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Heat in front of moving object



 
 
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  #11  
Old January 17th 10, 02:04 PM 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
...
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.


One favourite ploy of the illogical twerp is to say
"A {object/expression} is not a {different object/expression} "
as in
"An asteroid is not a supersonic aircraft!"
or
"A sausage is not a dog's breakfast!"
The dog may conclude otherwise and prove it by eating the sausage.
Obviously you have a illogicality problem.


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


That's not the first time you've made that claim.
Do you have any empirical evidence to support the ludicrous
assertion that you are capable of actually thinking?


everyone else who has read the thread understands this point.


What, slow and fast heat transfer?

Let's see... object moves through air at v1 mph.
surface temperate rises 1 degree a second.
core temperature rises 1 degree a second,
delayed by 100 seconds for heat transfer.

After 10 seconds the surface temperate is 10 degrees.
After 10 seconds the core temperate is 0 degrees.

After 100 seconds the surface temperate is 100 degrees.
After 100 seconds the core temperate is 0 degrees.

After 200 seconds the surface temperate is 200 degrees.
After 200 seconds the core temperate is 100 degrees.

Water boils at 100 degrees, object explodes after 200 seconds.

Object moves through air at v2 mph.
surface temperate rises 10 degrees a second.

After 50 seconds the surface temperate is 500 degrees.
core temperature rises 10 degrees a second,
delayed by 50 seconds for heat transfer.
After 50 seconds the core temperate is 0 degrees.

After 60 seconds the surface temperate is 600 degrees.
After 60 seconds the core temperate is 100 degrees.

Water boils at 100 degrees, object explodes after 60 seconds.

object moves through air at v3 mph.
surface temperature rises at 100 degrees / second.

After 10 seconds the surface temperate is 1000 degrees.
core temperature rises 100 degrees a second,
delayed by 10 seconds for heat transfer.
After 10 seconds the core temperate is 0 degrees, it
takes 10 seconds for the heat to transfer

After 20 seconds the surface temperate is 2000 degrees.
After 11 seconds the core temperate is 100 degrees.
After 12 seconds the core temperate is 200 degrees.
After 13 seconds nothing, the core exploded.
The surface temperature never got to 2000 degrees,
there is no surface.


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


At least you admit that now.

I am the one with the physics problem here. An asteroid entering the
atmosphere at 10 km/s is not a steam train.


One favourite ploy of the illogical twerp is to say
"A {object/expression} is not a {different object/expression} "
as in
"An asteroid travelling at 10 km/s is not a steam train!"
or
"Eight hotdogs are not a dog's breakfast!"
The dog may conclude otherwise and prove it by eating all the hotdogs.
Obviously you have a thermal transfer problem, but you are correct
in one respect: the boiler of the steam train would definitely explode
within seconds if it travelled in air at 10 km/s, as was so tragically
demonstrated by the shuttle Columbia.
Learn about heat transfer which is faster if there is a greater temperature
gradient, as anyone with a lick of common sense would know.





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)



Ads
  #12  
Old January 17th 10, 03:30 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
...
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.


One favourite ploy of the illogical twerp is to say
"A {object/expression} is not a {different object/expression} "
as in
"An asteroid is not a supersonic aircraft!"
or
"A sausage is not a dog's breakfast!"
The dog may conclude otherwise and prove it by eating the sausage.
Obviously you have a illogicality problem.


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


That's not the first time you've made that claim.
Do you have any empirical evidence to support the ludicrous
assertion that you are capable of actually thinking?


everyone else who has read the thread understands this point.


What, slow and fast heat transfer?

Let's see... object moves through air at v1 mph.
surface temperate rises 1 degree a second.
core temperature rises 1 degree a second,
delayed by 100 seconds for heat transfer.

After 10 seconds the surface temperate is 10 degrees.
After 10 seconds the core temperate is 0 degrees.

After 100 seconds the surface temperate is 100 degrees.
After 100 seconds the core temperate is 0 degrees.

After 200 seconds the surface temperate is 200 degrees.
After 200 seconds the core temperate is 100 degrees.

Water boils at 100 degrees, object explodes after 200 seconds.

Object moves through air at v2 mph.
surface temperate rises 10 degrees a second.

After 50 seconds the surface temperate is 500 degrees.
core temperature rises 10 degrees a second,
delayed by 50 seconds for heat transfer.
After 50 seconds the core temperate is 0 degrees.

After 60 seconds the surface temperate is 600 degrees.
After 60 seconds the core temperate is 100 degrees.

Water boils at 100 degrees, object explodes after 60 seconds.

object moves through air at v3 mph.
surface temperature rises at 100 degrees / second.

After 10 seconds the surface temperate is 1000 degrees.
core temperature rises 100 degrees a second,
delayed by 10 seconds for heat transfer.
After 10 seconds the core temperate is 0 degrees, it
takes 10 seconds for the heat to transfer

After 20 seconds the surface temperate is 2000 degrees.
After 11 seconds the core temperate is 100 degrees.
After 12 seconds the core temperate is 200 degrees.
After 13 seconds nothing, the core exploded.
The surface temperature never got to 2000 degrees,
there is no surface.


What the hell are you mumbling about?

The difference between core and surface temperatures is almost immaterial
for an asteroid entering the atmosphere at a typical 10/km/s speed, in terms
of causing a breakup. The surface gets very hot, but there is no time for
the heat to transfer to the interior The entire atmospheric entry takes
about 3-10 sec. Rock is a very good insulator.

What does get transmitted to the interior is a shockwave which can disrupt a
very large meteoroid once the shock builds up. The energy does not all go
into heating the asteroid, but into disrupting it. The small fragments will
then either turn to dust or burn up (if they are moving fast enough).

