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Question about Stellar Fusion

  1. Aug 13, 2013 #1

    DHF

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    A friend of mine is writing a Sci Fi tale set a few centuries in the future. While there will be futuristic technologies to make the plot go, she said she wants to try to make it realistic at least to the point where she inst violating the laws of physics.

    The part she asked me about involved Terrorists trying to set off a nuclear device in the upper atmosphere of Jupiter. Her rational is that since the planet is mostly hydrogen, the explosion would set off a chain reaction that would ignite the planet. I honestly don't know if its possible or not so I wanted to put it on the table here and see what everyone thought.

    Thank you.
     
  2. jcsd
  3. Aug 13, 2013 #2

    Bandersnatch

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    It won't work.

    You need very high temperature and pressure conditions for the hydrogen atoms to first ionise, and then overcome the repulsion of the positively charged nuclei(protons). In hydrogen bombs such conditions are achieved for a very short time by compressing the fissile material with a nuclear bomb(see: Teller-Ulam design).
    To maintain the reactions, these conditions need to be sustained, which in stars is achieved thanks to gravity compressing and heating all that gas. If the gravity is too low, any reaction that you may start artificially will quickly fizzle out.

    Additonally, hydrogen bombs use deuterium and lithium, as fusing protons together is an extremely slow reaction(see: beta-plus decay). This slow reaction rate is, by the way, the only reason why the stars are able to burn for billions of years.

    The only way to start fusion reactions in the core of Jupiter that I can think of, is to dump another dozen or so Jupiters onto it. This should net you a fainly glowing brown dwarf. It would most emphatically not explode it.
     
  4. Aug 13, 2013 #3

    DHF

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    ok Good to know. Thanks Bandersnatch, I will tell her to come up with some other way for the bad guys to wreck havoc.
     
  5. Aug 13, 2013 #4

    davenn

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    no as said wont work

    back in the 1994 comet Shoemaker-Levy disintegrated and then multiple fragments collided with Jupiter. the explosions were colossal, bigger than any of the nuclear blasts man has made. Fragment G, the largest one on its own produced an energy release equivalent to 6,000,000 megatons of TNT (600 times the world's nuclear arsenal)

    so there is ya problem :)

    Dave
     
  6. Aug 14, 2013 #5

    DHF

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    Ok that sparks my own question, Fusion not withstanding, during the Shoemaker-Levey event why didn't the strike ignite the atmosphere in a more traditional manner? from what I have read Hydrogen is very flammable.
    Is it because the concentration is too high (above 74%)? Will hydrogen only combust if combined with Oxygen or Chlorine?
     
    Last edited: Aug 14, 2013
  7. Sep 29, 2013 #6
    The hydrogen will need something to combine with, something that it is not already combined with. But there isn't anything for it to combine with that it has not combined with -- all the oxygen is already combined as water.
     
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