funny idea :)

Discussion in 'Projects & Proposals' started by jbehr, Sep 22, 2010.

  1. srimes
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    srimes Senior Member

    Call Russia, they have extras they'll sell cheap.

    Don't bother with a bubble. Just use 2 ropes and steer it like a kite. Be sure to get video for youtube.
     
  2. hoytedow
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    hoytedow Wood Butcher

  3. Vulkyn
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    Vulkyn Senior Member

    so whats the point again? To launch the guy into a wave catapult him in the air and send him to his icy depth? Im sure there are much cheaper and less elaborate ways to achieve that...

    It is a funny idea .... how to kill some one in the most horrific way ....

    really whats the point ?
     
  4. Vulkyn
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    Vulkyn Senior Member

  5. srimes
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    srimes Senior Member


    It's an American thing. You wouldn't understand. :p


    Spend some time on youtube. It's just the kind of thing we do over here :D
     
  6. latestarter
    Joined: Jul 2010
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    latestarter Senior Member

    The main flaw is that the high speed, high temperature exhaust gases will be hitting the sphere causing huge drag and burning it to a crisp.

    Even if you covered the sphere with tiles like the space shuttle there is no way of dissipating any heat reaching the inside of the sphere.
     
  7. Vulkyn
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    Vulkyn Senior Member

    I'm starting to think the concrete sub was not such a bad idea after all :S

    i think the rocket idea was inspired from star wars Episode one ( the racing pods scene).....
     
  8. Anytec1210
    Joined: Aug 2010
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    Anytec1210 Junior Member

    Buy a Zorb and strap you in. You are not the first.

    Perhaps you like to start with a plain motorboat first and not a JATO since the science of engineering rocket propelled inflatable devices is a somewhat unexplored area.

    Good luck!




    [​IMG]
     
  9. jbehr
    Joined: Sep 2010
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    jbehr Junior Member

    what if it was underwater rocket and sphere that would negate the effects of the waves and the heat
     
  10. apex1

    apex1 Guest

    You should cooperate with "Questor", his solar powered sub was as brilliant as your lunatic vessels. And employ "Kistinie" for propulsion questions and "goodwilltoall" to make it affordable, no matter how impossible it is. What a outstanding pool of knowledge that would be............:idea:

    You just must not listen to us naysayers, or believe in physics, everything is possible.

    Go for it!


    But go........................
     
  11. jbehr
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    jbehr Junior Member

    haha well still a valid point....either way is its just an idea
    you don't seem to like ideas very much :)
    anyways thanks for your input
     
  12. daiquiri
    Joined: May 2004
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    daiquiri Engineering and Design

    It would be a short and unpleasant ride.

    But since I have some time now and out of sheer curiosity to see what numbers will come out of it, I'll take it a bit more seriously. It is a quick math excercise anyways.
    So... A rocket thrust is given by the equation:
    T = Isp FC g
    where:
    • Isp is a quantity called specific impulse, which, on average, is a value between 250 and 450 (so assume a medium of 350)
    • FC is the rate of fuel consumption, in kg/s
    • g is gravity acceleration, 9.81 m/s^2
    A drag of a sphere is given by:
    D = 0.5 rho V^2 S Cd​

    where:
    • rho is water density, 1025 kg/m^3
    • V is speed, in m/s
    • S is the frontal area of the sphere, let me assume a diameter of 2 meters, so the frontal area is 3.14 square meters.
    • Cd is drag coefficient. 0.2 can be assumed for high Reynolds number flow.
    Since the thrust must equal drag, T = D (forget the acceleration in this first analysis), by substituting various values and constants, you have that the rocket propellant consumption would be given by:
    FC = 0.094 V^2​

    If you want the velocity in knots, it becomes:
    FC = 0.025 V^2​

    So, for various speeds you would have the following fuel consumptions:
    V (kts).....FC (kg/s)
    5...............0.63
    10.............2.50
    20............10.0​

    etc.
    At 10 knots, a 100 kg of propellant would be burned in 40 seconds!

    So I have to correct my 1st statement. It would be a very short, unpleasant and a extremenly costly ride. ;)
     
  13. srimes
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    srimes Senior Member

    LoL! You hear that Richard? That's the line we need to quote every time you explain why a stupid idea is stupid. The problem isn't the stupidity, it's that you don't like ideas :p!
     
  14. jbehr
    Joined: Sep 2010
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    jbehr Junior Member

    lets see so roughly 35 days to cross 9000 miles at 10 knots
    needing to maintain that speed would require somewhere around 3.5 mil kg of fuel :) ouch
     

  15. jbehr
    Joined: Sep 2010
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    jbehr Junior Member

    also he didn't explain anything just made condescending remarks
    and i didn't expect anyone to think it was brilliant
     
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