The shockwave energy can cause internal compressions and heating which
enhance the explosive disassembly of the asteroid. It has nothing to do
with conduction of heat from the surface.

Imagine the same experiment done on an iron meteorite, which would not be
disrupted because it has a very high tensile strength. It will reach the
surface intact, as actual observations of iron meteorites show.



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


At least you admit that now.

I am the one with the physics problem here. An asteroid entering
the atmosphere at 10 km/s is not a steam train.


One favourite ploy of the illogical twerp is to say
"A {object/expression} is not a {different object/expression} "
as in
"An asteroid travelling at 10 km/s is not a steam train!"
or
"Eight hotdogs are not a dog's breakfast!"
The dog may conclude otherwise and prove it by eating all the hotdogs.
Obviously you have a thermal transfer problem, but you are correct
in one respect: the boiler of the steam train would definitely explode
within seconds if it travelled in air at 10 km/s, as was so tragically
demonstrated by the shuttle Columbia.
Learn about heat transfer which is faster if there is a greater
temperature gradient, as anyone with a lick of common sense would
know.


Columbia was, regrettably, a well designed hypersonic glider with a hole in
one wing. The heat transfer via hot gases penetrating still took over a
minute to cause fatal damage to the craft. It wasn't a "boiler explosion"
but the wings falling off.


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


--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)

  #13  
Old January 17th 10, 04:25 PM 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
...
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.


One favourite ploy of the illogical twerp is to say
"A {object/expression} is not a {different object/expression} "
as in
"An asteroid is not a supersonic aircraft!"
or
"A sausage is not a dog's breakfast!"
The dog may conclude otherwise and prove it by eating the sausage.
Obviously you have a illogicality problem.


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


That's not the first time you've made that claim.
Do you have any empirical evidence to support the ludicrous
assertion that you are capable of actually thinking?


everyone else who has read the thread understands this point.


What, slow and fast heat transfer?

Let's see... object moves through air at v1 mph.
surface temperate rises 1 degree a second.
core temperature rises 1 degree a second,
delayed by 100 seconds for heat transfer.

After 10 seconds the surface temperate is 10 degrees.
After 10 seconds the core temperate is 0 degrees.

After 100 seconds the surface temperate is 100 degrees.
After 100 seconds the core temperate is 0 degrees.

After 200 seconds the surface temperate is 200 degrees.
After 200 seconds the core temperate is 100 degrees.

Water boils at 100 degrees, object explodes after 200 seconds.

Object moves through air at v2 mph.
surface temperate rises 10 degrees a second.

After 50 seconds the surface temperate is 500 degrees.
core temperature rises 10 degrees a second,
delayed by 50 seconds for heat transfer.
After 50 seconds the core temperate is 0 degrees.

After 60 seconds the surface temperate is 600 degrees.
After 60 seconds the core temperate is 100 degrees.

Water boils at 100 degrees, object explodes after 60 seconds.

object moves through air at v3 mph.
surface temperature rises at 100 degrees / second.

After 10 seconds the surface temperate is 1000 degrees.
core temperature rises 100 degrees a second,
delayed by 10 seconds for heat transfer.
After 10 seconds the core temperate is 0 degrees, it
takes 10 seconds for the heat to transfer

After 20 seconds the surface temperate is 2000 degrees.
After 11 seconds the core temperate is 100 degrees.
After 12 seconds the core temperate is 200 degrees.
After 13 seconds nothing, the core exploded.
The surface temperature never got to 2000 degrees,
there is no surface.


What the hell are you mumbling about?


http://en.wikipedia.org/wiki/Temperature_gradient
Look it up.




The difference between core and surface temperatures is almost immaterial
for an asteroid entering the atmosphere at a typical 10/km/s speed, in
terms of causing a breakup. The surface gets very hot, but there is no
time for the heat to transfer to the interior The entire atmospheric
entry takes about 3-10 sec.


I'm sure the crew of the shuttle will be surprised to hear they can land
in 3-10 seconds. What the hell are you mumbling about?


Rock is a very good insulator.

What does get transmitted to the interior is a shockwave which can disrupt
a very large meteoroid once the shock builds up. The energy does not all
go into heating the asteroid, but into disrupting it. The small fragments
will then either turn to dust or burn up (if they are moving fast enough).

The shockwave energy can cause internal compressions and heating


Good grief! Internal heating. Amazing for a very good insulator!
Perhaps it's a fission asteroid. That must be it.

which
enhance the explosive disassembly of the asteroid. It has nothing to do
with conduction of heat from the surface.


Let me see....

"For a large solid asteroid entering the atmosphere, the surface layer
heats to incandescence", "Heat does not have time to get from the
outside to the inside of the large object falling to Earth at several
km/sec", "I don't think there was time for frictional heating to cause
an explosion", but there is internal heating of a very good insulator
(carried by soundwaves which are not called soundwaves, they are
called "shock" waves).

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?


Imagine the same experiment done on an iron meteorite, which would not be
disrupted because it has a very high tensile strength. It will reach the
surface intact, as actual observations of iron meteorites show.


Experiment? Hang on, I'll just pop into space and direct a couple of
large solid asteroids to come your way. One iron and one rock,
you'll be able to compare them. Would you like a comet too?
They break up just from the sun heating them, they leave tails.
I doubt anyone would find a piece of tail of comet at Tunguska,
but you never know, you might find a snowball.
I found a rocky asteroid on a beach once. It had been rounded by
friction with the atmosphere. Unfortunately I dropped it among the
pebbles and couldn't find it again or I'd have kept it to show you.
We could have experimented with it, checked it for oxidation,
it was discoloured. Mind you, there was no frost on it.



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


At least you admit that now.

