It seems that in outer space, as it is on Earth, humanity is simply leaving far too much of its trash behind. According to a report released in April by the European Space Agency, the organisation is tracking about 54,000 pieces of orbital debris larger than 10cm. There are an additional 1.2 million fragments measuring between one and 10cm.
These bits and pieces may not sound like much at first – the cosmos is a big place – but as far back as the late 1970s, scientists were already worried. Some envisioned a scenario where spacecraft could come into contact with chunks of derelict satellite, fragments of spent launch vehicles and even tiny flecks of paint all moving unnervingly fast – up to seven or eight kilometres a second in low-Earth orbit, according to Nasa.
In 1978, the Journal of Geophysical Research carried a paper called “Collision frequency of artificial satellites: The creation of a debris belt”. Written by Nasa scientists Donald Kessler and Burton Cour-Palais, its mathematical model suggested that, as more satellites were launched into space, a single collision could create a cascade effect of dangerous particles and fragments.
Such cascades might eventually reach critical mass as particles struck one another. In the worst-case scenario, clouds of hurtling debris would keep on increasing independently. These would eventually envelop the Earth, putting the very idea of spaceflight in jeopardy by making attempts to leave the planet too dangerous. In this dystopian situation, humanity’s future in the stars might be over before it even really began.
This so-called Kessler effect is a troubling idea, one that was vividly brought to life in the 2013 film Gravity. The Hollywood blockbuster depicted a vertigo-inducing situation in which a US shuttle on a maintenance mission to the Hubble Space Telescope is struck by speeding shrapnel created by the shooting down of a decommissioned Russian spy satellite. The shuttle’s crew barely have time to react before their craft and the telescope are shredded by the cloud of whirling space junk.
Although most scientists see the Kessler effect unfolding over decades, rather than in minutes as depicted in Gravity, it remains a perturbing vision and one that continues to play on the minds of those involved in the growing space industry, even decades after Kessler and Cour-Palais’s 1978 paper.
Late last month, Ali Al Hashemi – the first Emirati to chair an international satellite operators’ body – said one of his priorities would be tackling the growing threat of space debris. Speaking to The National, he said the Global Satellite Operators’ Association is “trying to build a strong agreement that would help unify everyone’s views”. Mr Al Hashemi, who is also chief executive of space services at UAE technology company Space42, is right to focus on building consensus; although there is general agreement among scientists, engineers and other experts that Kessler’s basic idea is sound, there is disagreement on how severe the problem is and a lack of joined-up thinking about cleaning up our act before it is too late.
This is not to suggest that nothing is being done. The ESA and other space agencies are busy experimenting with different ways of cleaning up our growing collection of orbital junk. From using nets and harpoons to capture debris, or launching devices that will latch on to ageing satellites and either refresh their decaying orbits or guide them into the atmosphere to burn up, many of the technological solutions being put forward are truly the stuff of science fiction.
At the same time, more satellites are being designed and built with sustainability in mind. Many CubeSats and other smaller devices are launched with the understanding that their mission is temporary and that their orbits will decay in a few months or years, ending up in the atmosphere.
But these individual efforts lack international agreement and global co-operation, an issue that dogs this era of space exploration generally. Existing treaties and conventions lay down some rules about the exploration and exploitation of space but say little about removing the debris left in our wake. The Artemis Accords, a non-binding set of principles for space exploration signed by more than 50 nations, says signatories committed themselves to “plan for the mitigation of orbital debris” but some major spacefaring countries still remain outside this framework.
For now, there seems to be little sense of real urgency about the problem. Most space junk is in low-Earth orbit, meaning many pieces will eventually burn up in the atmosphere. But at higher orbits, those 800km above the Earth and beyond, it can take centuries or longer for debris to fall back into the atmosphere. Their lingering presence increases the chances of a major Kessler event taking place. Without international agreement, protocols or contingency plans for a rapid clean up, our journeys into space may be more dangerous than they have to be.
