How to Use Nuclear Bombs for Asteroid Deflection

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Lawrence Livermore National Lab has a new tool toA improves our understanding of the nuclear deflection’s radiation interactions on the asteroid’s surface while opening the door to new research on the shockwave dynamics affecting the inner asteroid.

The paper introduces an efficient and accurate library of X-ray energy deposition functions, developed using the Kull radiation-hydrodynamics code. High-fidelity simulations tracked photons penetrating surfaces of asteroid-like materials such as rock, iron, and ice, while accounting for more complex processes, such as reradiation. The model also considers a diverse set of initial conditions, including different porosities, source spectra, radiation fluences, source durations, and angles of incidence. This comprehensive approach makes the model applicable to a wide range of potential asteroid scenarios.

Should a real planetary defense emergency arise, high-fidelity simulation modeling will be critical in providing decision-makers with actionable, risk-informed information that could prevent asteroid impact, protect essential infrastructure and save lives.

Planetary Science Journal – X-Ray Energy Deposition Model for Simulating Asteroid Response to a Nuclear Planetary Defense Mitigation Mission

Abstract
In the event of a potentially catastrophic asteroid impact, with sufficient warning time, deploying a nuclear device remains a powerful option for planetary defense if a kinetic impactor or other means of deflection proves insufficient. Predicting the effectiveness of a potential nuclear deflection or disruption mission depends on accurate multiphysics simulations of the device’s X-ray energy deposition into the asteroid and the resulting material ablation. The relevant physics in these simulations span many orders of magnitude, require a variety of different complex physics packages, and are computationally expensive. Having an efficient and accurate way of modeling this system is necessary for exploring a mission’s sensitivity to the asteroid’s range of physical properties. To expedite future simulations, we present a completed X-ray energy deposition model developed using the radiation-hydrodynamics code Kull that can be used to initiate a nuclear mitigation mission calculation. The model spans a wide variety of possible mission initial conditions: four different asteroid-like materials at a range of porosities, two different source spectra, and a broad range of radiation fluences, source durations, and angles of incidence. Using blowoff momentum as the primary metric, the model-initiated simulation results match the full radiation-hydrodynamics results to within 10%.

17 thoughts on “How to Use Nuclear Bombs for Asteroid Deflection”

  1. What if, you made a double ended rocket. One pointed at the asteroid and one in the opposite direction. Connected together. It hovers right over the asteroid and blast it with it’s rocket blast. To keep it from moving away, a rocket on the other end blast it towards the asteroid. Rockets perpendicular to the two big rockets keep it oriented “if” gimbaled thrust doesn’t do the job. Like a big hovercraft in space. Think a double ended spacex rocket. Lot of thrust. Of course it would blast debris everywhere. Maybe even have some orbit around and bash the rocket so you would have to use it up fast.

  2. Any big project is going to benefit from cross-over functionality when it comes to getting funded.

    The laser infrastructure for sail propulsion of probes can also be used to deflect an asteroid.

    Either by directly focusing on smaller asteroids, or by propelling sails to impact larger asteroids.

    This would probably be the best bet for short notice response.

    And, it’s easier for politicians to explain spending ten billion dollars to “Defend Earth Now”, then to explain spending that money to get snap-shots of a gassy rock around another star –thirty years in the future.

    • Nukes contain a ridiculous amount of energy, far more than can be provided with even the most advanced laser systems. Lasers might be good for low mass space probes, but the energy required to shift an asteroid’s trajectory is so massive that it’s not really conceivable to laser it away.

      • Back when the laser sail idea was first being talked about, I googled how much energy a one gram sail, moving at 20% the speed of light would release if it hit something.

        Tons of others had already asked and answered the question.

        By those numbers, the impacting sail would release energy equivalent to half a kiloton of t+t.

        Thirty sails over time would be equal to the 15 kiloton Little Boy device.

        Then it’s all about how big the target is, how much time you have, and how quickly you can start launching sails.

        Not saying nukes are a bad solution.

        But, a laser system would be dual use, pushing probes all over the place while we wait.

        • The Little Boy nuke was really peanuts compared to what the massive thermonuclear bombs were capable of. The most powerful nuke in existence today, the B83, is equivalent to around 80 Little Boys, or, by your count, 2,400 sails. A single B83 weighs a little over a metric ton. A current Falcon Heavy can launch up to 58 of them to the moon.
          I would argue that even if we had laser-powered probes, there’s no way it would be more economical to use the lasers to deflect an asteroid than to launch a single rocket laden with nukes.

          • I’m not saying nukes have no role, but in all likelihood, any rock needing to be moved will distant or small, relatively speaking.

            The threats are on a sliding scale.

            If it’s a big, previously unknown planet killer, coming from within Earths orbit, hidden by the Sun’s glare, not much could be done.

            Nukes would be the best choice in the event of a big and close asteroid, but even that could be too little, too late.