I am the one with the physics problem here. An asteroid entering
the atmosphere at 10 km/s is not a steam train.


One favourite ploy of the illogical twerp is to say
"A {object/expression} is not a {different object/expression} "
as in
"An asteroid travelling at 10 km/s is not a steam train!"
or
"Eight hotdogs are not a dog's breakfast!"
The dog may conclude otherwise and prove it by eating all the hotdogs.
Obviously you have a thermal transfer problem, but you are correct
in one respect: the boiler of the steam train would definitely explode
within seconds if it travelled in air at 10 km/s, as was so tragically
demonstrated by the shuttle Columbia.
Learn about heat transfer which is faster if there is a greater
temperature gradient, as anyone with a lick of common sense would
know.


Columbia was, regrettably, a well designed hypersonic glider with a hole
in one wing. The heat transfer via hot gases penetrating still took over
a minute to cause fatal damage to the craft. It wasn't a "boiler
explosion" but the wings falling off.


And it only took 3-10 seconds to land, right?






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


--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)



  #14  
Old January 17th 10, 10:50 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
...
Androcles wrote:
"Mike Dworetsky" wrote in message
...
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.

One favourite ploy of the illogical twerp is to say
"A {object/expression} is not a {different object/expression} "
as in
"An asteroid is not a supersonic aircraft!"
or
"A sausage is not a dog's breakfast!"
The dog may conclude otherwise and prove it by eating the sausage.
Obviously you have a illogicality problem.


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

That's not the first time you've made that claim.
Do you have any empirical evidence to support the ludicrous
assertion that you are capable of actually thinking?


everyone else who has read the thread understands this point.

What, slow and fast heat transfer?

Let's see... object moves through air at v1 mph.
surface temperate rises 1 degree a second.
core temperature rises 1 degree a second,
delayed by 100 seconds for heat transfer.

After 10 seconds the surface temperate is 10 degrees.
After 10 seconds the core temperate is 0 degrees.

After 100 seconds the surface temperate is 100 degrees.
After 100 seconds the core temperate is 0 degrees.

After 200 seconds the surface temperate is 200 degrees.
After 200 seconds the core temperate is 100 degrees.

Water boils at 100 degrees, object explodes after 200 seconds.

Object moves through air at v2 mph.
surface temperate rises 10 degrees a second.

After 50 seconds the surface temperate is 500 degrees.
core temperature rises 10 degrees a second,
delayed by 50 seconds for heat transfer.
After 50 seconds the core temperate is 0 degrees.

After 60 seconds the surface temperate is 600 degrees.
After 60 seconds the core temperate is 100 degrees.

Water boils at 100 degrees, object explodes after 60 seconds.

object moves through air at v3 mph.
surface temperature rises at 100 degrees / second.

After 10 seconds the surface temperate is 1000 degrees.
core temperature rises 100 degrees a second,
delayed by 10 seconds for heat transfer.
After 10 seconds the core temperate is 0 degrees, it
takes 10 seconds for the heat to transfer

After 20 seconds the surface temperate is 2000 degrees.
After 11 seconds the core temperate is 100 degrees.
After 12 seconds the core temperate is 200 degrees.
After 13 seconds nothing, the core exploded.
The surface temperature never got to 2000 degrees,
there is no surface.


What the hell are you mumbling about?


http://en.wikipedia.org/wiki/Temperature_gradient
Look it up.




The difference between core and surface temperatures is almost
immaterial for an asteroid entering the atmosphere at a typical
10/km/s speed, in terms of causing a breakup. The surface gets very
hot, but there is no time for the heat to transfer to the interior The
entire atmospheric entry takes about 3-10 sec.


I'm sure the crew of the shuttle will be surprised to hear they can
land in 3-10 seconds. What the hell are you mumbling about?


Were they riding in a solid asteroid or a hollow spacecraft?



Rock is a very good insulator.

What does get transmitted to the interior is a shockwave which can
disrupt a very large meteoroid once the shock builds up. The energy
does not all go into heating the asteroid, but into disrupting it. The
small fragments will then either turn to dust or burn up (if
they are moving fast enough). The shockwave energy can cause internal
compressions and heating


Good grief! Internal heating. Amazing for a very good insulator!
Perhaps it's a fission asteroid. That must be it.


I can see you know nothing about the physics of meteoritic bodies in the
atmosphere.


which
enhance the explosive disassembly of the asteroid. It has nothing
to do with conduction of heat from the surface.


Let me see....

"For a large solid asteroid entering the atmosphere, the surface layer
heats to incandescence", "Heat does not have time to get from the
outside to the inside of the large object falling to Earth at several
km/sec", "I don't think there was time for frictional heating to
cause an explosion", but there is internal heating of a very good
insulator (carried by soundwaves which are not called soundwaves,
they are called "shock" waves).


The time for CONDUCTION of heat is very slow. The time for shockwaves is
very fast (of the order of soundspeed in rock). They are very different
methods of transmitting energy.


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?


Absolutely, as far as CONDUCTION is concerned.


Imagine the same experiment done on an iron meteorite, which would
not be disrupted because it has a very high tensile strength. It
will reach the surface intact, as actual observations of iron
meteorites show.


Experiment? Hang on, I'll just pop into space and direct a couple of
large solid asteroids to come your way. One iron and one rock,
you'll be able to compare them. Would you like a comet too?
They break up just from the sun heating them, they leave tails.
I doubt anyone would find a piece of tail of comet at Tunguska,
but you never know, you might find a snowball.
I found a rocky asteroid on a beach once. It had been rounded by
friction with the atmosphere. Unfortunately I dropped it among the
pebbles and couldn't find it again or I'd have kept it to show you.
We could have experimented with it, checked it for oxidation,
it was discoloured. Mind you, there was no frost on it.


