Kiera Jefferson
Rocket launches are an integral part of the 21st century, but they also contribute to air pollution. While the percentage of fossil fuels burned by the space industry is only about 1% of that burned by conventional aviation, the number of rocket launches has increased significantly, with a record-setting 180 launches in 2022. Rocket launches emit pollutants such as carbon dioxide, nitrogen oxides, alumina particles, and chlorine, which can deplete the ozone layer and contribute to climate change. The manufacturing of rockets and the re-entry of satellites and rocket boosters can also pollute the environment. Some companies are experimenting with new types of fuel that may burn cleaner, such as methane-based fuel, but the environmental impact of these alternatives is still unclear.
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What You'll Learn
Rocket fuel types and their environmental impact
Rocket launches have become increasingly common, with a record-setting 180 launches to orbit in 2022. This has brought the issue of rocket pollution into the spotlight. The environmental impact of rocket launches depends on the type of fuel used and the emissions produced.
One of the most notorious rocket fuels is Unsymmetrical Dimethylhydrazine (UDMH), also known as "devil's venom". UDMH was used in many rockets launched from the Baikonur Cosmodrome, the world's oldest spaceport. It is highly carcinogenic and is blamed for causing severe ecological damage to the Kazakh Steppe. UDMH spills from discarded rocket stages have poisoned the soil for decades.
Hybrid rocket engines, commonly used in space tourism ventures, burn solid fuel with a liquid or gaseous oxidizer. These engines are relatively simple and safe to operate, but they generate significant amounts of soot or black carbon. The soot particles, along with aluminum oxide, are injected into the higher layers of the atmosphere, affecting how the atmosphere absorbs heat and potentially leading to a stealthy but detrimental impact over time.
Liquid oxygen and liquid hydrogen (LOx/LH2) fuel, used in smaller rockets like Blue Origin's Blue Shepard, is considered environmentally friendly. Its exhaust is primarily water vapour, which has been extensively studied and found to have minimal impact on the atmosphere. However, LOx/LH2 has low energy density, requiring large tanks for lift-off, and is highly explosive, necessitating careful handling.
Methane-based fuels, such as those used by SpaceX's Starship, produce less soot residue than kerosene-based fuels, making engine reuse easier. However, they still emit methane, a potent greenhouse gas. The environmental implications of this are still unclear and require further research.
It is worth noting that the manufacturing process of rockets, involving the production of aluminium and steel, can have a more significant environmental impact than the launch itself. Additionally, rocket launches are not the only polluting aspect of the space industry. Discarded satellites, space debris, and the disposal of waste from the International Space Station also contribute to pollution, both in the atmosphere and in the oceans.
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Climate change and the ozone layer
While the space industry has been deemed small and unchanging, the number of rocket launches has been increasing at an average rate of about 8% per year for the past decade. This has led to a proportional increase in rocket engine emissions, which contain gases and particles that can affect the Earth's climate and ozone layer.
Rocket engines emit various gases and particles, including water vapour, carbon dioxide, carbon soot, carbon monoxide, nitrogen oxides, sulphur oxides, chlorine, alumina, and sulphuric compounds. Out of these, nitrogen oxides, sulphur oxides, carbon monoxide, chlorine, alumina, and nitrogen oxides are considered pollutants by the US Environmental Protection Agency (EPA). These emissions can have a detrimental effect on the Earth's climate and the planet's protective ozone layer.
The ozone layer is a critical component of the Earth's atmosphere, protecting all living things from the harmful impacts of ultraviolet radiation, including skin cancer, weakened immune systems, and disruptions to agriculture and ecosystems. Chlorine, alumina, and nitrogen oxides emitted by rockets are known to destroy ozone, and the accumulation of pollutants in the upper atmosphere can lead to the warming of those atmospheric layers. This warming can slow down subtropical jet streams, influencing the African and Indian summer monsoons, and degrade the protective ozone layer.
