Projected increase in space travel could damage the ozone layer

The projected growth of rocket launches for space tourism, moon landings and perhaps travel to Mars has made many dream of a new era of space exploration. But a NOAA study suggests that a significant increase in spaceflight activity could damage the protective ozone layer on the one planet we live on.

Kerosene burning rocket engines widely used by the global launch industry emit exhaust gases containing black carbon, or sootdirectly into the stratosphere, where a layer of ozone protects all living things on Earth from the harmful effects of ultraviolet radiation, including skin cancer and a weakened immune system in humans, as well as disturbances to agriculture and ecosystems.

According to new NOAA research published in the Journal of Geophysical Research: Atmospheresa tenfold increase in the number of launches based on hydrocarbons, which is plausible in the next two decades based on recent trends in space traffic growth, the ozone layerand change atmospheric circulation patterns†

“We need to learn more about the potential impact of hydrocarbon combustion engines on the stratosphere and on the Earth’s surface climate,” said lead author Christopher Maloney, a CIRES researcher who works in NOAA’s Chemical Sciences Laboratory. “With further research, we should be able to better understand the relative effects of different types of missiles on climate and ozone.”

Launch speeds have tripled

Launch rates have more than tripled in recent decades, Maloney said, and accelerated growth is expected in the coming decades. Rockets are the only direct source of man-made aerosol pollution above the troposphere, the lowest part of the atmosphere, which extends to an altitude of about four to six miles above the Earth’s surface.

The research team used a climate model to simulate the impact of about 10,000 tons of soot pollution injected into the stratosphere over the Northern Hemisphere every year for 50 years. Currently, an estimated 1,000 tons of rocket soot is emitted every year. The researchers caution that the exact amounts of soot emitted by the various hydrocarbon engines used around the world are poorly understood.

The researchers found that this level of activity would raise the annual temperature in the stratosphere by 0.5-2° Celsius (or about 1-4° Farenheit), changing global circulation patterns by as much as 3.5 degrees from the subtropical jet streams. %, and attenuation of the stratospheric tilting circulation.

How rocket exhausts are depleting the ozone layer

Stratospheric ozone is strongly influenced by temperature and atmospheric circulation, noted co-author Robert Portmann, a research physicist at the Chemical Sciences Laboratory, so it was no surprise to the research team that the model found that changes in stratospheric temperatures and winds also caused changes in the abundance of ozone. The scientists found that ozone reductions occurred toward latitude 30 degrees north, or roughly the latitude of Houston, in nearly all months of the year. The maximum reduction of 4% occurred at the North Pole in June. All other locations north of 30°N had at least some reduced ozone year-round. This spatial pattern of ozone loss directly coincides with the modeled distribution of black carbon and associated warming, Maloney said.

“The bottom line is that an increase in rocket launches could expose people in the Northern Hemisphere to increased harmful UV radiation,” Maloney said.

The research team also simulated two larger emissions scenarios of 30,000 and 100,000 tons of soot pollution per year to better understand the effects of an extremely large increase in future space travel using hydrocarbon-powered engines and to more clearly investigate the feedback that determines the response of the atmosphere. . † Results showed that the stratosphere is sensitive to relatively modest black carbon injections. The larger emissions simulations showed a similar, but more severe, atmospheric circulation disturbance and climate loss than the 10,000-tonne case.

Building a research base

The study built on previous research by members of the author’s team. A study from 2010 led by co-author Martin Ross, a scientist at The Aerospace Corporation, first examined the climate impact of an increase in soot production rocket launches† A second study conducted at NOAA in 2017Ross was a co-author, investigating the climate response to water vapor emissions from a proposed reusable space launch system that uses cleaner hydrogen-powered rockets.

“Our work highlights the importance of ozone depletion caused by soot particles emitted by liquid-fuelled rockets,” Ross said. “These simulations change the long-held belief that spaceflight was the only threat to the ozone layer from solid-fuel rockets. We showed that particles are the action for the impact of spaceflight.”

While the new research describes the impact soot in rocket exhaust has on climate and stratosphere composition, the scientists said it represents a first step in understanding the spectrum of effects on the stratosphere from increased spaceflight.

Combustion emissions from the different rocket ship species will need to be evaluated, they said. Soot and other particles generated by satellites that burn up when they fall out of orbit are also a growing, poorly understood source of emissions in the middle to upper atmosphere. These and other topics will require further research to get a full picture of the emissions from the space industry and their impact on the Earth’s climate and ozone layer.