back to article Soil and sand harden as SPEEDING MISSILES and METEORS SLAM into GROUND – boffins

Physicists have claimed that soil and sand toughen up when struck with hefty force from meteors and missiles hitting the ground at high speed. A lab-based test to simulate such impacts was carried out by boffins at Duke University, after they secured financial backing from the US Defense Threat Reduction Agency. They studied …

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    1. Paul Dx

      Or the old walking / running on custard as done by Brainiac

    2. This post has been deleted by its author

    3. John H Woods

      "Sounds like the old experiment you can do with cornflour" -- 1980s_coder

      +1 for ooblek reference, but is it really the same? In that liquid, it's the mechanics of the starch chains moving over each other (sliding or jamming) which is causing the behaviour --- seems to me that what is happening here is a sort of piling up of particles in front of a penetrating object, rather than any change in the inter-particle interactions?

    4. The Man Who Fell To Earth Silver badge
      Boffin

      Cornstarch & water is a well know example of a non-Newtonian fluid. The Duke experiment is not dissimilar. Next, they will confirm that pointy penatrators do much better than blunt penatrators.

  2. This post has been deleted by its author

    1. Captain DaFt

      Re: Research

      "When I read about what people have to do to earn money in the field of physics, it makes me glad that so many of them are unemployed."

      Yeah, because 'understanding' and 'learning' are such bogus concepts.

      Back in the day it was all 'Spirits' and 'Gods' and that worked soooo much better for us, dinnit?

      1. Anonymous Coward
        Anonymous Coward

        Re: Research

        @Captain DaFt

        When it comes to Learning about how best to detonate nuclear weapons in enclosed spaces filled with people, then yeah, i'd prefer people not to understand. There are better things they could use their IQs studying.

        1. Anonymous Coward
          Anonymous Coward

          Re: Research

          >There are better things they could use their IQs studying.

          Otto makes a new type of chemical>kinetic engine. Some people put his Diesel engines in tanks, some in ambulances. What did Otto think?

          1. Matt Bryant Silver badge
            Stop

            Re: AC Re: Research

            "Otto makes a new type of chemical>kinetic engine....." He did nothing of the sort, all he did was try and patent it everywhere. Diesel's work was an improvement on other designs, he in no way at all invented a brand new type of engine.

          2. Anonymous Coward
            Anonymous Coward

            Re: Research

            "What did Otto think?"

            Their grant is to help figure out how to get a nuke into a cave with people hiding in it. It is not something abstract like making an engine go faster.

            Hiding under the banner of "oh yeah but maybe research will have useful offshoots" is cowardly and disingenuous.

            There are many people who post on these forums that have the skills needed to work on one of these grants, but instead choose to research something more ethical with their skills. These people I admire.

            1. Swarthy Silver badge

              Re: Research

              How are you getting "nuke" out of this article? Yes, they talked about ground-penetrating weapons, but those tend to be thermoberic, not nuclear. Nukes are almost exclusively air-burst, Ground-burst nukes have potential to be too nasty even for the people that would set them off.

              And if you think that ground penetrating projectiles have no civilian use, Think about how much easier(and cheaper) that could make bridge building. Or allow for better foundations/footings for buildings, houses.

              1. x 7

                Re: Research

                " ground-penetrating weapons, but those tend to be thermoberic, not nuclear."

                Ground penetrating thermobaric weapons? What gobbledegook is that? Thermobaric weapons depend on the available air to create a shockwave front. They have to be exploded in the open air - or in an existing chamber with an air-space and plenty of oxygen.

                As for "Nukes are almost exclusively air-burst, Ground-burst nukes have potential to be too nasty even for the people that would set them off."

                Total BS. Virtually all first strike missile nukes would be aimed at reinforced silos in the opposing country - requiring ground burst to even getting near to taking them out. Yes, ground burst is messy due to fallout, but tough shit. Its not as if there would be anyone intending to live there afterwards

                1. Swarthy Silver badge

                  Re: Research

                  Yes, thermobaric devices need space, like a cave, bunker, silo, WMD manufacturing plant, etc. The things that tend to be hardened against "Death From Above"™. So you research methods of penetrating the crunchy exterior to incinerate the chewy center.

                  Also, cooking a target with a TB bomb is much less likely to piss off the whole world than even the smallest of nuclear bombs. Nukes are like the ad hominim attack in an online debate: as soon as you use 'em, no-one will be on your side.

