As noted above, the two types of space debris are artificial debris and natural debris:
- Natural debris comes from meteoroids that have orbited the Sun for millions of years and may come into our orbit if they are thrown off course, for example, by a collision. These objects can range in size from tiny dust particles to large boulders.
- Artificial debris is that which is left in orbit as a result of space missions, launches and activities. This man-made debris includes defunct satellites, rocket stages, fragments generated by collisions between operational satellites or other objects, and even pieces released during routine maintenance activities on board a spacecraft.
The main causes of artificial space debris are space launches, satellites and the uncontrolled reentry of artifacts.
- Space Launches: Every time a rocket or other craft is launched into space it leaves a trail of discarded parts behind. These parts include fuel tanks and upper stages that can remain in orbit for decades before they finally reenter the Earth’s atmosphere.
- Satellites: Operational satellites can generate space debris when they collide with each other or other items of debris. In addition, defunct satellites can remain in orbit for years, posing a threat to other satellites and space missions.
- Uncontrolled Reentry of Artifacts: Items that are orbiting the Earth can break up when they enter the atmosphere, leaving further debris behind. Examples of this include parts from past Space Shuttle missions and components from early Soviet ASAT testing (anti-satellite).
The presence of space debris poses several risks to astronauts and spacecraft in low-Earth orbits (LEO) and to operational satellites in geostationary orbits (GEO).
Should an astronaut or spacecraft in LEO get hit by even small pieces of space debris there is a real chance of damage to the craft or even serious injury to an astronaut, especially if they are travelling at high speeds relative to one another.
Operational satellites can also be damaged by collisions with space debris, potentially rendering them unusable or even destroying them and creating yet more debris.
As the amount of orbital junk increases, there is the potential for the ‘Kessler Syndrome’ to come into play, where space debris collisions have created so much new space junk that it is no longer safe to lunch missions into outer space, severely limiting our ability to explore space and conduct scientific research.
Organisations like NASA and the European Space Agency (ESA) have been working on strategies to mitigate the risks posed by large amounts of space debris orbiting the Earth. These strategies can be split into three main areas; active debris removal, deflecting debris, and prevention and mitigation of future debris, although each of them comes with their own challenges.
1. Active Debris Removal
As the name suggests, active debris removal involves the physical removal of debris from space. This can be done using various approaches, including the use of robotic arms, nets, and even space harpoons for larger items. Once collected, the debris can then be deorbited and allowed to burn up in the Earth's atmosphere. However, cost constraints have proven to be a challenge for launching these types of missions into space.
2. Deflecting Debris
This technique involves changing the trajectory of debris so that it no longer poses a threat to operational satellites, spacecraft or astronauts. This can include the use of ground-based lasers mounted on telescopes that can deflect items away from collision courses. Again, cost constraints for building lasers powerful enough to traverse long distances in space and deflect large objects away from potential collisions have limited the use of this method.
3. Prevention and Mitigation of Future Debris
Designing satellites and spacecraft so that they can be safely deorbited at the end of their lifespan without breaking up and using fuel efficient rockets for launches will help reduce the amount of debris that is being left in space. To be truly effective, this needs international collaboration to ensure everybody follows the same guidelines.
As we have become increasingly aware of the issue of space debris, several organisations have been working on finding solutions to the problem. Examples include:
1. The European Space Agency (ESA)
The ESA has created a programme dedicated to space debris mitigation and removal, including conducting research into the causes of space debris.
2. NASA
We can credit NASA with setting up an ‘Orbital Debris Program Office,’ tasked with reducing the risk posed to human spaceflight and orbiting satellites by space debris.
2. Inter-Agency Space Debris Coordination Committee (IADC)
This committee, composed of representatives from eleven different space agencies from around the world, is working to coordinate international efforts to mitigate space debris.
3. ClearSpace
Founded in 2018, this company is working to develop technologies for the removal of large pieces of space debris from orbit.
4. RemoveDebris
This international collaborative project is bringing businesses together with universities to research methods for capturing, deorbiting and disposing of small pieces of space debris safely and efficiently.
While space debris can be either natural or artificial, increasing amounts of artificial, man-made space debris in orbit around the Earth is posing an ever-greater risk to satellites, spacecraft, astronauts and even our ability to explore space at all.
A number of organisations have begun to investigate workable solutions for removing and preventing space debris.
To achieve the goal of making space activities safe, governments and international organisations need to collaborate to make sure rockets and satellites are designed with safety and their end-of-life in mind. International strategies are also needed for deflecting or removing existing space debris so that future generations can continue to explore outer space safely.
What is in Space Debris?
Space debris can refer to natural or artificial objects in space, but usually refers to defunct man-made items that are in orbit around the Earth. These can range from large objects such as obsolete satellites to small fragments of machinery and other materials left behind by humans. Explosions can be triggered by residual fuel that has remained in tanks or fuel lines, while space debris can pose a serious threat to manned and unmanned spacecraft. A piece of debris just a few centimetres across can have the explosive impact of a hand grenade if it strikes at object at high speeds.
How much Space Debris is there Right Now?
The European Space Agency (ESA) estimates that there are over 34,000 items of debris larger than 10cm across in orbit around the Earth. NASA says that there are over 500,000 pieces of space debris the size of a marble or larger, in addition to millions of smaller objects that are more difficult to track.
