• 3,000 inactive satellites are still in space.
  • Space debris can travel at 40,000 kilometres an hour.
  • A new space mission aims to remove defunct satellites from orbit.

On March 22, 2021, a craft resembling a washing machine with wings was catapulted into the sky from Kazakhstan on a Soyuz rocket, in what its inventors describe as, “the start of the world’s first commercial mission to prove the core technologies necessary for space debris docking and removal.”

The launch of the ELSA-d mission — the demonstration of a pioneering method to capture and safely remove space debris from orbit using magnetic retrieval — is part of efforts by a number of companies to conduct a celestial litter-picking exercise on a grand scale.

Created by Japanese start-up Astroscale, ELSA-d consists of two satellites stacked together. The first part is a service craft designed to safely remove debris from orbit. This is docked with a smaller satellite that replicates a piece of space debris during test flights.

image of the ELSA-d, which consists of two satellites stuck together
The ELSA-d has the ability to capture and safely remove space debris from orbit.
Image: Astroscale

Now that ELSA-d is in orbit, further trials will be carried out, in which the service satellite will release and subsequently dock magnetically with the smaller satellite; capture it while it is tumbling out of control, and then deliberately lose and recapture it.

The success of each of these tests will put Astroscale one step closer to the commercial application of its technology, where, once captured, the debris and service satellite will return to the Earth’s atmosphere together, burning up on re-entry.

A scrapyard in space

Since the Soviet Union put Sputnik 1, the first satellite, into space in 1957, the area of space known as low-earth orbit has become ever-more crowded.

a diagram showing that thousands of satellites are at risk of collision with space junk
Thousands of satellites are at risk of collision with space junk.
Image: UN Office for Outer Space Affairs/European Space Agency

There are more than 3,000 dead satellites and rocket stages currently floating in space, and up to 900,000 pieces of space junk ranging from 1 to 10 centimetres in size — all large enough to be a collision hazard and a potential cause for disruption to live missions. According to the United Nations Office for Outer Space Affairs (UNOOSA), with space traffic increasing, the number of in-space collisions are “expected to rise.”

In 2009, two satellites - one Russian, one American - collided over Siberia, breaking into hundreds of pieces of debris. That followed an incident in 2007 in which China destroyed one of its older weather satellites as part of an anti-satellite test, leaving around 2,500 pieces of debris in the Earth’s orbit.

Destructive particles

According to the European Space Agency’s Space Debris Office, even a tiny fragment of space junk circling Earth at 40,000 kilometres an hour could cause catastrophic damage to an active satellite.

“The energy contained in a one-centimetre particle hitting a satellite at that velocity roughly corresponds to an exploding grenade,” says Holger Krag, Head of the European Space Agency’s Space Debris Office, in a video about managing space debris. "The consequences of such a hit mean satellite failure, for larger objects, even satellite destruction and fragment generation, which, again, then has environmental consequences."

Krag says ongoing fragment collisions over the coming decades could also make certain areas of space unusable for space flight. The presence of debris could potentially disrupt the activities of the International Space Station, which narrowly avoided colliding with debris three times in 2020, as well as missions to the moon and to Mars.

Fishing for debris

There are multiple methods to ensnare rogue space debris. Another Japanese company, ALE, has developed an electrodynamic tether which can be added to a satellite pre-launch and extended in space at the end of a mission. It uses the Earth’s magnetic field and atmospheric drag to lower a satellite’s orbital altitude more rapidly, enabling craft to safely re-enter the Earth’s atmosphere and burn up.

Separately, ALE has developed a debris-capturing solution that involves wrapping a membrane around a satellite at the end of its operation, with atmospheric drag forcing it to leave orbit.

Since 2018, the RemoveDEBRIS consortium based at the University of Surrey in the UK has also trialled a range of capture technologies. A small space craft that it dispatched from the International Space Station, carries a harpoon and a giant net — both developed by consortium partners Airbus.

Astroscale Chief Executive Officer Nobu Okada is co-chair of the World Economic Forum’s Global Future Council on Space, which explores critical challenges for the sector, including its socio-economic impact and the need to maintain sustainable growth.

The Council is helping to develop a Space Sustainability Rating to encourage transparent debris mitigation efforts in line with the guidelines produced by the United Nations Office for Outer Space Affairs (UNOOSA).

Those guidelines include advice to pursue spacecraft design that limits the release of debris during normal operations. It also urges operators to limit the potential for break-ups during missions, and says intentional destruction should be avoided.

Such multilateral efforts, alongside technological innovation, are ensuring that the great space cleanup is well underway.