I believe samuelk is correct. I recall reading this elsewhere now. Still, I'm intrigued by the possibility of the idea of a force field control of aerodynamic heating.
I guess what I was trying to describe would be an artificially induced ‘slip flow’. According to early theory, the air-friction drag and heating of moving vehicles is due to the fact that air molecules cling to any surface; that they cling in clumps. The clumps contribute to air drag in this manner. Molecules leave clumps in random directions, giving no drag alleviation. A fast-moving air molecule strikes a clump and is stopped, giving up its momentum in kinetic energy. This gives drag plus heating. Laboratory wind tunnel tests showed, at least in the early days, that at a combination of low enough pressure and high enough speed and temperature, much of the adsorbed layer of air is knocked off the surface. In this condition the fast moving air molecules can bounce on a smooth surface and reflect off again without losing much energy. This desirable operating condition, in which drag and heating are dramatically reduced, is known as slip flow. Unfortunately, no way was found to knock the stubborn air molecules off even surfaces with the finest polishes. A corona discharge was used to try and keep the air molecules from sticking, but this didn’t work. My information is from the work of Paul R. Hill, who was a well-respected NASA scientist. His 1950s UFO sighting caused him to spend years trying to scientifically demonstrate how UFOs could demonstrate such extreme performance levels without defying the known laws of physics. Though he never published a book about his research himself, ‘Unconventional Flying Objects: a scientific analysis’ was published posthumously by his family.
But now we know that air compression in the shock wave ahead of the shuttle is responsible for a lot of the heat.
Still, it’s easy to imagine how a force field which absorbs the free-stream kinetic energy from the air as it approaches and comes close to the vehicle, then passes it back as it leaves, would resolve both the heating and the drag, but it is obviously difficult to imagine the details of such a system without an advanced engineering background. Nevertheless, I’ll continue to stick my neck out and suggest a possibility to debate.
samuelk: what would block radiated heat? What IS radiated heat? Excited atoms? Excited in a particular way, perhaps? Would it be possible to nullify the radiated heat by an exactly opposite pattern of radiation? I'm thinking of the way it is possible to nullify sound by generating exactly the opposite of the waves that create the sound
[This message has been edited by Randy (edited 02-06-2003).]
[quote]Originally posted by Melkor:
[b]Look sam, you don't go about saying things which fly in the face of conventional teachings by acting like what you're saying is how things are without citing some sources. Give me evidence, other than a blurb from an unknown source (which, though unlikely, could have been writen by you), that supports what you're saying and then I might have reason not to argue.[/b][/quote]
Thanks to google, sources for internet quotes are a bit superfluous. I just select a random sentence from the quote, type it in, and BOOM, instant source.
Like this one, for instance.
[url="http://www.eskimo.com/~billb/miscon/miscon4.html"]http://www.eskimo.com/~billb/miscon/miscon4.html[/url]
[quote][b]How many times have we heard about how spacecraft turn into blazing fireballs when they reenter the atmosphere due to "the heat of friction." True, spaceships hit the upper atmosphere at Mach 25, and there are flames. But if the friction of air rushing across the spacecraft's skin really causes those flames, then how could the space shuttle's fragile protective tiles, which even a fingernail or a raindrop can damage and which come off with small hand tools, survive such a hypersonic blast without wearing or tearing away?
It turns out that the friction of air rubbing against spaceship skin (the boundary layer) has little to do with the fireball. Rather, compression mostly creates the heat as the thin air is squeezed in the shock layer ahead of the onrushing spacecraft. The air can't get out of the way fast enough, like snow in front of a plow, so it piles up. [/b][/quote]
I noticed one contradictory thing in that explanation above you quoted from somewhere Samuel which bothers me.
The text says, that if the friction was a factor "[i]then how the fragile protective tiles would survive without wearing or tearing away?[/i]". Ok that's fine, but then how the heck the tiles can still at the same time stand the enormous pressure caused by the air compressing ahead of the ship, which is even many many times bigger force against the tiles than the friction could ever be?
[quote]samuelk: what would block radiated heat?[/quote]
Silca-ceramic tiles to a pretty darn good job. [img]http://216.15.145.59/mainforums/smile.gif[/img]
[quote]What IS radiated heat?[/quote]
Heat is simply electromagnetic energy. Radiated heat is simply energy that isn't transferred via conduction (passing through matter).
