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Heat in front of moving object
A fast-moving object like a meteorite compresses the air in front of
it, causing heat. Does an ordinary plane have a problem with this or is it not moving fast enough? The Siberian meteor of 1908 exploded in midair. Why do you suppose it did, as opposed to hitting the earth? |
#2
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Heat in front of moving object
"Richard Fangnail" wrote in message ... A fast-moving object like a meteorite compresses the air in front of it, causing heat. Does an ordinary plane have a problem with this or is it not moving fast enough? Yes, Concorde was designed to expand, although it wasn't an "ordinary" plane. http://physics.info/expansion/ "What's more, the aircraft expands by 15-25 centimetres during flight because of the scorching heat created by friction with air. Designers used rollers to isolate the cabin from the body, so that stretching doesn't rip the plane apart." Helen Pearson "Concorde wings its way into retirement." Nature Physics Portal. October 2003. "Concorde measures 204ft in length - stretching between six and ten inches in-flight due to heating of the airframe. She is painted in a specially developed white paint to accommodate these changes and to dissipate the heat generated by supersonic flight." http://www.britishairways.com/concor...#facts_figures The Siberian meteor of 1908 exploded in midair. Why do you suppose it did, as opposed to hitting the earth? |
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Heat in front of moving object
Dear Richard Fangnail:
On Jan 15, 11:08*am, Richard Fangnail wrote: A fast-moving object like a meteorite compresses the air in front of it, causing heat. Yes. The air can move no faster than the speed of sound in air. Heating and compression increase the speed of sound, allows the air to move out of the way. *Does an ordinary plane have a problem with this or is it not moving fast enough? Supersonic jets, such as Androcles provided reference to have issues with this. Fighter aircraft, SR-71, Concorde, all had heating to contend with. The Siberian meteor of 1908 exploded in midair. *Why do you suppose it did, as opposed to hitting the earth? Assuming it was a meteor, it could have been saturated with water. Water turns to steam as the rock heats, ruptures it, and now you have a large spread of superheated steam and glowing rock-bits. David A. Smith |
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Heat in front of moving object
On Jan 16, 2:08*am, Richard Fangnail
wrote: A fast-moving object like a meteorite compresses the air in front of it, causing heat. *Does an ordinary plane have a problem with this or is it not moving fast enough? The Siberian meteor of 1908 exploded in midair. *Why do you suppose it did, as opposed to hitting the earth? I'm told the skin of the SR-71, capable of Mach 5, glowed red at top speed even at high altitude. There was a cooling system built in. |
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Heat in front of moving object
On Fri, 15 Jan 2010 10:08:18 -0800 (PST), Richard Fangnail
wrote: A fast-moving object like a meteorite compresses the air in front of it, causing heat. Does an ordinary plane have a problem with this or is it not moving fast enough? The Siberian meteor of 1908 exploded in midair. Why do you suppose it did, as opposed to hitting the earth? SR-71 Blackbird would expand 11" due to heating. -- Boris |
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Heat in front of moving object
Richard Fangnail wrote:
A fast-moving object like a meteorite compresses the air in front of it, causing heat. Does an ordinary plane have a problem with this or is it not moving fast enough? Others have confirmed that supersonic aircraft need to have an allowance for expansion built into their designs. Passenger airliners fly at speeds of c 400-500 mph and there is certainly some frictional heating. The Siberian meteor of 1908 exploded in midair. Why do you suppose it did, as opposed to hitting the earth? It was moving at several km/sec and at that sort of speed, air resistance generates a shockwave that will propagate through the rock/ice/whatever and if the tensile strength is not great enough it will break up. I don't think there was time for frictional heating to cause an explosion via ice evaporation--the passage through the air lasted only a few seconds, and heating propagates very slowly through rock. If it was a stony object, like some asteroids that have been studied close up, it may have had a fairly loose structure so it is not hard to see why it would break up. I understand this is what is generally postulated. In contrast, consider an iron meteorite, which would have held together. They never found any indications of iron in the composition. -- Mike Dworetsky (Remove pants sp*mbl*ck to reply) |
#7
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Heat in front of moving object
