Some thoughts on sound...
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Pielander
Typing error I guess. You obviously meant to say even if it is in a vacuum.
A spaceship flying through space will make a lot of noise. Noise doesn't need air. It is a vibration of any medium.
I think this is what was nagging Turbofan. He was thinking all this commotion - where is it going to? And the answer is of course all the noise generated by smashing into the atmosphere isn't being generated (so no problem there) whilst the noise of the engines etc is propogating around the vessel but not transferring into the medium surrounding the vessel.
Typing error I guess. You obviously meant to say even if it is in a vacuum.
A spaceship flying through space will make a lot of noise. Noise doesn't need air. It is a vibration of any medium.
I think this is what was nagging Turbofan. He was thinking all this commotion - where is it going to? And the answer is of course all the noise generated by smashing into the atmosphere isn't being generated (so no problem there) whilst the noise of the engines etc is propogating around the vessel but not transferring into the medium surrounding the vessel.
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Touche.
Although, I have made the point before about the vibration propagating through the vessel/tree and been dissipated as heat. Again, it comes down to the definition of the word noise. Is it a noise unless it is being ransmitted through a fluid? Probably, but I hadn't thouht that far.
Also, what would a tree be doing in a vacuum? I would have to say it wouldn't be in a vacuum to fall down in the first place.
Pie
Although, I have made the point before about the vibration propagating through the vessel/tree and been dissipated as heat. Again, it comes down to the definition of the word noise. Is it a noise unless it is being ransmitted through a fluid? Probably, but I hadn't thouht that far.
Also, what would a tree be doing in a vacuum? I would have to say it wouldn't be in a vacuum to fall down in the first place.
Pie
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OK, the picture clears yet more...
Sooo...
Hang on, I need to think a little more.
[please pause here for a few minutes]
So basically the energy that's passed to the air (to create the pressure waves) is non-existent in space. That's the general concensus I'm getting.
OK, well let me put up another hurdle (unless I've missed something obvious, which is very likely at this time of night...). The craft has say 100 units of energy, and loses 10 to the air/sound/pressure waves. So does it just simply hold those 10 units when it's in space? (As say Kinetic Energy for example.) I would asume it would.
Comments...
Turbofan
Sooo...
Hang on, I need to think a little more.
[please pause here for a few minutes]
So basically the energy that's passed to the air (to create the pressure waves) is non-existent in space. That's the general concensus I'm getting.
OK, well let me put up another hurdle (unless I've missed something obvious, which is very likely at this time of night...). The craft has say 100 units of energy, and loses 10 to the air/sound/pressure waves. So does it just simply hold those 10 units when it's in space? (As say Kinetic Energy for example.) I would asume it would.
Comments...
Turbofan
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It's actually much more complicated and much simpler at the the same time, than all of the above.
The reason that aircraft fly is a result of the sound that is produced in the pursuit of entropy. Early aircraft were very loud for not much load or speed, the DoX for example had sixteen sound engines for about 100kts flat out with a dozen pax, but fortunately aerodynamic engineers have worked out how to get a much more efficient use of sound over the years. The new wide chord fans are a great example of this efficiency gain.
The bigger the aircraft the greater level, as distinct from volume of sound is required to "shake" itself between the air molecules and the ground thus producing what we quaintly call 'lift'.
It also explains why the higher the altitude the less actual noise is required, there are less air molecules to pry apart.
See.
Ever noticed how it's actually quite hard to "hear" an aircraft flying overhead at FL350 from the ground.
It is also why you don't see your average space shuttle running its engine as it orbits, no, or very few air molecules, to pry apart, so no sound required.
Just think of the proportion of time taken up in our training for dealing with the eventuality that it becomes quieter than normal or even
totally silent.
Ergo it's all to do with the amount of sound.
Less or no sound is a pilots worst nightmare.
Turbofan, there 'tis, simple really, I hope this makes you sleep a little easier.