[quote]Excited atoms? Excited in a particular way, perhaps? Would it be possible to nullify the radiated heat by an exactly opposite pattern of radiation? I'm thinking of the way it is possible to nullify sound by generating exactly the opposite of the waves that create the sound[/quote]
Well, you might be able to deflect the electromagnetic energy, but it's hard to say.
Sound waves are simply air pressure waves...I'm not sure if the two situations are analogous.
[quote]The text says, that if the friction was a factor "then how the fragile protective tiles would survive without wearing or tearing away?". Ok that's fine, but then how the heck the tiles can still at the same time stand the enormous pressure caused by the air compressing ahead of the ship, which is even many many times bigger force against the tiles than the friction could ever be?[/quote]
It's a matter of the relative strenghts of the forces.
If the heat were caused by air friction, the force of the air moving over the shuttle would have to be a LOT higher than the force needed to compress the air to get the very same temperature increase.
Plus, the air friction tends to have a shearing effect, whereas pressure in this case is more perpendicular to the tile surface. The strenght of many materials often depends on the angle/direction from which a force is applied.
[This message has been edited by samuelk (edited 02-06-2003).]
[quote]Originally posted by Randy:
[b]samuelk: what would block radiated heat? What IS radiated heat? Excited atoms? Excited in a particular way, perhaps? Would it be possible to nullify the radiated heat by an exactly opposite pattern of radiation? I'm thinking of the way it is possible to nullify sound by generating exactly the opposite of the waves that create the sound[/b][/quote]
Interesting idea.
Perhaps gravitation could be nullififed a similiar way too in the future.
[quote]Originally posted by samuelk:
[b] It's a matter of the relative strenghts of the forces.
If the heat were caused by air friction, the force of the air moving over the shuttle would have to be a LOT higher than the force needed to compress the air to get the very same temperature increase.
Plus, the air friction tends to have a shearing effect, whereas pressure in this case is more perpendicular to the tile surface. The strenght of many materials often depends on the angle/direction from which a force is applied.[/b][/quote]
That's true. But if the tiles were really as fragile as the text says; "[i]the space shuttle's fragile protective tiles, which even a fingernail or a raindrop can damage[/i]", then they wouldn't stand the pressure of the compressed air either which the shuttle has to stand in reality. The fragileness of the tiles was "a bit" exaggerated. If they were really that fragile they couldn't be used in the shuttle at all and on the other hand aluminium foil could be used just as well. [img]http://216.15.145.59/mainforums/wink.gif[/img]
[quote]That's true. But if the tiles were really as fragile as the text says; "the space shuttle's fragile protective tiles, which even a fingernail or a raindrop can damage", then they wouldn't stand the pressure of the compressed air either which the shuttle has to stand in reality. The fragileness of the tiles was "a bit" exaggerated. If they were really that fragile they couldn't be used in the shuttle at all and on the other hand aluminium foil could be used just as well. [/quote]
The tiles ARE fragile...but not in the way you might think. Sure a fingernail can damage them...raindrop? I'm not so sure about that, but it's possible. It's all about pressure. Your fingernail can exert more pressure (pounds per square inch) than air because the contact point is so small.
After all, your fingernail can damage a block of styrofoam, but wind may not harm it at all.
theres something wrong with visiting 1960's design concepts with 2002 technology ??
and if you care to look Sam I was rejecting the whole concept of the shuttle... multirole schmultirole....
A shuttle is a Jack of all Trades and master of none...
we dont need a Winnebago.. we need a bus and a flatbed truck, perhaps on the same chassis but with purpose built bodies
~~~~
Sam... pot/kettle....
~~~~
The world around me may indeed not think much of me rejecting it as flawed and me wanting to do something about it.. there's a degree of arrogance in even thinking in such a fashion, sosumi. Somebodys got to play the devils advocate, someone has to ask the questions no-one else has the balls/stupidity to ask.
[quote]theres something wrong with visiting 1960's design concepts with 2002 technology ??[/quote]
There is if you're NASA and you've done it before.
[quote]Sam... pot/kettle....[/quote]
If you're referring to insulting people and generally acting hostile, find a post on this entire forum where I've called someone names. You can't, because there isn't one.
[quote]I haven't called anyone names.[/quote]
Oh no?