"Mike Dworetsky" wrote in message ... Richard Fangnail wrote: A fast-moving object like a meteorite compresses the air in front of it, causing heat. Does an ordinary plane have a problem with this or is it not moving fast enough? Others have confirmed that supersonic aircraft need to have an allowance for expansion built into their designs. Passenger airliners fly at speeds of c 400-500 mph and there is certainly some frictional heating. The Siberian meteor of 1908 exploded in midair. Why do you suppose it did, as opposed to hitting the earth? It was moving at several km/sec and at that sort of speed, air resistance generates a shockwave that will propagate through the rock/ice/whatever and if the tensile strength is not great enough it will break up. I don't think there was time for frictional heating to cause an explosion via ice evaporation--the passage through the air lasted only a few seconds, and heating propagates very slowly through rock. Let me see if I have this right... If it moves slowly through air then it doesn't heat up, but if it moves quickly through air it doesn't have time to heat up. Is that what you are saying? I rather think the heat shield tiles on the shuttle will not agree with you. E = m . 1/2v^2 only if v goes to zero, otherwise it remains kinetic energy. If it was a stony object, like some asteroids that have been studied close up, it may have had a fairly loose structure so it is not hard to see why it would break up. I understand this is what is generally postulated. In contrast, consider an iron meteorite, which would have held together. They never found any indications of iron in the composition. -- Mike Dworetsky (Remove pants sp*mbl*ck to reply) |
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Heat in front of moving object
Androcles wrote:
"Mike Dworetsky" wrote in message ... Richard Fangnail wrote: A fast-moving object like a meteorite compresses the air in front of it, causing heat. Does an ordinary plane have a problem with this or is it not moving fast enough? Others have confirmed that supersonic aircraft need to have an allowance for expansion built into their designs. Passenger airliners fly at speeds of c 400-500 mph and there is certainly some frictional heating. The Siberian meteor of 1908 exploded in midair. Why do you suppose it did, as opposed to hitting the earth? It was moving at several km/sec and at that sort of speed, air resistance generates a shockwave that will propagate through the rock/ice/whatever and if the tensile strength is not great enough it will break up. I don't think there was time for frictional heating to cause an explosion via ice evaporation--the passage through the air lasted only a few seconds, and heating propagates very slowly through rock. Let me see if I have this right... If it moves slowly through air then it doesn't heat up, but if it moves quickly through air it doesn't have time to heat up. Is that what you are saying? I rather think the heat shield tiles on the shuttle will not agree with you. E = m . 1/2v^2 only if v goes to zero, otherwise it remains kinetic energy. Shuttle reentry lasts several minutes. Heat does not have time to get from the outside to the inside of the large object falling to Earth at several km/sec. Obviously you have a reading comprehension problem. Are you aware that fresh meteorites have been found that have frost on the outside, because the interiors were at very low temperatures in space and only the outer crust was heated by atmospheric entry. If it was a stony object, like some asteroids that have been studied close up, it may have had a fairly loose structure so it is not hard to see why it would break up. I understand this is what is generally postulated. In contrast, consider an iron meteorite, which would have held together. They never found any indications of iron in the composition. -- Mike Dworetsky (Remove pants sp*mbl*ck to reply) -- Mike Dworetsky (Remove pants sp*mbl*ck to reply) |
#9
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Heat in front of moving object
"Mike Dworetsky" wrote in message ... Androcles wrote: "Mike Dworetsky" wrote in message ... Richard Fangnail wrote: A fast-moving object like a meteorite compresses the air in front of it, causing heat. Does an ordinary plane have a problem with this or is it not moving fast enough? Others have confirmed that supersonic aircraft need to have an allowance for expansion built into their designs. Passenger airliners fly at speeds of c 400-500 mph and there is certainly some frictional heating. The Siberian meteor of 1908 exploded in midair. Why do you suppose it did, as opposed to hitting the earth? It was moving at several km/sec and at that sort of speed, air resistance generates a shockwave that will propagate through the rock/ice/whatever and if the tensile strength is not great enough it will break up. I don't think there was time for frictional heating to cause an explosion via ice evaporation--the passage through the air lasted only a few seconds, and heating propagates very slowly through rock. Let me see if I have this right... If it moves slowly through air then it doesn't heat up, but if it moves quickly through air it doesn't have time to heat up. Is that what you are saying? I rather think the heat shield tiles on the shuttle will not agree with you. E = m . 