10 Ways to Stop a Killer Asteroid


It does rather look like a potato.


10 Ways to Stop a Killer Asteroid

If you were being stalked by a killer, you would you try to stop him or her, right? Now let's say your killer is a space rock shaped like an Idaho spud. What would you do about that? Interestingly enough, the odds of you being murdered at the hands of a madman are about one in 210 [source: Bailey]. The odds of being killed by a cosmic potato are a tad lower -- about one in 200,000 to 700,000 over your lifetime, depending on who's making the calculation [sources: Bailey, Plait]. But here's the rub: No single person -- not even someone as evil as Hitler -- could wipe out the entire human race. An asteroid could. If a rock just 6 miles (10 kilometers) across struck our beautiful, blue world, it would be adiós muchachos for every last one of us [source: Plait].

So, stopping an asteroid from blindsiding Earth makes sense, but is it even possible? And if it's possible, can we afford it? The answer to the first question might surprise you, because there are, in fact, many different ways to thwart a space rock. (No one ever said they were smart.) How much it might cost remains uncertain at best. Money, however, shouldn't be the main concern when you're talking about the survival of the human race. So let's throw that question out the window and focus on the top 10 ways to stop a killer asteroid, no matter how crazy (or costly) they seem on paper.

Up first, we have a solution based on tried-and-true Cold War technology: nuclear weapons.

Check out the impactor that NASA used to rip open the surface of the Tempel 1 comet in 2005.

Image courtesy NASA

10: Drop the Big One on the Big One

Nuclear weapons may not be original, but they're a known entity and, as a result, a logical choice if you need to blast a boulder to smithereens. This supermacho approach involves slamming a nuclear warhead into an approaching asteroid. There's only one problem: A direct hit on a large object might only break it into several smaller pieces (remember "Deep Impact"?). A better option might be to detonate a warhead near the asteroid, letting heat from the explosion sear one side of the rock. As material vaporizes from its surface, the asteroid would accelerate in the opposite direction -- just enough (fingers crossed) to steer it away from Earth.

If explosions aren't your thing, but you still want to hit something, then you'll appreciate another technique known as kinetic impactor deflection. The "kinetic" in this case refers to kinetic energy, which all moving objects have and the universe conserves. But we're getting ahead of ourselves. Turn the page to learn how the behavior of billiard balls just might save our planet.

Hidalgo, Sancho and Don Quijote

Leave it to Europe to merge great literature with great impact. The European Space Agency's take on a kinetic impactor is dubbed Don Quijote and calls for two spacecraft -- an orbiter named Sancho and an impactor named Hidalgo. Sancho would arrive at the killer asteroid first, get the lay of the land and transmit details back to Hidalgo. Trailing behind its companion, Hidalgo would arrive with all the intelligence it needed to make a pinpoint strike.

9: Speak Softly and Carry a Big Thwack

If you've ever played pool, then you know about kinetic energy, which is the energy possessed by any moving object. The kinetic energy of a struck cue ball is what gets transferred to other balls on the table. Astronomers believe the same principle could deflect an earthbound asteroid. In this case, the cue ball is an unmanned spacecraft similar to the probe used in NASA's Deep Impact mission (not to be confused with the movie). The mass of the Deep Impact vessel was only 816 pounds (370 kilograms), but it was moving really, really fast -- 5 miles (10 kilometers) per second [source: NASA].

Kinetic energy depends on both the mass and speed of an object, so a small object moving fast still has a lot of energy. When mission engineers slammed the Deep Impact probe into the surface of the Tempel 1 comet in 2005, it was slated to deliver 19 gigajoules of kinetic energy. That's the equivalent of 4.8 tons of TNT, enough to shift the comet ever so slightly in its orbit [source: NASA].

Astronomers weren't looking to alter Tempel 1's trajectory, but they know now it could be done, should an asteroid or comet set its sights on Earth. Even with a success under their belt, scientists acknowledge the enormous challenge of such a mission. It's sort of like hitting a speeding cannonball with a speeding bullet. One wrong move, and you could miss your target completely or hit it off-center, causing it to tumble or crack into pieces. In 2005, the European Space Agency came up with the Don Quijote concept to improve the odds of a kinetic impactor mission (see sidebar).

You might classify nuclear weapons or kinetic impactors as instant-gratification solutions because their success (or failure) would be immediately apparent. Many astronomers, however, prefer to take the long view when it comes to asteroid deflection.

