Rocket Launches: Polluters Or Green Energy?

Rocket launches are an integral part of the 21st century, but they also contribute to air pollution. Rocket engines emit pollutants such as black carbon, alumina (Al2O3), chlorine, nitrogen oxides (NOx), hydroxyl, and water vapour, which can have a significant impact on the ozone layer and the climate. The number of rocket launches has been increasing, with a growth rate of about 8% per year for the past decade, and the rise of space tourism is expected to further accelerate this trend. While the immediate environmental impact of rocket launches may seem insignificant, the accumulation of rocket pollutants and space junk in the Earth's orbit is a growing concern. Studies and experts have highlighted the need for more research and preventive measures to address the potential environmental risks posed by the space industry.

Rocket propellant pollution

Rocket propellants, such as RP-1 (Rocket Propellant-1), a highly refined form of kerosene, and UDMH (unsymmetrical dimethylhydrazine), are responsible for emitting pollutants into the stratosphere and mesosphere. These upper layers of the atmosphere can trap emissions for a longer period, leading to a more prolonged impact on the environment. The pollution released by rocket propellants includes carbon dioxide, water, black carbon, alumina particles, nitrogen oxides, hydroxyl, and water vapour. These emissions contribute to ozone depletion through chemical reactions in the Earth's stratosphere.

The choice of rocket propellant can also impact the environment. For example, methane-based rocket propellants are being explored as a potential replacement for more polluting options. Methane, while a potent greenhouse gas, burns more cleanly than RP-1 and provides more energy. This could lead to more efficient propulsion units with minimal methane residue.

The lack of data and research on propellant emissions is a concern, as highlighted by Robert Heinecke of Breeze Technologies. Space companies and government agencies should prioritise collecting air quality data around launch sites to implement preventive measures and interventions. The impact of rocket propellant pollution is expected to increase as the space tourism market grows, with estimates projecting a market value of $2.58 billion by 2031 and a 17.15% growth rate annually over the next decade.

Additionally, the issue of "space junk" from derelict satellites, rocket stages, and other space debris re-entering the Earth's atmosphere cannot be ignored. These objects can affect atmospheric chemistry, and their impact on the environment needs further examination.

Climate change acceleration

Rocket launches are an integral part of the 21st century, but they contribute to climate change acceleration. The combustion-driven propulsion of rocket engines emits pollutants, with the type and quantity of emissions depending on the propellants and fuels used. While the current impact is considered relatively small compared to other industries, the growing space tourism market and increasing launch rates could significantly affect the Earth's climate and ozone layer.

Rocket launches emit various pollutants, including carbon dioxide (CO2), water vapour, hydrochloric acid, alumina (Al2O3), nitrogen oxides (NOx), hydroxyl (OH), black carbon, and chlorine. The specific emissions depend on the type of fuel used, with kerosene, hypergolic, liquid hydrogen, and solid fuels being the most common. Kerosene, for example, is a dominant fuel in the United States, Russia, and New Zealand, and it emits large amounts of black carbon.

The global space industry is experiencing a surge in rocket launches, with the launch rate more than doubling in the past decade. This increase is driven by innovations such as rocket reusability, satellite constellations, space tourism, and the growing demand for services like satellite internet. As the number of launches rises, so do the rocket engine emissions. The pollutants are released into the stratosphere and mesosphere, where they can persist for at least two to three years and have a more prolonged impact on the climate compared to earthbound sources of pollution.

While the space launch industry's contribution to atmospheric emissions is currently considered relatively small compared to commercial aviation, the growing space tourism market could change this. Space tourism is expected to become a $2.58 billion market in 2031, with a projected 17.15% annual growth over the next decade. As the number of rocket launches increases, so does the risk of accelerating climate change.

Additionally, "space junk" from disused satellites and other objects accumulating in Earth's orbit poses a growing concern. The unregulated nature of the space sector by international treaties, such as the Montreal Protocol, further highlights the potential environmental risks associated with rocket launches and the need for preventive measures and interventions.

Space junk

Most space junk is moving at extremely high speeds, reaching up to 18,000 miles per hour, which is almost seven times faster than a bullet. This high-speed junk can pose a significant threat to active satellites and spacecraft, as even small impacts can produce a cloud of plasma that poses an electrical risk to solar panels. Hundreds of collision avoidance manoeuvres are performed every year by satellites, including the International Space Station (ISS), to prevent potential damage or destruction.

The accumulation of space junk is a growing concern, as it can lead to a chain reaction of collisions and the creation of even more debris, as theorised by NASA scientist Donald Kessler in 1978. This scenario, popularly depicted in the movie "Gravity," could potentially render Earth's orbit unusable. While this extreme situation may not occur, experts agree that steps must be taken to mitigate the risk.

