Space Launches: Pollution, Costs, And Our Future

Rocket launches are an integral part of our 21st-century world. However, they are a source of pollution, with rockets requiring huge amounts of propellants to exit Earth's atmosphere and enter space. The pollution caused by rocket emissions is a growing concern, with the number of commercial rocket launches expected to increase significantly over the next two decades due to the increasing demand for services like satellite internet and space tourism. The exact implications of propellant emissions on the climate remain unclear, but scientists worry that if rocket launches continue to increase, spaceflight pollution could undermine the progress made on ozone recovery since the late 1980s.

Carbon dioxide emissions

Carbon dioxide (CO2) emissions are a significant concern when it comes to rocket launches. The amount of CO2 emitted by a rocket launch far exceeds that of a typical long-haul plane flight, which produces between 1 and 3 tonnes of CO2 per passenger. In contrast, rocket launches can generate between 50 and 75 tonnes of CO2 per passenger. For example, a single SpaceX Falcon 9 rocket launch emitted around 116 tonnes of CO2 in the first stage alone, which takes approximately 165 seconds. This is equivalent to the emissions of about 73 cars or 395 transatlantic flights.

While the number of rocket launches is currently relatively small compared to the over 100,000 daily airplane flights, the space industry is growing. The market for space tourism is projected to reach $2.58 billion in 2031, with a 17.15% annual growth rate over the next decade. This increase in demand for space travel, coupled with the development of larger rockets, has raised concerns among scientists about the potential environmental impact.

The SpaceX Starship, for instance, has been described as "one of the dirtiest" rockets due to its size. A single launch of the Starship is estimated to produce 76,000 metric tons of carbon dioxide equivalent, taking into account various greenhouse gases. This significant emission is attributed to the large amount of propellant used, with 4,600 metric tons of propellant potentially resulting in the aforementioned CO2 equivalent.

The impact of rocket emissions on the climate is complex and not fully understood. Most rocket pollution is released into the stratosphere and mesosphere, where it can persist for at least 2 to 3 years. This includes pollutants such as nitrogen oxides, alumina particles, and black carbon, which contribute to ozone depletion and can act as a form of geo-engineering by absorbing heat.

While the percentage of fossil fuels burned by the space industry is relatively low compared to conventional aviation, the increase in launch rates is notable. The number of launches has more than tripled in recent decades, with a record-breaking 223 attempted spaceflights worldwide in 2023. This steep rise in launches, along with the accumulation of their effects, is a cause for concern for scientists.

Kerosene-based fuels

Kerosene-fuelled rockets also produce carbon dioxide, a greenhouse gas that contributes to human-induced climate change. Rocket launches generate between 50 and 75 tonnes of CO2 per passenger, significantly more than a typical long-haul plane flight, which creates between 1 and 3 tonnes of CO2 per passenger. While the number of rocket flights is currently low compared to airplane flights, the growth of the space tourism industry could lead to a significant increase in rocket launches and their associated emissions.

The exact impact of kerosene-based fuels on the climate is not yet fully understood. More data is needed to properly identify and quantify the potential impact of space launches on the environment. However, it is clear that rocket launches, including those powered by kerosene-based fuels, contribute to air pollution and have the potential to affect the Earth's atmosphere, temperatures, and ozone layer.

Space junk

The problem of space junk is a growing concern, with close to 6,000 tons of material in LEO. The deliberate destruction of the Chinese Fengyun-1C spacecraft in 2007 and the accidental collision of an American and a Russian spacecraft in 2009 increased the debris in LEO by 70%. This debris moves at incredibly fast speeds, reaching up to 18,000 miles per hour, posing significant safety risks to people and property in space and on Earth.

The increase in space junk is expected to cause a 650% rise in re-entering space debris, leading to "potentially significant" ozone depletion. This debris generates "re-entry smoke particles" (RSPs) of unknown reactivity and composition, which can have an impact on the atmosphere. The higher the altitude of these particles, the longer they stay in the atmosphere, with some predicting that they could remain for 100 to 200 years.