There wouldn't be much difference in the effect on a loose gravel pile
asteroid and a cometary nucleus.




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

At least you admit that now.

I am the one with the physics problem here. An asteroid entering
the atmosphere at 10 km/s is not a steam train.

One favourite ploy of the illogical twerp is to say
"A {object/expression} is not a {different object/expression} "
as in
"An asteroid travelling at 10 km/s is not a steam train!"
or
"Eight hotdogs are not a dog's breakfast!"
The dog may conclude otherwise and prove it by eating all the
hotdogs. Obviously you have a thermal transfer problem, but you are
correct in one respect: the boiler of the steam train would definitely
explode within seconds if it travelled in air at 10 km/s, as was so
tragically demonstrated by the shuttle Columbia.
Learn about heat transfer which is faster if there is a greater
temperature gradient, as anyone with a lick of common sense would
know.


Columbia was, regrettably, a well designed hypersonic glider with a
hole in one wing. The heat transfer via hot gases penetrating still
took over a minute to cause fatal damage to the craft. It wasn't a
"boiler explosion" but the wings falling off.


And it only took 3-10 seconds to land, right?


Where did I say that? The reentry process had been underway for some time
(2-3 min?) before Columbia broke up. Columbia was moving at about 7 km/s to
start with, but it was controlled to reenter at a very shallow angle to
dissipate heat. Asteroids/cometary nuclei/meteoroids usually come in at
steep angles and even higher speeds.


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


--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)


--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)

  #15  
Old January 18th 10, 01:30 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
...
Androcles wrote:
"Mike Dworetsky" wrote in message
...
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.

One favourite ploy of the illogical twerp is to say
"A {object/expression} is not a {different object/expression} "
as in
"An asteroid is not a supersonic aircraft!"
or
"A sausage is not a dog's breakfast!"
The dog may conclude otherwise and prove it by eating the sausage.
Obviously you have a illogicality problem.


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

That's not the first time you've made that claim.
Do you have any empirical evidence to support the ludicrous
assertion that you are capable of actually thinking?


everyone else who has read the thread understands this point.

What, slow and fast heat transfer?

Let's see... object moves through air at v1 mph.
surface temperate rises 1 degree a second.
core temperature rises 1 degree a second,
delayed by 100 seconds for heat transfer.

After 10 seconds the surface temperate is 10 degrees.
After 10 seconds the core temperate is 0 degrees.

After 100 seconds the surface temperate is 100 degrees.
After 100 seconds the core temperate is 0 degrees.

After 200 seconds the surface temperate is 200 degrees.
After 200 seconds the core temperate is 100 degrees.

Water boils at 100 degrees, object explodes after 200 seconds.

Object moves through air at v2 mph.
surface temperate rises 10 degrees a second.

After 50 seconds the surface temperate is 500 degrees.
core temperature rises 10 degrees a second,
delayed by 50 seconds for heat transfer.
After 50 seconds the core temperate is 0 degrees.

After 60 seconds the surface temperate is 600 degrees.
After 60 seconds the core temperate is 100 degrees.

Water boils at 100 degrees, object explodes after 60 seconds.

object moves through air at v3 mph.
surface temperature rises at 100 degrees / second.

After 10 seconds the surface temperate is 1000 degrees.
core temperature rises 100 degrees a second,
delayed by 10 seconds for heat transfer.
After 10 seconds the core temperate is 0 degrees, it
takes 10 seconds for the heat to transfer

After 20 seconds the surface temperate is 2000 degrees.
After 11 seconds the core temperate is 100 degrees.
After 12 seconds the core temperate is 200 degrees.
After 13 seconds nothing, the core exploded.
The surface temperature never got to 2000 degrees,
there is no surface.

What the hell are you mumbling about?


http://en.wikipedia.org/wiki/Temperature_gradient
Look it up.




The difference between core and surface temperatures is almost
immaterial for an asteroid entering the atmosphere at a typical
10/km/s speed, in terms of causing a breakup. The surface gets very
hot, but there is no time for the heat to transfer to the interior The
entire atmospheric entry takes about 3-10 sec.


I'm sure the crew of the shuttle will be surprised to hear they can
land in 3-10 seconds. What the hell are you mumbling about?


Were they riding in a solid asteroid or a hollow spacecraft?

An aerodynamically streamlined hollow spacecraft designed
to slip though air with minimal resistance (drag) and hence
maximum speed, not a shapeless rock that will burn up and
decelerate rapidly.
The entire atmospheric entry SHOULD take about 1-5 sec
by your illogic. What the hell are you mumbling about?


Rock is a very good insulator.

What does get transmitted to the interior is a shockwave which can
disrupt a very large meteoroid once the shock builds up. The energy
does not all go into heating the asteroid, but into disrupting it. The
small fragments will then either turn to dust or burn up (if
they are moving fast enough). The shockwave energy can cause internal
compressions and heating


Good grief! Internal heating. Amazing for a very good insulator!
Perhaps it's a fission asteroid. That must be it.


I can see you know nothing about the physics of meteoritic bodies in the
atmosphere.


Funny that, I can see you know jack **** about time and speed.
I'm sure the crew of the shuttle will be surprised to hear they can land in
3-10 seconds if they ride a shapeless rock instead of streamlined hollow
spacecraft.

which
enhance the explosive disassembly of the asteroid. It has nothing
to do with conduction of heat from the surface.


Let me see....

"For a large solid asteroid entering the atmosphere, the surface layer
heats to incandescence", "Heat does not have time to get from the
outside to the inside of the large object falling to Earth at several
km/sec", "I don't think there was time for frictional heating to
cause an explosion", but there is internal heating of a very good
insulator (carried by soundwaves which are not called soundwaves,
they are called "shock" waves).


