Lesson learned on Satellite Thermal.
For years, we have been trying to demonstrate to students the extreme differences in Temperature of a satellite based simply on its color. In space, far from earth, here is what you should get for three identical satellites:
Black will be about +55 deg F White will be about -60 deg F Aluminum will be about +225 deg F
(from memory anyway)... But we have never been able to see the extreme temperature of the aluminum in our vacuum chamber. Of course, we are not using a SUN, but an incandescent lamp which has 95% of its radiation as heat and only 5% as light, so we attribtuted our wishy-washy results as due to the lack of real solar spectrum.
This year, we finally have a Tvac chamber that has a liguid nitrogen cold plate so we can actually better simulate the blackness (and cold) of space.. Again, same result. Aluminum was about the same as black. This was a frustrating result from this new chamber.
Then I noticed the fingerprints on the aluminum. I cleaned the aluminum with a swab of alcohol to eliminate all the surface contaminants, and fingerprints and re-did the test...
BINGO. Now the temperature of the aluminum goes up and off scale HOT, way way different from the black or White. And now the WHITE also goes colder..
So just the thinneest innvisible layer of surface contamination completely changed the thermal emissivity of the Aluminum. And we all know this anyway, since "low-E" coatings of glass and other materials is now so common. It is only the outer surface of molecules that set the absorbtivity and emissivity... And the differnce between Black and Aluminum is 30-to-1 (if the aluminum is clean)... That's why we wrap baked potatos in Aluminum foil! (don't use greasy hands)...
Of course we always clean our actual spacecraft to clean-room conditions before flight, so this does not impact our on-orbit results, but it sure does make a difference in the lab when we are demonstrating absorbtivity and emissivity in the chamber with samples handled by the students!
When I get a chance, Ill post the results...
Bob, WB4APR
On 11/18/2009 8:34 AM, Robert Bruninga wrote:
Lesson learned on Satellite Thermal.
For years, we have been trying to demonstrate to students the extreme differences in Temperature of a satellite based simply on its color. In space, far from earth, here is what you should get for three identical satellites:
Black will be about +55 deg F White will be about -60 deg F Aluminum will be about +225 deg F
snip...
This was sent by Bob on April 26, 1996. I found it interesting and kept it.
KEEPING ELECTRONICS COOL IN THE SUN.
WHile building a GPS unit for mounting on my dashboard and noting the comming summer months, I looked up the difference in absorption and emissivity for Aluminum, Black paint, and white paint. Satellite builders are well aware of these facts, but many of us landlubbers are not.
ALUMINUM will get 30 TIMES hotter than WHITE paint! (in a vacuum)
The following table is for a vacuum and accounts for RADIATIVE effects. It does not account for convective or conductive cooling (air)..
Absorbtion Emissivity Ratio Temp C
ALUMINUM .4 .03 11:1 400 STEEL .6 .4 3:2 150 BLACK PAINT .9 .9 1:1 110 WHITE PAINT .25 .85 1:3 72
Most people are aware that Black gets hotter than white, but the fact that bright, reflective, shinny Aluminum gets 10 times hotter than BLACK is a surprise to most people...
So, if it sits in the sun, paint it white! If you dont believe this, put an aluminum baking sheet in the sun. I baked my first roof mount GPS stand alone tracker thinking that the upside down baking pan would reflect the sun... WRONG! Painted it white and it is now as cool as a cucumber.
The difference in Aluminum is the POOR EMISSIVITY at infrared. It can't radiate the heat away...
Morning Bruce and everyone.
This really amazes me. Now is these spec's below for in a vacuum of space? Or on the earth's surface with Air.
Reason asking is, if this is indeed true, then why does every solar heat panel be painted black?
Not air panels by the numbers given below an Air panel being made black is near perfect it re radiates almost everything it absorbs.
But a closed loop liquid system where tubing is in the panel with fins attached to gather the energy. absorb it, and let the liquid take the heat away.
