asteroid defense

The solar system is a dangerous place with asteroids and comets zipping past the Earth on a daily basis. While there are no extinction-level cosmic rocks heading towards a collision with the Earth (that we know of), the disturbing increase in the number of near misses in recent years is bringing renewed attention to the concept of asteroid defense.

In the spirit of our upcoming game Orbit Path, which is all about avoiding cosmic collisions, I’ve done some research to collect the 3 best options we have when it comes to asteroid defense.

Option 1: Kinetic Deflection

Kinetic deflection is a fancy way to describe crashing one thing into another. With kinetic deflection, the idea proposed by scientists is to crash a probe into an incoming asteroid with the hope that change in momentum from the collision would be enough to deflect the asteroid from it’s cosmic date with Earth. Widely considered to be the most mature and effective defense, kinetic deflection was demonstrated as an unintended side effect of the Deep Impact space probe mission in 2005.

The Deep Impact probe used a planned collision with the comet Tempel 1 to help scientists understand the internal composition of comets. The 370 kg probe’s collision with Tempel 1 delivered roughly the equivalent of 4.8 tons of TNT. That impact is estimated to have knocked the comet 10 meters offits trajectory around the sun.

The European Space Agency is currently planning the AIDA mission to prove the viability of this method. Planned for launch in 2021, the impactor would target the asteroid 65803 Didymos. The goal of the mission to measure the change in momentum of an asteroid from a collision with the probe, thereby giving us an idea of how to go about building one of these devices should we detect an asteroid on a collision course with Earth.

Mission profile for the ESA's AIDA mission. Image credit: ESA / Science Office.
Mission profile for the ESA's AIDA mission. Image credit: ESA / Science Office.

Option 2: The Gravity Tractor

While our gut instinct to an Earth-bound asteroid might be ‘nuke the bastard’, the Gravity Tractor relies on nothing but Newton’s principles of gravity to gradually nudge an asteroid off a collision course with Earth. The idea behind a Gravity tractor is to launch a heavy unmanned satellite to orbit an incoming asteroid. The mass of the spacecraft and that of the asteroid mutually attracts them, meaning that over a period of years the asteroid will slowly accelerate to the satellite which could be enough of a shift in trajectory to push the asteroid safely away from the Earth. While Hollywood will probably never make a movie about a Gravity tractor, this defense is subtle and actually quite brilliant as it relies on the fundamental laws of gravity to work. The one downside to a Gravity tractor is that it requires that we have years of advanced warning for the scheme to work.

Gravity tractor for asteroid defense
The Gravity tractor planetary defense technique - http://www.nasa.gov/content/asteroid-redirect-mission-planetary-defense-demonstration/ (image link), Public Domain, https://commons.wikimedia.org/w/index.php?curid=39244378

Option 3: Nuke the Bastard

When all else fails and an asteroid impact is imminent we are left with the Michael Bay defense: a massive nuclear bomb. Nuking an asteroid isn’t as easy as punching in the coordinates and cracking off a salvo of Minuteman missiles. For one, most asteroids that are likely to cause an extinction level event (> 1 km in diameter) likely won’t be destroyed by a conventional nuclear warhead. Further, nuking an asteroid comes with the very real risk of causing 1 big asteroid to split into 2 or more pieces all of which could still be heading towards Earth.

In 1995 Edward Teller, the American scientist and ‘father of the hydrogen bomb’ proposed the creation of a 1 gigaton nuclear device, weighing 25-30 tons that would be launched atop of Russia’s Energia rocket and sent to obliterate any asteroid less than 1 km wide and deflect any up to 10 km in diameter. Teller’s scheme was designed to be a last ditch effort designed to be put in use in the event we had less than a year’s warning before collision. There is no word whether the US or Russia have developed such a massive nuclear weapon.

When all else fails there is always the nuclear option - photo credit: Getty Images
When all else fails there is always the nuclear option - photo credit: Getty Images

Unfortunately, asteroid defense has been given very little attention by world leaders and the scientific community broadly, as any solution would require billions of dollars of investment and multi-year commitments from the governments involved. It’s likely we’ll never know how effective any of these options are until the day comes when we need them. Asteroid defense is a lot like flood insurance, for most people they only realize they need it once they see the hurricane barreling towards them. Let’s hope for our sake it’s not too late when we do.

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