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Heat in front of moving object



 
 
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  #1  
Old January 15th 10, 07:08 PM posted to sci.astro
Richard Fangnail
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Posts: 7
Default 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  
Old January 15th 10, 07:16 PM posted to sci.astro
Androcles[_24_]
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Posts: 52
Default 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?



  #3  
Old January 15th 10, 10:25 PM posted to sci.astro
dlzc
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Posts: 1,426
Default 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
  #4  
Old January 16th 10, 04:56 AM posted to sci.astro
Frisbieinstein
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Posts: 55
Default 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.
  #5  
Old January 16th 10, 03:10 PM posted to sci.astro
Boris Mohar[_2_]
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Posts: 14
Default 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
  #6  
Old January 16th 10, 05:40 PM posted to sci.astro
Mike Dworetsky
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Posts: 715
Default 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  
Old January 16th 10, 06:03 PM posted to sci.astro
Androcles[_24_]
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Posts: 52
Default 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)



  #8  
Old January 16th 10, 11:00 PM posted to sci.astro
Mike Dworetsky
external usenet poster
 
Posts: 715
Default 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  
Old January 17th 10, 12:51 AM posted to sci.astro
Androcles[_24_]
external usenet poster
 
Posts: 52
Default 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  
Old January 17th 10, 11:14 AM posted to sci.astro
Mike Dworetsky
external usenet poster
 
Posts: 715
Default 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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