The head of planetary defence at NASA, Lindley Johnson, has spoken to Politico about how the organisation could defend the Earth against the unlikely and unwelcome possibility of an asteroid impact.
Johnson, a former Air Force officer who published a paper on the subject in 1994, is behind recent plans to prepare the planet for an encounter with a ‘Near-Earth Object' (NEO), of which there are three: nudging it off course; using a spacecraft to change its course using an artificial gravity well; and "the one everybody likes to talk about", the nuclear option.
Using a kinetic impact to redirect an asteroid is the simplest method, and NASA has plans to trial the technique with the Double Asteroid Redirect Test. Johnson says that DART will be "a significant increase on the planetary defence programme", and is responsible for a large budget increase for the department: from $60 million to $150 million in 2019, of which about $98 million is bookmarked for the initiative.
Politico says that this funding increase for the Planetary Defense Coordination Office may be delayed, which would also postpone the test (currently planned to take place in 2022). If NASA appropriations for 2019 are included in a continuing resolution, the the agency would need continue to operate at current spending levels until Congress passes a new budget.
The second option is the artificial gravity well, the idea being that a spacecraft of sufficient mass could slowly and passively tug an asteroid off of its impact trajectory. It wouldn't work for very large NEOs, but those of around 100m in size are viable targets. This programme "was going to be part of the asteroid redirect mission back in the last administration, but that programme didn't make it through the transition," said Johnson.
Finally is the method most beloved of Hollywood: a nuclear strike. Films like 'Armageddon' are, of course, unrealistic: planting a nuke inside an asteroid would simply result in "a bunch of buckshot headed at you."
A much more viable option is using a nuke to alter an asteroid's course by detonating it above the surface. Johnson said, "The nuclear radiation causes super heating of the asteroid surface and imparts a force on the asteroid in the opposite direction."
Oh, and in case you wondering, Johnson's favourite movie isn't 'Deep Impact' or 'Armageddon': it's 1979's 'Meteor'. "Sean Connery played me," he joked.
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