The time for CONDUCTION of heat is very slow. The time for shockwaves is
very fast (of the order of soundspeed in rock). They are very different
methods of transmitting energy.


Let me see...
"Heat does not have time to get from the outside to the inside of
the large object falling to Earth at several km/sec". "The entire
atmospheric entry takes about 3-10 sec."
Rocks fall faster than spacecraft, perhaps?
I have this strange feeling Galileo and Newton might not agree,
but I'm sure you know best. What would they know, eh?

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?


Absolutely, as far as CONDUCTION is concerned.


'Some men, reasoning preposterously, first establish some conclusion in
their minds which, either because of its being their own or because of their
having received it from some person who has their entire confidence,
impresses them so deeply that one finds it impossible ever to get it out of
their heads.'- Galileo Galilei


Imagine the same experiment done on an iron meteorite, which would
not be disrupted because it has a very high tensile strength. It
will reach the surface intact, as actual observations of iron
meteorites show.


Experiment? Hang on, I'll just pop into space and direct a couple of
large solid asteroids to come your way. One iron and one rock,
you'll be able to compare them. Would you like a comet too?
They break up just from the sun heating them, they leave tails.
I doubt anyone would find a piece of tail of comet at Tunguska,
but you never know, you might find a snowball.
I found a rocky asteroid on a beach once. It had been rounded by
friction with the atmosphere. Unfortunately I dropped it among the
pebbles and couldn't find it again or I'd have kept it to show you.
We could have experimented with it, checked it for oxidation,
it was discoloured. Mind you, there was no frost on it.


There wouldn't be much difference in the effect on a loose gravel pile
asteroid and a cometary nucleus.


I can see you know jack **** about scotch on the rocks. Drink it neat,
straight from the bottle, do you? You should try pouring it over ice
and hear the crack from the "shock" wave.



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

At least you admit that now.

I am the one with the physics problem here. An asteroid entering
the atmosphere at 10 km/s is not a steam train.

One favourite ploy of the illogical twerp is to say
"A {object/expression} is not a {different object/expression} "
as in
"An asteroid travelling at 10 km/s is not a steam train!"
or
"Eight hotdogs are not a dog's breakfast!"
The dog may conclude otherwise and prove it by eating all the
hotdogs. Obviously you have a thermal transfer problem, but you are
correct in one respect: the boiler of the steam train would definitely
explode within seconds if it travelled in air at 10 km/s, as was so
tragically demonstrated by the shuttle Columbia.
Learn about heat transfer which is faster if there is a greater
temperature gradient, as anyone with a lick of common sense would
know.

Columbia was, regrettably, a well designed hypersonic glider with a
hole in one wing. The heat transfer via hot gases penetrating still
took over a minute to cause fatal damage to the craft. It wasn't a
"boiler explosion" but the wings falling off.


And it only took 3-10 seconds to land, right?


Where did I say that?

"The entire atmospheric entry takes about 3-10 sec." - Mike Dworetsky

That's only for shapeless rocks, right?

The reentry process had been underway for some time (2-3 min?) before
Columbia broke up.


Ah, so mis-shapen rocks fall faster than streamlined spacecraft and you
can see I know nothing about the physics of meteoritic bodies in the
atmosphere.

I'm so glad I have a ****in' dork like you to teach me the physics
of meteoritic bodies in the atmosphere.




Columbia was moving at about 7 km/s to start with, but it was controlled
to reenter at a very shallow angle to dissipate heat. Asteroids/cometary
nuclei/meteoroids usually come in at steep angles and even higher speeds.


"The difference between core and surface temperatures is almost
immaterial for an asteroid entering the atmosphere at a typical
10/km/s speed, in terms of causing a breakup. " - Mike Dworetsky

"The entire atmospheric entry takes about 3-10 sec." - Mike Dork-etsky

How the **** do you get from 10 km/s and 3-10 sec
to 7 km/s and "underway for some time (2-3 min?)", DORK?

I'm so glad I have a ****in' dork, who can see I know nothing
about the physics of meteoritic bodies in the atmosphere, to teach me.

**** off, you dumb *******.



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

--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)


--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)



  #16  
Old January 18th 10, 03:05 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
...
Androcles wrote:
"Mike Dworetsky" wrote in message
...
Androcles wrote:
"Mike Dworetsky" wrote in
message ...
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.

One favourite ploy of the illogical twerp is to say
"A {object/expression} is not a {different object/expression} "
as in
"An asteroid is not a supersonic aircraft!"
or
"A sausage is not a dog's breakfast!"
The dog may conclude otherwise and prove it by eating the sausage.
Obviously you have a illogicality problem.


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

That's not the first time you've made that claim.
Do you have any empirical evidence to support the ludicrous
assertion that you are capable of actually thinking?


everyone else who has read the thread understands this point.

What, slow and fast heat transfer?

Let's see... object moves through air at v1 mph.
surface temperate rises 1 degree a second.
core temperature rises 1 degree a second,
delayed by 100 seconds for heat transfer.

After 10 seconds the surface temperate is 10 degrees.
After 10 seconds the core temperate is 0 degrees.

After 100 seconds the surface temperate is 100 degrees.
After 100 seconds the core temperate is 0 degrees.

After 200 seconds the surface temperate is 200 degrees.
After 200 seconds the core temperate is 100 degrees.

Water boils at 100 degrees, object explodes after 200 seconds.

Object moves through air at v2 mph.
surface temperate rises 10 degrees a second.

After 50 seconds the surface temperate is 500 degrees.
core temperature rises 10 degrees a second,
delayed by 50 seconds for heat transfer.
After 50 seconds the core temperate is 0 degrees.

