Greta Jimenez
Since the beginning of the space age in the 1950s, humans have launched thousands of rockets and satellites into orbit, many of which are still there. This has resulted in a growing problem of space junk or space pollution, with thousands of dead satellites and millions of smaller pieces of debris orbiting the Earth. This debris poses a significant threat to active satellites and spacecraft, with the risk of catastrophic collisions and damage. The International Space Station, for example, has had to manoeuvre multiple times to avoid potential collisions. As of 2021, the United States Space Surveillance Network tracked more than 15,000 pieces of space debris larger than 10 cm, with an estimated 200,000 pieces between 1 and 10 cm and millions of smaller pieces. While some debris burns up in the atmosphere, larger objects can reach the ground intact, contributing to air pollution.
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What You'll Learn
Space junk/debris
Since the 1950s, humans have launched thousands of rockets and satellites into space. Many of these are still orbiting Earth, along with tens of thousands of fragments of space debris. This space junk or space debris is any piece of machinery or debris left by humans in space, including dead satellites, derelict spacecraft, mission-related debris, and fragments from rocket bodies and spacecraft. While most of this debris burns up in the atmosphere upon re-entry, larger objects can reach the ground intact, contributing to pollution on Earth.
Space debris is a growing problem, with about 4,000 active and inactive satellites in space, alongside approximately half a million bits of floating space debris. This debris ranges in size from micro-millimetres to objects as large as two double-decker buses. The risk of a catastrophic collision between a space shuttle and a piece of space debris was estimated to be 1 in 300, and even higher for missions to the Hubble Space Telescope, at 1 in 185. This risk has led to the development of technologies to remove space debris, such as the DragEN device, which uses a conductive material to gather electric and magnetic forces to remove debris from orbit.
In addition to the physical risk posed by space debris, there are also economic concerns. Satellites worth billions of dollars are at risk of random destruction by collision with space debris. If these satellites were to be destroyed or go offline, it could take a significant amount of time to replace them, impacting businesses and industries that depend on them, such as telecommunications.
To address the issue of space debris, several technical approaches to mitigate its growth have been proposed and implemented. These include passivating spacecraft at the end of their useful lives, using upper stages that can reignite to decelerate and deorbit, and launching satellites into elliptical orbits so they quickly decay and are destroyed upon re-entry. Despite these efforts, the levels of space junk continue to rise, and there is a lack of comprehensive legal or cost assignment structures in place to reduce space debris effectively.
The vulnerability of satellites to debris has also raised concerns about the potential for attacks on LEO satellites to create debris clouds. Such an attack could heavily damage the LEO environment and increase the risk of collisions. While space junk does not currently pose a significant risk to exploration efforts, it is a growing problem that requires attention to prevent it from becoming a more serious issue in the future.
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Man-made pollution
Since the 1950s, humans have launched thousands of rockets and satellites into space. Many of these are still orbiting the Earth, alongside fragments of space debris. This debris, also known as space junk, space pollution, or cosmic debris, is any piece of machinery or debris left by humans in space. It includes derelict spacecraft, abandoned launch vehicle stages, mission-related debris, and fragmentation debris from the breakup of rocket bodies and spacecraft. In addition, space debris includes smaller objects such as paint flecks that have fallen off rockets, solidified liquids expelled from spacecraft, and unburned particles from solid rocket motors.
Space debris is a growing problem, with an ever-increasing risk of collisions as more objects are launched into space. There are currently about 4,000 active and inactive satellites in space, which are at risk of being hit by approximately half a million pieces of space junk. This junk travels at incredibly high speeds, with the potential to impact other objects at over 22,300 mph, faster than a speeding bullet. Even tiny pieces of space junk can cause significant damage, as evidenced by a collision with the International Space Station in 2006, which chipped a heavily reinforced window.