The responsibility of managing space debris falls on all spacefaring nations, and international collaboration is necessary to address this global challenge. Efforts to remove space junk have already begun, with the European Space Agency awarding a €120 million contract in 2019 for the ClearSpace-1 mission, which aims to remove a 94 kg satellite from orbit using robotic arms and drag it down to burn up in the Earth's atmosphere. Additionally, NASA has researched using a ground-based laser to slow down or alter the course of space junk, although this method has potential drawbacks, such as material degradation.

Overall, while space junk does not currently pose a significant risk, the increasing amount of debris in orbit underscores the importance of proactive measures and international cooperation to ensure the safe and sustainable exploration and utilisation of space.

Air quality impact

Rocket launches have a significant impact on air quality. The various rocket engine propellants produce different emissions, with the most common gaseous emissions being water vapour and carbon dioxide from liquid and solid fuels, as well as hydrochloric acid from solid fuels. The alumina (Al2O3), chlorine (converted 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. The long-term effects of rocket exhaust on air quality include climate change, as rocket launches release greenhouse gases such as carbon dioxide (CO2) and nitrogen oxides (NOx) into the atmosphere. These gases deplete the ozone layer, which is essential for protecting life on Earth from harmful UV radiation.

Rocket launches also contribute to air pollution, releasing gases such as nitrogen oxides (NOx), carbon monoxide (CO), sulfur dioxide (SO2), hydrogen chloride (HCl), and hydrochloric acid (HCl) into the atmosphere. These emissions can have harmful effects on both the environment and human health, causing respiratory problems and eye irritation. The impact of rocket emissions on air quality is expected to become more significant as the space industry grows, with an anticipated surge in the number of rocket launches in the coming years.

The pollution caused by rocket emissions can seem insignificant compared to other challenges, such as the impact of the aviation industry, and the benefits brought by the space industry. However, as the space industry grows, the impact of rocket launches on air quality will become more pronounced. The frequent use of single-use components in traditional rockets contributes to debris and pollution, but the development of reusable rockets aims to reduce this waste.

The impact of rocket launches on air quality is not uniform across all regions. The choice of fuel and launch site can affect the environmental impact of a rocket launch. For example, the fuel UDMH (unsymmetrical dimethylhydrazine), used in many rockets launched from the Baikonur Cosmodrome in Kazakhstan, was highly carcinogenic, turning a large area of the Kazakh Steppe into an ecological disaster zone. The selection of launch sites away from sensitive ecological areas can help to mitigate the environmental impact of rocket launches.

Overall, the impact of rocket launches on air quality is complex and multifaceted. While rocket launches do contribute to air pollution and climate change, the overall impact on the global climate and ozone layer is currently considered minor compared to other sources of emissions. However, with the anticipated growth in the space industry and the increasing number of rocket launches, the environmental impact of rocket emissions is expected to become more significant in the future.

Carbon dioxide emissions

Carbon dioxide (CO2) emissions are a significant concern when it comes to rocket launches. Rocket launches require large amounts of propellants to exit Earth's atmosphere, and the composition of these propellants determines the type and amount of air pollutants emitted. While the number of rocket launches is currently low compared to aircraft flights, the growth of the space tourism industry and the increasing demand for satellite internet services are expected to significantly increase the number of rocket launches in the coming decades. This will inevitably lead to a rise in carbon dioxide emissions.

Rocket launches using liquid or solid fuels emit carbon dioxide as one of the main gaseous emissions, along with water vapour and, in the case of solid fuels, hydrochloric acid. Water vapour and carbon dioxide emissions from rocket launches do not significantly affect the global climate or ozone layer, according to Larson et al. (2017). However, the impact of carbon dioxide emissions on the upper layers of the atmosphere, where they persist for longer periods, is a cause for concern.

The global space industry is on the verge of a significant increase in the number of rocket launches. This will inevitably lead to a proportional increase in rocket engine emissions, including carbon dioxide. The impact of these emissions on the Earth's climate and ozone layer is yet to be fully understood, but it is essential to recognise that rocket launches contribute to the overall pollution levels in the atmosphere.

The United States' Federal Aviation Administration (FAA) conducted an environmental assessment of SpaceX Falcon launches, examining air quality under the National Ambient Air Quality Standards (NAAQS). While this assessment found no significant impact on ground-level air quality, it is important to note that most rocket launch pollution is released into the stratosphere and mesosphere, where it can persist for at least two to three years. The alumina (Al2O3), chlorine, 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.

While rocket launches may not seem as polluting as other forms of transportation, it is important to recognise that they contribute to overall carbon dioxide emissions. The impact of these emissions on the environment and the potential for mitigation or reduction of these emissions should be further studied and addressed by the space industry and government agencies. As the space tourism market grows, the environmental cost of space travel will become more significant, and preventive measures and interventions will become increasingly crucial.

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