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| Cold Fusion |
 Posted: Sat Jul 19, 2008 1:53 am Post subject: Pure White |
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Does a perfectly white substance exist? I thought of a few applications of such a material, like coating the space shuttle with it. I remember from a movie, when the shuttle failed in various ways it became very hot, likely from the sun's light and the fact that heat can only be passively released form the shuttle in the form of electromagnetic radiation.
Even with a material like this, will the material experience any other losses? As in, could you have the light perfectly reflected without any loss to its energy level to the material?
What about mirrors? Compared to high quality white paint, which absorbs more energy?
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| Cold Fusion |
| Posted: Sat Jul 19, 2008 2:07 am Post subject: |
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I found Titanium dioxide on a forum; so is this the whitest? Does it also reflect UV and infrared?
Apparently they use this in paints....if I wanted to make a paint like substance out of this, which substance should I mix with it that ignores light (perfectly transparent, including UV and infrared)? I could use something like this to make a really nice looking computer case mod.
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Forget all that you know, achievements can only be accomplished by starting from nothing and selectively applying facts that are purely objective and absolutely necessary.
"Two things are infinite: the universe and human stupidity; and I'm not sure about the universe."
"Great spirits have always found violent opposition from mediocrities. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence"
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| SteveF |
| Posted: Sat Jul 19, 2008 6:58 am Post subject: |
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Understand that "white" is not a true physical property but an artificial concept determined by the frequency range of human vision. If another species, perhaps honeybees, could see further into the UV and less in the red portion of the spectrum, their "white" would appear bluish to us.
Your suggested application, reflection of as much radiation as possible, is best achieved by a shiny metallic reflector. This reflector would also handle the UV and IR portions of the spectrum. The color of the reflected light would appear to us (and also to the honeybees) the same as the color of the source.
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| Cold Fusion |
| Posted: Sat Jul 19, 2008 10:54 am Post subject: |
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Then I suppose the only reason they do not have a smooth mirror finish is due to the tremendous heat caused by re-entry. This would likely tarnish a finish of titanium dioxide or polished metal. If we could coat either one with a very powerful sealant it could be potentially tangible.
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Forget all that you know, achievements can only be accomplished by starting from nothing and selectively applying facts that are purely objective and absolutely necessary.
"Two things are infinite: the universe and human stupidity; and I'm not sure about the universe."
"Great spirits have always found violent opposition from mediocrities. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence"
-Einstein
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| MagiMaster |
| Posted: Sat Jul 19, 2008 2:14 pm Post subject: |
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| If blocking such radiation was the primary goal, it might be easiest to deploy a large (but thin) reflector between the ship and the radiation source, usually the sun (aka, a parasol). This could be brought back in during reentry. (An excellent site for information about theoretical spaceships is Atomic Rocket.) |
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| Janus |
| Posted: Sat Jul 19, 2008 2:38 pm Post subject: |
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The thing about poor radiation absorbers like white paint and reflective coatings is that they are also poor radiators of heat.
The problem with the space shuttle isn't with just sunlight, it is also the waste heat generated by its equipment and occupants. Paint it with a good radiation reflector and it won't be able to shed this waste heat fast enough to keep the interior temp down. This is why the inside of the cargo by doors have heat radiators on them. By keeping these surfaces turned away from the Sun, you can radiate heat away fast enough to keep up. For this reason the Shuttle always opens the cargo bay upon achieving orbit and doesn't close it until ready for re-entry. If for some reason the doors fail to open, they would have to cut the mission short.
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| William McCormick |
| Posted: Sat Jul 19, 2008 5:25 pm Post subject: Re: Pure White |
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Forum Ph.D.
Joined: 03 Apr 2008
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| Cold Fusion wrote: |
Does a perfectly white substance exist? I thought of a few applications of such a material, like coating the space shuttle with it. I remember from a movie, when the shuttle failed in various ways it became very hot, likely from the sun's light and the fact that heat can only be passively released form the shuttle in the form of electromagnetic radiation.
Even with a material like this, will the material experience any other losses? As in, could you have the light perfectly reflected without any loss to its energy level to the material?
What about mirrors? Compared to high quality white paint, which absorbs more energy? |
Nothing reflects rays. They either let them pass through as they are. Slow them more, or accelerate them to undetectable darkness.
Powerful light hits a piece of flat black metal. On the other side of the 90 percent space or hollow metal no light is visible. It is because the light was accelerated to dark speeds.
There is no trouble from space radiation. However if you can stop radiation. You can bring a small force to Washington DC and suffer ultimate victory.
Sincerely,
William McCormick
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| Cold Fusion |
| Posted: Mon Jul 21, 2008 1:50 am Post subject: |
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| Quote: |
| Paint it with a good radiation reflector and it won't be able to shed this waste heat fast enough to keep the interior temp down. |
Is this because internal reflection occurs?
I read about a "gate of no return" that was made to allow particles to only pass in one direction, but not the other. Maybe this could be applied to allow heat to come out but not in.
_________________
Forget all that you know, achievements can only be accomplished by starting from nothing and selectively applying facts that are purely objective and absolutely necessary.
"Two things are infinite: the universe and human stupidity; and I'm not sure about the universe."
"Great spirits have always found violent opposition from mediocrities. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence"
-Einstein
http://boinc.berkeley.edu/download.php
Use your computing strength for science! |
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| Pong |
| Posted: Mon Jul 21, 2008 3:18 am Post subject: |
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I imagine the reason space shuttles aren't coated with reflective metal is, metal's a great thermal conductor. That initial air to solid boundary is where we most need to stop heat from "jumping aboard". Also, a shuttle must present seams, inevitably, and reentry heat would conduct into metal seams. Better use insulating tiles of any colour.