              2. This post has been deleted by its author

                1. x 7

                  Re: Research

                  "about detonating nukes in caves."

                  For "caves" read underground reinforced Iranian or NorK reinforced bunkers housing centrifuges and other tools for refining uranium and plutonium

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                    1. x 7

                      Re: Research

                      What am I implying? That the penetration rounds are for destroying hidden WMD manufacturing capability. Its the machinery that counts - but if the operators get killed along the way, all the better. Its easy to train people, its not so easy to replace the equipment.

                      If you can eliminate the centrifuges, you eliminate the risk of nuclear escalation. And the Iranian centrifuges are now all deeply buried - as a result of the Israeli surface attacks of a few years ago - hence the need for a penetration round

        2. Mark_S

          Re: Research

          "When it comes to Learning about how best to detonate nuclear weapons in enclosed spaces filled with people, then yeah, i'd prefer people not to understand. There are better things they could use their IQs studying"

          What is the purpose of an army?

          Recognizing that many bad guys have armies, should your country have one too, at least for self defense?

          If no, please abolish your army so that I can bring mine to your country and appoint myslef emporer.

          If yes, what exactly is the problem with armies trying to develop ways to perform their function more effectively?

      2. elDog Silver badge

        Re: Research

        And there is a ton of money shoveled to projects like this - I've worked on a few over the years. The Advanced Research Projects Agency (ARPA) has probably funded 10's of billion$ on seemingly stupid ideas. Some of them (like the internet) actually have been demonstrably useful. Many of them may appear to be more Darwin Award category but I'd rather the money was spent there than on weaponry.

        This particular experiment seems a bit grade-school level but I'm thinking that all the major powers have already looked at the physics of hardening. Probably back to those days when all we had were earthenware berms.

    2. Richard Jones 1

      Re: Research

      Well I guess that several towns, residents and developers 'out East' are really glad that this physics research was not bothered with sooner. They are the ones who had their buildings collapse due to slow differential settlement that caused the building to tip then topple over. They probably did some fairly high impact soil compaction tests and thought that it would be fine. But buildings do not hit the ground fast, they accumulate weight over time and many soils can flow under these situations. I do not know what splendid research you would like money to be wasted on, but it is a shame that some of these alleged unemployed physics type were not able to do more useful research, e.g. on thorium power generation.

      1. This post has been deleted by its author

        1. Richard Jones 1

          Re: Research

          I take soil liquefaction to be the result of vibration, e.g. earth quakes when the soil can almost appear to boil and once buried items can 'float' to the surface. However, this was not what I was talking about, rather the atypical, unpredictable behaviour of some soils, (but which ones and why?) when under 'duress'.

    3. Dave 126 Silver badge

      Re: Research

      >When I read about what people have to do to earn money in the field of physics, it makes me glad that so many of them are unemployed.

      Yeah okay, physicists never got poor by chasing DoD funding, you're right. Bunker-penetrating warheads - always handy! And yeah, many scientists and engineers could be put to work improving the lot of humanity instead of making better weapons. But hey, there's overlap: Sooner or later our planet will be struck by a meteorite that will cause serious damage to our species.

      It will be quite nice to know a couple of days in advance roughly how fucked we will be when it hits.

  3. neillanwarne
    Mushroom

    I can understand his point though. It'd be nice if the research wasn't just used to make better bombs.

    1. Anonymous Coward
      Anonymous Coward

      Iran wasn't even mentioned!

      1. Martin Budden
  4. Mark 85 Silver badge
    Holmes

    The bow wave effect?

    This seems to be another study on this type of effect where as the projectile/aircraft/boat/submarine move forward, what's in front gets compressed except it's simulated dirt. Dirt just doesn't move out of the way as easily as air or water.

    1. Martin Budden

      Re: The bow wave effect?

      Seems to me like a sonic boom type thing (which might be what you were getting at). If the projectile is travelling faster than the speed of sound in dirt it gets a fairly solid shock.

  5. chivo243 Silver badge
    Facepalm

    Like trying to push your way through a crowded room

    I find a strategically timed lack of a shower(s) can speed progress through a crowded room.

    1. Anonymous Coward
      Anonymous Coward

      Re: Like trying to push your way through a crowded room

      Is that like a dirty bomb ?

      1. Mark 85 Silver badge

        Re: Like trying to push your way through a crowded room

        Is that like a dirty bomb ?

        More like chemical warfare...

