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The rocket industry has a climate problem

Researchers say more launches are putting black carbon soot high in the atmosphere

A SpaceX rocket carries four passengers into space.
This story was published on our Space Business newsletter, A glimpse at the economic possibilities of space.

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Welcome to Quartz’s newsletter on the economic possibilities of the extraterrestrial sphere. Please forward widely, and let me know what you think. This week: Quantifying the climate cost of space access, double crater all the way, and the latest updates on NASA’s return to the Moon.

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Rockets will play a larger role in climate change than previously thought, as the number of annual launches around the world continues to increase. That’s according to a new study of how space transportation alters atmospheric chemistry.

The good news? The worst effects in the study are based on an unrealistic scenario. The bad news? Some of the biggest impacts the researchers found are tied to trends that will only increase.

The study examined two different questions: How do the emissions from launch vehicles effect the ozone layer, and how do the emissions affect climate change? The researchers broke down the types of fuel used by different rockets, how often they launch, and from where, as well as the chemicals produced by rocket stages and returning hardware burning up in the atmosphere. They tested one scenario measuring the emissions for 10 years of launches growing steadily from what was actually flown in 2019, and another, more speculative scenario measuring three years of those launches plus a boom in space tourism.

The researchers measure how rocket emissions contribute to radiative forcing, or the change in energy being retained (or released) by Earth’s atmosphere. While they acknowledge substantial uncertainty around these figures, their best estimates for 10 years of space missions at 2019’s pace add 3.9 milliwatts per square meter of radiative forcing, while the 3-year tourism scenario generates 7.9 milliwatts per square meter. For some context, one estimate of the aviation industry’s total contribution to global warming from 1940 to 2018 is 149.1 milliwatts per square meter.

A key caveat for that tourism scenario: It anticipates Virgin Galactic and Blue Origin launching suborbital tourist flights on a daily basis, and SpaceX launching a weekly tourist mission into orbit. None of that is likely. Blue Origin has launched tourists twice this year, Virgin hasn’t flown at all in 2022, and SpaceX has launched just one tourist flight this year and is unlikely to do another.

On the other hand, the 2019-base scenario is already being outstripped by reality. In 2019, there were 102 orbital launches. In 2020, there were 104, and in 2021, 133. This year has already seen 73 launches, and there could be more than 150 total attempts. That would exceed the 5.6% annual growth rate the researchers used in their first scenario.

Critics of the space industry are going to highlight the space tourism scenario because the findings are dramatic and because wealthy people having fun is a faux pas, but the industry itself will need to take the baseline findings far more seriously.

The bulk of the warming caused by rockets comes from exhaust in the upper atmosphere. Some of the worst contributors are solid rockets and hypergolics, toxic fuels that ignite when combined. But the biggest problem the researchers identified is how rockets fueled with kerosene, like the prolific SpaceX Falcon 9 and Russian Soyuz, expel black carbon soot. When the substance is placed directly in the upper atmosphere, it is much more effective at trapping heat than when it is created by airliners or coal plants at lower altitudes—as much as 500 times more effective.

“That really did astound us,” study co-author Eloise Marais, a professor at the University College of London, told Quartz.

On the positive side, major rocketmakers are trying to transition toward more efficient engines using cleaner-burning methane and hydrogen, which would produce less black carbon in the atmosphere. The scientists think that hybrid solid fuel systems, like that used by Virgin Galactic, could be particularly problematic; but many propulsion experts are skeptical that Virgin’s unique engine will catch on broadly. Solid rocket boosters are also being phased out, at least for many frequently flown launch vehicles.

One thing we can expect a lot of in the future, however, is more hardware burning up in the atmosphere. While future reusable rockets might not be discarding entire stages, the massive growth of the satellite industry means more defunct satellites being disposed of in orbit. Increasing the cadence of human spaceflight means more frequent re-entry of spacecraft that rely on heat shields that generate problematic particles—indeed, even Blue Origin’s comparatively environmentally friendly, hydrogen-powered New Shepard releases nitrogen oxides when it re-enters the atmosphere. And if industrial activity in space increases, more stuff will presumably return to Earth.

