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How Missile ballast stability works?

  1. Apr 26, 2017 #1
    launching a missile from the water, how the ballast stability works?
     
  2. jcsd
  3. Apr 26, 2017 #2

    Mech_Engineer

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    Have you considered trying a simple internet search for "ship ballast stabilization"?
     
  4. Apr 26, 2017 #3
    yes, i m working on that, but i feel like ship have big ballast system compare to missile which is 1m diameter, also i would need some exact work on, missile stability
     
  5. Apr 26, 2017 #4

    berkeman

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    Staff: Mentor

    Welcome to the PF.

    Your question does not make sense as you have asked it. Could you please provide a lot more detail and some sketches of what you are asking?

    Missiles do not carry ballast. And ships that launch missiles would generally not need to do anything with their ballast when launching missiles, since the reaction forces involved in the launch are a tiny fraction of the weight of the ship.

    https://s-media-cache-ak0.pinimg.com/originals/59/d9/29/59d9293c7f45df8e0c5a0951f2f8d0cb.jpg
    59d9293c7f45df8e0c5a0951f2f8d0cb.jpg
     
  6. Apr 26, 2017 #5
    yes, you are right but what i m working on is totally different thing, have you heard about sea dragon or seabee or if you could visit to www.rippleaerospace.com
    here you will see the missile launch. what i want to work is on the `Missile control system and ballast stability``

    thank you very much.
     
    Last edited: Apr 26, 2017
  7. Apr 26, 2017 #6

    anorlunda

    Staff: Mentor

    Are you designing a weapon to attack the USA?

    The reference you provided says that the missile is underwater only 2 seconds after launch.

    Inertia will be an important factor, perhaps the dominant factor. You need a dynamic model, including the spatial distribution of buoyancy, and including the hydrodynamics of the water passing over the outside shell at a pretty good speed. That is not simple. The data you need from real missiles is probably classified.

    Do you have access to the missile data and dynamic computer models?
     
  8. Apr 26, 2017 #7
    Haha, No access to any data. just working on a university project.
     
  9. Apr 26, 2017 #8

    berkeman

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    I only read a little at the link. Why do they use that technique to launch the missile? It seems like it would be much easier to just launch it from a small boat that is towed by the ship. What advantage is there to having it in the water held upright by a ballast before launch?
     
  10. Apr 26, 2017 #9

    anorlunda

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    That's a question for a sailor.:wink:

    For many consecutive days, seas can be too rough to have a rocket free standing vertically without toppling and /or spoiling the launch angle.

    If you bolt it to the deck, it could capsize the boat because the c.g. is too high.
     
  11. Apr 26, 2017 #10

    anorlunda

    Staff: Mentor

    If you have no data, then make a computer model and run a range of cases covering a range of assumptions about ballast distribution.

    With only 2 seconds underwater, even an unstable ballast distribution may not tip enough to ruin the launch. It takes time to tip.
     
  12. Apr 27, 2017 #11
    its not important that i have to do all what is in that website, but that is just an example.
     
  13. Apr 27, 2017 #12
    my focus area is `Dynamics of Missile ballast`, not the whole System.
     
  14. Apr 29, 2017 #13

    JBA

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    It appears that they intend for the rocket to be buoyant for towing to the launch site and if it is to be towed then the longitudinal buoyancy cg must be in the center of the rocket length so they require a ballast to hold it vertical for launch.

    At the same time I have rarely seen so much technobabble to promote a concept that is not very different from the method used for launching rockets and ICBM's from submarines, where the rockets are ejected vertically from the submarines before firing.
     
  15. May 27, 2017 #14
    can any body help me? im in critical condition
     
  16. May 27, 2017 #15

    anorlunda

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    Help you how?
     
  17. May 27, 2017 #16

    berkeman

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  18. May 28, 2017 #17
    the rocket is layed in th water, we fill the ballast with water to upheld(stand) the rocket.
    Rocket Specifications:
    Length: 7m
    Weight: 602 kg
    Diameter: 0.52 m
    the length of the ballast is 2m
    the rocket is two stage rocket.
    the Ballast have 5 chambers for water to fill in.
    how much water is need in the ballast to make the rocket stand?
    what is rocket stability calculations during standing and launch?
    how much pressure is released during the launch?
    and other specification related to the dynamics of the ballast system
    thank you in advance, any body can give detail.
     
  19. May 28, 2017 #18

    anorlunda

    Staff: Mentor

    You don't expect us to do the whole project for you, do you?

    Please show us what calculations you have done so far.
     
  20. May 28, 2017 #19
    i have completed the theory part
    now need to work on the calculations, also did design and simulations.
    but not yet how to calculate the stability in the water, the behaviour of the surounding(wind and water wave) during tilting an standing( the angle of heel).
     
  21. May 28, 2017 #20

    berkeman

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    Staff: Mentor

    Show us your work or this schoolwork project thread or it will be closed. Do the work please and show us.
     
    Last edited: May 30, 2017
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