Greta Jimenez
Rocket launches are an integral part of the 21st century, but they also contribute to air pollution. The extent of the impact of rocket launches on Earth's atmosphere is not yet fully understood, but scientists are examining the issue more closely as space travel becomes more frequent. Rocket launches release gases and particles into the middle and upper atmosphere, including alumina, chlorine, nitrogen oxides, hydroxyl, water vapour, and black carbon, which contribute to ozone depletion and climate change. While the space industry only accounts for a small percentage of fossil fuel usage compared to aviation, the impact per passenger is much higher, with a single rocket passenger responsible for 100 times more climate-changing pollution than an airline passenger. The type of fuel used also affects the level of pollution, with some newer rockets using cleaner-burning fuels like methane and liquid hydrogen. As the frequency of rocket launches increases, it is important to consider the environmental impact and find ways to mitigate the pollution caused by these launches.
| Characteristics | Values |
|---|---|
| Number of rocket launches in 2020 | 114 |
| Number of airplane flights per day | 100,000 |
| Percentage of fossil fuels burned by the space industry compared to conventional aviation | 1% |
| Amount of black carbon released by rockets that use RP-1 | 1 gigagram or 1,000 metric tons |
| Projected amount of black carbon released by rockets that use RP-1 in a couple of decades | 10 gigagrams |
| Projected temperature rise in parts of the stratosphere | 1.5 degrees Celsius |
| Pollutants in rocket launch plumes | Alumina (Al2O3), chlorine (converted from hydrochloric acid, HCl), nitrogen oxides (NOx), hydroxyl (OH), water vapour (H2O) |
| Pollutants produced by burning RP-1 | CO2, water vapour, NOx, carbon soot, carbon monoxide, sulfur compounds |
| Estimated amount of CO2 per launch | 76,000 tons |
| Other pollutants per launch | Lithium, aluminum, copper, lead, sodium, and black soot |
| Pollutants from manufacturing a rocket | CO2 |
| Pollutants from rocket engines | Carbon dioxide, water, black carbon, and alumina particles |
| Pollutants from space junk | Derelict satellites, rocket stages, and other space debris |
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What You'll Learn
Rocket propellant emissions
The specific pollutants and their effects depend on the type of propellant used. For example, RP-1, a highly refined jet fuel, produces CO2, water vapour, NOx, carbon soot, and carbon monoxide when burnt. On the other hand, UDMH (unsymmetrical dimethylhydrazine), used in the world's first artificial satellite and the first human spaceflight, Sputnik 1 and Vostok 1, was highly carcinogenic and poisoned the soil for decades.
The amount of pollution released by rocket propellant emissions is also a concern. While rocket launches are relatively infrequent compared to commercial flights, the number of rocket launches is expected to increase significantly in the coming decades with the growth of the space tourism industry. Each year, rocket launches that use RP-1 expel around 1 gigagram, or 1,000 metric tons, of black carbon into the stratosphere. As the number of rocket launches increases, the amount of black carbon expelled into the atmosphere could reach 10 gigagrams per year or even more, leading to a potential temperature rise in parts of the stratosphere and a thinning of the ozone layer.
The impact of rocket propellant emissions on the atmosphere is complex and not yet fully understood. While most of the pollution from rocket launches is released at higher altitudes, the specific effects of these emissions on the microphysics of the atmosphere and atmospheric chemistry are still being studied. Additionally, the interactions between the Earth's atmosphere and exhaust from methane-fueled rocket engines have not been adequately modelled, according to researcher Ross.
To address the environmental risks posed by rocket propellant emissions, there have been calls for more comprehensive data collection on air quality around launch sites and preventive measures to mitigate their impact. As the space industry continues to grow, it is crucial to strike a balance between the benefits it brings and the potential harm caused by rocket propellant emissions to the Earth's atmosphere.
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Climate impact of rocket emissions
Rocket launches are an integral part of the 21st century, but they also contribute to climate change. The climate impact of rocket emissions depends on the type of fuel used and the altitude at which the emissions are released.
Rocket fuels vary in composition and environmental impact. RP-1, a highly refined jet fuel, produces CO2, water vapour, NOx, carbon soot, carbon monoxide, and sulfur compounds when burnt. Hypergolic fuels, which spontaneously combust when the fuel and oxidizer come into contact, are stable at room temperature and commonly used in missiles. Historically, UDMH (unsymmetrical dimethylhydrazine) was used as rocket fuel, but it was highly carcinogenic and poisoned the soil, earning it the nickname "devil's venom".
Rocket emissions are released at high altitudes, up to 80 km, in the stratosphere and mesosphere. This is significant because the pollutants can persist at these altitudes for at least 2-3 years and have a climate impact. Alumina (Al2O3), chlorine (from hydrochloric acid, HCl), nitrogen oxides (NOx), hydroxyl (OH), and water vapour (H2O) in rocket plumes contribute to ozone depletion through chemical reactions in the Earth's stratosphere. The warming effect of alumina particles, previously thought to cool the Earth, has also been highlighted by Martin Ross, a lead author of a United Nations report on rocket emissions.
The amount of pollution from rocket launches is relatively small compared to other industries, such as aviation. Rocket launches are less frequent than commercial flights, and most pollution from rockets is released at higher altitudes, reducing the impact on ground-level air quality. However, as the space tourism industry grows, the cumulative effect of rocket emissions could become more significant. Additionally, the lack of data and understanding of propellant emissions and their microphysics makes it challenging to fully grasp the climate impact.