After 60 seconds the surface temperate is 600 degrees.
After 60 seconds the core temperate is 100 degrees.

Water boils at 100 degrees, object explodes after 60 seconds.

object moves through air at v3 mph.
surface temperature rises at 100 degrees / second.

After 10 seconds the surface temperate is 1000 degrees.
core temperature rises 100 degrees a second,
delayed by 10 seconds for heat transfer.
After 10 seconds the core temperate is 0 degrees, it
takes 10 seconds for the heat to transfer

After 20 seconds the surface temperate is 2000 degrees.
After 11 seconds the core temperate is 100 degrees.
After 12 seconds the core temperate is 200 degrees.
After 13 seconds nothing, the core exploded.
The surface temperature never got to 2000 degrees,
there is no surface.

What the hell are you mumbling about?

http://en.wikipedia.org/wiki/Temperature_gradient
Look it up.




The difference between core and surface temperatures is almost
immaterial for an asteroid entering the atmosphere at a typical
10/km/s speed, in terms of causing a breakup. The surface gets
very hot, but there is no time for the heat to transfer to the
interior The entire atmospheric entry takes about 3-10 sec.

I'm sure the crew of the shuttle will be surprised to hear they can
land in 3-10 seconds. What the hell are you mumbling about?


Were they riding in a solid asteroid or a hollow spacecraft?

An aerodynamically streamlined hollow spacecraft designed
to slip though air with minimal resistance (drag) and hence
maximum speed, not a shapeless rock that will burn up and
decelerate rapidly.
The entire atmospheric entry SHOULD take about 1-5 sec
by your illogic. What the hell are you mumbling about?


Rock is a very good insulator.

What does get transmitted to the interior is a shockwave which can
disrupt a very large meteoroid once the shock builds up. The
energy does not all go into heating the asteroid, but into
disrupting it. The small fragments will then either turn to dust
or burn up (if they are moving fast enough). The shockwave energy can
cause
internal compressions and heating

Good grief! Internal heating. Amazing for a very good insulator!
Perhaps it's a fission asteroid. That must be it.


I can see you know nothing about the physics of meteoritic bodies in
the atmosphere.


Funny that, I can see you know jack **** about time and speed.
I'm sure the crew of the shuttle will be surprised to hear they can
land in 3-10 seconds if they ride a shapeless rock instead of
streamlined hollow spacecraft.

which
enhance the explosive disassembly of the asteroid. It has nothing
to do with conduction of heat from the surface.

Let me see....

"For a large solid asteroid entering the atmosphere, the surface
layer heats to incandescence", "Heat does not have time to get from
the outside to the inside of the large object falling to Earth at
several km/sec", "I don't think there was time for frictional
heating to cause an explosion", but there is internal heating of a
very good insulator (carried by soundwaves which are not called
soundwaves, they are called "shock" waves).


The time for CONDUCTION of heat is very slow. The time for
shockwaves is very fast (of the order of soundspeed in rock). They
are very different methods of transmitting energy.


Let me see...
"Heat does not have time to get from the outside to the inside of
the large object falling to Earth at several km/sec". "The entire
atmospheric entry takes about 3-10 sec."
Rocks fall faster than spacecraft, perhaps?
I have this strange feeling Galileo and Newton might not agree,
but I'm sure you know best. What would they know, eh?

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?


Absolutely, as far as CONDUCTION is concerned.


'Some men, reasoning preposterously, first establish some conclusion
in their minds which, either because of its being their own or
because of their having received it from some person who has their
entire confidence, impresses them so deeply that one finds it
impossible ever to get it out of their heads.'- Galileo Galilei


Imagine the same experiment done on an iron meteorite, which would
not be disrupted because it has a very high tensile strength. It
will reach the surface intact, as actual observations of iron
meteorites show.

Experiment? Hang on, I'll just pop into space and direct a couple of
large solid asteroids to come your way. One iron and one rock,
you'll be able to compare them. Would you like a comet too?
They break up just from the sun heating them, they leave tails.
I doubt anyone would find a piece of tail of comet at Tunguska,
but you never know, you might find a snowball.
I found a rocky asteroid on a beach once. It had been rounded by
friction with the atmosphere. Unfortunately I dropped it among the
pebbles and couldn't find it again or I'd have kept it to show you.
We could have experimented with it, checked it for oxidation,
it was discoloured. Mind you, there was no frost on it.


There wouldn't be much difference in the effect on a loose gravel
pile asteroid and a cometary nucleus.


I can see you know jack **** about scotch on the rocks. Drink it neat,
straight from the bottle, do you? You should try pouring it over ice
and hear the crack from the "shock" wave.



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

At least you admit that now.

I am the one with the physics problem here. An asteroid
entering the atmosphere at 10 km/s is not a steam train.

One favourite ploy of the illogical twerp is to say
"A {object/expression} is not a {different object/expression} "
as in
"An asteroid travelling at 10 km/s is not a steam train!"
or
"Eight hotdogs are not a dog's breakfast!"
The dog may conclude otherwise and prove it by eating all the
hotdogs. Obviously you have a thermal transfer problem, but you
are correct in one respect: the boiler of the steam train would
definitely explode within seconds if it travelled in air at 10
km/s, as was so tragically demonstrated by the shuttle Columbia.
Learn about heat transfer which is faster if there is a greater
temperature gradient, as anyone with a lick of common sense would
know.

Columbia was, regrettably, a well designed hypersonic glider with a
hole in one wing. The heat transfer via hot gases penetrating
still took over a minute to cause fatal damage to the craft. It
wasn't a "boiler explosion" but the wings falling off.

And it only took 3-10 seconds to land, right?


