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Power density and shockwave velocity limit in large explosions.

  1. Sep 16, 2010 #1
    A larger yield explosion has more energy, and presumably more power. However, is there a point where the power and power density drop of to become constant, and is this also the same with windspeed velocities generated?

    Let's say you had an asteroid, which hit the Earth with an energy equal to 1 Gigaton. Then let's say that there was a larger asteroid, the collision energy of which was comparable to 100 Gigaton of TNT. We could also say that instead of asteroids, we have two nukes: one with 1 Megaton, and one with 100 Megaton power.

    Does the collision (of this same type) with 100 times more energy, also have 100 times more power, or does it release the energy more slowly? Furthermore, at any point you could stand and be exposed to thermal radiation from the impacts, there will be a given density of power (watts per square meter). At 1km from the 1 Gigaton blast, would you receive 100th the thermal flux as in the 100 Gigaton blast? And the windspeed generated. Would it also be scaled linearly? The fireball expansion speed too.

    I know that an explosion with 100 times the energy won't have a fireball 100 times as wide, but that's because of simple cube scaling. It will have (approximately, at least) 100 times the volume. If it has proportionate volume scaling, then it should have proportionate thermal flux and things like that, but there could be something I'm missing here.

    What I'm thinking about with all of this is that in conventional explosions, limits arrive irrespective of simple geometric scaling. A TNT explosion has an absolute limit for explosive velocity, correct? Is this true for all releases of energy,(including the nukes and the asteroids) or just a chemical property of TNT?

    EDIT: This should be in General Physics, not Classical Physics.
  2. jcsd
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