Space Travel's Pollution Problem: How Bad Is It?

Since the first space launch in 1957, humans have been launching thousands of projectiles into space, and all of this space travel has had a significant impact on the environment. The atmosphere is polluted with thousands of objects, and the increase in artificial light at night has led to the deterioration of the health of biotic species, the degradation of the aesthetic view of the night sky, and cosmic observation hindrance due to excessive lighting. In addition, space travel has contributed to the creation of space junk, which includes derelict spacecraft, mission-related debris, and fragmentation debris from the breakup of rocket bodies and spacecraft. This space junk poses a risk to functioning satellites and spacecraft, and it has been estimated that there are about 2,000 active satellites and 3,000 dead ones orbiting the Earth. Furthermore, rocket launches have been found to inject about 1,000 tons of soot into the upper atmosphere per year, which contributes to climate change and damages the ozone layer.

Rocket launches inject about 1,000 tons of soot into the upper atmosphere per year

Rocket launches are a significant contributor to pollution in the Earth's atmosphere and beyond. According to a study by the National Oceanic and Atmospheric Administration (NOAA), global rocket launches inject about 1,000 tons of soot into the upper atmosphere annually. This figure is based on the 180 rocket launches that occurred in the year the study was conducted. With the space industry expanding, the amount of soot injected into the upper atmosphere is expected to increase.

Soot from rocket launches lingers in the atmosphere for up to five years, absorbing heat and contributing to climate change. It also damages the ozone layer, exposing the planet to harmful ultraviolet (UV) radiation. The ozone layer is particularly vulnerable to temperature changes, and the increase in rocket launches is projected to lead to reduced ozone levels in the Northern Hemisphere, where most rocket launches take place. This will result in higher levels of harmful UV radiation reaching the Earth's surface, posing risks to human health and the environment.

The type of fuel used in rockets plays a crucial role in determining the amount of pollution produced. For instance, SpaceX's Starship spacecraft uses methane instead of kerosene, which produces less black soot. Blue Origin's New Shepard rocket is even cleaner, burning liquid oxygen and liquid hydrogen and producing only water vapour as exhaust. However, water vapour in the upper atmosphere can still trap and retain heat, contributing to the warming of the planet.

In addition to soot emissions, rocket launches also contribute to space pollution, also known as space junk or space debris. Since the first space launch in 1957, thousands of rockets and satellites have been sent into orbit, and many of them are still there. This space junk includes dead satellites, fragments from rocket bodies and spacecraft, and even smaller particles such as paint flecks. The risk of collision between space objects is a significant concern, as it can create thousands of new pieces of dangerous debris. Space agencies are constantly monitoring potential threats to their equipment and astronauts, and collision avoidance manoeuvres are frequently performed.

The impact of space travel on the environment extends beyond pollution and includes other factors such as the release of atmospheric pollutants from satellite thrusters, the incineration of orbital debris, and the accidental release of persistent pollutants. Additionally, the increase in artificial light at night due to satellites has negative consequences for the health of biotic species and the aesthetic view of the night sky. Overall, while rocket launches may not be the primary source of pollution, the growing space industry's impact on the Earth's atmosphere and climate cannot be ignored.

Hydrocarbon-fuelled launches damage the ozone layer and change atmospheric circulation patterns

According to a study by the National Oceanic and Atmospheric Administration (NOAA), global rocket launches inject about 1,000 tons of soot into the upper atmosphere per year. This amount is expected to increase as the space industry continues to expand. The soot released by rockets lingers for up to five years, absorbing heat, contributing to climate change, and damaging the ozone layer. This damage to the ozone layer, in turn, exposes the planet to dangerous ultraviolet (UV) radiation.

NOAA research published in the Journal of Geophysical Research Atmospheres indicates that a tenfold increase in hydrocarbon-fuelled launches is plausible within the next two decades, given the recent trends in space traffic growth. This increase in hydrocarbon-fuelled launches would damage the ozone layer and change atmospheric circulation patterns. The research team simulated the impact of approximately 10,000 metric tons of soot pollution injected into the stratosphere over the Northern Hemisphere annually for 50 years. They found that this level of activity would increase stratospheric temperatures by 0.5–2° Celsius or approximately 1–4° Fahrenheit. This increase in temperature would, in turn, change global circulation patterns by slowing the subtropical jet streams by as much as 3.5% and weakening the stratospheric overturning circulation.

The type of fuel used in rockets can make a difference in terms of pollution. For instance, SpaceX's Starship spacecraft uses methane instead of kerosene. While methane is a potent greenhouse gas, it burns cleaner than kerosene, producing less black soot. Blue Origin's New Shepard rocket is even cleaner, burning liquid oxygen and liquid hydrogen and producing only water vapour as exhaust. However, water vapour in the upper atmosphere can still trap and retain heat, contributing to climate change.

In addition to the pollution caused by rocket launches, space travel also generates space junk or space debris. This includes dead satellites, rocket debris, paint flecks, and collision fragments. There are currently thousands of dead satellites and millions of smaller pieces of space junk orbiting the Earth, posing a risk of collision with functioning satellites and other space objects. While space junk does not currently pose a significant risk, the increasing number of satellite launches could lead to more collisions and the creation of additional space junk.

