The popularity of space tourism has taken off in recent years and growth in the industry is expected to skyrocket in coming decades, which could harm the Earth's atmosphere, warn scientists with the National Oceanic and Atmospheric Administration (NOAA).
NOAA research predicts that, based on current space-traffic growth trends, space tourism could realistically grow tenfold in the next 20 years, according to a NOAA statement released June 21. The findings also indicate the increase in space flight "may damage the protective ozone layer on the one planet where we live.
Rocket engines commonly used by the private spaceflight industry are fueled by kerosene, a type of hydrocarbon, NOAA reports. Exhaust from these engines contains soot, or black carbon, that is released directly into the ozone layer, which protects life on Earth from harmful ultraviolet radiation, the statement reports.
"Rockets are the only direct source of human-produced aerosol pollution above the troposphere," NOAA states in the report, "the lowest region of the atmosphere, which extends to a height of about 4 to 6 miles above the Earth’s surface."
Approximately 1,000 metric tons of soot are emitted annually by rocket engines, according to the report. Researchers used models to study the effects of 10,000 metric tons of black-carbon pollution on the northern hemisphere's atmosphere, released annually for 50 years, NOAA reports. The studies found these levels would increase annual stratosphere temperatures by approximately 1-4°F, or 0.5 - 2° Celsius. Subtropical jet streams would slow by 3.5%, which would alter and weaken circulation patterns around the globe, NOAA reports. These changes are shown to reduce the amount of ozone, the research finds.
“The bottom line is projected increases in rocket launches could expose people in the Northern Hemisphere to increased harmful UV radiation,” lead author and research scientist Christopher Maloney said in the report.
Studies in 2010 by scientist Martin Ross of the Aerospace Corporation first investigated the impact of rocket-soot emittions on the climate; a 2017 NOAA study that Ross co-authored studied the effect of water-vapor emissions from reusable launch systems fueled by cleaner hydrogen-powered rockets.
“Our work emphasizes the importance of ozone depletion caused by soot particles emitted by liquid-fueled rockets,” Ross said in the report. “These simulations change the long-held belief that spaceflight’s only threat to the ozone layer was from solid-fueled rockets. We’ve shown that particles are where the action is for spaceflight’s impacts.”
Recent research indicating rocket-exhaust black carbon has damaging impacts on the climate and stratosphere is only "an initial step in understanding the spectrum of impacts on the stratosphere from increased space flight," the NOAA report states.
“We need to learn more about the potential impact of hydrocarbon-burning engines on the stratosphere and on the climate at the surface of the Earth,” Maloney said in the report. “With further research, we should be able to better understand the relative impacts of different rocket types on climate and ozone."