Where did I say that?

"The entire atmospheric entry takes about 3-10 sec." - Mike Dworetsky

That's only for shapeless rocks, right?

The reentry process had been underway for some time (2-3 min?) before
Columbia broke up.


Ah, so mis-shapen rocks fall faster than streamlined spacecraft and
you can see I know nothing about the physics of meteoritic bodies in the
atmosphere.

I'm so glad I have a ****in' dork like you to teach me the physics
of meteoritic bodies in the atmosphere.




Columbia was moving at about 7 km/s to start with, but it was
controlled to reenter at a very shallow angle to dissipate heat.
Asteroids/cometary nuclei/meteoroids usually come in at steep angles
and even higher speeds.


"The difference between core and surface temperatures is almost
immaterial for an asteroid entering the atmosphere at a typical
10/km/s speed, in terms of causing a breakup. " - Mike Dworetsky

"The entire atmospheric entry takes about 3-10 sec." - Mike Dork-etsky

How the **** do you get from 10 km/s and 3-10 sec
to 7 km/s and "underway for some time (2-3 min?)", DORK?

I'm so glad I have a ****in' dork, who can see I know nothing
about the physics of meteoritic bodies in the atmosphere, to teach me.

**** off, you dumb *******.


Yeah, you're a real sweetheart. Build a strawman, then start swearing and
insulting when I refuse to support your strawman. This conversation ends.


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

--


--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)

  #17  
Old January 18th 10, 03:39 PM posted to sci.astro
Mike Dworetsky
external usenet poster
 
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?

The Siberian meteor of 1908 exploded in midair. Why do you suppose it
did, as opposed to hitting the earth?


The object (either a stony asteroid or a small cometary nucleus--there are
models of both concepts to explain Tunguska) entered the atmosphere at a
speed estimated to be around 10 km/sec or more. That's fast--it would take
only a few seconds to pass from space through the upper atmosphere to the
altitude where it exploded, depending on the exact angle of descent and
speed. The ram pressure rapidly built up to the point where the object
exploded (from a shock wave propagating into the solid body--in effect, the
air in front of it was so compressed it exerted a force similar to that of
hitting a solid surface, and that air was extremely hot from the
compression). Most of the remaining kinetic energy turned into heat very
quickly (microsecs), resulting in a fireball similar to a thermonuclear
explosion. The shockwave from that explosion resulted in the damage and
sound effects observed on the surface.

http://en.wikipedia.org/wiki/Tunguska_event

Estimates vary, but it is thought to have been around 60 metres across.

--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)

  #18  
Old January 18th 10, 03:57 PM posted to sci.astro
Androcles[_24_]
external usenet poster
 
Posts: 52
Default Heat in front of moving object


"Mike Dworetsky" wrote in message
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Androcles wrote:
"Mike Dworetsky" wrote in message
...
Androcles wrote:
"Mike Dworetsky" wrote in message
...
Androcles wrote:
"Mike Dworetsky" wrote in
message ...
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.

One favourite ploy of the illogical twerp is to say
"A {object/expression} is not a {different object/expression} "
as in
"An asteroid is not a supersonic aircraft!"
or
"A sausage is not a dog's breakfast!"
The dog may conclude otherwise and prove it by eating the sausage.
Obviously you have a illogicality problem.


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

That's not the first time you've made that claim.
Do you have any empirical evidence to support the ludicrous
assertion that you are capable of actually thinking?


everyone else who has read the thread understands this point.

What, slow and fast heat transfer?

Let's see... object moves through air at v1 mph.
surface temperate rises 1 degree a second.
core temperature rises 1 degree a second,
delayed by 100 seconds for heat transfer.

After 10 seconds the surface temperate is 10 degrees.
After 10 seconds the core temperate is 0 degrees.

After 100 seconds the surface temperate is 100 degrees.
After 100 seconds the core temperate is 0 degrees.

After 200 seconds the surface temperate is 200 degrees.
After 200 seconds the core temperate is 100 degrees.

Water boils at 100 degrees, object explodes after 200 seconds.

Object moves through air at v2 mph.
surface temperate rises 10 degrees a second.

After 50 seconds the surface temperate is 500 degrees.
core temperature rises 10 degrees a second,
delayed by 50 seconds for heat transfer.
After 50 seconds the core temperate is 0 degrees.

After 60 seconds the surface temperate is 600 degrees.
After 60 seconds the core temperate is 100 degrees.

Water boils at 100 degrees, object explodes after 60 seconds.

object moves through air at v3 mph.
surface temperature rises at 100 degrees / second.

After 10 seconds the surface temperate is 1000 degrees.
core temperature rises 100 degrees a second,
delayed by 10 seconds for heat transfer.
After 10 seconds the core temperate is 0 degrees, it
takes 10 seconds for the heat to transfer

After 20 seconds the surface temperate is 2000 degrees.
After 11 seconds the core temperate is 100 degrees.
After 12 seconds the core temperate is 200 degrees.
After 13 seconds nothing, the core exploded.
The surface temperature never got to 2000 degrees,
there is no surface.

What the hell are you mumbling about?

http://en.wikipedia.org/wiki/Temperature_gradient
Look it up.




The difference between core and surface temperatures is almost
immaterial for an asteroid entering the atmosphere at a typical
10/km/s speed, in terms of causing a breakup. The surface gets
very hot, but there is no time for the heat to transfer to the
interior The entire atmospheric entry takes about 3-10 sec.

I'm sure the crew of the shuttle will be surprised to hear they can
land in 3-10 seconds. What the hell are you mumbling about?

Were they riding in a solid asteroid or a hollow spacecraft?

