The Case for Building a Death Star

By Corey S. Powell | February 20, 2013 12:07 pm

I got a call yesterday from a producer at Fox News, who asked me if I wanted to comment on a proposal by two California physicists to build a “Death Star” that would protect our planet from incoming asteroids. The answer to a question like that is inevitably going to be “Of course!” so I appeared on Fox News earlier this morning to discuss the idea. (View the story here.)

Conceptual illustration shows how DE-STAR could vaporize an asteroid and power a space probe at the same time…if we could ever build such a thing. (Credit: Philip M. Lubin)

The proposal, which was announced by press release and press conference, comes from cosmologist Philip Lubin of the University of California at Santa Barbara and engineer Gary Hughes of California Polytechnic State University. Calling it a Death Star immediately makes the idea sound both sexy and goofy. The researchers use the term┬áDirected Energy Solar Targeting of Asteroids and exploRation (DE-STAR), which isn’t much better. Setting aside the name, though, the idea is interesting.

Lubin and Hughes envision building a scalable, phased array, space-based laser system, powered by large solar panels. Solar power is abundant and uninterrupted in space; developing large, lightweight photovoltaic arrays would be a useful technology for future space stations or power-hungry scientific experiments. Laser beams could be useful for characterizing the composition of near-earth asteroids, and for conducting experiments on how laser heating or laser vaporization could alter an asteroid’s orbit. And phased arrays are an intriguing way to create a steerable light beam from a flat surface without turning it.

DE-STAR begins to look less convincing when you consider the scale of what Lubin and Hughes are proposing. The scientists speculate loosely about a 10-kilometer wide DE-STAR 4 capable of vaporizing a 500-meter-wide asteroid in about one year. Such a device is well beyond the capability of today’s engineering and space infrastructure, and its cost would certainly be in the hundreds of billions of dollars, if not more (Lubin and Hughes did not discuss budget). Space-based lasers obviously would have enormous military value, raising delicate political concerns and violating current treaties.

At any rate, talking about Death Stars is fun but the really meaningful challenge is finding a way to build a technology test bed to see if the DE-STAR concept makes sense. There are many other promising suggestions of how to deflect an Earth-approaching asteroid. Whacking it with a kinectic impactor, pulling it with a heavy mass (aka “gravity tractor“), attaching a rocket to the surface, or even painting or covering the asteroid to alter the push of solar radiation all might prove more cost-effective. The old blast-it-with-a-nuke approach could work as well, though the goal would be to alter the asteroid’s course, not to disintegrate it.

For any deflection scheme, the single biggest obstacle is that we currently cannot detect small asteroids before they hit. The Russians had exactly zero warning that a meteor was incoming over Chelyabinsk. NASA’s funding in this area is puny, as I posted earlier. Or as I mentioned on Fox News, the total federal spending on asteroid detection is about 1/5th of the free postage budget allocated to Congress every year. That’s an easy statistic to harp on, since everybody loves bashing Congress. The real point is that early detection is both fairly cheap and an essential preliminary step before anybody starts building an expensive, complicated asteroid defense.

Companies like the B612 Foundation, Deep Space Industries, and Planetary Resources have plans to build private detection networks. But why is our government walking away from such a low-cost, high-payoff, and universally useful task?

CATEGORIZED UNDER: astronomy, select, space, Top Posts
  • Buddy199

    How large of a nuclear weapon would it take to vaporize an object as big as Mt. Everest, the same sized meteorite that hit the Earth 65 million years ago? Or just knock it off course?

    • m12345

      It wouldnt vaporize a mountain it would split it into lots of little
      radiative pieces and gas that would engulf the planet and cause cancer
      and coughing.

      However if you redesigned the weapon
      so it had more neutron material, the ensuing explosion would consume
      more of the material ejected in the explosion.

      When you think of a rock that large, nothing we do will be enough unless we had decades of time and a multiple methods.
      Most attempts will fail to move or do anything to it. I believe it was
      200 kilometers across and would make Everest look like a small hill. Eveery nuke in the world would not be enough to vaporise it, however they might..might move it if exploded next to it.

