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Simple Solution to Railgun Power Requirement?

  1. Aug 18, 2014 #1
    Old navy guns had shells and magazines that contained many [dangerous] shells below the turrets.

    With the new 1000+ Farad Capacitors on the market, would it not be possible to have "Capacitor Shells" that are obviously charged on land/factory and then stored in a magazine? Using this method, the navy ship would not have to divert power to the Railgun.

    Also, why not create railguns with a gauge that allows you to set the width between them. This would allow the ship to change the size of the shot. Different "capacitor shells" combined with different masses/sizes of ammunition would allow for a very flexible power/speed.

    Also, it should be possible to reach automatic speeds with the railgun if its using very small bullets and capacitors.

    ????

    The capacitor shells could also be recharged on land.
     
  2. jcsd
  3. Aug 18, 2014 #2

    berkeman

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    Welcome to the PF.

    Capacitors are a very inefficient way to store energy. Chemical energy storage (gunpowder, gasoline, etc.) or nuclear energy storage are much more efficient.

    And the Navy is definitely working on putting rail guns on ships:

    http://defensetech.org/2014/01/16/navy-rail-gun-showing-promise/

    :smile:
     
  4. Aug 18, 2014 #3
    Yes, it's inefficient, but that doesn't matter in a time of war. It's better to have 10,000 inefficiently pre-charged capacitors from the factory then using nuclear/gas to power the railguns, simply because it's more "efficient."

    http://powerelectronics.com/passive-components/1000-3000-and-5000-farad-ultracapacitors

    The voltage is what matters on these ultra-caps. We'd simply need to increase it. They are 2.7 V
     
  5. Aug 18, 2014 #4

    berkeman

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    Sorry, but that makes no sense. By inefficient, I mean that a capacitor the size of an artillery shell will barely be able to pop the projectile out the end of the gun, let alone reach multi-mach velocity. You need the efficiency to store the needed energy in a practical size container.

    Look at how they are powering the rail guns now that the Navy is developing. They have plenty of electrical energy available...
     
  6. Aug 18, 2014 #5
    If you want to get into the math, a 10v 5000 Farad Ultracap delivers 250,000 KJ, the ones on the civilian market are 2.7v
     
  7. Aug 18, 2014 #6

    berkeman

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    I think you slipped a couple decimal points there...

    E = 1/2 * C * V^2 = 1/2 * 5000 * 100 = 250,000J

    Take a look at this page, about half-way down where they are comparing "Energy Release" of different forms of energy. The stick of dynamite has E = 2MJ. How many equivalent sticks of dynamite do you think are in a typical Naval artillery round? :smile:

    EDIT -- I forgot the link: http://www.si.edu/Content/consortia/Zimbelman_presentation.pdf

    .
     
  8. Aug 18, 2014 #7

    davenn

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    of course it matters, you want to blow the enemy out of the water before they blow you out of the water, not tickle them a little


    D
     
  9. Aug 18, 2014 #8

    Baluncore

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    Every time a projectile is launched an EM pulse will be generated, that will reveal the location of the launch vehicle and the time of launch. That will give the enemy sufficient time to launch an accurate response before closing their concrete doors.
     
  10. Aug 18, 2014 #9

    davenn

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    That's an interesting thought
    I wonder how they are going to overcome that ?


    D
     
  11. Aug 18, 2014 #10
    Is it possible to utilize enough shielding to minimize the range at which it can be detected?
     
  12. Aug 18, 2014 #11

    berkeman

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    It does seem like there is some self-shielding of the rail/barrel, but they probably do need to stop the rails some distance before the end of the barrel. When the projectile breaks contact with the rails, there is probably a pretty good spark that needs to be shielded...
     
  13. Aug 18, 2014 #12

    berkeman

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    Interesting short video:

    Sounds like recent tests are around 33MJ...
     
    Last edited by a moderator: Sep 25, 2014
  14. Aug 18, 2014 #13

    Baluncore

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    Their effective antenna is a small rectangular current loop with a noisy very high current flow. It will have a non-directional pattern so any interferometer array will fix it quite accurately. The EMP can be expected to generate several kW of EIRP.

    The wide band pulse would be like a very short lightning stroke. I am confident that I could detect it at sea level from 50 miles without any problem from ionospheric reflection. It will almost certainly be observable, out to the projectile range of 100 miles by either high angle ionospheric reflection (OHR) or directly (LOS) from 30,000 ft. If the weapon was deployed from the air at 30,000 ft you could do it all from the ground.

    The other advantage of the enemy producing a local EMP is that it becomes the driver of a passive radar array. Any nearby ships will re-radiate the pulse, an interferometer with cross-correlators will identify the number and positions of all vessels in the task force.
     
  15. Aug 19, 2014 #14
    How are they getting to 33MJ?

    Also why are the projectiles so large and massive?

    Why not fire something 1/10 the mass for 1/10 the energy and shape the round for penetration? There would be less heat and wear on the rails as well.
     
    Last edited by a moderator: Sep 25, 2014
  16. Aug 19, 2014 #15

    davenn

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    cool video

    but now I'm confused .... I thought the rail gun system was an electromagnetic propulsion of the projectile ??
    Why is there a massive explosion as the projectile leaves the gun as tho its being propelled by a standard explosive charge ?


    Dave
     
    Last edited by a moderator: Sep 25, 2014
  17. Aug 19, 2014 #16
    What you saw the guy load is what is needed to encase the projectile. The curved end is the push part, the side parts protect and guide the round during firing. The actual projectile would be aerodynamically shaped to travel the supposed 100 miles. Diameter of projectile would be about 1/3 to 1/2 or about the same as the cylindrical section seen.

    In the video the whole thing is shot as unit. In real action, the projectile will separate from the other sections.
     
  18. Aug 19, 2014 #17
    A lot of sparking which heats up the air.
     
  19. Aug 19, 2014 #18
    Interesting stuff.

    If the weapon is proven to be effective, the 10 or 15 minute lag from detection of EMP to target might have a psychological effect upon the enemy - ie are we the target or not. Anything within 100 miles better be on continuous high alert, or just plain stay away and not engage.
     
  20. Aug 19, 2014 #19
    Hmm, would these heat effects by heavily mitigated in a vacuum? Perhaps this would increase rail longevity.
     
  21. Aug 20, 2014 #20
    On a related note beyond efficency - having multiple Pre-charged, large capacitors - charged, transported, loaded on ships and stored there - is still hazardous. Generating the energy locally VIA the ships nuke plant is much more effective, controllable and safe.
     
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