Upper air pollution from rocket exhaust could affect Earth’s climate

A new research demonstrates how air pollution from rocket launches travels through the stratosphere, potentially triggering harmful heat at previously unpolluted altitudes.

A group of researchers from the University of Nicosia in Cyprus investigated how pollution, such as carbon dioxide and soot, travels through the air when a rocket ascends through the atmosphere.

The scientists discovered that the concentrations of various contaminants in the mesosphere (a layer of the atmosphere between 50 and 80 kilometers altitude) stay dangerously high for a long period after each launch. The major climatic gas, carbon dioxide, is one of these pollutants, and scientists are concerned because local warming of the upper atmosphere might have far-reaching consequences on the Earth's climate.

The researchers used data from one of today's most popular rockets, SpaceX's Falcon 9, which uses RP1 rocket fuel and liquid oxygen to burn. Carbon dioxide and water vapor, as well as various quantities of soot, nitrogen oxides, and sulfur, are all produced by such rockets. Greenhouse gases such as carbon dioxide, water vapor, and nitrogen oxides absorb heat and warm our planet.

According to the researchers models, a rocket's passage through the mesosphere generates a considerable local and short-term rise in carbon dioxide concentration.

“The mass of carbon dioxide released when a rocket rises to a height of 1 kilometer in the mesosphere is equivalent to the mass contained in 26 cubic kilometers of atmospheric air at the same height,” the researchers said in a statement, adding that such concentrations are undoubtedly significant.

The circulation of the atmosphere eventually eliminates these greenhouse gases, bringing their concentration back to "standard" levels. However, it is unknown how long the concentrations will remain elevated or what influence they will have on the temperature of the mesosphere.

Previously, other impacts of rocket launches on the mesosphere were described. The creation of stunning polar mesospheric clouds, the highest sort of clouds known to occur in the Earth's atmosphere, has been linked to NASA space shuttle flights, for example. Scientists are also worried about the impact of aluminum oxide and other particles in rocket exhaust on stratospheric ozone and the Earth's thermal equilibrium.

According to the Institute for Environmental and Energy Studies, rocket launches contribute less than 1% of aviation's carbon footprint, which accounts for only 2.4 percent of yearly worldwide carbon emissions.

The spaceflight business, on the other hand, is expanding, and the number of launches is increasing every year. Although the effects of rocket pollution on the environment are still unknown, the findings of this study suggest that it would be prudent to keep a careful check on the issue.

“We hope that commercial flight companies such as SpaceX, Virgin Galactic and New Shepard and their associated engine manufacturers take these effects into account in future developments,” said study co-author Dimitris Drikakis, a professor of multidisciplinary sciences at the University of Science and Technology. 

That's correct. Metalox methane fuel is used in the next-generation rockets of both SpaceX and Blue Origin, the firm behind the New Shepard rocket (Starship and New Glenn, respectively). According to the National Academies' Emission Index Database, modern research demonstrates that metalox burns highly effectively throughout operation, emitting just carbon dioxide, water vapor, and a minor quantity of nitrogen oxides.