Power density and shockwave velocity limit in large explosions.

In summary, there is a point where the power and power density of an explosion become constant, and this is also true for windspeed velocities generated. The energy is not released all at once, so the power does not necessarily increase linearly with energy. Factors such as atmospheric conditions and composition also play a role in determining the effects of an explosion.
  • #1
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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.
 
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  • #2


I can confirm that there is a point where the power and power density of an explosion become constant, and this is also true for windspeed velocities generated. This is due to the concept of energy dissipation, where the energy from an explosion is spread out over a larger area as it travels away from the source.

In the case of your example with the asteroids and nukes, the collision with 100 times more energy would not necessarily have 100 times more power. This is because the energy is not released all at once, but rather over a period of time. The speed at which the energy is released is also a factor in determining the power.

The thermal flux, or the amount of thermal energy per unit area, would also not necessarily be 100 times less at a distance of 1km from a 100 Gigaton blast compared to a 1 Gigaton blast. This is because the thermal energy is also affected by factors such as the composition of the explosion and atmospheric conditions.

As for the fireball expansion speed, it would not be scaled linearly as the energy increases. This is due to factors such as atmospheric resistance and the amount of energy that is converted into kinetic energy versus thermal energy.

In terms of limits for explosive velocity, this is not just a chemical property of TNT but is also influenced by other factors such as the amount of energy released and the physical properties of the explosive material. So, this could also apply to other sources of energy release, such as nuclear explosions or asteroid collisions.

I hope this helps to answer your questions and provide some insight into the complexities of energy release and its effects.
 

1. What is power density in relation to large explosions?

The power density of an explosion is the amount of energy released per unit area. It is a measure of the explosive force and can be calculated by dividing the total energy released by the area of the explosion.

2. How does power density affect the severity of an explosion?

A higher power density means that more energy is released in a smaller area, resulting in a more intense explosion. This can lead to greater damage and destruction.

3. What is the shockwave velocity limit in large explosions?

The shockwave velocity limit is the maximum speed at which the shockwave from an explosion can travel. This limit is determined by the strength of the explosive material and the density of the surrounding medium.

4. How does the shockwave velocity limit impact the damage caused by an explosion?

If the shockwave velocity limit is exceeded, the shockwave can cause more damage to structures and objects in its path. This is because the shockwave becomes stronger and more destructive as it travels at higher velocities.

5. Can the power density and shockwave velocity limit of an explosion be controlled?

Yes, the power density and shockwave velocity limit of an explosion can be controlled by using different types and amounts of explosives, as well as regulating the distance between the explosion and surrounding structures. However, it is important to note that even with control measures, large explosions can still be highly destructive and dangerous.

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