Every one of these are also painted black.
in this case wouldn't it be better to leave it bare aluminum? for it absorbs it but doesn't re radiate it away so it has more efficiency of getting the heat into the liquid.
anyone?
Joe WB9SBD
*The Original Rolling Ball Clock http://www.idle-tyme.com*
Bruce wrote:
On 11/18/2009 8:34 AM, Robert Bruninga wrote:
Lesson learned on Satellite Thermal.
For years, we have been trying to demonstrate to students the extreme differences in Temperature of a satellite based simply on its color. In space, far from earth, here is what you should get for three identical satellites:
Black will be about +55 deg F White will be about -60 deg F Aluminum will be about +225 deg F
snip...
This was sent by Bob on April 26, 1996. I found it interesting and kept it.
KEEPING ELECTRONICS COOL IN THE SUN.
WHile building a GPS unit for mounting on my dashboard and noting the comming summer months, I looked up the difference in absorption and emissivity for Aluminum, Black paint, and white paint. Satellite builders are well aware of these facts, but many of us landlubbers are not.
ALUMINUM will get 30 TIMES hotter than WHITE paint! (in a vacuum)
The following table is for a vacuum and accounts for RADIATIVE effects. It does not account for convective or conductive cooling (air)..
Absorbtion Emissivity Ratio Temp CALUMINUM .4 .03 11:1 400 STEEL .6 .4 3:2 150 BLACK PAINT .9 .9 1:1 110 WHITE PAINT .25 .85 1:3 72
Most people are aware that Black gets hotter than white, but the fact that bright, reflective, shinny Aluminum gets 10 times hotter than BLACK is a surprise to most people...
So, if it sits in the sun, paint it white! If you dont believe this, put an aluminum baking sheet in the sun. I baked my first roof mount GPS stand alone tracker thinking that the upside down baking pan would reflect the sun... WRONG! Painted it white and it is now as cool as a cucumber.
The difference in Aluminum is the POOR EMISSIVITY at infrared. It can't radiate the heat away...
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.707 / Virus Database: 270.14.72/2511 - Release Date: 11/18/09 01:50:00
Top Post: The huge difference in Aluminum, White and Black will only be seen in space where there is only radiation heat transfer and no Conduction and no convection. On Earth, in air, convection cooling dominates. These numbers only apply to Radiation heat transfer.
Black absorbs 90% of sunlight and emits 90% heat - nice White absorbs 30% of sunlight and emits 90% heat - cool Al... Absorbs 30% of sunlight and emits 3% heat - gets hot!
BUT, if you have air, and especially moving air, then anything can get rid of most of its heat to the air which is a larger effect.
Second Lesson: BUT "natural convection" which we all know cools things... depends on gravity! Remove gravity, and there is no natural convection... That is why you have to wear earplugs on the Space Station... Because every little thing has to have a FAN to move the air. Without it, things and the air around them just get hotter and hotter...
-----Original Message----- From: Idle-Tyme [mailto:nss@mwt.net] Sent: Wednesday, November 18, 2009 11:33 AM To: kk5do@amsat.org Cc: bruninga@usna.edu; amsat-bb@amsat.org Subject: Re: [amsat-bb] Re: Satellite Thermal Lesson
Morning Bruce and everyone.
This really amazes me. Now is these spec's below for in a vacuum of space? Or on the earth's surface with Air.
Reason asking is, if this is indeed true, then why does every solar heat panel be painted black?
Not air panels by the numbers given below an Air panel being made black is near perfect it re radiates almost everything it absorbs.
But a closed loop liquid system where tubing is in the panel with fins attached to gather the energy. absorb it, and let the liquid take the heat away.
Every one of these are also painted black.
in this case wouldn't it be better to leave it bare aluminum? for it absorbs it but doesn't re radiate it away so it has more efficiency of getting the heat into the liquid.
anyone?