The reason that aircraft fly is a result of the sound that is produced in the pursuit of entropy. Early aircraft were very loud for not much load or speed, the DoX for example had sixteen sound engines for about 100kts flat out with a dozen pax, but fortunately aerodynamic engineers have worked out how to get a much more efficient use of sound over the years. The new wide chord fans are a great example of this efficiency gain.
The bigger the aircraft the greater level, as distinct from volume of sound is required to "shake" itself between the air molecules and the ground thus producing what we quaintly call 'lift'.
It also explains why the higher the altitude the less actual noise is required, there are less air molecules to pry apart.
See.
Ever noticed how it's actually quite hard to "hear" an aircraft flying overhead at FL350 from the ground.
It is also why you don't see your average space shuttle running its engine as it orbits, no, or very few air molecules, to pry apart, so no sound required.
Just think of the proportion of time taken up in our training for dealing with the eventuality that it becomes quieter than normal or even
totally silent. Ergo it's all to do with the amount of sound.
Less or no sound is a pilots worst nightmare.
Turbofan, there 'tis, simple really, I hope this makes you sleep a little easier.
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gaunty:
Eh? Wot u been smokin'?
Sound is not what causes aeroplanes to fly. The principles of aerodynamic flight don't apply in space anyway. The noise comes mostly from the engines, either in the air of out of it, and the noise itself is caused by turbulent flow, whether it be over the wing, in the exhaust stream, or in the engine itself.
The main reaqson why you can't hear an aircraft at FL420 is because it's 8 miles away.
Pie
Eh? Wot u been smokin'?
Sound is not what causes aeroplanes to fly. The principles of aerodynamic flight don't apply in space anyway. The noise comes mostly from the engines, either in the air of out of it, and the noise itself is caused by turbulent flow, whether it be over the wing, in the exhaust stream, or in the engine itself.
The main reaqson why you can't hear an aircraft at FL420 is because it's 8 miles away.
Pie
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LOL!
Hey Pielander, I think he just may be taking the p!ss... I hope it's that, 'cos Gaunty, you've lost me mate...
Keep in mind folks that this isn't really about sound, it's about energy transference. (I hope that's a word - yes it is, I just looked it up )
[This message has been edited by Turbofan (edited 06 July 2001).]
[This message has been edited by Turbofan (edited 06 July 2001).]
Hey Pielander, I think he just may be taking the p!ss...
I hope it's that, 'cos Gaunty, you've lost me mate...Keep in mind folks that this isn't really about sound, it's about energy transference. (I hope that's a word - yes it is, I just looked it up
)[This message has been edited by Turbofan (edited 06 July 2001).]
[This message has been edited by Turbofan (edited 06 July 2001).]
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Tangential, but it may be youse guys could answer a vexed question which has long been the subject of debate in my place of work, to wit, what is the speed of sound on Mars? (surface level). No, we couldn't find out how many grammes per cubic metre either. Not very many though.
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Hi All,
"In space, nobody can hear you scream"... but you can get a cracking suntan.
Let's see if I've understood all this banter:
A rocket is whizzing about space at full throttle. 90% of the energy dissipates in a cloud of nasty, hot, smelly, propulsive particles kicked out at a zillion MPH to keep Newton happy. Stay away from the blunt end, then, huh? However, 10% of the energy boings around the aeroshell (smart arse tech term) causing it to vibrate like an AC-DC concert stage.
Can't hear much of either the vibes, or the propulsion, 'cos the vacuum is unable to conduct sound waves. Also 'cos no one is daft enough to be anywhere near the sodding thing. The wibbly-wobbly panels continue to vibrate like buggery, but ultimately get damped by all those molecules tap dancing together. Wobbling molecules generate heat energy causing said aeroshell to heat up.