Space junk, or debris, can collide with other objects and create more debris

Space exploration has resulted in a large amount of space junk or debris. As of November 2022, the US Space Surveillance Network reported 25,857 artificial objects in orbit above the Earth, including 5,465 operational satellites. However, these are just the objects large enough to be tracked. There are also more than 128 million pieces of debris smaller than 1 cm, about 900,000 pieces of debris 1–10 cm, and around 34,000 pieces larger than 10 cm.

Space debris is any piece of machinery or debris left by humans in space, including defunct satellites, derelict spacecraft, and fragments from rocket bodies, spacecraft, and collisions. These objects can collide with other objects and create more debris, a scenario known as the Kessler syndrome. First proposed by NASA scientist Donald Kessler in 1978, the Kessler syndrome describes a situation in which the density of objects in low Earth orbit becomes so high 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, and could potentially render certain orbital regions unusable. For example, in 2016, a space debris fragment only a few millimeters wide punched a 16-inch-wide hole in one of the solar panels of Europe's Earth-observing satellite Sentinel 2. While Sentinel 2 survived the incident, engineers said that if the space junk had hit the craft's main body, the mission could have been over. In another instance, a three-decade-old Soviet satellite disintegrated in orbit some 870 miles (1,400 kilometers) above Earth, likely due to a space debris strike.

The risk of collisions is further exacerbated by the increasing number of satellites being launched into orbit. Several companies, including SpaceX and Amazon, plan to launch thousands of satellites to achieve global satellite internet coverage, potentially adding 50,000 satellites to those already in orbit. This will also mean a lot more collision avoidance maneuvers will need to be performed.

Solid rocket fuels are considered the worst in terms of byproduct emissions

While rockets are a tiny contributor to overall emissions, they are the single direct source of emissions in the upper stratosphere. The type of fuel used in rockets can make a difference in terms of byproduct emissions. Solid rocket fuels are considered the worst in this regard. They emit nasty toxic compounds and deplete the ozone layer. The shuttle's solid engines used a crystalline compound called ammonium perchlorate, which releases hydrochloric acid as a byproduct.

Solid rocket boosters are also very bad for the environment. NASA's new Space Launch System moon rocket, which first launched in November 2022, is an especially polluting machine. While it uses a liquid oxygen-hydrogen mix in its four main engines, its two attached solid fuel engines, which account for most of the vehicle's thrust, produce the ozone-damaging pollutant chlorine.

Solid rocket boosters are also used by large rockets such as ESA's Ariane 5 and 6, which need them to overcome the initial pull of Earth's gravity. SpaceX's massive, 33-engine Starship spacecraft also uses solid rocket boosters. Each passenger aboard a rocket is responsible for 100 times more climate-changing pollution than a passenger aboard an airplane. The soot from rockets lingers for up to five years, absorbing heat, contributing to climate change, and damaging the ozone layer, which exposes the planet to dangerous ultraviolet (UV) radiation.

The increasing frequency of rocket launches has researchers worried about the future of the stratosphere and the world. Predictions for rocket traffic in the coming decades point dramatically upward. Should the sun heat up enough of the particles from the fuel trails, space travel could become a significant driver of climate change.

The increase in artificial light at night has led to the deterioration of the health of biotic species

Space travel and exploration have contributed significantly to pollution, with thousands of dead satellites and pieces of debris orbiting the Earth. This space junk not only poses a collision risk but also adds to the pollution problem. The increase in artificial light at night from satellites has led to the deterioration of the health of biotic species, affecting their bioenvironment and causing aesthetic degradation of the night sky. This light pollution also hinders cosmic observation due to excessive lighting.

The impact of space travel on the environment extends beyond just physical debris. Rocket launches contribute to atmospheric pollution, with each launch injecting about 1,000 tons of soot into the upper atmosphere per year. This soot lingers for several years, absorbing heat and contributing to climate change. Additionally, the type of fuel used in rockets plays a significant role in pollution levels. While methane is a potent greenhouse gas, it burns cleaner than kerosene, producing less soot. NASA's Space Launch System moon rocket, which first launched in November 2022, uses a mix of liquid oxygen and hydrogen, but its solid fuel engines produce ozone-damaging chlorine pollutants.

The accumulation of space debris, or orbital debris, has led to the creation of a well-recognized orbital debris cloud that continues to grow. This debris includes derelict spacecraft, mission-related debris, fragmentation debris from broken rocket bodies, and even paint flecks. The risk of collision is a significant concern, as collisions can result in the creation of thousands of new pieces of dangerous debris. While most debris burns up in the atmosphere, larger objects can reach the ground intact, contributing to air pollution.

Furthermore, the pollution caused by space travel extends beyond the atmosphere and into space itself. Metals, plastics, and composites released from satellites, such as sodium-potassium alloys (NaK), contribute to the pollution problem. NaK, leaked from the cooling loop of a Russian satellite's nuclear reactor, is highly corrosive and ignitable, posing risks of explosion upon contact with air or water. This corrosive nature also contributes to the formation of more orbital debris, increasing the volume of the orbital debris cloud.

The impact of space travel on the environment is undeniable, and it is essential to recognize that our actions in space have consequences. As we strive to protect our planet and address pollution on Earth, we must also address the pollution and damage caused by space travel and take responsibility for cleaning up the mess we have created beyond our planet.

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