Joe WB9SBD
file:///C:/Documents%20and%20Settings/Joe%20Mayenschein/My%20 Documents/Sig/CLEAN-IDLE-TYME-LOGO-100-50.jpg The Original Rolling Ball Clock http://www.idle-tyme.com
Bruce wrote:
On 11/18/2009 8:34 AM, Robert Bruninga wrote:
Lesson learned on Satellite Thermal.For years, we have been trying to demonstrate to students the extreme differences in Temperature of a satellite based simply on its color. In space, far from earth, here is what you should get for three identical satellites: Black will be about +55 deg F White will be about -60 deg F Aluminum will be about +225 deg F
snip...
This was sent by Bob on April 26, 1996. I found it interesting and kept it.
KEEPING ELECTRONICS COOL IN THE SUN.
WHile building a GPS unit for mounting on my dashboard and noting the comming summer months, I looked up the difference in absorption and emissivity for Aluminum, Black paint, and white paint. Satellite builders are well aware of these facts, but many of us landlubbers are not.
ALUMINUM will get 30 TIMES hotter than WHITE paint! (in a vacuum)
The following table is for a vacuum and accounts for RADIATIVE effects. It does not account for convective or conductive cooling
(air)..
Absorbtion Emissivity Ratio Temp CALUMINUM .4 .03 11:1 400 STEEL .6 .4 3:2 150 BLACK PAINT .9 .9 1:1 110 WHITE PAINT .25 .85 1:3 72
Most people are aware that Black gets hotter than white, but the fact that bright, reflective, shinny Aluminum gets 10 times hotter than BLACK is a surprise to most people...
So, if it sits in the sun, paint it white! If you dont believe this, put an aluminum baking sheet in the sun. I baked my first roof mount GPS stand alone tracker thinking that the upside down baking pan would reflect the sun... WRONG! Painted it white and it is now as cool as a cucumber.
The difference in Aluminum is the POOR EMISSIVITY at infrared. It can't radiate the heat away...
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.707 / Virus Database: 270.14.72/2511 - Release Date: 11/18/09 01:50:00
At 05:46 AM 11/18/2009, Bruce wrote:
On 11/18/2009 8:34 AM, Robert Bruninga wrote:
Lesson learned on Satellite Thermal.
For years, we have been trying to demonstrate to students the extreme differences in Temperature of a satellite based simply on its color. In space, far from earth, here is what you should get for three identical satellites:
Black will be about +55 deg F White will be about -60 deg F Aluminum will be about +225 deg F
snip...
This was sent by Bob on April 26, 1996. I found it interesting and kept it.
KEEPING ELECTRONICS COOL IN THE SUN.
WHile building a GPS unit for mounting on my dashboard and noting the comming summer months, I looked up the difference in absorption and emissivity for Aluminum, Black paint, and white paint. Satellite builders are well aware of these facts, but many of us landlubbers are not.
ALUMINUM will get 30 TIMES hotter than WHITE paint! (in a vacuum)
The following table is for a vacuum and accounts for RADIATIVE effects. It does not account for convective or conductive cooling (air)..
Absorbtion Emissivity Ratio Temp CALUMINUM .4 .03 11:1 400 STEEL .6 .4 3:2 150 BLACK PAINT .9 .9 1:1 110 WHITE PAINT .25 .85 1:3 72
Most people are aware that Black gets hotter than white, but the fact that bright, reflective, shinny Aluminum gets 10 times hotter than BLACK is a surprise to most people...
So, if it sits in the sun, paint it white! If you dont believe this, put an aluminum baking sheet in the sun. I baked my first roof mount GPS stand alone tracker thinking that the upside down baking pan would reflect the sun... WRONG! Painted it white and it is now as cool as a cucumber.
The difference in Aluminum is the POOR EMISSIVITY at infrared. It can't radiate the heat away...
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Yep, a hard lesson for the uninitiated working in the desert in summer: lay those shiny metal tools in the sun for ten minutes and you better wear gloves to pick em up. They get extremely hot and will burn skin. We always took care to lay the tools in shade or cover them with a cloth.
