in an episode from Star Trek: The Next Generation, a few outspoken scientists reveal how warp drives — the show’s ubiquitous propulsion system used to propel travelers through space — can be incredibly environmentally destructive. From then on, the characters make sure to limit the damage of their spaceflights.
Could a similar scenario play out in the real universe now, minus the faster-than-light engines? Atmospheric scientist Christopher Maloney believes so. In a new study, he and his colleagues have modeled how black carbon regurgitated from rocket launches around the world is likely to gradually warm parts of the middle atmosphere and deplete the ozone layer. She their findings published on June 1 in the Journal of Geophysical Research† atmospheres.
“There’s a lot of momentum right now in terms of rocket launches and satellite constellations going up, so it’s important to start exploring this to study what effects we might see,” said Maloney, who works with the National Oceanic and Atmospheric Administration. (NOAA) Laboratory of Chemical Sciences in Boulder, Colorado.
Maloney and his colleagues’ models begin with typical launch trajectories, where rockets blast a jet of tiny particles called aerosols from their engine nozzles. The most dangerous part of the exhaust is black carbon, or soot. Rockets release tons of those microscopic particles into the stratosphere, especially between 15 and 40 kilometers above the ground, above where planes fly. Modern jet engines also emit black carbon, but in much smaller amounts. Falling defunct satellites also emit aerosols, as they burn up in the stratosphere. Since these particles remain in the stratosphere for about four years, they can accumulate, especially in areas where space traffic is concentrated.
Maloney and his team used a high-resolution climate model to predict the effects this pollution will have on the atmosphere, studying how aerosols of different sizes could heat or cool areas of space at different latitudes, longitudes and altitudes. They found that within two decades, temperatures in parts of the stratosphere could rise by as much as 1.5 degrees Celsius or 2.7 degrees Fahrenheit and that the ozone layer in the Northern Hemisphere could thin somewhat. They generally conclude that more missiles means more warming and more ozone loss, which could pose a problem, especially since humans, wildlife and crops need the ozone layer to protect them from ultraviolet radiation.
According to their accounts, rocket launches collectively expel about 1 gigagram, or 1,000 metric tons, of black carbon into the stratosphere each year. Within two decades, that could easily rise to 10 gigagrams or more, thanks to the growing number of rocket launches. The researchers consider multiple scenarios for black carbon emissions, including levels of 30 and 100 gigagrams, which, while extreme, could happen within a few decades if rocket engine technologies and trends don’t change much. They focus their analysis on common rocket engines that burn kerosene, such as the SpaceX Falcon first stage boosters, Rocket Lab Electron and Russian Soyuz rockets.
Now that the global launch rate is increasing by approx 8 percent per year, they expect to detonate as many as 1,000 hydrocarbon-burning rockets each year by 2040. That’s partly due to falling launch costs and the burgeoning commercial space industry, as well as the rockets needed to launch growing satellite networks like SpaceX’s Starlink, Amazon’s Project Kuiper and OneWeb. Suborbital spaceflights, such as those from Blue Origin and Virgin Galactic, also penetrate the stratosphere.