Researchers Find That Rocket Exhaust Pollution Remains in the Earth's Atmosphere for an Uncomfortably Long Period of Time

 Scientists have been able to examine the air emissions from rockets by modelling the fluid dynamics of rocket exhaust gases.

Reusable space technology have gained popularity as a way to achieve space transportation at a lower cost because to commercial spaceflights conducted by companies like SpaceX and Virgin Galactic. However, little is known about how much heating and chemical alterations the propulsion emissions from rockets create in the atmosphere.

By examining the heat and mass transfer and the fast mixing of the combustion byproducts for altitudes up to 67 kilometers into the atmosphere, researchers from the University of Nicosia in Cyprus analyzed the possible consequences of a rocket launch on air pollution. On May 17, 2022, AIP Publishing published their research in Physics of Fluids.

Co-author Dimitris Drikakis stated, "Improved knowledge of rocket emissions needs modeling and simulation of fluid dynamics of rocket exhaust gases into the atmosphere.

The scientists created plumes at various altitudes along the average trajectory of a conventional modern rocket by modeling the exhaust gases. They did this as a model for a two-stage rocket that might carry passengers and cargo into orbit around the Earth and beyond.

According to co-author Ioannis Kokkinakis, "we demonstrate that rocket pollution should not be underestimated since frequent future rocket launches might have a major cumulative influence on the Earth's climate."

The researchers discovered that the production of thermal nitrogen oxides (NOx), which are combustion exhaust components, can continue to be high up to altitudes where the ambient atmospheric pressure is above or even just slightly below the nozzles' exit pressure, or below an altitude of about 10 km.

As the rocket ascends 1 kilometer in altitude, the amount of carbon dioxide it emits is equivalent to 26 cubic kilometers of atmospheric air at that same altitude. The mesosphere is the region of the atmosphere between the thermosphere and the stratosphere, and it is located at an altitude of 30-50 miles or 50-80 kilometers.

They discovered that the mesosphere may have a considerable influence locally and briefly on the atmosphere. The time frame during which this occurs is unclear, but air currents will ultimately spread and mix the exhaust CO2 throughout the atmosphere, bringing it back down to its naturally occurring levels.

The researchers think there may still be a threshold of rocket launches at which mesospheric carbon dioxide may build up over time and alter our climate by raising naturally occurring levels.

According to their findings, in the worst-case scenario, enough NOx could be produced in the time it takes a rocket to travel up to an altitude of 10 kilometers to contaminate more than 2 cubic kilometers of atmospheric air with a level of NOx concentration that would be dangerous to human health, according to the World Health Organization.

We expect that commercial aerospace firms like SpaceX, Virgin Galactic, and the New Shepard, as well as the accompanying engine suppliers, would take these impacts into account in upcoming designs.