Studies have found that the projected increase in rocket launches, particularly those burning fossil fuels and hydrocarbon fuels, will likely result in ozone depletion and altered atmospheric circulation patterns. For example, a tenfold increase in hydrocarbon-fuelled launches within the next two decades is predicted to damage the ozone layer. Additionally, the rise of space tourism and the re-entry of megaconstellation satellites into the atmosphere could further contribute to ozone depletion.
While the aviation industry burns about 100 times more fuel than all rockets launched globally, the unique nature of rocket combustion and the high altitudes at which they emit pollutants can have significant impacts on the climate and ozone layer.
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Space junk and re-entering satellites
Space junk, or space debris, is any piece of machinery or debris left by humans in space. It can refer to large objects such as dead or broken satellites that have failed or been left in orbit at the end of their mission. It can also refer to smaller things, like bits of debris or paint flecks that have fallen off a rocket. There are about 2,000 active satellites orbiting Earth, with 3,000 dead ones also in orbit.
Space junk is the result of us launching objects from Earth, and it remains in orbit until it re-enters the atmosphere. Objects in lower orbits of a few hundred kilometres can return quite quickly, often re-entering the atmosphere after a few years and burning up before they reach the ground. However, larger objects that survive the fall (like satellites) may not burn up entirely and can crash to the Earth's surface. On average, 200 to 400 pieces of tracked space debris fall through Earth's atmosphere every year.
Objects left at higher altitudes of 36,000 kilometres can continue to circle the Earth for hundreds or thousands of years. The presence of this space junk has led to concerns about the Kessler syndrome, also known as the Kessler effect, collisional cascading, or ablation cascade. This is a scenario proposed by NASA scientists Donald J. Kessler and Burton G. Cour-Palais in 1978. It describes a situation in which the density of objects in low Earth orbit (LEO) becomes so high due to space pollution that collisions between these objects cascade, exponentially increasing the amount of space debris over time. This proliferation of debris poses significant risks to satellites, space missions, and the International Space Station, potentially rendering certain orbital regions unusable and threatening the sustainability of space activities for many generations.
On average, one satellite is destroyed by collision with other satellites or space junk every year. As of 2009, there had been four collisions between catalogued objects, including a collision between two satellites in 2009. In March 2021, a Chinese satellite broke up after a collision with a piece of a Russian rocket. In June 2021, a small piece of unidentified space junk slammed into the International Space Station's robotic arm, damaging it.
Several companies have proposed novel solutions to the problem of space junk, including removing dead satellites from orbit and dragging them back into the atmosphere, where they will burn up. Methods include using a harpoon, net, magnets, or lasers to grab or pull down the satellite.
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Manufacturing rockets and carbon output
The carbon output of manufacturing rockets is a complex issue that involves various factors and variables. Let's delve into the details and explore the environmental impact of rocket manufacturing.
Rocket manufacturing, particularly the production of rocket fuel, contributes significantly to carbon emissions. The process of manufacturing rockets involves the use of fossil fuels, which are a major source of carbon dioxide (CO2) emissions. This is particularly true for traditional rocket fuels such as kerosene, methane, and carbon-based fuels. These fuels are derived from fossil sources, and their production and refinement contribute to the carbon footprint of the rocket manufacturing process. Additionally, the energy required for rocket manufacturing, including electricity usage, also contributes to Scope 2 emissions, as defined by SpaceX.
The type of rocket fuel used plays a crucial role in determining the carbon output during manufacturing. For example, kerosene-based fuels, commonly used in SpaceX rockets, have a significant carbon footprint due to the refinement process. On the other hand, alternative fuels like bio-propane, a renewable biofuel created as a waste product from biodiesel production, offer a more sustainable option. Companies like Orbex are turning to bio-propane, which they claim can reduce emissions by up to 90% compared to traditional rocket fuels.
Another important aspect to consider is the ozone-depleting potential of rocket fuels. Rocket launches emit substances such as chlorine, alumina, and nitrogen oxides, which contribute to ozone depletion. This depletion of the ozone layer can have severe consequences, including increased exposure to harmful UV radiation for life on Earth. Additionally, the emission of black carbon or soot from rocket engines can have a warming effect, particularly when released into the upper atmosphere. This can further contribute to climate change and impact the Earth's atmosphere.