Regarding painting dishes white, all the dishes at Goldstone were painted white. What you may find interesting was that receive waveguide was painted white while transmit waveguide was flat-black. The heat buildup in the transmit waveguide required water-cooling by silver soldering cooling tubes to the surface of the waveguide. I suppose the black color aided black-body radiation.
73, Ed - KL7UW, WD2XSH/45 ====================================== BP40IQ 500 KHz - 10-GHz www.kl7uw.com 500-KHz/CW, 144-MHz EME, 1296-MHz EME DUBUS Magazine USA Rep dubususa@hotmail.com ======================================
At 05:46 AM 11/18/2009, Bruce wrote:
On 11/18/2009 8:34 AM, Robert Bruninga wrote:
Lesson learned on Satellite Thermal.
For years, we have been trying to demonstrate to students the extreme differences in Temperature of a satellite based simply on its color. In space, far from earth, here is what you should get for three identical satellites:
Black will be about +55 deg F White will be about -60 deg F Aluminum will be about +225 deg F
snip...
This was sent by Bob on April 26, 1996. I found it interesting and kept it.
KEEPING ELECTRONICS COOL IN THE SUN.
WHile building a GPS unit for mounting on my dashboard and noting the comming summer months, I looked up the difference in absorption and emissivity for Aluminum, Black paint, and white paint. Satellite builders are well aware of these facts, but many of us landlubbers are not.
ALUMINUM will get 30 TIMES hotter than WHITE paint! (in a vacuum)
The following table is for a vacuum and accounts for RADIATIVE effects. It does not account for convective or conductive cooling (air)..
Absorbtion Emissivity Ratio Temp CALUMINUM .4 .03 11:1 400 STEEL .6 .4 3:2 150 BLACK PAINT .9 .9 1:1 110 WHITE PAINT .25 .85 1:3 72
Most people are aware that Black gets hotter than white, but the fact that bright, reflective, shinny Aluminum gets 10 times hotter than BLACK is a surprise to most people...
So, if it sits in the sun, paint it white! If you dont believe this, put an aluminum baking sheet in the sun. I baked my first roof mount GPS stand alone tracker thinking that the upside down baking pan would reflect the sun... WRONG! Painted it white and it is now as cool as a cucumber.
The difference in Aluminum is the POOR EMISSIVITY at infrared. It can't radiate the heat away...
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Second thought on this: I painted my eme dish flat-gray for visual environmental reasons, but the color aids melting ice/snow from the surface. It was previously white.
73, Ed - KL7UW, WD2XSH/45 ====================================== BP40IQ 500 KHz - 10-GHz www.kl7uw.com 500-KHz/CW, 144-MHz EME, 1296-MHz EME DUBUS Magazine USA Rep dubususa@hotmail.com ======================================
Hi Bob, WB4APR
Very interesting !
73" de
i8CVS Domenico
----- Original Message ----- From: "Robert Bruninga" bruninga@usna.edu To: amsat-bb@amsat.org Sent: Wednesday, November 18, 2009 3:34 PM Subject: [amsat-bb] Satellite Thermal Lesson
Lesson learned on Satellite Thermal.
For years, we have been trying to demonstrate to students the extreme differences in Temperature of a satellite based simply on its color. In space, far from earth, here is what you should get for three identical satellites:
Black will be about +55 deg F White will be about -60 deg F Aluminum will be about +225 deg F
(from memory anyway)... But we have never been able to see the extreme temperature of the aluminum in our vacuum chamber. Of course, we are not using a SUN, but an incandescent lamp which has 95% of its radiation as heat and only 5% as light, so we attribtuted our wishy-washy results as due to the lack of real solar spectrum.
This year, we finally have a Tvac chamber that has a liguid nitrogen cold plate so we can actually better simulate the blackness (and cold) of space.. Again, same result. Aluminum was about the same as black. This was a frustrating result from this new chamber.
