When gunpowder blows up the energy of the explosion is in the form of expanding gas, heat, and sound mostly. This expanding gas is what knocks stuff over. I assume most of the gas is just the explosive converted to gas. When an atom bomb explodes is the kinetic energy that knocks stuff over high velocity air that was accelerated mainly from the heat of the explosion? ERS
The expanding gas also consists of air heated by the reaction. I imagine the shock waves from conventional and from nucluer are very similar in that respect.
Yes. The nuclear reaction over a few nanoseconds results in the emission of intense radiation, mostly X-rays. These heat the immediate surroundings to incandescence, including the bomb components and casing, the chemical explosives that triggered the nuclear reaction, all the air in the vicinity and anything else close by. It is the immediate expansion of these superheated gasses that forms the fireball that produces the shockwave that radiates outward. The fireball itself quickly rises and cools, sucking up dirt and debris into the mushroom cloud seen afterward.
If you watch movies of the wooden structures being destroyed in the American tests immediately after WW2, you see them being set on fire by the flash of secondary infrared radiation, then you see the fire being blown out by the shockwave that knocks the buildings over, and then a second or so later a strong blast of air coming back the other way as it rushes in to replace the air displaced by the rising fireball.
Not quite.
The bomb emits a large amount of x-rays. These are so hot that they only pass a short distance into the air until they are absorbed.
The air then reradiates the energy, and the air slightly further out absorbs it. This process proceeds out until the fireball surface hits a temperature of somewhere under 4000K. At this point, the radiation can escape as the air is largely transparent. However, the shockwave builds up a layer of highly compressed air in front of it, and this obscures the fireball for a bit. The output then rises after the fireball expands past this.
The visual emission looks like a very fast (microseconds) rising spike, as the initial fireball expands, followed by dropping to a few percent of its peak, then rising over the next second or so as the fireball continues to expand.
Yes, that's why the DoD's VELA series satellites were programmed to look for the characteristic "double flash" of a nuclear detonation. Nothing else looks like it.
Note also that, because of the way the shockwave is formed, it has a much steeper wavefront than a comparable magnitude conventional explosion would have. So you can't accurately model its effects simply by scaling up from the effects of conventional explosions. That's why the DOE had to spend a chunk of money on the world's fastest super- computer in order to run the hydrodynamic codes which can accurately model the process. Before that, the only sure way to tell what would happen was to have actual test detonations.
Gary
Back in the early 1970's Western Union developed an equipment rack full of descrete open layout circuit boards that was supposed to look for this "double flash" pulse and automatically send a telegraph message to "somewhere". By the time the equipment was built and delivered, it was obsolete. A friend at Western Union gave it to me. It was a wonderful cache of power supplies and components along with the nice looking 5 foot tall enclosure.
Soon after, Western Union started shutting down their offices and he was given his freedom along with other good people.
Earle Rich Mont Vernon, NH
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