      • Ronald Woodaman

        Given the distances involved in space, if you can project that a big asteroid will hit earth a few months in advance, you may need to shift the asteroid’s trajectory by only a few arc seconds. This may only require a small nuke detonated perpendicular to the asteroid’s course. The trajectory is shifted just a wee bit – but 2000 hours later it misses us by 50,000 miles (which is still super close – just not impact).

        Obviously for the smaller bodies like the recent bolide – we gotta find them first.

        • Nullius in Verba

          Just for fun…

          If you work in the freefalling frame of reference moving with the asteroid’s original orbit, then over a small fraction of an orbit you can treat it as inertial.

          So to move a body 50,000 miles in 2000 hours you need to change it’s velocity by about 25 miles per hour.

          If a mass m is blasted out of the side of an asteroid of mass M, at a speed v so as to move the asteroid at speed V, then momentum balance says mv = MV or v = VM/m.

          A 100 megaton bomb releases an amount of energy around E = 4.2E17 J. If all of this is converted to kinetic energy, 2E = mv^2 + MV^2 = m(VM/m)^2 + MV^2 = (M/m + 1)MV^2.

          Now I’m not sure what the maximum speed of a bomb’s output is, but if we guess 1000 mph, the momentum balance says we have to have M/m = 40 at least. We would have to eject almost 2% of the mass of the asteroid.

          2E/(41 V^2) = 1.6E14 kg = 160 billion tons. Quite big. If that was made of ice, it would be around 34 km radius. But the chunk we’d have to knock off would need to be around 4 billion tons which would be a ball 10 km in radius. You would need to drill a shaft several km deep to put the bomb in to eject that much.

          The basic problem is that if you set the bomb off on the surface, it doesn’t penetrate very deeply and you don’t get much reaction mass. A nuclear bomb has more than enough power, but it can’t get a grip, so to speak. It’s too light.

          So the limit is actually how deeply you can bury the bomb in the time you’ve got. If you can only drill a tenth as deep, you can only shift a thousandth of the mass.

          Drilling ice wouldn’t be so bad, you just need heat. But drilling nickel-iron in zero-g would be tricky.

          That’s why most serious proposals think in terms of a slow and steady thrust, over months.

          Alternatively, if you can break it up into fragments smaller than 10 metres across, they’ll all burn up in the air. That would be useful if you can do it. But again, you probably need to bury it for the bomb to not simply bounce off. It might work for comets, though.

  • jeffgoin

    Agreed that the nuke idea is a last resort, reserved for either failed efforts at redirecting or late detection objects. It’s often mentioned that blowing up a rock would just make for a lot of smaller impacts. But wouldn’t that be preferable because those remaining smaller asteroid bits lose more energy (relatively) harmlessly in the atmosphere?

  • Sunny D

    Sure, let’s just spend millions of dollars on stopping Earth-impact large asteroids that randomly will become suspiciously more common in the near future than in the entire past combined.

    • coreyspowell

      (author) Right now nobody is spending anything at all on stopping asteroids. Zero. The only money we’re spending is devoted to *detecting* potentially hazardous asteroids, which is a very sensible precaution and which costs incredibly little. At present we spend less than 1/1,000,000th of the federal budget on this project.

  • http://www.facebook.com/people/Vincent-Wolf/100000568457300 Vincent Wolf

    The best way to destroy incoming asteroids or comets is to simply use them against each other. Capture small asteroids from 20 feet to 200 feet into permanent orbits around the Moon. Then refuel the craft which pushed them into orbit for use in pushing them out of orbit, and slingshot them around the Earth at high speeds of over 25,000 mph and into the path of incoming asteroids. By capturing about 25 of these big rocks into Moon orbits they will always be there for future generations to use to ‘throw rocks’ at rocks.

    We already know we can land on an asteroid it’s been done twice and we can impact them that’s been done twice also. And as the recent Russian asteroid has shown those high speed impacts contain more energy than even nuclear bombs. A 200 foot asteroid accelerated to 40,000 mph would have more energy when it impacted an asteroid coming the other direction at 20,000 mph or more with more energy than all the nuclear weapons on Earth.

    And we don’t actually have to sling them directly at them but can sling them into a parallel orbit and with remaining fuel use gravity to drag them away.

    It would only take as asteroid of 10 feet to destroy an incoming asteroid of 100 feet. Or a 200 feet one to destroy an incoming one of about 2000 feet across which covers about 98% of all potential incoming asteroids.