An aerodynamically streamlined hollow spacecraft designed
to slip though air with minimal resistance (drag) and hence
maximum speed, not a shapeless rock that will burn up and
decelerate rapidly.
The entire atmospheric entry SHOULD take about 1-5 sec
by your illogic. What the hell are you mumbling about?


Rock is a very good insulator.

What does get transmitted to the interior is a shockwave which can
disrupt a very large meteoroid once the shock builds up. The
energy does not all go into heating the asteroid, but into
disrupting it. The small fragments will then either turn to dust
or burn up (if they are moving fast enough). The shockwave energy can
cause
internal compressions and heating

Good grief! Internal heating. Amazing for a very good insulator!
Perhaps it's a fission asteroid. That must be it.

I can see you know nothing about the physics of meteoritic bodies in
the atmosphere.


Funny that, I can see you know jack **** about time and speed.
I'm sure the crew of the shuttle will be surprised to hear they can
land in 3-10 seconds if they ride a shapeless rock instead of
streamlined hollow spacecraft.

which
enhance the explosive disassembly of the asteroid. It has nothing
to do with conduction of heat from the surface.

Let me see....

"For a large solid asteroid entering the atmosphere, the surface
layer heats to incandescence", "Heat does not have time to get from
the outside to the inside of the large object falling to Earth at
several km/sec", "I don't think there was time for frictional
heating to cause an explosion", but there is internal heating of a
very good insulator (carried by soundwaves which are not called
soundwaves, they are called "shock" waves).

The time for CONDUCTION of heat is very slow. The time for
shockwaves is very fast (of the order of soundspeed in rock). They
are very different methods of transmitting energy.


Let me see...
"Heat does not have time to get from the outside to the inside of
the large object falling to Earth at several km/sec". "The entire
atmospheric entry takes about 3-10 sec."
Rocks fall faster than spacecraft, perhaps?
I have this strange feeling Galileo and Newton might not agree,
but I'm sure you know best. What would they know, eh?

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?


Absolutely, as far as CONDUCTION is concerned.


'Some men, reasoning preposterously, first establish some conclusion
in their minds which, either because of its being their own or
because of their having received it from some person who has their
entire confidence, impresses them so deeply that one finds it
impossible ever to get it out of their heads.'- Galileo Galilei


Imagine the same experiment done on an iron meteorite, which would
not be disrupted because it has a very high tensile strength. It
will reach the surface intact, as actual observations of iron
meteorites show.

Experiment? Hang on, I'll just pop into space and direct a couple of
large solid asteroids to come your way. One iron and one rock,
you'll be able to compare them. Would you like a comet too?
They break up just from the sun heating them, they leave tails.
I doubt anyone would find a piece of tail of comet at Tunguska,
but you never know, you might find a snowball.
I found a rocky asteroid on a beach once. It had been rounded by
friction with the atmosphere. Unfortunately I dropped it among the
pebbles and couldn't find it again or I'd have kept it to show you.
We could have experimented with it, checked it for oxidation,
it was discoloured. Mind you, there was no frost on it.

There wouldn't be much difference in the effect on a loose gravel
pile asteroid and a cometary nucleus.


I can see you know jack **** about scotch on the rocks. Drink it neat,
straight from the bottle, do you? You should try pouring it over ice
and hear the crack from the "shock" wave.



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

At least you admit that now.

I am the one with the physics problem here. An asteroid
entering the atmosphere at 10 km/s is not a steam train.

One favourite ploy of the illogical twerp is to say
"A {object/expression} is not a {different object/expression} "
as in
"An asteroid travelling at 10 km/s is not a steam train!"
or
"Eight hotdogs are not a dog's breakfast!"
The dog may conclude otherwise and prove it by eating all the
hotdogs. Obviously you have a thermal transfer problem, but you
are correct in one respect: the boiler of the steam train would
definitely explode within seconds if it travelled in air at 10
km/s, as was so tragically demonstrated by the shuttle Columbia.
Learn about heat transfer which is faster if there is a greater
temperature gradient, as anyone with a lick of common sense would
know.

Columbia was, regrettably, a well designed hypersonic glider with a
hole in one wing. The heat transfer via hot gases penetrating
still took over a minute to cause fatal damage to the craft. It
wasn't a "boiler explosion" but the wings falling off.

And it only took 3-10 seconds to land, right?


Where did I say that?

"The entire atmospheric entry takes about 3-10 sec." - Mike Dworetsky

That's only for shapeless rocks, right?

The reentry process had been underway for some time (2-3 min?) before
Columbia broke up.


Ah, so mis-shapen rocks fall faster than streamlined spacecraft and
you can see I know nothing about the physics of meteoritic bodies in the
atmosphere.

I'm so glad I have a ****in' dork like you to teach me the physics
of meteoritic bodies in the atmosphere.




Columbia was moving at about 7 km/s to start with, but it was
controlled to reenter at a very shallow angle to dissipate heat.
Asteroids/cometary nuclei/meteoroids usually come in at steep angles
and even higher speeds.


"The difference between core and surface temperatures is almost
immaterial for an asteroid entering the atmosphere at a typical
10/km/s speed, in terms of causing a breakup. " - Mike Dworetsky

"The entire atmospheric entry takes about 3-10 sec." - Mike Dork-etsky

How the **** do you get from 10 km/s and 3-10 sec
to 7 km/s and "underway for some time (2-3 min?)", DORK?

I'm so glad I have a ****in' dork, who can see I know nothing
about the physics of meteoritic bodies in the atmosphere, to teach me.

**** off, you dumb *******.


Yeah, you're a real sweetheart. Build a strawman, then start swearing and
insulting when I refuse to support your strawman. This conversation ends.


Did you expect me to kiss you and thank you for your erudition?
As I said, **** off, you dumb *******.




 




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