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Old Nov 4th 2015, 12:46 PM   #1
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Space shuttle, energy loss, heat

Hello

Space shuttle enters the atmosphere. (i) What happens to the transferred energy? (ii) how do the high temperatures generated in the shuttle enters the Earth atmosphere relate to the material used for the underside of the shuttle surface? Why is the underside not made from aluminium or iron?

THIS IS MY ANSWER. Please tell where I am correct or wrong and further advice.

The kinetic energy of the space shuttle will be transferred to the air molecules. This slows the shuttle down. As the shuttle loses energy, the air molecules will be gaining energy when they are hit by the shuttle.

The Shuttle's enters the atmosphere at such a high velocity that the air under its path does not have an opportunity to disperse and is compressed. Compressing a gas causes it to heat. The radiant heat from the air that has been heated (by the compression) begins to heat the incoming shuttle itself.
The shuttle is acting like a piston and compressing the air and is slowed down because of the resistance to compression.

Temperatures are very high so black silica (a product of sand) tiles line the under-surface of the shuttle, that are able to protect the craft. Metals such as aluminium (melting point 660 C) are not used because they would melt under the immense heat.


Thank you

Last edited by Hero; Nov 4th 2015 at 12:50 PM.
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Old Nov 5th 2015, 09:05 AM   #2
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Frictional Heating - Radiant Cooling

Hello Hero,

Thermodynamic and heat transfer considerations of reentry shuttles are intricate.
In particular the "frictional heating" versus "radiant cooling"
any device must accomplish (not to burn completely) are difficult to
predict and to design to avoid. Thousands of book address the aspects.

At my sight is a greatly simplified calculation regarding reentry.
The approximations I use are extreme (some have said "silly") but
are needed to make basic calculations at the level of a beginner.
So you can see some "talk" and "numbers" as this URL.

http://www.thermospokenhere.com/wp/0...e/shuttle.html

Good luck with your studies. Jim
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Old Nov 5th 2015, 12:06 PM   #3
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Thanks for your answer Jim,
I'm looking for a basic few line answer at High School level.
Even the answer I posted is too much information I think. I'm working through a text book.

I've been searching for an answer for a while now but have only seen complex information on the Internet. The answer in the book I think is wrong so I'm ignoring it.

Regarding the transfer of energy : is thermal energy created by friction of the shuttle against the air OR from kinetic energy of the fast moving shuttle being transferred into thermal energy to the air molecules when it compresses the air OR is thermal energy just created out of nothing because of the compression.

What is hearing the shuttle? Heat from the friction that it caused or from the compression that it caused
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Old Nov 5th 2015, 12:11 PM   #4
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Temperatures are very high so black silica (a product of sand) tiles line the under-surface of the shuttle, that are able to protect the craft. Metals such as aluminium (melting point 660 C) are not used because they would melt under the immense heat.
What about iron?

I think they would do more than just melt.

What is the combustion temperature of
1) Aluminium
2) Iron
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Old Nov 5th 2015, 12:32 PM   #5
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Originally Posted by studiot View Post
What about iron?

What is the combustion temperature of
1) Aluminium
2) Iron

I know what you're suggesting - that the metals may ignite. But that require oxygen and I don't think there's much oxygen in the upper atmosphere (just guessing / assuming )
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Old Nov 5th 2015, 12:36 PM   #6
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There may not be much, but

1) What is causing the shuttle to heat up if not atmospheric gases?

2) At the speed the shuttle is travelling it can pass/scoop a lot of even thin atmosphere.
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Old Nov 5th 2015, 12:43 PM   #7
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Originally Posted by studiot View Post
There may not be much, but

1) What is causing the shuttle to heat up if not atmospheric gases?

2) At the speed the shuttle is travelling it can pass/scoop a lot of even thin atmosphere.
Okay the metals would melt then boil then ignite.
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Old Nov 5th 2015, 01:25 PM   #8
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Reentry: the toughest HS science topic:

Mr. Hero,

Reentry prediction is an enormously complicated endeavor. There is no meaningful "... basic few line answer at High School level."

"Regarding the transfer of energy:" ..once into the atmosphere the shuttle "at very high speed" has complicatedly combined friction and momentum interactions with ambient air. Increased thermal energy of the craft is caused by friction shuttle-through-air. Resistance also costs craft speed (KE) so it slows, coming down but the air density increases.

"What about heating of the shuttle?" The shuttle becomes hotter not by "heat" but by friction. The shuttle does not melt because it has heat; it radiates thermal energy to space.

I admire your intention. Alas, reentry is not a HS topic.

Perhaps a HS science might be at my site:

http://www.thermospokenhere.com/wp/0...oc/00_toc.html

Good Luck to you,

Jim
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Old Nov 5th 2015, 02:47 PM   #9
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I thought your initial answer was quite good (if perhaps a little inelegant).

I must however take issue with the "thermal energy just created out of nothing" line.

The kinetic energy comes from the difference in speed between the shuttle and the air.
The reaction of the air to having all this energy suddenly transferred to it is to heat up.
This could be viewed as just an extreme example of the heating observed when you put energy in to compress air in a bicycle pump.

It might also be noted that it is actually desirable for all this heat to be generated,
it is necessary to get rid of all the Shuttles kinetic energy so that it can land at a sensible speed.
All the shuttles huge kinetic energy is converted to heat and carried away by the air (plus some radiation from the white hot tiles).
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Old Nov 5th 2015, 03:21 PM   #10
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Originally Posted by THERMO Spoken Here View Post

Reentry prediction is an enormously complicated endeavor. There is no meaningful "... basic few line answer at High School level."

Sir, physicists are clever people. They've taken us to the moon and back.




Originally Posted by THERMO Spoken Here View Post

"Regarding the transfer of energy:" ..once into the atmosphere the shuttle "at very high speed" ....... Increased thermal energy of the craft is caused by friction shuttle-through-air. Resistance also costs craft speed (KE) so it slows, coming down but the air density increases.
Sir, I'll make an attempt again.

Energy is transferred from KINETIC ENERGY in the shuttle to KINETIC ENERGY in the air molecules when they are pushed by the shuttle to THERMAL ENERGY from friction between the air and shuttle.

More KINETIC ENERGY is lost by the resistance to compression of the air.

Some THERMAL ENERGY is lost from the air into the other air all around.

THERMAL ENERGY from the air that has just been has just been given energy by the shuttle is transferred the shuttle that gets hot too.

Last edited by Hero; Nov 5th 2015 at 03:23 PM.
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