This four-quadrant solar sail system (66 feet on each side!) gets poked and prodded at NASA's Glenn Research Center at Plum Brook Station in 2005.

Image courtesy NASA

8: Throw a Few Photons at the Problem

Electromagnetic energy produced by the sun applies pressure to any object in the solar system. Astronomers like to call it solar, or radiation, pressure and have long thought this stream of energy could be a source of propulsion for rockets. Just strap some sails onto a spacecraft, let them catch a few rays and the ingenious vessel will slowly, gradually, pick up speed as incoming photons transfer their momentum to the sail. Could something similar work on an asteroid? A couple of scientists think so. Assuming you had some time -- we're talking decades here -- you could fasten some solar sails on an asteroid, do a little tacking and steer the rock away from Earth.

Of course, even Bruce Willis might not be extreme enough to land on a hunk of rock and try to convert it into a cosmic sailboat. Another option would be to wrap the asteroid in foil or coat it with highly reflective paint. Either solution would have the same effect as a solar sail, harnessing the energy of incoming photons. Then again, who's going to try to wrap foil around a giant potato traveling, say, at 16 miles (25 kilometers) per second [source: Jessa]? Or carry a few million gallons of paint into space?

Luckily, there's another sun-centered solution that might not seem so wacky.



7: Turn the Rock Into a Puffball





In theory, a spacecraft like Dawn, seen in this artist's concept orbiting the asteroid Vesta, could alter an asteroid's orbit enough for us all to breathe a huge sigh of relief.

Image courtesy NASA/JPL-Caltech

6: Invite the Asteroid to a Tractor Pull

Every object in the universe, even something as small as a pebble, has gravity. You can't feel a pebble's gravity because its mass is so small, but it's still there, tugging away on anything that comes close. The close part is important because gravity is also related to the distance separating two objects. The closer they are, the greater the gravitational attraction.

A spacecraft zipping through the solar system obeys the same principles, exerting a gravitational pull directly proportional to its mass and inversely proportional to the distance between it and another object. Now, compared to an asteroid, which might have the mass of Mount Everest, a spacecraft is pretty puny, but its gravity can still make things happen. In fact, if you place an unmanned probe in a close orbit around an asteroid, it will pull ever so slightly on the rock. Over a period of 15 years or more, this almost infinitesimal tug could deflect the asteroid's orbit just enough to protect Earth from a nasty blow [source: BBC News].

Astronomers refer to this as a gravitational tractor and think it's a viable solution -- as long as they know about a potential collision years in advance. Early detection is just as critical to the next idea on the list.

Sort of like that, but imagine that the smaller boat is a spaceship and the larger vessel is a bothersome asteroid.


5: Get Pushy With the Planetoid

If the gravitational tractor concept seems too delicate and prissy, you're in luck. A few scientists are proposing another way to make use of a spacecraft that doesn't require slamming it into an asteroid or entering a passive orbit. They studied busy harbors here on Earth and observed how tugboats nudge large ships up to the wharf. Then they developed an asteroid-deflection scenario using a similar technique.

Here's how it works: First, you build a special ship with powerful plasma engines and an array of radiator panels to dissipate heat from the onboard nuclear reactors. After you're alerted of a threat, you launch the vessel and fly it to the offending asteroid. Then you ease the space tug close to the rocky surface and attach the vessel using several segmented arms. Finally, you go easy on the throttle and start a slow, gentle push. If all goes well, 15 to 20 years of pushing in the direction of the asteroid's orbital motion will deflect it just enough to avoid a catastrophe [source: Schweickart].

Still not convinced? Then grab your mitt and keep moving to the next page.

Entertaining Yourself Until the World Ends

No, REM, we don't feel fine at all, but we might as well get some books and flicks in while we wait. Here are some (non-escapism) picks:

  • "Lucifer's Hammer" by Larry Niven and Jerry Pournelle
  • "Death From the Skies!" by Phil Plait
  • "The Road" by Cormac McCarthy
  • "The Walking Dead" (either the graphic novels or the TV series)
  • "The Day of the Triffids"
  • "Melancholia"
  • South Park's "Deeply Impacted" episode

4: Throw a Few Fastballs

Remember those baseball pitching machines you faced when you were a kid? They had a feeder tube and a wheel assembly to shoot the balls out at 50 to 60 miles (80 to 97 kilometers) an hour. Wouldn't it be great if you could set up a pitching machine on an asteroid? Not to take batting practice, but to save the world?

