The author is an astronomer, science communicator and professor of science education at UQAM.
On April 19, the United States pledged to no longer conduct anti-satellite missile tests in space, tests that generate thousands of dangerous pieces of debris. We can only welcome this decision, hoping that it will be followed by all the countries active in space, first and foremost Russia, India and China. But one can also wonder why it took so long to wait for such a decision to be taken, given the very real dangers posed to satellites, space stations and other orbital vehicles by this cloud of space debris of which we do not know still don’t know how to get rid…
If there’s one thing decades of space exploration have taught us, it’s that anything that unfolds in space tends to stay there for a very, very long time. In the absence of air and any form of erosion, the footprints left in the lunar regolith by the twelve astronauts of the Apollo missions will still be there millions of years from now. Around the Earth, except for the lowest orbits, where atmospheric braking eventually brings the craft back to the ground, satellites can orbit our planet literally indefinitely. This also results in a very real congestion of the most “useful” orbits, which can limit their use in the medium and long term.
But what about the debris caused by unintentional collisions between spacecraft, explosions of rocket stages or, even worse, the deliberate destruction of satellites? In what increasingly looks like a dangerous race to weaponize space, China voluntarily destroyed one of its own satellites in 2007 to test such technologies. According to the Secure World Foundation, based in Washington and Colorado, this test alone generated more than 3,000 pieces of debris of all sizes.
India conducted a similar test in 2019; in November 2021, Russia launched a missile that destroyed one of its Soviet-era satellites, creating a minimum of 1,500 pieces of debris large enough to spot from Earth. As for the United States, it tested anti-satellite technologies on several occasions in 1985, 1986 and 2008, again according to the Secure World Foundation.
During each of these explosions, hundreds of thousands of debris too small to be detected are generated; despite their small size, these particles nevertheless pose a mortal danger to satellites and astronauts on board orbital stations. In 2016, NASA discovered a 7mm diameter crack in one of the windows of the International Space Station. According to the US space agency, this breakage was likely caused by a projectile measuring just a few millimeters in diameter and which could be a paint chip or a small piece of metal.
In Earth orbit, where objects typically travel at over 30,000 km/h, a postage stamp-sized splinter of paint has the same destructive knockout power as a bowling ball thrown at 100 kph.
Also according to NASA, there are today in space around the Earth more than 23,000 pieces of debris the size of a baseball, more than 500,000 pieces larger than a marble and approximately 100 million debris measuring 1 mm or more. This count makes more and more likely a disaster scenario envisaged in 1978 by the American astronomer Donald J. Kessler and known since as Kessler syndrome: collisions between space debris create new debris and increase their number, which increases strongly the probability of new impacts creating new debris. Beyond a certain threshold, this “snowball” effect gets out of hand and could eventually render several Earth orbits completely unusable, for several generations.
What to do ? Of course, urgently stop this madness of blowing up satellites in space. Second, to ensure that all spacecraft have a return-to-Earth mechanism that will allow them to enter the atmosphere safely at the end of their useful life, usually over the Pacific. Finally, develop technologies to “sweep” certain orbits, as already proposed by some companies that are developing concepts for this purpose. Until then, let’s cross our fingers so that a disaster at Gravitythe 2013 film starring Sandra Bullock and George Clooney, does not take place in space…