With the Chelyabinsk meteor that entered the Earth's atmosphere over Russia back in 2013 and numerous other asteroids and near-Earth objects (NEOs) set to make their way past our planet, many scientists are focusing on planetary defense strategies to ensure its protection in extreme situations. Some of these strategies include kinetic impactors, robotic mining and gravity tractors, although one has garnered the attention as one of the most serious proposals: laser beams.
Project DE-STAR (Directed Energy System for Targeting of Asteroids and exploRation) aims to use large phased-array lasers in the Earth's orbit for deflecting asteroids, comets and any other NEOs that put the planet in danger. In addition, a smaller, similar system called DE-STARLITE that would travel alongside the aforementioned laser system is also being considered for development.
The ultimate goal of these projects is to create a planetary defense system in the Earth's orbit that is capable of heating hazardous NEOs to the point of vaporization, which would lead to the ejection of vaporized material and thus a reactionary force that would push the object onto a new path.
"Generally speaking, the technology is available today. The main challenge with building a full DE-STAR is the necessary scale to be effective," said Qicheng Zhang, one of the authors of the project.
Zhang and his team believe that if DE-STAR possessed a 330-feet-wide phased laser array, it could combat volatile-laden asteroids 330 feet in diameter and initiate battle with them from around 2 million miles away. However, they also claim that DE-STARLIE is the more practical option in terms of size and investment.
"The bigger the NEO, the longer the time needed. The bigger the laser, the shorter the time needed," Zhang said. "With a very small 20 kW DE-STARLITE, a 300-meter-wide (1,000 foot) asteroid can be deflected in 15 years. Smaller asteroids can be deflected in under a year, after the spacecraft's arrival at the asteroid."
However, DE-STARLITE would not be effective at deflecting NEOs on short notice, which means that the DE-STAR system would be more practical for last-minute defense options.
As improbable as an NEO collision may seem, the most recent mass extinction was caused by an impact from a comet or asteroid approximately 10 kilometers wide. Although these events are rare, when they do occur, the results can be catastrophic.
"In the last roughly 100 years, we've had two significant impacts that we know of," experimental cosmologist Philip Lubin said. "One was the 1908 event in Tunguska, Russia, with an estimated yield equivalent to 10 to 15 megatons of TNT, essentially as large as the largest nuclear weapon the U.S. has ever detonated. The second was the Chelyabinsk event, also in Russia, in 2013, which had an estimated yield of about a half-megaton, equivalent to a medium-sized thermonuclear weapon in the U.S. and Russian arsenals."
