Over the past 60 years of space exploration, thousands of rockets have launched to space, resulting in a sea of space junk circling the Earth.
Space junk is inactive machinery or debris left by humans in space. These ranges from less than a millimetre to the size of a rocket stage. To date, it is estimated that there are over 30 thousand tracked objects that are over 10 cm, about 500,000 marble-sized debris and over 100 million debris that are 1 mm or smaller. Tiny debris resulting from fallen parts of satellites pose huge risks to other operational satellites in orbit. They travel at a speed of 10 km/s, and a tiny piece of junk could easily damage spacecraft or satellites upon collision. In worst cases leading to leaks or mixing of fuel components, this triggers self-ignition and explosion.
What goes up doesn’t come down, except for space junk in very low Earth orbit (LEO) that will re-enter the Earth after a short period of time. With an annual launch rate of 110, and future break-ups of 10 to 11 per year, the population of space debris in orbit will continue to grow. Over time, the accumulated mass of space debris will result in a chain reaction of collisions generating more space junk to a point that the Earth’s orbit is no longer usable. This is known as the Kessler syndrome proposed by Donald Kessler, a NASA scientist, in 1978. At that point, satellite applications we relied on in modern day to day life, such as telecommunication, navigation, weather forecasting, and Earth observation will be affected. This is a long lasting problem that will affect generations.
Some scientists described the space junk problem as a “tragedy of the commons”, and urged the United Nations to treat the orbital space environment as part of the global commons that are worthy of protection. NASA has established and signed the Artemis Accords with seven other founding member nations to create a sustainable, safe, peaceful and prosperous future in space, and ESA has introduced the zero debris approach, with the aim to eliminate debris production in the Earth orbits by 2030.
The outlook of the space sector is switching towards commercialization. There is a rise in demand for space data, related products and services. With the advancement of technology, the costs of launches have decreased by 95% from $65,000 per kilogram to $1,500 per kilogram. Launches are more affordable than before, leading to an increase in launch frequencies (22% increase in 2022) from new and current players in the space industry, and the LEO is becoming congested.
Fortunately, the growing problem of space junk has attracted attention. Big players such as SpaceX are developing reusable launch vehicles, with a focus on reusability in near and long term. Missions such as the RemoveDEBRIS project and space companies such as ClearSpace are testing and developing the best methods to remove space debris actively. Other measures such as satellites “end-of-life” disposal manoeuvres, in which satellites deorbit after they reach the end of their operational life to prevent them from converting to space junk.
Image description: Artistic impression of plastic pollution in orbit