THE WOODLANDS, Texas – If you want to use a nuclear weapon to save the world from an asteroid, do not try to do it the way Bruce Willis did in "Armageddon," NASA's planetary defense
"If you've seen those movies, they're completely bogus," said Lindley Johnson, the planet's defense officer at NASA headquarters, during a media session on asteroids and the art of ] protecting Earth from them held at the Lunar and Planetary Science Conference taking place this week. "This is not how we would use a nuclear explosive device to do that at all."
But nuclear weapons are one of three techniques, the planet defense experts have their eyes on for nudging an asteroid off course if its orbit seems to carry it too close to Earth for comfort. Another method, impacting an asteroid, will be tested for the first time during the Double Asteroid Redirection Test and the NASA mission scheduled to launch in June 2021
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Another tactic would use gravity And then there's the nuclear option, which is the best option for larger asteroids more than 1 mile in diameter.
All three of these techniques take the same basic approach: adjust the asteroid's orbital speed so that its path no longer intersects with our own. "We just need to change that speed by maybe a couple of centimeters per second," Johnson said. "If we do that a few years in advance, the change that occurs in the orbit as it comes around several years later to that impact point – the change in velocity will cause it to arrive early or late to the impact point. . "
To get that change in velocity from a nuclear explosion, however, there is no need to actually touch the asteroid directly, Johnson said. Instead, the trick is to set off the explosion of several hundreds of meters up. "That causes an irradiation of the surface of the asteroid on that side, heats it up, superheats the surface," he said. "That surface will then blow away from the asteroid."
And because the laws of physics still apply, that dramatic action triggers an equal and opposite reaction, with the asteroid rebounding away – precisely what's needed to avert a catastrophe here on Earth . (19659002) It was a nice thought, Bruce