The accumulation of space debris has been caused by several factors, including institutional and systemic factors such as political, legal, economic, and cultural influences. There is a lack of commercial incentive to address the issue, as the cost of cleanup falls on all users of space technology rather than the entities producing the debris. Additionally, the focus on space exploration in the early days of the space age led to a lack of concern for the potential consequences of leaving debris in space.
To address the issue of space debris, several technical approaches have been proposed and tested. These include methods to mitigate the creation of new debris, such as launching satellites into elliptical orbits that will quickly decay and cause the satellite to burn up upon re-entry into the Earth's atmosphere. For spacecraft in higher orbits, passivation and the use of upper stages that can decelerate and deorbit the spacecraft have been suggested. To deal with existing space debris, technologies such as harpoons, magnets, and nets have been proposed to remove debris from orbit and allow it to burn up in the atmosphere.
While space debris is a pressing issue, it is important to note that it primarily affects the low Earth orbit (LEO), with 85% pollution in this region. Beyond Earth's orbit, the amount of space junk is limited and does not currently pose a significant problem.
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Natural micrometeoroid pollution
Natural micrometeoroids are a form of space pollution. They are tiny particles that orbit the Earth at hypervelocity speeds of 10 km/s (22,000 mph). These micrometeoroids are a natural form of space junk, distinct from the human-made debris also polluting the Earth's orbit.
Micrometeoroids pose a significant threat to space exploration and spacecraft. With an average velocity of 10 kilometres per second relative to a spacecraft in orbit, micrometeoroids can cause constant degradation of the outer casing of spacecraft. This is due to the high-velocity impact, which can be likened to sandblasting. Long-term exposure to these micrometeoroids can threaten the functionality of spacecraft systems. The risk is especially high for objects that spend long periods of time in space, such as satellites.
The issue of micrometeoroids impacting spacecraft has been addressed through the use of the Whipple shield, also known as a meteor bumper. This technology involves a thin foil film held a short distance away from the spacecraft's body. When a micrometeoroid strikes the foil, it vaporises into a plasma that quickly spreads out and dissipates before it can penetrate the structural material of the spacecraft. This innovation has allowed for the construction of lighter spacecraft, as the structural integrity of the body is not dependent on its ability to withstand direct meteoroid strikes.
Despite the implementation of protective measures such as the Whipple shield, micrometeoroids continue to be a concern for space exploration. The high velocities and constant presence of micrometeoroids in Earth's orbit contribute to the ongoing challenge of mitigating their impact. Additionally, micrometeoroids have been found to affect the age and appearance of Saturn's rings. Simulations of micrometeoroid impacts on the icy ring particles suggest that non-icy material may not accumulate as expected, resulting in limited pollution of the particles. This finding has implications for understanding the age of Saturn's rings, which may be older than previously estimated.
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The risk of collision
Since the 1950s, thousands of rockets and satellites have been launched into space, with many still orbiting the planet. This has resulted in an ever-increasing risk of collision as more objects are sent into orbit. The issue of space junk or space debris, which includes both large objects such as dead satellites and smaller debris like paint flecks, poses a significant threat to active satellites and spacecraft.
The increasing number of objects in orbit, including active and dead satellites, rocket bodies, and smaller debris, has led to a higher probability of collisions. As more countries and companies launch satellites and space missions, the Kessler Syndrome becomes a more pressing concern. This scenario describes a situation where the density of objects in low Earth orbit becomes so high that collisions create a cascade effect, exponentially increasing the amount of space debris over time.
To mitigate the risk of collision, space agencies and companies perform "collision avoidance manoeuvres". However, as the number of objects in orbit increases, these manoeuvres become more challenging and frequent. In addition, the removal of space debris, particularly large and dangerous objects, is a complex task due to the high speeds and explosion risks associated with these objects.
The continued creation of space debris and the increasing risk of collisions highlight the importance of adopting debris mitigation measures. Prudent vehicle design, careful choice of orbits, and the development of new technologies to passivate and dispose of missions are crucial steps to address this issue. By reducing the generation of new orbital debris and actively managing existing debris, we can minimise the risk of collisions and ensure the safe and sustainable use of space for future generations.
