin Galactic and New Shepard, and their associated engine manufacturers, will consider these effects in future designs,” Drikakis said.

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Material provided by American Institute of Physics. Note: Content may be edited for style and length.

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