Human activity creates waste. The problem isn’t new and space is no exception to the rule. Dead satellites, rocket stages, debris from explosions and more are cluttering up Earth’s orbit and threaten the future safety of satellites and space stations. They are getting dangerously close to a critical threshold and the need to “clean up” space has become an international issue. The next Space Tuesday (Mardi de l’espace) will look at the challenges and what’s at stake with such an undertaking. The CNES, in partnership with MyScienceWork and the Bar des sciences, invites you to take part in the discussion with two experts, Christophe Bonnal of the CNES, Chairman of the IAA Space Debris Committee, and Jacques Arnould, in charge of ethical questions at the CNES. Join us today, Tuesday 18 November, from 7:30pm at the Café du Pont Neuf in Paris, or on Twitter via the hashtag #CNESTweetup.
Space debris in orbit (Credit: Cnes)
700,000 objects over one centimeter, in orbit around our planet. The number is already impressive, but it could increase considerably. “We’re afraid we’re on the verge of reaching, if it’s not already the case, a critical threshold,” explains Christophe Bonnal. “The risk could increase exponentially if a self-sustaining chain reaction gets started, which we call the Kessler syndrome.” In that case, even if we stopped all space activity, the future of space systems orbiting our planet would be seriously threatened.
Even if the situation is not catastrophic – yet – it is worrying. Experts have deplored the 50 or so probable collisions between debris and satellites seen up to now. According to a recent study by the CNES, “the probability of death by collision for a satellite over the course of its lifetime is 5% at certain particularly congested altitudes (between 700 and 1,100 km)”, reveals Christophe Bonnal. And even in orbits with very little debris, between 350 and 450 km, for example, there is still risk: the International Space Station has already carried out 4 maneuvers this year to avoid an impact.
Current detection systems are capable of locating objects over 10 centimeters, but most of these objects are smaller. In spite of their size, they represent a real danger. At a speed of 54,000 km/h, an object one centimeter in diameter inflicts the same damage as a car moving at 130 km/h.
If the Kessler syndrome became reality, Earth’s orbit would turn into a minefield. “All the space agencies have been ramping up their efforts for several years now on concepts for space junk clean-up. Several projects are being carried out,” explains Christophe Bonnal. “NASA, for example, is working on a satellite equipped with a pulsed laser, capable of identifying small debris and slowing it down to change its trajectory.” Other methods are also being studied: clean-up satellites that can dock onto a satellite and force it back down to Earth, a giant electrodynamic “net”... All of these techniques represent a certain challenge, but that is not even the thorniest issue.
Jacques Arnould, the ethics specialist for the CNES, feels the biggest challenge lies in the realm of international relations and funding. Who is responsible for this or that piece of debris? For a satellite at the end of its lifespan, the answer is obvious, but for smaller debris? “It’s basically an ethical question. This debris is a call for us to consider space differently. A way to grasp the importance of this zone,” he insists. “When the CNES started looking closely at ethical questions, this was the first theme put on the table.”
Awareness of the problem has come a long way. The film Gravity is both proof and a contribution. Our orbits need to be cleaned up, but be better regulated, too. There are also possible solutions to avoid producing more debris, in the first place. What are they? Will they be put to use? Can we establish international regulations? For the answers to these questions and others that you may be wondering about, join us today, 18 November, at 7:30pm Paris time, at the Café du Pont Neuf, or on Twitter via the hashtag #CNESTweetup.