Mirrors in orbit against asteroids

Mirror, mirror of my desires: who is the biggest asteroid in the realm? But since size doesn’t matter, which one is the most dangerous? While waiting to reveal these and other doubts, a team of scientists from the University of Glasgow, led by the Italian Massimiliano Vasile, has drawn up a ranking of better methods for attempting to deflect the trajectory of a space stone dangerous: and the mirrors ended up in the first place.

This is no joke: many small satellites, all equipped with an inflatable reflective surface, which concentrate the sunlight on a point of the asteroid, vaporizing its surface, and producing a thrust such as to change its direction. It is not child’s play, given that for a thing of 150 meters in diameter – quite common around the Earth – it would take a dozen satellites equipped with 20-meter mirrors. at work for three years .

If you want to go fast, it would be enough to send a hundred aircraft to meet the giant nugget: in that case a few days would be enough, as long as you can get into position without breaking 100 satellites all at once. For an asteroid similar to the one that apparently killed off the dinosaurs, a 20-kilometer monster, it would take 5,000 : fortunately, one of those big ones goes by every six million years.

The mirror method is therefore the most suitable for small objects: not that 10 satellites at a time are a walk, but as Vasile himself explains to New Scientist, a dozen satellites in position are the equivalent of the GPS network: something that has already been done therefore, and which could be repeated.

In second place in the ranking was placed the method of the gravitational tractor: a small spaceship, launched into orbit around an asteroid, would divert its trajectory solely due to its modest attractive force . With 20 tons and a year of time, deflecting a 200-meter-diameter body shouldn’t be a problem, says NASA. Which, moreover, agrees with Vasile on the risk of using the science fiction idea of ​​nuclear missiles . Although, in fact, a hydrogen bomb would guarantee the necessary thrust, the risk of transforming a large asteroid into a series of small uncontrollable debris is too high: and at that point, stopping many objects en route to earth could become impossible.

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