As crazy as it sounds, astronomers have an idea to do just that. They call their machine a mass driver, but it works the same way. It scoops up rocks from the surface of an asteroid and hurls them out into space. With each throw, the machine applies a force to the rock, but the rock, thanks to Newton's action-reaction law, applies a force back to the machine -- and to the asteroid. Throw a few hundred thousand rocks, and you'll actually shift the asteroid's orbit.

Of course, the concept has invited some criticism. How do you get the mass driver on the asteroid? And how do you keep it powered? A pitching machine plugs into an electrical supply, but extension cords are tough to manage out in space. And what if the darn thing breaks down? A relief pitcher may not be available to finish the game.

Maybe baseball is the wrong sport. Maybe another backyard favorite offers a better solution.

Tethers prove awfully handy in space, whether you're out taking a stroll or trying to move an asteroid.

Sightseeing Archive/Getty Images

3: Play Tetherball With the Asteroid

In 2009, a doctoral candidate at North Carolina State University proposed a novel asteroid-deflection technique in his dissertation. This was the idea: Attach one end of a tether to an asteroid and the other end to a massive weight known as a ballast. The ballast acts like an anchor, changing the asteroid's center of gravity and diverting its trajectory over the course of 20 to 50 years, depending on the size of the rock being moved and the weight of the ballast.

The student didn't work out every detail, but he estimated that the tether would need to be somewhere between 621 miles and 62,137 miles (1,000 and 100,000 kilometers) long. He also suggested a crescent-shaped attachment bar similar to those found on globes. This would allow the asteroid to rotate without tangling the tether (no one likes a tangled tether).

Now, if you think this sounds just too wacky to work, you should know that astronomers have embraced space tethers for years. In fact, NASA has used them successfully on several missions to move payloads in Earth's orbit. Future missions call for delivering material to the moon by handing off payloads across a series of tethers.

Still, a tether and ballast system, like most solutions in our countdown, requires time. And time requires early detection. As we'll see next, asteroid detection may be far more important than deflection.



2: Increase Your Reaction Time






Land or Ocean?



1: Prepare for the Worst





Lots More Information

Author's Note: 10 Ways to Stop a Killer Asteroid

A few years back, I saw a TV program about the increased contact occurring between humans and sharks. There was one amazing shot that stuck with me: It showed an aerial view of swimmers just off the coast of Nags Head, and, unbeknownst to them, hundreds of sharks swam nearby. You could see their shadows among the bathers, dark and sinister. Had the people in the water known what was lurking nearby, they would have been on the beach in seconds. I feel the same way about NASA's NEO detection program. Are we better off knowing all those rocks are out there, circling us like sharks? Sometimes it seems better to be the oblivious bodysurfer who swims in ignorant bliss.

Related ArticlesSources
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  • Boston.com "How to stop a killer asteroid." Boston Globe infographic. Jan. 10, 2010. (March 11, 2012) http://www.boston.com/bostonglobe/ideas/articles/2010/01/10/Asteroid/
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  • Forward, Robert L. and Robert P. Hoyt. "Space Tethers." Scientific American. February 1999.
  • Jessa, Tega. "Eros Asteroid." Universe Today. June 7, 2011. (March 11, 2012) http://www.universetoday.com/87301/eros-asteroid/
  • Minard, Ann. "How to Keep Asteroids Away: Tie Them Up." Universe Today. Apr. 17, 2009. (March 11, 2012) http://www.universetoday.com/29317/how-to-keep-asteroids-away-tie-them-up/
  • NASA. "Deep Impact's Impactor." Deep Impact: Mission to a Comet. (March 11, 2012) http://www.nasa.gov/mission_pages/deepimpact/spacecraft/impactor.html
  • NASA. "How many near-Earth objects have been discovered so far?" Near Earth Object Program FAQs. March 18, 2012. (March 18, 2012) http://neo.jpl.nasa.gov/faq/
  • Plait, Phil. "Death by meteorite." Bad Astronomy, Discover Magazine. Oct. 13, 2008. (March 11, 2012) http://blogs.discovermagazine.com/badastronomy/2008/10/13/death-by-meteorite/
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