A 15 kilometer wide asteroid is headed toward the Earth, but NASA scientists spot it three years before impact. Movie lore not withstanding, what the hell are we supposed to do? Could we even organize the global community enough to stop this flaming ball that astronomers call a near-Earth object (NEO)? Let's find out.
Top image: A rendition of the MADMEN project.
How would we spot an incoming asteroid in the first place?
NASA has surveyed 90% of Near-Earth Objects (NEOs) greater than 1 kilometer in diameter. A1 kilometer diameter asteroid appears to be the lower limit for high destructive probability, with some theoreticians suggesting that an asteroid 10 kilometers in diameter could end all life on earth.
What will we do to stop the impact?
Stopping an asteroid headed toward Earth has been the talk of academic circles for decades. The possibility was mentioned in the 1964 book, Islands in Space and a 1967 MIT graduate student experiment, Project Icarus, wherein students were challenged to build an asteroid deflection system using an assortment of hydrogen bombs kept on standby at Cape Canaveral.
By 2028, NASA hopes to catalog all objects greater than 140 meters in diameter, essentially covering any object posing a threat (however minor) to life on earth.
Shoot something at it
A nuclear strike is the most obvious and quickest option. Send up a nuclear payload, ala Armageddon, and blow up the asteroid. This plan could take place on the shortest timetable, however, we wouldn't really know if we broke the asteroid into small enough pieces to prevent harm.
Fracturing a 10 kilometer asteroid into a six kilometer and four kilometer asteroid is great, but they might still be on target for our lovely little planet and carry worldwide devastation in tow. Nuclear defenses, however, are likely the first option for destroying an extinction level asteroid or knocking it off course.
While we are concerning ourselves with hitting a 10 kilometer target, we could also shoot a "non-explosive" object at the NEO. A really big, dense Nerf football for example - something with enough kinetic energy to alter the NEO's own kinetic energy and nudge it out of the earth's path. The European Space Agency is pioneering this option, using a carrier craft and an impactor that could be released on command.
Push the rock out of the way
Using a gravitational tractor is a nice way to slowly annoy an asteroid to death over the course of several years. With this method, we place an unmanned spacecraft in proximity to the NEO, and over time (we are talking years here), gravitational attraction moves the two objects together, altering course of the asteroid. A spacecraft is used as its thrust could be altered as needed to change the direction and further impact the asteroid's course.
Strap a rocket onto the asteroid
A quite traditional method by which a rocket would be attached to the asteroid has been proposed by theoreticians at Johns Hopkins University, allowing the propulsion of an attached rocket rocket to move the asteroid off of its course just enough to evade earth.
One other method involving non-destructive contact with the asteroid would be the MADMEN concept. In the MADMEN approach, a series of disassembles are docked on the NEO. The disassemblers would use the asteroid itself to create small pebbles and eject them away from the asteroid. Designers of the MADMEN theory believe it would only take weeks or months to significantly decrease both the mass of the NEO and the heliocentric velocity, making it a reasonable alternative to using nuclear or chemical explosives.
Let several countries take a shot
Money would not be an object in the face of an extinction level event. Such an event could propel humanity to look at itself as a connected planet, and not as a group of nation states. As millennia pass, another extinction level even will occur. It might not be all bad; humanity would hopefully spread to several planets by then, leaving our first home as a starting point for another organism. In the meantime, we might as well have a couple of plans.