Broadband expansion could trigger dangerous surge in space junk

Plans to launch “mega constellations” of thousands of communications satellites to allow for global wireless internet could lead to a rise in collisions and build-up of dangerous space junk in Earth’s orbit, a study warns. Google, SpaceX, Boeing and Samsung are among the companies vying to launch global broadband networks by deploying thousands of tiny satellites into low orbit. The first launches are planned for next year. Dr Hugh Lewis, a senior lecturer in aerospace engineering at the University of Southampton, ran a 200-year simulation to assess the possible consequences of such a rise in orbital traffic. He found it could create a 50% increase in the number of catastrophic collisions between satellites. Such crashes would probably lead to a further increase in the amount of space junk in orbit, he said, leading to the possibility of further collisions and potential damage to the services the satellites were intended to provide. “The constellations that are due to be deployed from next year contain an unprecedented number of satellites, and a constellation launched without much thought will see a significant impact on the space environment because of the increased rate of collisions that might occur,” he said. With about 750,000 objects larger than 1cm orbiting Earth, the junk surrounding the planet is already a major obstacle to attempts to exploit space. At average speeds of 40,000 km/h, impacts on space hardware would deliver roughly the energy equivalent to the explosion of a hand grenade, with potentially dramatic consequences for operational satellites.

The European Space Agency, which funded Lewis’s research, is calling for the satellites planned for orbital mega-constellations to be able to move to low altitudes once their missions are over so they burn up in Earth’s atmosphere. They must also be able discharge all batteries, fuel tanks and pressure tanks to prevent explosions that would scatter debris. Dr Holger Krag, the head of the space debris office at the ESA, said many of the companies proposing to launch services provided by such mega constellations lacked experience of the difficulties of working in Earth’s orbit. He expressed concern at ambitions to manufacture satellites at a fraction of the cost and many times the rate of the current batch of taxpayer-funded spacecraft, while still meeting exacting guidelines for disposing of them at the end of their missions. “They are companies so they have competitors, so they have pressure,” Krag said. “Under these conditions they would have to manufacture satellites that are reliable enough after five years of operations to reliably conduct this disposal manoeuvre. “Right now, under all the taxpayer-funded space flight we are doing today is only able to achieve 60% of success rate for that manoeuvre. How can they be better under commercial pressure and with cheaper satellites? That’s the worry we have.” Lewis is presenting his research this week at the European conference on space debris at the ESA’s centre in Darmsadt, Germany. Krag said he expected some of the companies planning launches to attend. “Even with good intentions it remains an extremely high technological challenge to manage to [meet the ESA’s proposed guidelines],” he said. “Let them achieve a success rate of 90%, which would be extremely good compared with what we do now, and it still means a few hundred satellites will be lost and at that altitude it’s not good. It’s as simple as that.”
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