The UK is pioneering a path to make satellite operations in Earth orbit sustainable in order to help mitigate damage from orbiting space debris.

What is space debris?
Cluttering up the near-Earth space environment with unwanted junk and debris could be storing up a catastrophic problem for humankind because the global economy is now increasingly reliant on space services for everyday activities.

Space debris is defined as any type of anthropogenic space object that is no longer in active use. It can range from a spacecraft the size of a bus right down to tiny fragments that hurtle around Earth at breakneck speeds.

Larger objects are monitored and catalogued through the use of radar and other technologies but the smaller shards and fragments, often broken up from larger items, are the most worrying because they are impossible to track or measure accurately.

Space debris has been getting progressively worse since the start of the Space Age in 1957. Since then, there have been more than 6,300 successful rocket launches, placing nearly 15,000 satellites in Earth’s orbit. Of these, almost 10,000 are still in space today and a staggering one-third of them are either inactive or defunct.

In reality, satellites and spent rocket stages comprise only a small percentage of the estimated 32,000 objects larger than 10 cm orbiting our planet in low Earth’s orbit (LEO) that contribute to the bludgeoning space junk problem facing humankind.

The larger objects tracked by global space surveillance networks are only a small proportion of an estimated 131 million pieces of hazardous space debris that cannot be monitored. The unpredictability and high speed of the smaller fragments mean they are potentially an even bigger threat.

Where does space debris come from?
Launching satellites into Earth’s orbit is the most obvious source of space debris. The process of deploying a spacecraft involves discarding spent rocket bodies, protective shields, covers, and other incidental hardware items.

Some fragments burn up in Earth’s atmosphere but others just stay in orbit and add to the escalating debris problem. Even blocks of ice from the waste management systems of Space Shuttle missions up to several decades ago continue to hurtle around Earth.

However, it is collisions or ‘fragmentation events’ that are thought to be the largest source of space debris. Since 1961, a staggering 630 such events have been recorded, with three countries (China 42%, USA 27.5% and Russia 25.5%) responsible for roughly 95% of the fragmentation debris currently in Earth’s orbit.

The destruction of satellites in space is another worrying source of orbital debris. Anti-satellite tests (ASAT), where a country deliberately destroys one of its own satellites, are increasingly contentious.

Such actions potentially release thousands of extra untrackable debris fragments into orbit, all travelling at speeds of up to 10 km/s, which is 10 to 20 times faster than a bullet.

Collisions of these lightning-fast fragments with larger objects can theoretically cause a cascading effect, with each impact generating ever-more debris. This is known as the “Kessler Syndrome”, named after NASA scientist Donald J. Kessler, who first proposed in 1978 the possibility of such a self-sustaining chain reaction of space debris collisions.