10 Megajoule Weapon

Discussion in 'Physics & Math' started by Orleander, Jan 31, 2008.

  1. BenTheMan Dr. of Physics, Prof. of Love Valued Senior Member

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    This seems a bit large... I mean, coservation of momentum is a bitch---if you mounted one of these rail guns on something that weighs 10^6 kg, you'd end up with a backwards velocity of 30 m/s, which is like 80 miles per hour.

    I'd imagine that they can damp the kick somehow. Anyone know how they deal with this?
     
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  3. BenTheMan Dr. of Physics, Prof. of Love Valued Senior Member

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    I guess a better question would be, how much does a battleship weigh?
     
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  5. Orleander OH JOY!!!! Valued Senior Member

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    how is a railgun different than another gun? I just kept thinking it was on railroad tracks on a ship so they could move it around easier. no?
     
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  7. shichimenshyo Caught in the machine Registered Senior Member

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    Rail guns use electromagnetic fields to launch projectiles at high velocities, they dont use gun powder to propell the projectiles.


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    Last edited: Feb 1, 2008
  8. Orleander OH JOY!!!! Valued Senior Member

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    <doh> got nothing to do with a railroad then, huh. lol
    The rails are inside and a charge build up between then then right?
     
  9. shichimenshyo Caught in the machine Registered Senior Member

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    Yes, then they use the magnetic charge to propell the projectile out of the gun. The problem is that almost all rail guns suffer damage everytime they fire, so the technology is expensive and not reliable enough to really justify any widespread military use ...at least for now.
     
  10. Echo3Romeo One man wolfpack Registered Senior Member

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    Battleships are active no longer. A DDG displaces ~8500 tons, a CG ~9500.

    The Navy has been playing with railguns for quite some time. Surface warfare is about the only application where one might be feasible in the foreseeable future, in part because a shipboard weapon will always be in close proximity to a high flux power source. They're still in the research stage at this time however.

    http://www.defensetech.org/archives/003978.html
     
  11. cosmictraveler Be kind to yourself always. Valued Senior Member

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    So what happens to a target that gets hit with one of these rails anyway? If you say it travels 20 miles then what's its impact at the target?
     
  12. Sarkus Hippomonstrosesquippedalo phobe Valued Senior Member

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    I'm not sure of the exact mechanisms used - but I think it's basically done by storing the recoil energy in something like a spring, which can release the energy in a controlled fashion.

    But I'm guessing the recoil is why most conceptual designs (esp. in sci-fi) for their usage revolve aroung the railguns being along the central axis of the craft, to minimise effect of the recoil.
     
  13. Sarkus Hippomonstrosesquippedalo phobe Valued Senior Member

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    It depends on the mass of the projectile and the muzzle velocity (and any drag effects from muzzle to target).
    9 MJ is apparently sufficient to propel a 2kg mass at 3000 m/s.

    A rifle typically fires a c.0.15kg bullet at under 1000 m/s.

    The energy in just a 9MJ railgun is thus 120 times more than that of a rifle.
    One shot would most likely penetrate a modern tank.

    A 32MJ weapon is likely to be as damaging as a typical surface missile.
    They're not necessarily more destructive (at present) but will ultimately be far cheaper per round and far safer to use (no explosives).
     
  14. joepistole Deacon Blues Valued Senior Member

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    In addition to the above, handling explosives on ship is dangerous. If a ship takes an enemy missle to its munitions storage area, you have a big explosion and fire. Getting rid of or lessening the explosives carried on ships (especially fast frigates) dramatically improves the odds that a ship can withstand an enemy assualt.
     
  15. cosmictraveler Be kind to yourself always. Valued Senior Member

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    From 20 miles away? These are being deployed on ships so just what impact happens at the 20 mile limit of their range? Also if the rail gun does hit something wouldn't it only damage that one thing unlike a bomb which can destroy a very wide area with just one hit?
     
  16. 2inquisitive The Devil is in the details Registered Senior Member

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    You are still a little confused as to what is being developed. The 10 megajule railgun that was just tested is not for use as a weapon, it is only a testing phase. The actual railgun that will be mounted in ships will be a 64 megajule advanced version capable of launching large projectiles over 200 nautical miles. The projectiles will have a guidance system in them, somewhat like rocket propelled missiles. The projectiles will strike their target at extremely high velocities, causing the projectile to 'explode' without the use of explosives inside the projectile itself. Here are a couple of links to the Navy's site, plus one about the recent test gun. BAE is one of the contractors being used in the development phase before the final design of the 64 mj weapon version is arrived at and built.
    http://www.onr.navy.mil/emrg/faqs-electromagnetic-railgun.asp
    http://www.spacedaily.com/reports/B...r_Electro_Magnetic_Rail_Gun_Programs_999.html
     
  17. cosmictraveler Be kind to yourself always. Valued Senior Member

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    Thank you for that information BUT neither of those links provides us with any real time images of this railgun in action. Why don't they show it working and what happens when it hits something 200 miles away?From what I gathered it was "shooting" a projectile which was NOT a bomb or was it? That's what confuses me, wether or not the projectile is a bomb or a piece of metal traveling at high speeds. :shrug:
     
  18. 2inquisitive The Devil is in the details Registered Senior Member

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    cosmictraveler,
    A link of the test is listed on their website, below. I haven't watched it because it requires Windows Media Player, which I don't use.
    http://www.onr.navy.mil/emrg/electromagnetic-railgun.asp

    What they tested was not the 64 mj weapon that has yet to be built, but a simple, lower-powered, preliminary testing of the EM power concept. It is just a phase leading to the development of the final weapon version.

    No, it is not being developed to shoot a 'bomb'. I imagine the test just conducted only launched some type of metal 'bullet' (projectile), but the future weapon-grade version will lauch larger metal 'shells'(also called projectiles). When a solid object traveling at very high speed strikes another solid object, the effects are much the same as a bomb exploding even though no explosives are used. Have you seen the photos of meteor craters that are much, much larger than the actual meteorite that struck? Or what happens to a watermellon when was struck by a high velocity rifle bullet? Same principle.
     
  19. cosmictraveler Be kind to yourself always. Valued Senior Member

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    Thanks again! I guess my problem is that I understand it when a bomb is shot because a highly explosive shell is launched into the air at a angle that will allow it to go up then down into its intended target. Does this do the same thing whenever it "projects" its projectiles? Say a tank was going down a street inside a town would the projectile go over the towns buildings then land or hit the tank missing everything else in its path?
     
  20. BenTheMan Dr. of Physics, Prof. of Love Valued Senior Member

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    cosmic---

    I think that this type of technology would not be used to target tanks and things that are moving. If you're shooting something from 200 miles away, you can't be quite as accurate as a tank, I would imagine. I think that this could be used to target stationary things like buildings and strategic targets.

    Plus, I'd imagine that one of these projectiles does similar damage as a bomb (remember...conservation of energy) for much less cost, and at much less danger to the crew on the ship.
     
  21. cosmictraveler Be kind to yourself always. Valued Senior Member

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    Thanks for the info.

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  22. BenTheMan Dr. of Physics, Prof. of Love Valued Senior Member

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    Don't take my word for it, though. I'm just speculating

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  23. Dr_Zinj Registered Senior Member

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    Sounds like the supercavitation bubbles work to form a lower friction envelope around the missile.

    At first I though they were using a massive cavitation bubble itself to destroy the torpedo by collapsing it on it, and only needed the hypervelocity missile to create the bubble. Sort of like a transfer of energy from a kinetic energy weapon.
     

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