Two California scientists are warning it's only a matter of time before the planet takes a direct hit from an asteroid, and they say it’s time to take defensive action.

They are proposing a massive, solar-powered "orbital defence system" that could harness the power of the sun to destroy space rocks long before they came within striking distance of Earth.

Their proposal is getting attention a week after a large meteor exploded in the sky over Russia, an event that occurred on the same day a 50-metre asteroid made a close approach to Earth. The meteor injured more than 1,000 people in Russia, and the asteroid came within 27,000 km of Earth, the closest pass in recorded history.

"We have to come to grips with discussing these issues in a logical and rational way," said University of California Santa Barbara physicist Philip M. Lubin, who has spent more than a year working on the project.

"We need to be proactive rather than reactive in dealing with threats. Duck and cover is not an option."

The proposed system is called Directed Energy Solar Targeting of Asteroids an exploRation, or DE-STAR for short – an admittedly Star Wars-inspired acronym.

And though it sounds like something straight out of a science-fiction film, Lubin and his partner on the project, Gary B. Hughes, a professor from California Polytechnic State University, San Luis Obispo, say they are serious about the proposal.

Their plan would see the construction of a large solar panel that would orbit the Earth, capturing energy from the sun which would then be converted into electricity.

That would power a massive laser array, which could be focused and aimed at incoming threats that are still years away.

The laser beam would literally boil the surface of an asteroid, causing it to evaporate and eventually break up altogether, eliminating the threat long before the object came close to Earth.

“The idea is you heat it up so hot the material begins to evaporate from the surface, the same as if you heat up water it begins to boil and eventually it’s all gone,” Lubin said in a Skype interview from Bologna, Italy where he is attending a conference.

The professors have come up with a range of possible sizes for the DE-STARs. At 100 metres across, or roughly the same size as the International Space Station, the DE-STAR 2 would have the laser power necessary to nudge comets or asteroids out of their orbits, essentially changing their trajectory away from the Earth.

At a massive 10 kilometres in diameter, or roughly 100 times the size of the ISS, the DE-STAR 4 could deliver 1.4 megatons of energy to its target per day. Over the course of a year that would effectively vaporize an asteroid up to 500 metres in diameter, Hughes and Lubin claim.

The professors say the technology needed for their project exists today, just not at the scale that would be necessary. What doesn’t exist, Lubin said, is the engineering capability to build something so large in space.

“This is beyond normal human engineering skills at this point of our evolution but it’s not beyond our ability to imagine something like this. It doesn’t require a miracle,” Lubin said.

“This doesn’t violate any of the laws of physics at all. This is simply a really tough engineering project.”

The California professors aren't the only ones who feel urgent action is needed to track, predict, and redirect or even destroy asteroids or meteors that pose a potential risk to Earth.

The European Union-funded NEO (Near Earth Object) Shield consortium is focused on investigating the best ways to deal with an object hurtling towards the planet. One option outlined on the group's website is to use "kinetic impactor mitigation" -- essentially, flying spacecraft into an asteroid at high speed, in order to trigger a change in velocity and direction.

Another option under consideration by NEO Shield is known as "gravity tractor." The concept was first devised by American astronauts Ed Lu and Stan Love, and operates under the premise that a spacecraft could hover near an asteroid, relying on the small gravitational attraction between the two to change the asteroid's course of travel.

"NEO Shield will look at the effectiveness of a number of gravity tractor solutions, as well as look at the technical challenges of a gravity tractor mission," NEO Shield said on its website.

In the event that a major threat was posed by an asteroid, NEO Shield would also consider using a nuclear weapon, but only as a last resort.

Watch a video simulation showing how a kinetic impactor would deflect an asteroid away from Earth.