Then I noticed the fingerprints on the aluminum. I cleaned the aluminum with a swab of alcohol to eliminate all the surface contaminants, and fingerprints and re-did the test...
BINGO. Now the temperature of the aluminum goes up and off scale HOT, way way different from the black or White. And now the WHITE also goes colder..
So just the thinneest innvisible layer of surface contamination completely changed the thermal emissivity of the Aluminum. And we all know this anyway, since "low-E" coatings of glass and other materials is now so common. It is only the outer surface of molecules that set the absorbtivity and emissivity... And the differnce between Black and Aluminum is 30-to-1 (if the aluminum is clean)... That's why we wrap baked potatos in Aluminum foil! (don't use greasy hands)...
Of course we always clean our actual spacecraft to clean-room conditions before flight, so this does not impact our on-orbit results, but it sure does make a difference in the lab when we are demonstrating absorbtivity and emissivity in the chamber with samples handled by the students!
When I get a chance, Ill post the results...
Bob, WB4APR
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Please do post the results. excellent
Robert WB5MZO
From: bruninga@usna.edu To: amsat-bb@amsat.org Date: Wed, 18 Nov 2009 09:34:18 -0500 Subject: [amsat-bb] Satellite Thermal Lesson
Lesson learned on Satellite Thermal.
For years, we have been trying to demonstrate to students the extreme differences in Temperature of a satellite based simply on its color. In space, far from earth, here is what you should get for three identical satellites:
Black will be about +55 deg F White will be about -60 deg F Aluminum will be about +225 deg F
(from memory anyway)... But we have never been able to see the extreme temperature of the aluminum in our vacuum chamber. Of course, we are not using a SUN, but an incandescent lamp which has 95% of its radiation as heat and only 5% as light, so we attribtuted our wishy-washy results as due to the lack of real solar spectrum.
This year, we finally have a Tvac chamber that has a liguid nitrogen cold plate so we can actually better simulate the blackness (and cold) of space.. Again, same result. Aluminum was about the same as black. This was a frustrating result from this new chamber.
Then I noticed the fingerprints on the aluminum. I cleaned the aluminum with a swab of alcohol to eliminate all the surface contaminants, and fingerprints and re-did the test...
BINGO. Now the temperature of the aluminum goes up and off scale HOT, way way different from the black or White. And now the WHITE also goes colder..
So just the thinneest innvisible layer of surface contamination completely changed the thermal emissivity of the Aluminum. And we all know this anyway, since "low-E" coatings of glass and other materials is now so common. It is only the outer surface of molecules that set the absorbtivity and emissivity... And the differnce between Black and Aluminum is 30-to-1 (if the aluminum is clean)... That's why we wrap baked potatos in Aluminum foil! (don't use greasy hands)...
Of course we always clean our actual spacecraft to clean-room conditions before flight, so this does not impact our on-orbit results, but it sure does make a difference in the lab when we are demonstrating absorbtivity and emissivity in the chamber with samples handled by the students!
When I get a chance, Ill post the results...
Bob, WB4APR
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
_________________________________________________________________ Windows 7: I wanted simpler, now it's simpler. I'm a rock star. http://www.microsoft.com/Windows/windows-7/default.aspx?h=myidea?ocid=PID247...
Hi Bob,
Very interesting work. I appreciate you sharing the results. This issue of thermal stabilization has been a very interesting "art" although some will say it's a science. Your aluminum cleanliness find goes a long way to helping me understand it as science.
Regards...Bill - N6GHz
Robert Bruninga wrote:
Lesson learned on Satellite Thermal.
For years, we have been trying to demonstrate to students the extreme differences in Temperature of a satellite based simply on its color. In space, far from earth, here is what you should get for three identical satellites:
Black will be about +55 deg F White will be about -60 deg F Aluminum will be about +225 deg F
(from memory anyway)... But we have never been able to see the extreme temperature of the aluminum in our vacuum chamber. Of course, we are not using a SUN, but an incandescent lamp which has 95% of its radiation as heat and only 5% as light, so we attribtuted our wishy-washy results as due to the lack of real solar spectrum.