1/2v^2 only if v goes to zero, otherwise it remains kinetic energy. Shuttle reentry lasts several minutes. Heat does not have time to get from the outside to the inside of the large object falling to Earth at several km/sec. Yeah, you've already said that. Repeating it won't make it true either. Obviously you have a reading comprehension problem. Not at all, I fully comprehend your ridiculous bull****. If it moves slowly through air then it doesn't heat up, but if it moves quickly through air it doesn't have time to heat up. So it doesn't heat up. Obviously you have a illogical problem. Are you aware that fresh meteorites have been found that have frost on the outside, because the interiors were at very low temperatures in space and only the outer crust was heated by atmospheric entry. Are you aware that energy and heat can be exchanged, we've only been making steam trains running on coal fires and capable of 100 mph for 200 years? E = m . v^2/2 only if v goes to zero, otherwise it remains kinetic energy. That means deceleration is converted to heat, no matter how long it takes. Obviously you have a physics problem. If it was a stony object, like some asteroids that have been studied close up, it may have had a fairly loose structure so it is not hard to see why it would break up. I understand this is what is generally postulated. In contrast, consider an iron meteorite, which would have held together. They never found any indications of iron in the composition. -- Mike Dworetsky (Remove pants sp*mbl*ck to reply) -- Mike Dworetsky (Remove pants sp*mbl*ck to reply) |
#10
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Heat in front of moving object
Androcles wrote:
"Mike Dworetsky" wrote in message ... Androcles wrote: "Mike Dworetsky" wrote in message ... Richard Fangnail wrote: A fast-moving object like a meteorite compresses the air in front of it, causing heat. Does an ordinary plane have a problem with this or is it not moving fast enough? Others have confirmed that supersonic aircraft need to have an allowance for expansion built into their designs. Passenger airliners fly at speeds of c 400-500 mph and there is certainly some frictional heating. The Siberian meteor of 1908 exploded in midair. Why do you suppose it did, as opposed to hitting the earth? It was moving at several km/sec and at that sort of speed, air resistance generates a shockwave that will propagate through the rock/ice/whatever and if the tensile strength is not great enough it will break up. I don't think there was time for frictional heating to cause an explosion via ice evaporation--the passage through the air lasted only a few seconds, and heating propagates very slowly through rock. Let me see if I have this right... If it moves slowly through air then it doesn't heat up, but if it moves quickly through air it doesn't have time to heat up. Is that what you are saying? I rather think the heat shield tiles on the shuttle will not agree with you. E = m . 1/2v^2 only if v goes to zero, otherwise it remains kinetic energy. Shuttle reentry lasts several minutes. Heat does not have time to get from the outside to the inside of the large object falling to Earth at several km/sec. Yeah, you've already said that. Repeating it won't make it true either. Obviously you have a reading comprehension problem. Not at all, I fully comprehend your ridiculous bull****. If it moves slowly through air then it doesn't heat up, but if it moves quickly through air it doesn't have time to heat up. So it doesn't heat up. Obviously you have a illogical problem. An asteroid is not a supersonic aircraft, which is hollow and flies for hours at a time, hence of course its skin heats up during flight. For a large solid asteroid entering the atmosphere, the surface layer heats to incandescence and breaks up or evaporates (carrying off a large amount of the heat via ablation). The bulk of the interior remains at the temperature it had in interplanetary space. The reason is, that the rate at which heat is transmitted through a solid body is rather slow, and the passage through the atmosphere only lasts a few seconds. If the asteroid has a weak structure, as many comet nuclei and asteroids appear to have from in-situ investigations, it is likely to be disrupted by shock waves from the hypersonic entry speed into the atmosphere. I have no illogical problems with these concepts from basic thermodynamics, but you have several. I think everyone else who has read the thread understands this point. Are you aware that fresh meteorites have been found that have frost on the outside, because the interiors were at very low temperatures in space and only the outer crust was heated by atmospheric entry. Are you aware that energy and heat can be exchanged, we've only been making steam trains running on coal fires and capable of 100 mph for 200 years? E = m . v^2/2 only if v goes to zero, otherwise it remains kinetic energy. That means deceleration is converted to heat, no matter how long it takes. Obviously you have a physics problem. I don't think I am the one with the physics problem here. An asteroid entering the atmosphere at 10 km/s is not a steam train. If it was a stony object, like some asteroids that have been studied close up, it may have had a fairly loose structure so it is not hard to see why it would break up. I understand this is what is generally postulated. In contrast, consider an iron meteorite, which would have held together. They never found any indications of iron in the composition. -- Mike Dworetsky (Remove pants sp*mbl*ck to reply) -- Mike Dworetsky (Remove pants sp*mbl*ck to reply) -- Mike Dworetsky (Remove pants sp*mbl*ck to reply) |
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