Space junk — a problem spinning out of control
If you want to catch a last glimpse of Chinese satellite Tiangong-1, you better hurry. Circling the earth at a speed of 28,000km/h every 90 minutes, the 8.5-tonne satellite will likely have vanished by the end of this weekend, to reappear as a fireball for up to a minute or more somewhere over the skies of southern Europe — or perhaps somewhere else.
While nobody can be certain where exactly the disintegrating satellite may literally fall from the sky — with pieces weighing up to 100kg expected to make it to the Earth’s surface — the satellite’s fate has long been sealed. And even if you miss this one, scientists say there’s plenty more to come in the junk-strewn skies of Earth’s near orbit.
First warning signs for the Chinese station appeared in 2016 when it failed to respond to commands by its operators.
Tiangong-1, a name that translates as “heavenly palace”, would eventually turn into a man-made meteor.
While the threat of the debris hitting a human is extremely small, the visual drama that might unfold this weekend may only be a first glimpse into a growing problem that will manifest itself over the next decades, according to some bleak predictions.
The European Space Agency estimates that there are now more than 170 million pieces of space debris in circulation, though only
29,000 of those are larger than about
6cm. While such smaller space debris objects may not pose a threat to Earth because they would disintegrate before reaching the surface, the European Space Agency warns: “Any of these objects can cause harm to an operational spacecraft. For example, a collision with an object would entail a catastrophic fragmentation of a typical satellite.”
Smaller pieces could still destroy spacecraft systems or penetrate shields, possibly making bigger satellites unresponsive and turning them into massive pieces of space debris themselves.
Since the first satellites were launched in the mid-20th century, the Earth’s orbit has long been treated by nations as a waste site nobody felt responsible for. Spent rockets or old satellites now mingle with smaller pieces of trash left behind by human space programmes. All of those pieces zig around faster than speeding bullets. And while the international community is gradually becoming more aware of the challenges this poses, much of the damage is already done.
Speaking at a conference in 2011, General William Shelton, a commander with the US Air Force Space Command, predicted that much of the orbit around the Earth “may be a pretty tough neighbourhood . . . in the not too distant future”, according to the astronomy news website Space.com.
The US military and Nasa are both in charge of perhaps the most elaborate scheme to track objects bigger than 6cm to predict their flight paths and move active equipment out of the way.
The problem, Shelton indicated at the time, is that the accumulation of space debris itself is already sufficient to lead to an exponential rise in circulating pieces. The more pieces there are, the higher the likelihood that they will eventually collide — and create even more, smaller objects that can still be extremely dangerous to other satellites or space labs.
One possible solution that has been proposed would be to convince nations to limit their debris and to prevent a repeat of past mistakes. Congestion isn’t spread evenly around Earth: While you have some scattered pieces further away, there is a concentration of objects within the so-called geosynchronous region, at about 35,785km altitude.
But the highest density of objects can be found in low Earth orbit within 1995km of Earth. That’s also where most satellites can be found.
With more than 50 nations now operating their own space programmes, initiatives to limit the release of space debris have hardly become any easier.
Some technological advances have had a limited impact, for instance by making spent rocket boosters fall back to earth quicker than in the past. Meanwhile, other nations, such as Britain and Switzerland, have experimented with schemes to clean up the mess by collecting the debris in circulation.
But the proposed programmes are costly and inefficient, legal challenges aside.
Some academics are already arguing that the lower orbit might soon be lost altogether.
Instead, they believe, scientists should start developing smaller satellites that can circulate closer to Earth — and a safe distance from a part of the orbit that may eventually become a kill zone for satellites.