  6. Osgard Leach

    Seems damned strange, just lobbing things in slowly like that. Un-American.

    I know NASA's got a .22 rifle that takes about a bin bag full of gunpowder; hypersonic jobbie, own shed. Surely more the ticket?

    1. Fink-Nottle
      Thumb Up

      Ultimate in Shed One-Upmanship

      > hypersonic jobbie, own shed.

      "My shed? Oh, it's ex-NASA."

    2. Richard 12 Silver badge

      Hypersonic jobbie?

      Eeewww! That's a hideous image...

      1. Andy The Hat Silver badge

        Re: Hypersonic jobbie?

        ... just the result of a Sprout Chilli Massala ...

  7. John Brown (no body) Silver badge
    Joke

    Well obviously...

    ...it's a DARPA project to develop a "mole" machine to attack the inhabitants of Pellucidar and steal the underground oil manufacturing machines.

    What? You thought oil was a natural product?

    1. Anonymous Coward
      Anonymous Coward

      Re: Well obviously...

      Well, if oil's NOT a natural product, explain the Jatropha (NOT a joke).

  8. jr424242

    Soon, scientists like these will break the 15 MPH barrier.

    And what will that portend for worldkind and dogkind?

  9. Kev99

    Well, DUH! IT's just a variation on fluid dynamics. Slowly push your hand into water and there's no problem. Slam your hand into the water and you end up hurting. Obviously those boffins never did belly flops as kids.

  10. Charles 9 Silver badge

    OK, now repeat the experiment with a pointed tip, much as how a very high diver positions his hands in a specific way to minimize surface area on impact.

    1. Alan Brown Silver badge

      "OK, now repeat the experiment with a pointed tip"

      Such things end up blunting very quickly on things more solid than water.

      1. Charles 9 Silver badge

        Even tungsten or DU with its high density?

  11. x 7

    Why do I get the feeling that someone has just reinvented thixotropics?

  12. Anonymous Coward
    WTF?

    Am I really missing something?

    Or is this pretty basic schoolboy physics?

    Push you had slowly on a thick liquid it goes in easily, smack it hard and your more likely to break your hand then go in deeply.

    1. Paul Kinsler

      Re: Am I really missing something?

      "Or is this pretty basic schoolboy physics?"

      Yes, you are missing something: mainly that your schoolboy demo didn't involve a careful experimental design and setup, comprehensive results/image taking, and proper analysis of the results. And that your "thick liquid" is under no compulsion to behave like the granular materials tested here.

      Why on earth do you think a rewrite of a press release and a simple analogy aimed at the wider public constitutes the entirely of this research work? Let alone what will make up the content of the PRL?

      Why not visit http://journals.aps.org/prl/ and look at a couple of the articles there that are open access, and test your schoolboy physics against those? It might give you an idea of the level of technical detail this kind of press-release science jornalism leaves out . And don't forget, since PRL has a page limit, the writeup there is often somewhat abbreviated.

  13. Alister Silver badge

    So, these scientists have never laid a patio then? Otherwise they might have come across the idea that you compact sand into a hard surface (on which to lay your concrete slabs) by hitting it repeatedly with a tamper device?

  14. x 7

    "a tamper device"

    oooh....posh words. On all the sites I've worked on, it was called a "wacker"

    1. Alister Silver badge

      oooh....posh words. On all the sites I've worked on, it was called a "wacker"

      :-)

      Given the debauched nature of the majority of commentards, I hesitated to type "hit repeatedly with a whacker"...

  15. W T Riker

    What! No Video...

    Video please.

    1. Paul Kinsler

      Re: What! No Video...

      There are videos, which are very nice - but without access to the journal you're probably stuck.

      The group's website is http://behringer.phy.duke.edu/ ... it has some vids but not those for this article as far as I can see. There are some other articles of theirs on arXiv - see e.g.

      http://arxiv.org/find/cond-mat/1/au:+Behringer_R/0/1/0/all/0/1

      1. Paul Kinsler

        Re: What! No Video...

        I forgot to say - the videos show exactly the "the network of force chains buried in the beads" referred to in the article - there are annoyingly tinysnapshots on the journal article's abstract page (url below), but they appear to be too tiny to see much.

        http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.114.144502

  16. Brewster's Angle Grinder Silver badge

    A step closer to Dune-style shield technology.

  17. x 7

    I see that a number of inflammatory posts have been deleted from this thread by its author......I wonder why..? Trolling backfiring on him maybe?

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