    For dinosar killers it might take a couple of 500 feet asteroids and use the gravity tractor method instead of impact method.

  • mtthwbrnd

    That’s a great idea and we can like totally trust our fully trustworthy and honest government to not somehow find a way to use it against the people. Like, totally can trust them, dude. Projects like these always come in on budget and on time as well dude, so it will be good value for the tax payer dude.

    What is the carbon footprint of a Death Star? I guess we could raise taxes to pay for some carbon offsets. It is very important, to make sure that we reduce carbon, like, totally important dude. But seriously dude, just do what Bruce Willis did. He went up there and blew that mother up man.

  • http://www.facebook.com/people/Vincent-Wolf/100000568457300 Vincent Wolf

    We may already be doomed even before Science and NASA get busy looking for more asteroids.

    Why?

    Because one of the cousins of the asteroid that hit Russia recently could be visiting Mars soon and cause us BIG problems back here on Earth!

    How so?

    NASA has recently discovered a Comet named C/2013 A1 (Siding Spring)
    that is going to pass within 67,000 miles of Mars and once additional
    measurements are made — the ‘probability cone’ for impact may actually
    include Mars itself and so it could actually collide with Mars.

    Why is that a problem for us when Mars is so far away?

    Because this Comet is 125 times more volume than the one that killed
    the dinosaurs 65 million years ago here on Earth–and will be traveling
    at 126,000 mph when it approaches Mars.

    To put that in perspective–the 6 mile wide asteroid that hit
    Chixilub created a 180 mile wide crater. If this one does indeed hit Mars it
    will create a crater over 1000 miles across (probably 2000 miles across) and throw up an enormous amount of material out into space—millions of rocks from inches across to hundreds of feet across.

    And much of that will exceed the escape velocity and become ‘Martian Asteroids’.

    Thus we could be in the path of a huge Martian Asteroid swarm as it
    heads away from Mars in every direction and in about 6 to 7 months later
    when the Earth swings around the sun we could be in BIG trouble.

    To see this in a diagram visit this link http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2013A1;cad=1;orb=1;cov=0;log=0#orb

    The energy of the impact is estimated at 20 billion megatons. That’s
    more than an order of magnitude bigger than the biggest Shoemaker Comet that hit Jupiter.

    Comet C/2013 A1 is nearly 34 times larger than largest Comet that hit
    Jupiter (Shoemaker 9)–the largest of which was 9.3 miles across and
    created a plume bigger than the Earth itself.

    So if this Comet DOES hit Mars will be able to see the light show
    from Earth during broad daylight as it will shine brighter than the sun
    for a moment–almost like a Super Nova as seen from millions of light
    years away–it will be a stupendous explosion and the energy released
    will be truly awesome. This Comet won’t have the energy slow down from
    an atmosphere like on Earth or the massive ‘digester’ atmosphere that is
    on Jupiter.

    So Earth could very well get hit from the ‘fallout’.

    Which would be a meteor storm unlike anything the Earth has experienced in millions if not hundreds of millions of years.

    Insane huh?

    • coreyspowell

      (author) A few caveats, if I may. The odds of collision are still very low–less than 1 in 25,000 by my back of the envelope calculations. We don’t know exactly how large the comet is, so we don’t know exactly what the impact would be like if it happened. And even then there is no superhighway that leads debris from Mars to Earth. Very little of the debris would reach escape velocity, and then very little of that would find its way to Earth.

      Major impact on Earth are extremely rare. True, one could happen at any time. But the likelihood of one happening almost as soon as we start looking is very very low.

  • Reese Houser

    YES to this one.
    For pretty much all the reasons you said. I think, if this one lives up to
    its premise, it’ll be insanely fantastic.

    http://www.brilliantpapers.com

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Notes from the far edge of space, astronomy, and physics.

About Corey S. Powell

Corey S. Powell is DISCOVER's Editor at Large and former Editor in Chief. Previously he has sat on the board of editors of Scientific American, taught science journalism at NYU, and been fired from NASA. Corey is the author of "20 Ways the World Could End," one of the first doomsday manuals, and "God in the Equation," an examination of the spiritual impulse in modern cosmology. He lives in Brooklyn, under nearly starless skies.

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