[quote]try putting something constructive into your critisism... otherwise you will continue to look like a twat.. [/quote]
[quote]you Sam... are a fool[/quote]
[quote]for those twats making light of Drazis situation...[/quote]
[quote]and please A#, learn how to freakin spell, you have no idea how much of knob you look like when you spell SWORD, sward...[/quote]
Here is my understanding of heat. Heat is nothing more than infrared electromagnetic radition, just like visible light, x-rays, etc. Now electromagnetic radiation has wavelike properties, hence a counterwave would indeed null the incoming radiation. Now if this would work with the heat generated from the air, I do not know.
Yes heat is a form of EM radiation..but it's also caused by the impact of atoms against each other. It's a weird duality. You might, in theory, be able to create a "heat blocker" that used a counterwave, but when an air molecule hits the surface, it will still transfer heat to it, since it hits the atoms of the surface and makes them move.
Yes, pressure is the cause of much of the heat..friction still has some small part to play, but not nearly as much.
The thing that no one has yet said..or at least clearly in my mind is this. IF you are using some kind of "force field" to push the air away, you will still get all of the energy loss that you would with a physical barrier. Why? Simple. It's just like two magnets with the same ploarity. They repluse one another... The beauty of it all is that the plasma around the shuttle IS electrically energized, so it would be even easier to do...
[QUOTE][i]Originally posted by samuelk [/i]
[B]The tiles ARE fragile...but not in the way you might think. Sure a fingernail can damage them...raindrop? I'm not so sure about that, but it's possible. It's all about pressure. Your fingernail can exert more pressure (pounds per square inch) than air because the contact point is so small.
After all, your fingernail can damage a block of styrofoam, but wind may not harm it at all. [/B][/QUOTE]
Sure a wind may not harm a styrofoam, but it's not a small wind we're talking about here. It's an enormous pressure, which would destroy a piece of styrofoam just like that. And styrofoam is a different kind of material anyway.
Anyway, I know what you mean, but if you can scratch the surface of the tiles with your fingernail that doesn't make the tiles fragile as a whole, just the surface.
[QUOTE][i]Originally posted by Keyan [/i]
[B]The thing that no one has yet said..or at least clearly in my mind is this. IF you are using some kind of "force field" to push the air away, you will still get all of the energy loss that you would with a physical barrier. Why? Simple. It's just like two magnets with the same ploarity. They repluse one another... The beauty of it all is that the plasma around the shuttle IS electrically energized, so it would be even easier to do... [/B][/QUOTE]
Ummmm...... could you explain that again? I'm not quite sure if I understood that right.
If you were using a "force field" that worked on the principle of pushing the plasma away from the surface so that it didn't touch the surface, you would still have the same amount of decelerating force. A force field doesn't protect you from kinetics, it simply repulses matter, just like two magnets when you put the same ends together. So you will still have a "push" back against the object, like the shuttle. Since the plasma around the shuttle actually has an electrical charge to it, if you could create a field with the same polarity, they would repulse one another. In theory, I would think this would be easier to do than to create a field that would actually push away uncharged air.
Comments
I guess what I was trying to describe would be an artificially induced ‘slip flow’. According to early theory, the air-friction drag and heating of moving vehicles is due to the fact that air molecules cling to any surface; that they cling in clumps. The clumps contribute to air drag in this manner. Molecules leave clumps in random directions, giving no drag alleviation. A fast-moving air molecule strikes a clump and is stopped, giving up its momentum in kinetic energy. This gives drag plus heating. Laboratory wind tunnel tests showed, at least in the early days, that at a combination of low enough pressure and high enough speed and temperature, much of the adsorbed layer of air is knocked off the surface. In this condition the fast moving air molecules can bounce on a smooth surface and reflect off again without losing much energy. This desirable operating condition, in which drag and heating are dramatically reduced, is known as slip flow. Unfortunately, no way was found to knock the stubborn air molecules off even surfaces with the finest polishes. A corona discharge was used to try and keep the air molecules from sticking, but this didn’t work. My information is from the work of Paul R. Hill, who was a well-respected NASA scientist. His 1950s UFO sighting caused him to spend years trying to scientifically demonstrate how UFOs could demonstrate such extreme performance levels without defying the known laws of physics. Though he never published a book about his research himself, ‘Unconventional Flying Objects: a scientific analysis’ was published posthumously by his family.
But now we know that air compression in the shock wave ahead of the shuttle is responsible for a lot of the heat.