Said heat doesn't have the nous to leap into the hot, propulsive gases, so they're not going to make much of a contribution to the going forward thing. So the heat says 'sod it' and simply radiates (slowly) in all directions into the vacuum via the electro-magnetic spectrum whatsit. Contrary to what the Hoover Company says, vacuums propagate photons nicely, but are useless at getting dust out of a corner.
Seeing as the rocket, vacuum, gases, electro-magnetic radiation, Coca-Cola logo, and the astronaut with a suntan, are all within the same Universe, then energy is fully conserved, so we can all sleep at night.
TW
"In space, nobody can hear you scream"... but you can get a cracking suntan.
Let's see if I've understood all this banter:
A rocket is whizzing about space at full throttle. 90% of the energy dissipates in a cloud of nasty, hot, smelly, propulsive particles kicked out at a zillion MPH to keep Newton happy. Stay away from the blunt end, then, huh? However, 10% of the energy boings around the aeroshell (smart arse tech term) causing it to vibrate like an AC-DC concert stage.
Can't hear much of either the vibes, or the propulsion, 'cos the vacuum is unable to conduct sound waves. Also 'cos no one is daft enough to be anywhere near the sodding thing. The wibbly-wobbly panels continue to vibrate like buggery, but ultimately get damped by all those molecules tap dancing together. Wobbling molecules generate heat energy causing said aeroshell to heat up.
Said heat doesn't have the nous to leap into the hot, propulsive gases, so they're not going to make much of a contribution to the going forward thing. So the heat says 'sod it' and simply radiates (slowly) in all directions into the vacuum via the electro-magnetic spectrum whatsit. Contrary to what the Hoover Company says, vacuums propagate photons nicely, but are useless at getting dust out of a corner.
Seeing as the rocket, vacuum, gases, electro-magnetic radiation, Coca-Cola logo, and the astronaut with a suntan, are all within the same Universe, then energy is fully conserved, so we can all sleep at night.
TW
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I cant believe you are all so ignorant of the facts.
Its all very simple.
When the craft is in space there is no sound that can be heard externally because there is no air to conduct it. However, if the craft is using its engine to acclerate a tiny fraction of the energy of the exhaust can by conducted back through the nozzle, vibrating the craft and manifest as a faint noise inside the craft where there is (hopefully) some air. Most spacecraft do not run thier engines in space unless they are accelerating or changing orbit. This is because there is no drag (no air) and so the craft can maintain speed almost indefinitely without using any power (conservation of energy). Thus a satellite can remain in space for years without using its rocket motors other than for minor corrections.
Its also seems there is a serious misunderstanding here about heat energy of a spacecraft. The craft can dissipate some energy as heat by infra-red radiation which requires no air as it is an electromagnetic form of energy. However, (to contradist Bally Heck) it cannot conduct heat to its surroundings or convect heat whcich requires the presence of air. Incidentally, Bally Heck mentins the difference between the temperature of space and the craft. What are you on about. As a vacuum cannot contain any heat by defintion, there can be no conduction due to a difference in temperature. Radiation on the other hand is not affected by the difference in temperature between the two mediums, only by the radiating body's temerature.
Is that all clear now?
Its all very simple.
When the craft is in space there is no sound that can be heard externally because there is no air to conduct it. However, if the craft is using its engine to acclerate a tiny fraction of the energy of the exhaust can by conducted back through the nozzle, vibrating the craft and manifest as a faint noise inside the craft where there is (hopefully) some air. Most spacecraft do not run thier engines in space unless they are accelerating or changing orbit. This is because there is no drag (no air) and so the craft can maintain speed almost indefinitely without using any power (conservation of energy). Thus a satellite can remain in space for years without using its rocket motors other than for minor corrections.
Its also seems there is a serious misunderstanding here about heat energy of a spacecraft. The craft can dissipate some energy as heat by infra-red radiation which requires no air as it is an electromagnetic form of energy. However, (to contradist Bally Heck) it cannot conduct heat to its surroundings or convect heat whcich requires the presence of air. Incidentally, Bally Heck mentins the difference between the temperature of space and the craft. What are you on about. As a vacuum cannot contain any heat by defintion, there can be no conduction due to a difference in temperature. Radiation on the other hand is not affected by the difference in temperature between the two mediums, only by the radiating body's temerature.
