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Ground Or Not To Ground Receiving Antenna In Storm ?
On Sun, 18 Dec 2005 12:39:09 -0800, Roy Lewallen
wrote: Russ wrote: Doesn't the delta P of a fuel-air bomb travel at greater than the speed of sound? No. Roy Lewallen, W7EL The definition of dentonation includes the flame front moving at supersonic speeds. http://www.globalsecurity.org/milita...itions/fae.htm R |
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Ground Or Not To Ground Receiving Antenna In Storm ?
Russ wrote:
On Sun, 18 Dec 2005 12:39:09 -0800, Roy Lewallen wrote: Russ wrote: Doesn't the delta P of a fuel-air bomb travel at greater than the speed of sound? No. Roy Lewallen, W7EL The definition of dentonation includes the flame front moving at supersonic speeds. http://www.globalsecurity.org/milita...itions/fae.htm Yes, I can understand the flame front moving faster than sound, if it's not a pressure wave. I don't know the mechanism, but presume it's propagated by radiant heat. That is, a flame occurs, and its heat radiates and superheats nearby material, causing it to flame. That would be propagation by electromagnetic wave, i.e., infrared "light". The radiation would travel at the speed of light, with the apparent speed of the front being dictated by how fast the material is heated and ignited by the radiated heat. Propagation by this mechanism and at this speed would end as soon as the flame front reached the outside of the vapor cloud, beyond which the resulting pressure wave would travel at the speed of sound. I'm not an expert at this, but I'm quite sure that the only way you can get a mechanical wave to travel faster than sound is if the behavior of the air becomes nonlinear at some compression level. That could conceivably happen as a result of an explosion, but I don't think so. If anyone has any references describing such nonlinear behavior, I'd love to learn more about it. Roy Lewallen, W7EL |
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Ground Or Not To Ground Receiving Antenna In Storm ?
Roy Lewallen wrote:
I'm not an expert at this, but I'm quite sure that the only way you can get a mechanical wave to travel faster than sound is if the behavior of the air becomes nonlinear at some compression level. Carrier velocity is linear and must be taken into account. Relative to a measurement point at the center of the earth, sound waves traveling East in the surface atmosphere are moving faster than Mach 2. Do the carriers move during an explosion? -- 73, Cecil http://www.qsl.net/w5dxp |
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Ground Or Not To Ground Receiving Antenna In Storm ?
This has been an interesting discussion, and prompted me to do a tiny
bit more research. It seems to me that if there's any nonlinear phenomenon which allows some pressure waves to travel through air faster than the speed of sound, surely a nuclear blast would produce enough pressure to excite it. But it doesn't seem to. From http://www.globalsecurity.org/wmd/intro/nuke-blast.htm: "During the time the blast wave is passing through the superheated atmosphere in the fireball, it travels at supersonic velocities. After it leaves the vicinity of the fireball, it slows down to the normal speed of sound in the atmosphere. As long as the blast wave is expanding radially, its intensity decreases approximately as the square of the distance. When the expanding blast wave from a nuclear air burst strikes the surface of the earth, however, it is reflected, and the reflected wave reinforces and intensifies the primary wave." Roy Lewallen, W7EL |
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