This year, we finally have a Tvac chamber that has a liguid nitrogen cold plate so we can actually better simulate the blackness (and cold) of space.. Again, same result. Aluminum was about the same as black. This was a frustrating result from this new chamber.
Then I noticed the fingerprints on the aluminum. I cleaned the aluminum with a swab of alcohol to eliminate all the surface contaminants, and fingerprints and re-did the test...
BINGO. Now the temperature of the aluminum goes up and off scale HOT, way way different from the black or White. And now the WHITE also goes colder..
So just the thinneest innvisible layer of surface contamination completely changed the thermal emissivity of the Aluminum. And we all know this anyway, since "low-E" coatings of glass and other materials is now so common. It is only the outer surface of molecules that set the absorbtivity and emissivity... And the differnce between Black and Aluminum is 30-to-1 (if the aluminum is clean)... That's why we wrap baked potatos in Aluminum foil! (don't use greasy hands)...
Of course we always clean our actual spacecraft to clean-room conditions before flight, so this does not impact our on-orbit results, but it sure does make a difference in the lab when we are demonstrating absorbtivity and emissivity in the chamber with samples handled by the students!
When I get a chance, Ill post the results...
Bob, WB4APR
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Hi Bob,
Interesting!
As it happens we have included a material science experiment/demonstration into the requirements for the educational payload of FUNcube. It will actually measure the temperature of two pieces of aluminium facing the same direction in space.
We had already concluded to have a black anodised finish on one and a silver finish on the other but we will now ensure that a final careful cleaning process is undertaken just before the satellite is placed in the deployer.
A very timely "heads up" for us.
Many thanks
Graham G3VZV
----- Original Message ----- From: "Robert Bruninga" bruninga@usna.edu To: amsat-bb@amsat.org Sent: Wednesday, November 18, 2009 2:34 PM Subject: [amsat-bb] Satellite Thermal Lesson
Lesson learned on Satellite Thermal.
For years, we have been trying to demonstrate to students the extreme differences in Temperature of a satellite based simply on its color. In space, far from earth, here is what you should get for three identical satellites:
Black will be about +55 deg F White will be about -60 deg F Aluminum will be about +225 deg F
(from memory anyway)... But we have never been able to see the extreme temperature of the aluminum in our vacuum chamber. Of course, we are not using a SUN, but an incandescent lamp which has 95% of its radiation as heat and only 5% as light, so we attribtuted our wishy-washy results as due to the lack of real solar spectrum.
This year, we finally have a Tvac chamber that has a liguid nitrogen cold plate so we can actually better simulate the blackness (and cold) of space.. Again, same result. Aluminum was about the same as black. This was a frustrating result from this new chamber.
Then I noticed the fingerprints on the aluminum. I cleaned the aluminum with a swab of alcohol to eliminate all the surface contaminants, and fingerprints and re-did the test...
BINGO. Now the temperature of the aluminum goes up and off scale HOT, way way different from the black or White. And now the WHITE also goes colder..
So just the thinneest innvisible layer of surface contamination completely changed the thermal emissivity of the Aluminum. And we all know this anyway, since "low-E" coatings of glass and other materials is now so common. It is only the outer surface of molecules that set the absorbtivity and emissivity... And the differnce between Black and Aluminum is 30-to-1 (if the aluminum is clean)... That's why we wrap baked potatos in Aluminum foil! (don't use greasy hands)...
Of course we always clean our actual spacecraft to clean-room conditions before flight, so this does not impact our on-orbit results, but it sure does make a difference in the lab when we are demonstrating absorbtivity and emissivity in the chamber with samples handled by the students!
When I get a chance, Ill post the results...
Bob, WB4APR
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
participants (8)
-
Bill Ress -
Bruce -
Edward Cole -
Graham Shirville -
i8cvs -
Idle-Tyme -
Robert Bruninga -
Rocky Jones