Is that all clear now?
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And now for something completely different.
Turbofans sleepless nights are shared by many with useful results.
We are now all more edumakated about matters rocketry.
And.
A fantastic example the application of this science to aviation, is the discovery of the use of the difference in speed of transmission of sound in different media in the investigation of aircraft accidents, specifically bombs or explosions.
Detailed frequency/amplitude analysis of the CVR tape of an aircraft brought down by a bomb showed a very small trace immediately before the sound of the explosion in the cockpit.
A very smart insomniac suspected that it may have been the vibration of the bomb "noise" through the airframe, which being solid transmitted the "noise" at a faster speed than the air.
By measuring the time difference beteween the two and using a little calculus it was possible to calculate the distance of the "noise" from the CVR.
Bingo!!! or Eureka if you are Greek, when they checked the results from this and other accidents it was confirmed to the very seat.
Awesome hey.
Turbofans sleepless nights are shared by many with useful results.
We are now all more edumakated about matters rocketry.
And.
A fantastic example the application of this science to aviation, is the discovery of the use of the difference in speed of transmission of sound in different media in the investigation of aircraft accidents, specifically bombs or explosions.
Detailed frequency/amplitude analysis of the CVR tape of an aircraft brought down by a bomb showed a very small trace immediately before the sound of the explosion in the cockpit.
A very smart insomniac suspected that it may have been the vibration of the bomb "noise" through the airframe, which being solid transmitted the "noise" at a faster speed than the air.
By measuring the time difference beteween the two and using a little calculus it was possible to calculate the distance of the "noise" from the CVR.
Bingo!!! or Eureka if you are Greek, when they checked the results from this and other accidents it was confirmed to the very seat.
Awesome hey.
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Mr Proach,
I feel I must beg to differ on a point or two. My posting mentioned neither conduction or convection, both of which require a medium to operate in.
Space is not a vaccuum. It is certainly a partial vaccuum but is still rich in matter.
If space contains no heat, then by definition it must be at absolute zero (0 degrees Kelvin) this is the theoretical temperature at which a perfect gas would cease to exist and is theoretical I believe isofar as it cannot be attained. (although scientists have been remarkably close)
I am working from memory here now but back in my engineering days we were taught that the quantity of heat radiated from a body was proportional to the square of the temperature diffference between the body and it's surroundings. Thus if a body is at a temperature of 1000C, and it's surroundings are at 1000C, no heat will be radiated. If the surroundings are close to absolute zero then it will radiate heat with great vigour and perspicacity. The surroundings will consequently increase in temperature. (See the first law of thermodynamics) and the rate of radiation will decrease.
Is that a doughnut.....or a meringue.
(best said with a Scottish accent)
I feel I must beg to differ on a point or two. My posting mentioned neither conduction or convection, both of which require a medium to operate in.
Space is not a vaccuum. It is certainly a partial vaccuum but is still rich in matter.
If space contains no heat, then by definition it must be at absolute zero (0 degrees Kelvin) this is the theoretical temperature at which a perfect gas would cease to exist and is theoretical I believe isofar as it cannot be attained. (although scientists have been remarkably close)
I am working from memory here now but back in my engineering days we were taught that the quantity of heat radiated from a body was proportional to the square of the temperature diffference between the body and it's surroundings. Thus if a body is at a temperature of 1000C, and it's surroundings are at 1000C, no heat will be radiated. If the surroundings are close to absolute zero then it will radiate heat with great vigour and perspicacity. The surroundings will consequently increase in temperature. (See the first law of thermodynamics) and the rate of radiation will decrease.
Is that a doughnut.....or a meringue.
(best said with a Scottish accent)