For a movie that scientists were able to pull apart and identify 168 science flaws, I find it hard to believe that it got anything right, but according to Bong Wie, of Iowa State University, who spoke at Wednesday's 2012 NASA Innovative Advanced Concepts (NIAC) meeting in Virginia, there's one facet of the movie storyline that may be an inescapable truth (if you intend to blow up an asteroid with a nuclear warhead, that is).
Dealing With Asteroids
We can talk about the various asteroid deflection techniques until the cows come home, but the only sure-fire way to deal with this continuous threat to our planet is to develop an in-space infrastructure so we can deal with an incoming space rock should we discover one. We also need to learn as much as we can about them - particularly their structure and composition.
Plans are afoot to send astronauts and robots to asteroids - the Japanese space agency JAXA has even carried out a partially successful asteroid sample return mission. Also, there's a network of international observatories that form the backbone of "Spaceguard," all keeping a watchful eye on the skies. Independent groups such as the B612 Foundation are even financing their own space telescope that will survey interplanetary space for the infrared signal of previously undiscovered asteroids.
Should we discover a large asteroid on an orbital path that will hit Earth years or decades in the future, one can imagine a mission to the celestial menace that would employ one of the subtle (theoretical) asteroid deflection techniques - such as using a gravity tractor, giving the asteroid a paint job or attaching some ion thrusters to the thing all in the aid of slowly pushing the asteroid off-course.
But say if we discovered a Tunguska-sized asteroid - less than 100 meters wide - that is on a collision course with one of the world's metropolitan regions, with only weeks or months to spare?
That would likely be a time when we see the nukes being rolled out. But how would they be used? There are, after all, conflicting ideas as to the impact of detonating a nuke on or near an asteroid. The weapon may have little to no effect (or have a nasty side-effect), although other studies have set lower limits on the yield of warhead we'd likely need to blow it to smithereens.
So, Wie and his team has come up with a variant on this asteroid-nuking idea.
Bury That Nuke
Back to Bruce Willis fumbling in asteroid dirt: If you had the misfortune to watch Armageddon to the end, you'll know that Willis and his crew of oil riggers had to tunnel a shaft into the asteroid before they could plant their warhead and detonate it. Correct! This is the rare moment when Armageddon scored +1 for science (which, in itself, was likely a mistake).
According to Wie's calculations, to optimize the impact of a nuclear blast on an asteroid of around 100-meters wide, it would need to be detonated inside the asteroid. If the nuke can be detonated at a depth of only 3 meters, the bomb's destructive power will be multiplied 20-fold.
How will this be achieved? Wie is heading a team that is developing the Hypervelocity Asteroid Intercept Vehicle, or HAIV (PDF), a project that has already succeeded in securing two rounds of funding. In its basic form, the HAIV unmanned spacecraft is comprised of two impactors: the "leader" and the "follower."
As the HAIV speeds toward an asteroid target, the two components will separate. The leader will slam into the surface of the asteroid, excavating a 100-meter wide crater. A split second later, the follower (containing the nuclear weapon) will fly into the fresh hole and then detonate below the surface. Asteroid decimation will ensue.
The resulting asteroid debris may well hit Earth, but they will be small enough to disintegrate during atmospheric entry rather than hitting the ground as a large, solid lump of rock.
The best thing about this concept is that it's based on an impactor mission that NASA has already carried out - the Deep Impact probe that slammed into the nucleus of Comet Tempel 1 in 2005. "Basically, our proposed concept is an extension of the flight-proven $300 million Deep Impact mission," Wie told SPACE.com.
"Our ultimate goal is to be able to develop about a $500 million flight demo mission within a 10-year timeframe."