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Cleaning up space pollution
Space debris, also known as space junk, refers to defunct human-made objects in space that no longer serve a useful function. This includes derelict spacecraft, mission-related debris, and fragmentation debris from the breakup of rocket bodies and spacecraft. The issue of space junk has become increasingly prominent since the dawn of the space age in the 1950s, with thousands of dead satellites and rocket fragments currently orbiting the Earth. This debris poses a significant threat to active satellites and spacecraft, with collisions resulting in further debris and potential damage or destruction.
The recognition of the problem has led to the development of various methods to address and mitigate space pollution. Here are some approaches to cleaning up space pollution:
Removal of Dead Satellites
The removal of dead satellites from orbit is a crucial aspect of space pollution mitigation. Several techniques have been proposed, including using a harpoon, a net, magnets, or even lasers to capture and deorbit these satellites, causing them to burn up upon re-entry into the Earth's atmosphere.
Controlled Deorbiting and Reusable Technologies
Spacecraft operators are exploring controlled and uncontrolled reentry methods for satellite decommissioning. By designing satellites for controlled deorbiting at the end of their mission, the risk of collisions and the creation of additional debris can be reduced. Additionally, the use of reusable technologies, such as reusable rockets, can help address the issue of space junk.
Active Debris Removal Missions
Active debris removal missions involve sending specialized technology into space to capture or remove space junk. For example, the European Space Agency (ESA) plans to use a robotic arm in a 2025 mission to capture a piece of debris and pull it out of orbit, allowing it to burn up during re-entry.
Space Traffic Management and Collision Avoidance
Improving space traffic management and collision avoidance systems is essential for preventing collisions and the subsequent generation of more space debris. This includes tracking and monitoring the position and trajectory of space objects to facilitate predictive models and manoeuvres that avoid potential collisions.
Policy and Regulatory Efforts
In addition to technological solutions, legislative and regulatory efforts are necessary to address space pollution. The United Nations, for instance, has requested that companies remove their satellites from orbit within 25 years of their mission's end. However, enforcement of such policies remains challenging, and there is currently no comprehensive legal regime or cost assignment structure in place to reduce space debris effectively.
The issue of space pollution is a pressing concern that requires a multifaceted approach. While various methods for cleanup and mitigation have been proposed, the implementation of these solutions and the coordination between different entities will be crucial in ensuring the sustainability of space exploration and the safety of active satellites and spacecraft.
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Frequently asked questions
Space pollution, also known as space junk, space waste, space trash, space garbage, or cosmic debris, refers to defunct human-made objects in space that no longer serve a useful function. This includes derelict spacecraft, mission-related debris, and fragmentation debris from the breakup of derelict rocket bodies and spacecraft.
As of 2021, the United States Space Surveillance Network was tracking more than 15,000 pieces of space debris larger than 10 cm across. It is estimated that there are about 200,000 pieces between 1 and 10 cm across and millions of pieces smaller than 1 cm. In total, there could be half a million bits of floating space debris, ranging from microscopic chips of paint to the size of two double-decker buses.
Space pollution poses a threat to both manned and unmanned spacecraft, as well as the Earth's inhabitants. A collision with even a small piece of space debris can damage a spacecraft due to the high speeds at which objects orbit the Earth. In addition, space debris contributes to air pollution when it burns up in the atmosphere and can also reduce ozone concentration.
There have been several technical approaches to mitigate the growth of space debris, such as passivating spacecraft at the end of their useful life and using upper stages that can decelerate to deorbit. The United Nations has also requested that companies remove their satellites from orbit within 25 years after their mission ends. However, enforcement is challenging, and there is currently no comprehensive legal regime or cost assignment structure in place to reduce space debris effectively.