The growing space industry, with its increasing number of rocket launches and satellites, is contributing to this issue. Experts are racing to address this emerging threat before it's too late, as the accumulation of space junk in LEO could trigger the world's next big environmental emergency.

Pollutants in upper layers of the atmosphere

The pollutants emitted by rockets are released from the Earth's surface to the mesosphere, which includes the upper layers of the atmosphere. The mesosphere is located between 30 and 50 miles (50 and 80 kilometers) above the Earth's surface.

Rocket propellant exhaust is released into the stratosphere and mesosphere, where it can remain for at least 2-3 years. The alumina (Al2O3), chlorine (from hydrochloric acid, HCl), nitrogen oxides (NOx), hydroxyl (OH), and water vapour (H2O) in rocket launch plumes all contribute to ozone depletion through chemical reactions in the Earth's stratosphere. This poses a risk to humanity as the ozone layer protects the Earth from harmful UV radiation. Water vapour leads to increased cloud formation in the stratosphere and mesosphere, and alumina and black carbon can cause radiative forcing, which can result in cooling.

Black carbon, or soot, is a significant pollutant in the upper layers of the atmosphere. It is almost 500 times more efficient at holding heat in the atmosphere than all other sources of soot combined, leading to an enhanced warming climate effect. The increase in space tourism launches is expected to more than double black carbon emissions in just three years, which may undermine the recovery of the ozone layer.

The atmospheric incineration of satellites also produces aluminium oxide, which can alter the planet's thermal balance and deplete the ozone layer. The increase in space debris falling back to Earth has doubled over the past 10 years, and the concentration of aluminium oxide in the mesosphere and stratosphere is predicted to increase by 650% in the coming decades.

Overall, the impact of rocket launches and space debris on the upper layers of the atmosphere is a growing concern, and more research is needed to understand the full extent of the pollution and its potential consequences.

Lack of data on propellant emissions

The impact of rocket propellant emissions on the climate is not yet fully understood due to a lack of comprehensive data. While rocket launches are known to emit pollutants, the specific composition and quantity of these emissions vary depending on the type of propellant used. Rocket propellants can include carbon dioxide (CO2), lithium, aluminum, copper, lead, sodium, and black soot, among other substances. The choice of propellant determines the type and amount of air pollutants released during launch.

Currently, there is a dearth of information regarding the environmental impact of propellant emissions, particularly in the context of the growing space tourism industry. As the number of rocket launches increases, the potential consequences for the Earth's atmosphere become more concerning. The pollutants released by rocket engines, such as black carbon or soot, can have long-lasting effects at high altitudes. However, the full scope of these effects remains unclear due to insufficient data.

The United States' Federal Aviation Administration (FAA) has recognized the potential environmental impact of rocket launches and has conducted environmental assessments. Nonetheless, more comprehensive and systematic data collection is needed to properly identify and quantify the effects of propellant emissions. This includes studying the air quality around launch sites and considering the broader implications for the stratosphere and mesosphere, where rocket pollutants are released.

The space industry, including government agencies and private companies, should prioritize addressing this knowledge gap. Preventive measures and interventions are crucial to mitigating the potential environmental risks associated with rocket propellant emissions. As the space tourism market continues to grow, the window of opportunity to take proactive measures may close. Therefore, it is imperative to devote the necessary time and resources to understanding and addressing this issue effectively.

Furthermore, it is important to acknowledge that the discussion surrounding rocket pollution extends beyond just propellant emissions. The burning of solid rocket fuels, for example, contributes to a hefty carbon footprint, while the production of hydrogen fuel can also lead to significant carbon emissions. Additionally, the accumulation of space junk, including discarded satellites and rocket debris, poses a growing concern that needs to be addressed in conjunction with propellant emissions to comprehensively understand the environmental impact of space exploration activities.

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