There’s a spectator sport quality to the billionaire space race. Pick your favorite rich guy and your favorite rocket—Elon Musk’s Falcon 9, Richard Branson’s VSS Unity, Jeff Bezos’s New Shepard—and start your own cheering section. And while it’s not always easy to root for the fabulously rich to get even more fabulous, there’s something in the space race for all of us. Space tourism, after all, is becoming a growth industry, and as the frequency of flights goes up and the cost comes down, we can all dream of earning our astronaut wings.
But according to a new study published this month in the journal Earth’s Future, all the new joyriding could come at a steep environmental price. The more rockets that get launched, the more black soot gets injected into the upper atmosphere, not to mention pollutants including nitrogen oxides, aluminum oxide, hydrochloric acid, and chlorine, as well as water vapor. Together, all of that output not only contributes to global warming but also to the depletion of the ozone layer.
There’s been limited information on the emissions impact of space travel, the study notes. And the sector is largely absent from international climate treaties. The new paper, therefore, “allows us to enter the new era of space tourism with our eyes wide open to the potential impacts,” said co-author Robert Ryan, a research fellow at the University College London’s geography department, in a statement. “The conversation about regulating the environmental impact of the space industry needs to start now so we can minimize harm to the stratospheric ozone layer and climate.”
To conduct their work, the researchers chose 2019—before the three companies began carrying crews to space—as a baseline. In that year, there were 103 space launches worldwide—most by government-run space exploration programs—all of which contributed their own pollutants to the atmosphere. Compared to that, space tourism by Blue Origin, Virgin Galactic, and SpaceX is just a blip. Since 2020, Virgin has carried only a single crew of space tourists, SpaceX has carried two, and Blue Origin has carried five, just since last July. But that slow start belies big plans.
Virgin in particular boasts that it ultimately will be launching on a daily basis; Blue Origin is moving more slowly, aiming to double its launches this year over last. SpaceX is more of a mixed bag. It is unlikely to launch as many paying crews due to the $50 million price tag for a ride to Earth orbit aboard its Crew Dragon spacecraft as compared to the $450,000 Virgin charges for their 12-minute suborbital flights. (Blue Origin does not currently disclose what it will charge for tickets when regular flights begin.) But SpaceX’s nine-engine Falcon 9 rocket—which launches the company’s crewed spacecraft—also carries satellite payloads and NASA astronauts to the International Space Station and is the workhorse of the company’s fleet. Since its first flight more than a decade ago, 159 Falcon 9s have been launched. Also part of the SpaceX lineup is the thrice-flown Falcon Heavy rocket, with 27 engines, and its massive 33-engine Super Heavy, which should have its first flight this year. Taken together, the three companies could eventually leave the 103 launches achieved in 2019 in the dust.
Of all of the pollutants the rockets release, it is the black soot that causes the greatest concern. Conventional airplanes and other vehicles create plenty of heat trapping soot of their own, but not nearly as high in the sky as rockets do. When expelled into the upper atmosphere—at altitudes of 50 km (38 mi) or more—black soot is 500 times more efficient at causing warming than it is when emitted by, say, a commercial airliner flying at a mere 11,000 m (35,000 ft.).
“[Black soot] directly injected to the upper atmosphere has a greater climate forcing efficiency than other sources [of pollution],” the authors write. That’s bad news every time a rocket flies but it’s especially bad given the billionaire space race. Just three years of tourism flights at the frequency the companies predict, the authors estimate, could more than double the black soot emissions of the last decade of contemporary rocket launches.
The private rocket companies push back at this, especially Bezos’s Blue Origin, which uses liquid hydrogen and oxygen as its fuel and thus produces less-damaging exhaust. “New Shepard’s engine is fueled by highly efficient and clean liquid oxygen and hydrogen. During flight, the only byproduct of New Shepard’s engine combustion is water vapor with no carbon emissions,” said a company spokesperson in an email to TIME. Water vapor, however, does have a greenhouse gas impact.
It’s not just the warming effect of tourism flights that worries the researchers; so too does the damage to the ozone layer. The 1987 Montreal Protocol, phasing out the use of ozone-depleting chlorofluorocarbons, has long been seen as one of the environmental movement’s great success stories. But rocket exhaust does the ozone no favors.
Even at the 2019 rate of launches, the researchers predict an increase in ozone loss of 8.5 parts per billion, or 10% of the ozone recovery achieved by the Montreal accords, by the end of this decade. Add the billionaire rocketeers into the mix, and the loss jumps to 13 parts per billion—or 16% of what was recovered by Montreal. “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 Ryan in his statement. “We weren’t expecting to see ozone changes of this magnitude, threatening the progress of ozone recovery.”
The greatest loss in ozone is in the spring in the Arctic—stripping away part of the Earth’s shield against dangerous ultraviolet rays from space, and harming humans and the underlying ecosystem. The rocket-related damage is due not just to the exhaust put out by the engines, but to reentry and incineration of the second stage of multi-stage rockets. In this case, Virgin and Blue Origin are blameless, since their rockets are entirely reusable. It is SpaceX and other orbital launchers with expendable stages that do this part of the ozone damage. And they do a lot of it indeed: in the stratosphere of the high northern latitudes, reentry incineration of space debris accounts for 51% of rocket-related ozone loss.
The billionaire space race was never going to come cheap—those head-spinning ticket prices alone prove that. But increasingly it seems that it’s not just the tourists who are paying the freight; it’s the environment—and thus the rest of us—too.
Correction, June 28:
The original version of this story stated that the researchers studied nitrous oxide, aluminum oxide, hydrochloric acid, and chlorine, as well as water vapor and carbon dioxide. In fact, they studied nitrogen oxides, aluminum oxide, hydrochloric acid, and chlorine, as well as water vapor.
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Write to Jeffrey Kluger at email@example.com