The Soviets employed circulatory systems in their Venus lander shells. That was besides the expendable entry heatshield. So, just to combat the oven-like ambient heat.
There is a foundry stunt whereby the calloused old worker licks a finger and runs it through a vat of molten steel. The film of saliva is vapourizing - explosively - so forms a protective cloud around what passes for flesh. Maybe we could do similar for re-entry vehicles? If it cut launch weight it would be worthwhile. Porous tiles or perforated membrane wetted from within? A sweaty space shuttle! |
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| SteveF |
| Posted: Mon Jul 21, 2008 3:40 am Post subject: |
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Forum Bachelors Degree
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Â
The "gate of no return" is purely hypothetical. The idea was introduced in 1871 by James Clerk Maxwell and it has intrigued physicists ever since. It is popularly known as Maxwell's Demon. See the Wiki article over here:
http://en.wikipedia.org/wiki/Maxwell's_demon
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| Cold Fusion |
| Posted: Mon Jul 21, 2008 3:49 am Post subject: |
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http://www.sciencenews.org/view/generic/id/33454/title/Left_in_the_cold_
_________________
Forget all that you know, achievements can only be accomplished by starting from nothing and selectively applying facts that are purely objective and absolutely necessary.
"Two things are infinite: the universe and human stupidity; and I'm not sure about the universe."
"Great spirits have always found violent opposition from mediocrities. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence"
-Einstein
http://boinc.berkeley.edu/download.php
Use your computing strength for science! |
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| Cold Fusion |
| Posted: Mon Jul 21, 2008 3:51 am Post subject: |
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Forum Ph.D.
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10101010101011101010100101010101111010101010001
_________________
Forget all that you know, achievements can only be accomplished by starting from nothing and selectively applying facts that are purely objective and absolutely necessary.
"Two things are infinite: the universe and human stupidity; and I'm not sure about the universe."
"Great spirits have always found violent opposition from mediocrities. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence"
-Einstein
http://boinc.berkeley.edu/download.php
Use your computing strength for science!
Last edited by Cold Fusion on Mon Jul 21, 2008 5:50 pm; edited 3 times in total |
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| MagiMaster |
| Posted: Mon Jul 21, 2008 11:37 am Post subject: |
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Joined: 16 Jul 2006
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| Pong wrote: |
I imagine the reason space shuttles aren't coated with reflective metal is, metal's a great thermal conductor. That initial air to solid boundary is where we most need to stop heat from "jumping aboard". Also, a shuttle must present seams, inevitably, and reentry heat would conduct into metal seams. Better use insulating tiles of any colour.
The Soviets employed circulatory systems in their Venus lander shells. That was besides the expendable entry heatshield. So, just to combat the oven-like ambient heat.
There is a foundry stunt whereby the calloused old worker licks a finger and runs it through a vat of molten steel. The film of saliva is vapourizing - explosively - so forms a protective cloud around what passes for flesh. Maybe we could do similar for re-entry vehicles? If it cut launch weight it would be worthwhile. Porous tiles or perforated membrane wetted from within? A sweaty space shuttle! |
That would be called an ablative heat shield. It's much more efficient from a purely thermodynamic perspective, but there are a lot of practical problems with it. (For one, it's not going to be lighter.)
For a lot of good info on heat radiators in space, see here.
Edit: Actually this page is better. |
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| Cold Fusion |
| Posted: Sat Jul 26, 2008 4:10 pm Post subject: |
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http://www.lanl.gov/orgs/pa/science21/LaserCooling.html
They mention in this article a means to cool a spaceship through lasers. I believe they are currently using this method to make BEC's. How practically could this be used to cool the shuttle in the future? Obviously we can adequately cool it currently, but with the advent of more powerful computers and devices we may need more cooling power.
How exactly does laser cooling work? Their description seems to defy the laws of thermodynamics in that it is forcing expedited quantum cooling. Its hard to believe that we tricked nature into doing something this unnatural.
Notice the part that mentions cooling computers with this technology. Soon people will be saying, "Nice laser cooled system Joe!".
_________________
Forget all that you know, achievements can only be accomplished by starting from nothing and selectively applying facts that are purely objective and absolutely necessary.
"Two things are infinite: the universe and human stupidity; and I'm not sure about the universe."
"Great spirits have always found violent opposition from mediocrities. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence"
-Einstein
http://boinc.berkeley.edu/download.php
Use your computing strength for science! |
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| William McCormick |
| Posted: Sat Jul 26, 2008 5:39 pm Post subject: |
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Joined: 03 Apr 2008
Posts: 1052
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| Cold Fusion wrote: |
http://www.lanl.gov/orgs/pa/science21/LaserCooling.html
They mention in this article a means to cool a spaceship through lasers. I believe they are currently using this method to make BEC's. How practically could this be used to cool the shuttle in the future? Obviously we can adequately cool it currently, but with the advent of more powerful computers and devices we may need more cooling power.
How exactly does laser cooling work? Their description seems to defy the laws of thermodynamics in that it is forcing expedited quantum cooling. Its hard to believe that we tricked nature into doing something this unnatural.
Notice the part that mentions cooling computers with this technology. Soon people will be saying, "Nice laser cooled system Joe!". |
We had no trouble cooling space ships or space suits.
But if overheating will help stop space exploration, space exploration that would put globally destructive knowledge and power into everyone's hands. I am sure it is, or would be a big problem. For sure.
Sincerely,
William McCormick
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