It is worth noting that while rocket launches have a significant environmental impact, their overall contribution to carbon emissions is relatively small compared to other industries, such as aviation. However, with the growing demand for space tourism and satellite services, the number of rocket launches is expected to increase, leading to a corresponding rise in carbon emissions. This highlights the importance of developing sustainable alternatives and reducing the carbon footprint associated with rocket manufacturing and launches.
In conclusion, the manufacturing of rockets and the production of rocket fuel contribute significantly to carbon output. However, advancements in alternative fuels, such as bio-propane, and the efforts by companies to reduce their carbon footprint provide a glimmer of hope for more sustainable space exploration. As the demand for space-related activities increases, finding environmentally conscious solutions will become increasingly crucial to mitigate the impact on our planet.
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The future of the space industry
The space industry has evolved from an industry dominated by NASA to one that includes private space companies. As the industry has grown, so has the number of launches per year, with 104 successful launches in 2020, 133 in 2021, and a record-setting 180 launches to orbit in 2022. This growth is expected to continue, driven by demand for services like satellite internet and space tourism.
However, the increase in launches has led to concerns about the environmental impact of the space industry, particularly the pollution caused by rocket launches and space junk. Rocket launches emit pollutants such as carbon dioxide, water vapour, soot, nitrogen oxides, alumina particles, and chlorine, which can deplete the ozone layer, leading to potential health risks such as skin cancer, cataracts, and immune disorders. The soot from rockets is also much more efficient at heating the atmosphere compared to soot from other sources.
The space industry is also contributing to the problem of space junk, with decommissioned satellites, rocket debris, and remnants of old space stations left in Earth's orbit or ditched in the Pacific Ocean. This debris can interfere with the operation of satellites and pose a threat to the environment.
Despite these concerns, some companies are experimenting with new types of fuel and propulsion systems that may reduce pollution. For example, SpaceX's Starship uses a mix of liquid methane and liquid oxygen, which produces less soot than kerosene-based fuels. Blue Origin's BE-4 rocket runs on liquified natural gas, and while it still releases methane, a potent greenhouse gas, it produces less soot.
In addition, the reuse of rockets can help to reduce the carbon output associated with the manufacturing process. Rockets powered by hydrogen or methane can also become carbon neutral if the production of the fuels is powered by renewable energy sources.
As the space industry continues to grow, it is important to consider ways to mitigate its environmental impact. This may include the development and adoption of cleaner fuels and propulsion systems, the reuse of rockets, and the implementation of regulations and standards to promote more emissions-friendly practices. By addressing these challenges, the space industry can strive for sustainable growth while minimizing its impact on the environment.
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Frequently asked questions
Rocket launches are a human activity that injects emissions above the troposphere, into the stratosphere and mesosphere. The pollution from rocket launches is expected to reach 10 gigagrams a year in a couple of decades, along with a temperature rise in parts of the stratosphere of as much as 1.5 degrees Celsius, and a thinning of the ozone layer.
The composition of rocket propellants determines the kind of air pollutants that are emitted during the launch process. Carbon dioxide (CO2) is a common emission, as well as nitrogen oxides, alumina particles, water vapour, and chlorine.
The percentage of fossil fuels burned by the space industry is only about 1% of that burned by conventional aviation. Rocket launches account for less than 0.01% of all CO2 emissions. However, the manufacturing of a rocket is much worse for the environment than the launch itself.
Some companies are experimenting with new types of fuel that may burn cleaner. For example, SpaceX’s Starship burns liquid natural gas, which is almost pure methane, and produces less soot residue. A rocket running on hydrogen or methane can become mostly carbon neutral if the production of the fuels is powered by a renewable energy source.
Aside from rocket launches, the space industry also pollutes in other ways. Discarded satellites and rocket debris burn up and leave a stream of pollutants in the atmosphere. The re-entry of satellites and rocket boosters has been found to change the composition of the stratosphere, which houses the ozone layer.
