When a tiny piece of space junk cut a 5mm hole in the International Space Station’s (ISS) robotic arm last year, it came as little surprise. The near-Earth space environment has become so clogged with defunct orbiters and scraps of wreckage orbiting at up to eight times the speed of a bullet that NASA estimates half a million dangerous pieces of debris the size of a marble or larger (1cm plus) pose a constant threat to working satellites, whose number is growing rapidly as well.

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