The amount of space debris has been growing since the launch of Sputnik 1 in 1957 due to the increased use of assets such as communications satellites in the ensuing years. Collisions between existing debris and new launches continues to increase the amount of space debris orbiting the Earth.
Can Space Debris Hit Earth?
While most of the pieces of space debris burn up in the Earth’s atmosphere, it is still possible for items to make it through and cause damage on the planet’s surface. An incident in 1997 saw a piece of debris strike a home in Texas, although fortunately nobody was injured. NASA, the ESA and other organisations have been tracking space debris and are working on solutions to remove existing debris from orbit.
How does Space Debris Affect Us?
Space debris poses a significant risk to astronauts, satellites and spacecraft. Even the smallest pieces of debris can cause significant damage or injury, with pieces of debris travelling at speeds of up to around 17,500 mph.
In March 2023, for example, the International Space Station (ISS) had to fire it’s thrusters to avoid an object that was getting dangerously close.
As well as posing a danger for space missions, the build-up of space debris threatens to become so great as to impact our ability to launch space exploration programmes, conduct scientific research or even launch new satellites into orbit at all.
What are the risks associated with space debris?
Space debris poses a risk to astronauts, satellites, spacecraft and even to our ability to explore space at all. Space debris is at its most dangerous when it is travelling at high speeds, leading to hypervelocity impacts. These impacts, between two pieces of debris, can cause explosions that can severely damage nearby spacecraft and satellites. Fragments of space debris from such collisions create debris clouds that make space even more hazardous to navigate.
Metallic space debris can also cause electromagnetic interference that disrupts communication signals between orbiting spacecraft and ground stations, leading to loss of contact or mission failure.
The materials that are released into space as a result of a collision can be toxic, potentially contaminating the Earth’s atmosphere or even other planets or moons.
How do scientists detect and track space debris?
The most common method for detecting and tracking space debris is with radar systems that use radio waves to detect and measure the position, velocity, size, shape, and other characteristics of space debris. Optical telescopes can also be used to locate and observe larger objects that reflect sunlight.
Both techniques are often used together, with radar systems offering information on the position of space debris and optical telescopes then being used to observe how the debris is travelling. Combined, this information makes it possible to plot a potential trajectory for an object and determine if it poses any risk of collision with other spacecraft or satellites.
How does space debris affect satellites?
Space debris can pose a significant threat to satellites, especially if they are struck at high speeds. At speeds of up to 17,500 mph, even a small piece of debris can render a satellite useless. In addition, collisions with satellites can lead to the creation of more space debris, increasing the risk of even more collisions in the future. Metal space debris can also interfere with signals between the satellites and the Earth, compromising their effectiveness.
What can be done to reduce the risk of space debris?
The first challenge in reducing the risk of space debris involves developing technologies that can successfully capture and remove this space junk from orbit. Space junk can also be deflected so that it changes trajectory to a safer route or towards the Earth where it can safely burn up in the atmosphere. In addition to removing or deflecting existing space debris, efforts are needed to prevent the further accumulation of orbital junk by designing spacecraft and satellites with better shielding against collisions, and systems that do not leave debris behind in space.
How do space missions help reduce space debris?
Space missions are tackling space debris in a range of ways. These include reorbiting spacecraft and other items into ‘disposal orbits’ and removing large items of debris by bringing them back into the Earth’s orbit where they can burn up. Future missions are also being designed with an end-of-life plan to minimise the amount of debris left in orbit.
What are the laws and guidelines relating to space debris?
There are a number of laws and guidelines to regulate the creation and disposal of space debris. The United Nations Committee on the Peaceful Uses of Outer Space (UNCOPUOS) has been at the forefront of developing regulations for space activities since 1959. In 1972, UNCOPUOS adopted the first set of international guidelines for space debris mitigation, updating them in 2007. These guidelines recommend that all spacecraft are designed with end-of-life disposal plans to minimise the amount of debris created during reentry into Earth's atmosphere. Additionally, they suggest that operators should track their spacecraft and take measures to avoid collisions with other objects in orbit.
Individual nations have also created laws related to space debris. The United States, for example, passed The Space Debris Act in 1995 that requires government agencies to develop plans for disposing of spacecraft once they are no longer operational. This law also prohibits the launching of any object into space that is likely to create significant amounts of debris or cause harm to other spacecraft or people on Earth.
Other laws, guidelines and bodies include the Outer Space Treaty and the Inter-Agency Space Debris Coordination Committee.
What is being done to clean up space debris?
Organisations like the European Space Agency and NASA have been joined by private companies in seeking solutions for cleaning up space debris. These include a range of potential solutions, including the ELSA-d spacecraft, which consists of two satellites stacked together, each equipped with a magnetic docking system to capture and de-orbit debris. In addition, the US Space Force has partnered with Swiss startup, ClearSpace, to develop a debris-removing spacecraft.
Other ideas for cleaning up space debris include nets, laser blasts, harpoons, giant foam, balloons, self-destructing janitor satellites, walls of water, space pods and tungsten bullets.
There are many proposed solutions for cleaning up space debris, but more research and testing needs to be done before any of them can be implemented effectively.
How can I get involved in combating space debris?
The best way to support efforts to combat space debris is to support organisations that are working to develop technologies to actively remove it from orbit or mitigate against the future production of orbiting debris.