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Asteroid billiards: This wild idea to protect the Earth just might work

Artist illustration of a dangerous asteroid streaks toward the Earth.

(European Space Agency)

Protect the Earth against hazardous space rocks could require a small asteroid-on-asteroid violence.

The researchers propose a new arrow to our planetary defense quiver: control small, benign near-Earth asteroids (NEAs) in large and dangerous, in a dramatic, high-stakes game of cosmic billiards.

This idea is not as crazy as it sounds, the architects say. [Photos: Potentially Dangerous Asteroids]

“It will be a while before we can do this sort of thing, but I think it’s not promising,” David Dunham, chief mission design engineer for the Arizona-based company KinetX Aerospace, said last month during a presentation with NASA’s Future In-Space Operations (FISO) working group.

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A cosmic shooting gallery

Earth zooms around the sun in a shooting gallery, sharing space with millions of NEAs. These space rocks slam into our planet on a regular basis, as the world was reminded on Feb. 15, 2013.

On that day, a meteorite exploded in the sky above the Russian city of Chelyabinsk, generating a powerful shockwave that shattered thousands of windows in the buildings below. About 1500 people were injured by flying shards of broken glass.

Scientists believe that the Chelyabinsk object was only 65 feet (20 meters) or so wide. And there are much larger — and thus more dangerous — space rocks cruising around there in the dark depths, the vast majority of them unseen and unknown.

For example, only one-third of the NEAs at least 460 feet (140 m) wide have been found and followed to date, NASA officials have said. This difference in knowledge is a little painful; the chances of the Earth getting hit by a large asteroid in the next 100 years at 1 percent, Dunham said, the same chance that you (or I, or anyone else) will die in a car accident. (There is also good news, however: NASA scientists believe they have determined that more than 90 percent of the mountain-sized NEAs, that there are, are the ones who are in a state of the end of civilization if they hit us. And none of these monsters are a threat for the foreseeable future.)

But we don’t have to just sit back and wait for destruction. Indeed, scientists and engineers around the world are working on ways to the Earth of asteroids’ visor.

The most sensational of these is the nuclear-bomb strategy, which was made famous by the 1998 disaster film “Armageddon.” But the real-life version of this technique would rely completely on robotic spacecraft, not noble self-sacrificing miners.

And researchers regarding nuclear weapons as a last resort strategy, used only when the asteroid is sufficiently large, and is detected so late in the game, that no other method would work. Blasting the asteroid apart with a bomb, after all, would generate a lot of space-rock shrapnel that could imperil the Earth. [Photos: Asteroids in Deep Space]

If time is on our side, if we have years or, ideally, decades — we could put “kinetic impactors,” slamming one or more (non-nuke-carrying) spacecraft in the impending asteroid to knock it off course, investigators said. We could also make use of the “gravity-tractor method, that would start with a probe to fly, together with the hazardous NEA. Ultimately, this spacecraft modest appeal would nudge the space rock to a benign course.

And then there is the asteroid-billiards idea.

Fight rock with rock

This is a concept that Dunham laid down in his FISO talk, is basically a scaled-up version of the kinetic-impactor method.

It is going to launch a robot spacecraft from a small NEA — a 33-foot (10 m) wide or so. The probe would land on (and anchor) the asteroid, then fire the thrusters to set up a “gravity assist” flyby of the Earth. (You can also use the probe could pluck a boulder from a larger asteroid and fly away to that rock, Dunham said.)

This speed increase, trajectory-changing flyby would send the spacecraft-asteroid combo in the direction of the dangerous object. As it was nearing her goal, the rock-and-riding-probe would refine the course to use the board, ranging from instruments and reflectors, and transponders placed on the large and dangerous rock, Dunham said.

The impact, when it came, would be much more powerful and effective than a smashup generated by a naked spacecraft serve as the kinetic impactor, ” he said.

There would be a lot of extra mass and momentum involved. Consider, for example, that the Mbozi meteorite in Tanzania, that scientists first spotted in 1930 is only a 10 foot (3 m) long, but that weighs 18 tons (16 tonnes).

There are plenty of small NEAs flying around in the Earth near to making this strategy a real possibility, Dunham said. Indeed, the calculations that he, Natan Eismont of the Space Research Institute of the Russian Academy of Sciences, and their colleagues performed suggest that humanity could feasibly snag a dozen such nearby asteroids and send them to the holding-pattern jobs; these cosmic missiles could be “activated” when needed.

“So, you’d have a whole bunch of these things ready to throw at an asteroid come to you,” Dunham said.

This asteroid arsenal can be especially useful when dealing with long-periodic comets, which are the largest part of their lives in the dark depths of the outer solar system and are, therefore, very difficult to find and follow, he added.

The asteroid-snagging idea has applications beyond planetary defense, Dunham said pre-positioned space rocks could serve as inviting targets for a manned exploration efforts. Indeed, NASA was to develop a plan until last year, when the Trumpet administration cancelled the agency’s Asteroid Redirect Mission.

Dunham emphasized that the asteroid-billiards concept should be examined in much more detail before it can be fully implemented. He would like to see the idea shown first on a benign target rock, with an indication of NASA’s proposed Double Asteroid Redirection Test (DART) mission as an illustrative example.

If all goes according to plan, DART would slam a spacecraft in the 500-meter-wide (150 m) moon of the asteroid (65803) Didymos in October 2022, in a test of the textbook kinetic-impactor deflection strategy.

Originally published on Space.com.

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