To mitigate the climate impact of rocket emissions, reusable rockets can help spread out the manufacturing emissions over the rocket's lifetime, reducing total emissions. Preventive measures, interventions, and further research are crucial as economic activity in space surges and the pace of rocket launches is expected to increase.
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Rocket launch frequency
SpaceX's Falcon 9 rocket has been launched 503 times as of June 2025, with 500 full mission successes, two mission failures during launch, one mission failure before launch, and one partial failure. The Falcon 9 Block 5, the active version of the rocket, has flown 435 or 436 times with one failure. Falcon Heavy, a heavy-lift derivative of Falcon 9, has been launched 11 times.
Falcon 9 rockets were launched 77 times from June 2010 to the end of 2019, with 75 full mission successes, one partial failure, and one total loss of the spacecraft. From January 2020 to the end of 2022, Falcon 9 was launched 117 times, all successful, and landed boosters successfully 111 times out of 114 attempts. In 2023, the Falcon family of rockets had 96 successful launches, and in 2024, SpaceX broke their own record with 134 total Falcon flights, 133 of which were successful.
The Electron rocket, built and operated by Rocket Lab, has been launched 64 times with 60 successes and four failures. The first launch in May 2017 was destroyed due to a ground software failure. Electron experienced its first successful launch in January 2018 and has since completed several missions for NASA, the U.S. Air Force, and the National Reconnaissance Office. In 2020, Rocket Lab planned to deliver monthly launches for the remainder of the year and into 2021.
In addition to these launches, SpaceX has also launched the Falcon Heavy rocket, the Electron rocket for Rocket Lab, and the DART rocket for the Australian government. SpaceX has also been launching batches of Starlink V2 Mini satellites into low Earth orbit.
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Space junk
The issue of space junk is expected to be included in the United Nations 2018 Quadrennial Global Ozone Assessment, which will delve into the substances responsible for ozone depletion. Space junk generates "re-entry smoke particles" (RSPs) of unknown composition and reactivity. These particles have been found to contain metals that have vaporized from the re-entry of satellites and rocket boosters.
ClearSpace, a spin-off from the Swiss EPFL Space Center, is developing technologies to remove unresponsive or derelict satellites from space. The startup plans to remove the first pieces of debris from space by 2025. The Swiss are taking responsibility for their own space junk and plan to remove their debris first.
While the number of rocket launches is still relatively small compared to commercial aviation, the impact of space junk on the atmosphere cannot be ignored. As economic activity in space surges, scientists are reexamining how rockets might harm Earth's atmosphere.
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Rocket fuel types
Liquid hydrogen is one of the most popular rocket fuels used by companies like NASA because it has the lowest mass possible for a rocket fuel. However, it needs to be kept at very high pressures and/or very cold temperatures. Liquid methane is gaining popularity as a rocket fuel because it is more efficient, cheaper to produce, and more environmentally friendly than RP-1. However, it also requires specialised equipment to maintain it as a liquid.
RP-1 (Refined Petroleum-1) is another common type of rocket fuel. It is a highly refined jet fuel or kerosene with higher purity and thermal stability. It is safer to handle than liquid hydrogen, as it is liquid at room temperature and atmospheric pressure. It is also cheaper to manufacture, transport, and store. However, it produces less mass in space with the same amount of fuel.
Solid rocket fuel is a broad category that includes just about anything used to propel rockets into the air, as long as it is in a solid form when ignited. Solid rocket propellants come in two main types: composites and single-, double-, or triple-base propellants. Composites are mostly a mixture of granules of solid oxidizers, such as ammonium nitrate, with flakes or powders of energetic fuel compounds. Single-, double-, or triple-base propellants are homogeneous mixtures of one to three primary ingredients, including fuel and oxidizer.
Bipropellant liquid rockets use a mixture of reducing fuel and oxidising oxidiser, which is converted into a huge volume of gas at high temperature and pressure. This creates an opposing force that propels the rocket forward.
Upper stages of rockets, which mostly or only operate in the vacuum of space, tend to use high-energy, high-performance, low-density liquid hydrogen fuel.
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Frequently asked questions
Rocket launches release pollutants such as carbon dioxide, water, black carbon, alumina, chlorine, nitrogen oxides, hydroxyl, carbon soot, carbon monoxide, and sulfur compounds into the stratosphere and mesosphere. The exact amount of pollution is unknown, but estimates range from 1 gigagram to 76,000 tons of carbon dioxide per launch.
The pollution from rocket launches is influenced by the type of fuel and propellant used. For example, UDMH (unsymmetrical dimethylhydrazine), a fuel used in early rocket launches, was highly carcinogenic and caused ecological damage.
The space industry burns about 1% of the fossil fuels burned by conventional aviation. Rocket launches are also relatively infrequent compared to commercial flights, with only 114 attempted orbital launches in 2020 compared to over 100,000 airplane flights per day.
The pollution from rocket launches can contribute to ozone depletion and climate change. Additionally, "space junk," such as discarded satellites and rocket debris, can accumulate in Earth's orbit and interfere with important satellite functions.
To reduce pollution, reusable rockets can be utilized to spread out the manufacturing emissions over the lifetime of the rocket. Additionally, alternative fuels and propellants that produce less pollution can be explored. More research and data collection are also needed to fully understand the impact of rocket launches on the environment.
