The Climate Impact of Space Tourism Is Significantly Worse Than We Thought

In the past, I have mused about the carbon footprint of space tourism, concluding it wasn't much in the grander scheme of things. But a new study—"Impact of Rocket Launch and Space Debris Air Pollutant Emissions on Stratospheric Ozone and Global Climate"—comes up with a different result, mainly because it looks at a different kind of carbon.

Published in Earth's Future by researchers from the University College London, MIT, and the University of Cambridge, the study found that many of the rockets emitted black carbon or soot. What is startling is this space soot was 500 times more effective at retaining heat in the atmosphere than surface and aircraft sources of soot, because it is released so much higher in the atmosphere.

In the aforementioned earlier post, I noted that firing a few rich people into space had a far lower impact than flying hundreds of thousands of people in airplanes. But in a statement, study co-author Dr. Eloise Marais contradicts this.

"Rocket launches are routinely compared to greenhouse gas and air pollutant emissions from the aircraft industry, which we demonstrate in our work is erroneous," said Marais. "Soot particles from rocket launches have a much larger climate effect than aircraft and other Earth-bound sources, so there doesn't need to be as many rocket launches as international flights to have a similar impact. What we really need now is a discussion amongst experts on the best strategy for regulating this rapidly growing industry."

The researchers analyzed all 103 rocket launches in 2019 from around the world, looking at what fuel they used and whether the rockets were returnable, and incorporated these data into a 3D atmospheric chemistry model. All rocket fuels release water vapor and nitrogen oxides; most soot comes from using kerosene in SpaceX rockets and the synthetic rubber fuel used in Virgin Galactic. Solid fuels pump out alumina particles and chlorine.

And it doesn't just cause global heating: It also damages the stratospheric ozone layer and undoes the work of the Montreal Protocol. "The only part of the atmosphere showing strong ozone recovery post-Montreal Protocol is the upper stratosphere, and that is exactly where the impact of rocket emissions will hit hardest," said study co-author Dr. Robert Ryan. "We weren't expecting to see ozone changes of this magnitude, threatening the progress of ozone recovery."

This research raises some questions. Of the 103 launches analyzed in 2019, exactly zero were dedicated to space tourism, which took off in 2021. So we already have a significant problem with rocket exhaust, but it is not from tourism.

The researchers' concern with space tourism is that it will grow dramatically. However, they note that only Richard Branson's Virgin Galactic has announced how many flights are planned, with a hyperbolic projection of 400 flights per year. They assume daily suborbital launches by Virgin Galactic and Blue Origin and weekly SpaceX orbital launches.

Ryan noted: "This study allows us to enter the new era of space tourism with our eyes wide open to the potential impacts. The conversation about regulating the environmental impact of the space launch industry needs to start now so we can minimize harm to the stratospheric ozone layer and climate."

Perhaps we also need a study determining the size of the market for space tourism. Indeed, the price per ticket will drop from a quarter of a million dollars for a 15-minute ride, but it will always be the preserve of the billionaire, and even among them, there will be a limited pool willing to take this risk. Also, if they are going to be launching every day, at some point, there will be a Hindenburg moment that will either shut down the industry or give people serious pause about trying this.

The bigger question raised by this study is how polluting the space transport industry is, even without tourism, and how much of it is necessary. Look at what is happening with satellite internet services: We have Elon Musk firing his rockets to put up to 42,000 satellites in low orbit for his Starlink internet service; Jeff Bezos and Amazon propose launching 3,236 satellites for his competing Project Kuiper; and internationally, the United Kingdom-based One Web, Canada's Telesat, the European Union, and China are promoting their own systems.

The sky will be covered with competing satellite systems in low earth orbit, all of which fall back to earth and burn up in relatively short order, as little as five years. The metal and stuff that these satellites are made of don't just disappear; it just adds more pollutants to the upper atmosphere. How many of these systems and satellites does the world need, given their impact on the climate?

Reading this study and learning about the impact of dumping all this soot and all this other stuff into the upper atmosphere, it seems clear to me we don't have a space tourism problem as much as we have a much more immediate rocket problem.