The paper suggests that 10 years of steadily increasing rocket launches from 2019 would reverse 10% of the gains in ozone accumulation generated by the Montreal Protocol, the landmark 1987 environmental deal which is helping to close the hole in the ozone layer.

Before the rocket revolution in recent years, space activity was largely seen as not contributing very much to climate change, simply because launches were rare compared to so many other human activities that alter atmospheric chemistry. The incredible growth of the industry, combined with momre understanding of the affects of emissions at high altitudes, show this is changing.

Rockets are still contributing far less to climate change than the rest of the transportation sector, electricity generation or manufacturing. But the space industry is planning on a future where launches are happening on a daily basis around the globe; it will need to anticipate regulators and activists asking it to justify its work and clean up its practices. And it will have to help scientists studying the atmosphere learn more: Marais says she is currently seeking funding for a research project that would use space-based sensors to validate the climate models she and her colleagues have developed.

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Imagery interlude

A chunk of a rocket found on a collision course with the Moon earlier this year sparked controversy when it was first identified as originating from a SpaceX launch, and then later pegged as a Chinese rocket, although China denies that. Now there are even more questions to be answered, after researchers at Arizona State University discovered what they believe is its impact point on the lunar surface—which created two craters instead of the expected one.

Two craters on the moon scientists say were caused by the impact of a rocket body.
Image copyright: NASA/GSFC/Arizona State University

Professor Mark Robinson, whose team operates the Lunar Reconnaissance Orbiter that captured this image, speculated that the double crater could have been caused by hardware carried on the Chinese rocket to simulate the mass of a future lunar lander.



An (unofficial) Artemis update. An outline of NASA’s plan for future lunar missions was obtained by Ars Technica, and it highlights long-standing contradictions between the Artemis program’s vision and reality. There are multi-year gaps between missions intended to occur on an annual basis, and continued ambiguity about the Lunar Gateway, a proposed way space station orbiting the Moon, which might not be necessary and would likely delay investments in habitats on the surface of the Moon itself. Meanwhile, the Artemis program kicked off in earnest with the launch of the Capstone mission on June 28.

Chinese rocket maker raises $257 million. Expace, the commercial subsidiary of state-owned defense contractor China Aerospace Science and Industry Corporation, marked the largest-ever fundraising round for an ostensibly private Chinese launch firm. The company operates a small solid-fueled rocket used to launch satellites, and is developing a new, liquid-fueled engine.

Dragon delayed until mid-July. NASA and SpaceX have been working through issues discovered on a Dragon capsule that will take supplies to the International Space Station next month. Leaking propellant led engineers to replace parts of the vehicle’s propulsion systems; they also will replace its parachutes. This particular vehicle has flown to space twice before, and while these issues may be idiosyncratic, they also reflect the challenges of flying reusable spacecraft.

Virgin Orbit plots two firsts. The company postponed its first night-time launch yesterday. It’s also aiming to perform the first satellite launch from the UK in August, which also will be Virgin Orbit’s first launch outside the US.

Space stocks find their way into a major index. A handful of space-focused companies have been added to the Russell 3000 index, which attempts to benchmark the 3,000 largest publicly held US equities. Those companies include Planet, Rocket Lab, Redwire, Spire, Terran Orbital, Momentus, and Astra. The inclusion of these firms should expose them to more investment from big institutions and fund managers, and reflects the growing importance of space firms to the market. But will there ever be a pure-play space firm in the S&P 500, the real mover and shaker of market measures?

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This was issue 140 of our newsletter. Hope your week is out of this world! Please send your analysis of the latest Artemis outline, schemes for regulating rocket emissions, tips, and informed opinions to

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