Still, it’s easy to imagine how a force field which absorbs the free-stream kinetic energy from the air as it approaches and comes close to the vehicle, then passes it back as it leaves, would resolve both the heating and the drag, but it is obviously difficult to imagine the details of such a system without an advanced engineering background. Nevertheless, I’ll continue to stick my neck out and suggest a possibility to debate.
samuelk: what would block radiated heat? What IS radiated heat? Excited atoms? Excited in a particular way, perhaps? Would it be possible to nullify the radiated heat by an exactly opposite pattern of radiation? I'm thinking of the way it is possible to nullify sound by generating exactly the opposite of the waves that create the sound
[This message has been edited by Randy (edited 02-06-2003).]
[b]Look sam, you don't go about saying things which fly in the face of conventional teachings by acting like what you're saying is how things are without citing some sources. Give me evidence, other than a blurb from an unknown source (which, though unlikely, could have been writen by you), that supports what you're saying and then I might have reason not to argue.[/b][/quote]
Thanks to google, sources for internet quotes are a bit superfluous. I just select a random sentence from the quote, type it in, and BOOM, instant source.
Like this one, for instance.
[url="http://www.eskimo.com/~billb/miscon/miscon4.html"]http://www.eskimo.com/~billb/miscon/miscon4.html[/url]
It turns out that the friction of air rubbing against spaceship skin (the boundary layer) has little to do with the fireball. Rather, compression mostly creates the heat as the thin air is squeezed in the shock layer ahead of the onrushing spacecraft. The air can't get out of the way fast enough, like snow in front of a plow, so it piles up. [/b][/quote]
I noticed one contradictory thing in that explanation above you quoted from somewhere Samuel which bothers me.
The text says, that if the friction was a factor "[i]then how the fragile protective tiles would survive without wearing or tearing away?[/i]". Ok that's fine, but then how the heck the tiles can still at the same time stand the enormous pressure caused by the air compressing ahead of the ship, which is even many many times bigger force against the tiles than the friction could ever be?
- PJH
Silca-ceramic tiles to a pretty darn good job. [img]http://216.15.145.59/mainforums/smile.gif[/img]
[quote]What IS radiated heat?[/quote]
Heat is simply electromagnetic energy. Radiated heat is simply energy that isn't transferred via conduction (passing through matter).
[quote]Excited atoms? Excited in a particular way, perhaps? Would it be possible to nullify the radiated heat by an exactly opposite pattern of radiation? I'm thinking of the way it is possible to nullify sound by generating exactly the opposite of the waves that create the sound[/quote]
Well, you might be able to deflect the electromagnetic energy, but it's hard to say.
Sound waves are simply air pressure waves...I'm not sure if the two situations are analogous.
[quote]The text says, that if the friction was a factor "then how the fragile protective tiles would survive without wearing or tearing away?". Ok that's fine, but then how the heck the tiles can still at the same time stand the enormous pressure caused by the air compressing ahead of the ship, which is even many many times bigger force against the tiles than the friction could ever be?[/quote]
It's a matter of the relative strenghts of the forces.
If the heat were caused by air friction, the force of the air moving over the shuttle would have to be a LOT higher than the force needed to compress the air to get the very same temperature increase.
Plus, the air friction tends to have a shearing effect, whereas pressure in this case is more perpendicular to the tile surface. The strenght of many materials often depends on the angle/direction from which a force is applied.
[This message has been edited by samuelk (edited 02-06-2003).]
[b]samuelk: what would block radiated heat? What IS radiated heat? Excited atoms? Excited in a particular way, perhaps? Would it be possible to nullify the radiated heat by an exactly opposite pattern of radiation? I'm thinking of the way it is possible to nullify sound by generating exactly the opposite of the waves that create the sound[/b][/quote]
Interesting idea.
Perhaps gravitation could be nullififed a similiar way too in the future.
- PJH
[b] It's a matter of the relative strenghts of the forces.
If the heat were caused by air friction, the force of the air moving over the shuttle would have to be a LOT higher than the force needed to compress the air to get the very same temperature increase.
Plus, the air friction tends to have a shearing effect, whereas pressure in this case is more perpendicular to the tile surface. The strenght of many materials often depends on the angle/direction from which a force is applied.[/b][/quote]
That's true. But if the tiles were really as fragile as the text says; "[i]the space shuttle's fragile protective tiles, which even a fingernail or a raindrop can damage[/i]", then they wouldn't stand the pressure of the compressed air either which the shuttle has to stand in reality. The fragileness of the tiles was "a bit" exaggerated. If they were really that fragile they couldn't be used in the shuttle at all and on the other hand aluminium foil could be used just as well. [img]http://216.15.145.59/mainforums/wink.gif[/img]
- PJH
The tiles ARE fragile...but not in the way you might think. Sure a fingernail can damage them...raindrop? I'm not so sure about that, but it's possible. It's all about pressure. Your fingernail can exert more pressure (pounds per square inch) than air because the contact point is so small.
