Armageddon

The place of a final battle between the forces of good and evil, prophesied to occur at the end of the world. – Dictionary.com

A famous blockbuster hollywood movie released on 1998, starring Bruce Willis, featuring as a deep core driller, sent to space and drill into the surface of the doomsday asteroid that was on collision course with the earth, to plant and detonate a nuclear weapon to split the asteroid into two halves.

Even-though the movie depicts a high tech masala, the ideology of deflecting the course of asteroids and avoiding the catastrophical collision on the earth by using technology is still on course.  The Association of space explorers, an international group of astronomers and cosmonauts released a recent report Asteroid Threat: A call for Global Response, urging UN/International Institutions to appoint a governing body to identify the Near Earth Object(NEO) asteroids, pinpoint the exact location of the impact,predict the potential devastation, issue warnings of mass evacuation to the city or country under threat, deploy technology and devise plans to deflect the path of the asteroid,funding and assigning the job to specific space agency,point finger for accepting liabilities due to failure in technology or wrong predictions. Whether such a governing body will be formed in-spite of the political, technological and economical risks associated with this – an impossible dream or distant reality, only timeline can answer.

Figure: Asteroid Collision Illustration

The million dollar question is “What is the technology used to deflect the path of the NEOs?” – Is that same as Hollywood Drama by Bruce Willis?

The strategy for such a technology, conceived during a study carried in 2005 by Ed Lu and Stan Love, both astronauts and founders of B612 Foundation, and published in the November edition of Nature. In order to analyze the performance of Gravity Tractor, a B612 contract was issued to JPL in 2008, to conduct a formal performance analysis.A detailed report, facts and figures can be obtained from B612 foundations website

The study shows that, even a weak gravitational pull from a near by space craft is sufficient to change the orbital path of asteroid, as big as 140 meters across, the size big enough to cause a regional devastation if it hit earth. The conceptual design becoming reality in the near future is the Gravity Tractor.

The asteroids or other foreign bodies when approaches the earth, gets attracted due to the earth’s gravitational pull and form new unstable orbital path,revolves around the earth and eventually crash on the earth’s surface.

Figure: Asteroid’s Unstable Orbital Path

In spite of  the vastness of the space, the foreign bodies were to pass through a small region of space called gravitational keyhole, which is a few hundred kilometers, so as to get pulled by earth’s gravity.

Even though the chances of a foreign body’s orbit path, fall in line with the keyhole is meagre, the use of a device like gravity tractor has to be deployed much advance in time, before the asteroid is nearing the keyhole. The gravity tractor weighing about 1 ton in weight is positioned about 155 meters away from the asteroid surface and exert a very gentle gravitational force, could alter the asteroid’s velocity by 0.22 microns/second per day. But on prolonged exposure of force on a long enough time scale, the course of the asteroid will be changed so that it is avoiding the keyhole entry and subsequent bashing on earth. The success of the gravity tractor is due to its precision of exerting the force on to the asteroid.

                              Figure: Gravity Tractor functions Illustrated

Suppose if the hypothetical orbit of the asteroid exists on a direct path to impact, then the use of gravity tractor alone cannot do the trick. Instead scientists proposed a second method called two-punch.

Initially a space craft is crashed directly to the asteroid, that would create a much change in asteroid’s orbital path, then the gravity tractor will be employed to move the asteroid away from the collision course.

Sounds interesting. The NEO threat in the nearest future may happen on a Easter Sunday, April 13, 2036, in the name of “Apophis”. The chances of Apophis hitting the earth is less than 1 in 45000. However, the Apophis will be in close encounters with earth on Friday, April 13, 2029 – 29,470 Kms from the earth, appearing to the naked eye as a moderately bright point of light moving rapidly across the sky.

Figure: APOPHIS Orbital Path

NOTE: NASA’s collision probability calculation of 1 in 45000, is challenged by a 13 year old German student Nico Marquardt, as 1 in 450. His assumptions indicate that, when the Apophis is nearing earth on 2029, could hit any of the 40,000 Geosynchronous satellites positioned around a band of 30,000 Kms from the earth’s surface, causing its orbital path to drift and thereby increasing the possibility of hitting the earth on April 13,2036. Although NASA denied this estimations, the fate of the earth remains a mystery until 2013, by then space observers can predict the exact path of Apophis.