            Such big ones are rare, though, on the order of one every few hundred thousand years.

            Smailer threats are far more likely.

            Something in the 165 foot range, big enough to reach ground, could be “moved” by a number of sail impacts, delivered on short notice.

            The actual energy released by a sail would depend on how long they can be accelerated, meaning each sail would impact with less energy the shorter the distance of travel to the object.

            Bigger rocks will be seen further out, allowing for higher energy impacts over a longer period.

            Smaller rocks might be found so close, there’s little space for sail acceleration, but less energy would be required to divert the smaller mass.

            Any mission using nukes would need to be pre-positioned off-Earth, or be on short notice to fly.

            It would require enough heads up to get a standby Falcon Heavy loaded with a package and launched.

            How fast could that be done?

            Probably want a back-up rocket, just in case. So you have two Falcon Heavy on continuous standby, serving no other purpose.

            You would also need a rack of multiple nukes of different yields, as the size of the device needed would depend on the rock.

            A laser sail system would be able to act almost instantly to engage the most likely threats; smaller, closer rocks.

            A larger, more distant threat could be engaged over a long period with higher energy sails.

            In the mean time, and to my point, the laser is pushing sails all over the place, including a string of sails taking photos of gassy rocks around other stars.

            Of course, the four mile wide interstellar comet that intersects us from above the Solar plane is just going to do that.

  3. This is obviously just an update to an idea that dates back to the 1960’s:

    “MIT Saves the World: Project Icarus (1967)
    1960s MIT professor Paul Sandorff assigns best homework ever: create a plan to hijack the Apollo project and launch Saturn V rockets to deflect an asteroid that’s about to hit Earth.”

    https://www.wired.com/2012/03/mit-saves-the-world-project-icarus-1967/

    No more Saturn 5’s of course, but we have (or soon will have) something better; Super-heavy wedded to “Starship” that can deliver to orbit the equivalent of said Saturn 5 but reusable. So if anything the plan alluded to above is more practical than when originally proposed. A “nuke” is a last ditch effort to deflect said incoming asteroid; obviously with sufficient lead time (and a robust human presence in space anyway) other options would be preferred. After all if we are mining asteroids like “UW158”:

    “Meet the Asteroid That’s Made of $5 Trillion Worth of Platinum”

    https://futurism.com/meet-asteroid-thats-made-5-trillion-worth-platinum

    Given the ability to land on and mine an asteroid we can certainty deflect it.

  4. There is no way other than mikes to deflect a rubble pile asteroid.
    I used to do calculations of the temperature and blow off of satellites exposed to nukes in space. Most of the output of a nuke is low energy X-rays and with a nuke exploded several tens of km from the asteroid the entire rubble would be exposed to uniform fluency of a few joules/cm2 of soft X-rays giving the entire rubble pile a uniform impulse. This uniform impulse is important to keep the pile from turning into a large threat cloud.
    Different nukes produce different energy X-rays (the X-rays are black body radiation) and absorption depth of the X-rays is strongly energy and rubble material dependent. This is very important work if we are threatened by an asteroid.

  5. Color me purple and call me an eggplant … but … wasn’t the Big Deal, the Ginormous Breakthrough in so-called extinction event deflection, the use of moderately massive (mostly fuel-and-oxidizer) space ships that would hover a kilometer or so above the asteroid upon intercept, and stay hovering for weeks, using the rocket-fuel to stay on one side, and the mutual gravity between the rocket and the asteroid to deflect it?

    It was ingenious. And very, very safe. No blasting of nuclear fragments all over Hêll and gone. Not very sexy, I guess, not spectacular. Not SciFi 3D ray-traced particle graphics glitzy. But marvelously effective. Just no crowd pleasing action movies to show for it.

    The integrated deflection of a few hundred newtons of mutual counteracted gravitational attraction could move a billion-ton incoming asteroid or comet nucleus a few meters per second (in a few months) — or hundreds of kilometers per day — out of Earth’s path. And that’d solve the impact problem.

    And the fly-by would also be absolutely precise in outcome.
    Not a big messy blob of meteor bits whinging all over the place.
    No ejecta whatsoever.

    As I said. A purple Eggplant.

    ⋅-⋅-⋅ Just saying, ⋅-⋅-⋅
    ⋅-=≡ GoatGuy ✓ ≡=-⋅

    PS: The ‘goatish’ take on this is that it is the product of a wishful Science Grant given to a bunch of starving PhD candidates, trying to eke out a fine sounding Physics project from the Lawrence Livermore Labs nuclear physics codes developed in the last 50+ years. A very nice piece of rah-rah work, destined for the dustbin of big-but-useless ideas. Then again, I’m something of a skeptic by nature.

  6. I’m glad to see them thinking outside of the box. Maybe a demonstration of our nuclear weapons out in space could serve as a deterrence to any would-be adversary.

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