After all, your fingernail can damage a block of styrofoam, but wind may not harm it at all.
and if you care to look Sam I was rejecting the whole concept of the shuttle... multirole schmultirole....
A shuttle is a Jack of all Trades and master of none...
we dont need a Winnebago.. we need a bus and a flatbed truck, perhaps on the same chassis but with purpose built bodies
~~~~
Sam... pot/kettle....
~~~~
The world around me may indeed not think much of me rejecting it as flawed and me wanting to do something about it.. there's a degree of arrogance in even thinking in such a fashion, sosumi. Somebodys got to play the devils advocate, someone has to ask the questions no-one else has the balls/stupidity to ask.
Reality sucks... so I intend to change it.
~~~~
I haven't called anyone names.
There is if you're NASA and you've done it before.
[quote]Sam... pot/kettle....[/quote]
If you're referring to insulting people and generally acting hostile, find a post on this entire forum where I've called someone names. You can't, because there isn't one.
[quote]I haven't called anyone names.[/quote]
Oh no?
[quote]try putting something constructive into your critisism... otherwise you will continue to look like a twat.. [/quote]
[quote]you Sam... are a fool[/quote]
[quote]for those twats making light of Drazis situation...[/quote]
[quote]and please A#, learn how to freakin spell, you have no idea how much of knob you look like when you spell SWORD, sward...[/quote]
[img]http://216.15.145.59/mainforums/biggrin.gif[/img]
Make the vehicle for the job it needs to do.
Take offs should be more plane like out and slower in to avoid the pressure build up.
------------------
[b]May You Live Forever, and The Last Voice You Hear, Be Mine! [/b]
Yes, pressure is the cause of much of the heat..friction still has some small part to play, but not nearly as much.
The thing that no one has yet said..or at least clearly in my mind is this. IF you are using some kind of "force field" to push the air away, you will still get all of the energy loss that you would with a physical barrier. Why? Simple. It's just like two magnets with the same ploarity. They repluse one another... The beauty of it all is that the plasma around the shuttle IS electrically energized, so it would be even easier to do...
Its also a very rich journalistic tradition to take things out of context, grab the most incriminating sound bytes...
two of them arent even direct...
one of them was much laughed about...
in fact its only you whom I've called a fool...
I get called a fool basically every day... and I havent reached for the razorblades just yet.
[B]The tiles ARE fragile...but not in the way you might think. Sure a fingernail can damage them...raindrop? I'm not so sure about that, but it's possible. It's all about pressure. Your fingernail can exert more pressure (pounds per square inch) than air because the contact point is so small.
After all, your fingernail can damage a block of styrofoam, but wind may not harm it at all. [/B][/QUOTE]
Sure a wind may not harm a styrofoam, but it's not a small wind we're talking about here. It's an enormous pressure, which would destroy a piece of styrofoam just like that. And styrofoam is a different kind of material anyway.
Anyway, I know what you mean, but if you can scratch the surface of the tiles with your fingernail that doesn't make the tiles fragile as a whole, just the surface.
- PJH
[B]The thing that no one has yet said..or at least clearly in my mind is this. IF you are using some kind of "force field" to push the air away, you will still get all of the energy loss that you would with a physical barrier. Why? Simple. It's just like two magnets with the same ploarity. They repluse one another... The beauty of it all is that the plasma around the shuttle IS electrically energized, so it would be even easier to do... [/B][/QUOTE]
Ummmm...... could you explain that again? I'm not quite sure if I understood that right.
- PJH
If you were using a "force field" that worked on the principle of pushing the plasma away from the surface so that it didn't touch the surface, you would still have the same amount of decelerating force. A force field doesn't protect you from kinetics, it simply repulses matter, just like two magnets when you put the same ends together. So you will still have a "push" back against the object, like the shuttle. Since the plasma around the shuttle actually has an electrical charge to it, if you could create a field with the same polarity, they would repulse one another. In theory, I would think this would be easier to do than to create a field that would actually push away uncharged air.
Of course, the whole thing is pretty far fetched.