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CX2SA > SATDIG 19.11.09 13:04l 889 Lines 30153 Bytes #999 (0) @ WW
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Today's Topics:
1. Re: AMSAT, ITAR, More AMSAT-NA Volunteers & Such . (Alex, N3SQ)
2. Re: AMSAT, ITAR, More AMSAT-NA Volunteers & Such .
(Alan P. Biddle)
3. SatPC32 Auto Doppler (Howard Kowall)
4. Re: SatPC32 Auto Doppler (Howard Kowall)
5. Re: Problem with Basic Stamp based tracker box serial display
(Mark L. Hammond)
6. Re: SatPC32 Auto Doppler (Mark L. Hammond)
7. EK19 activation !! (Alvaro de Leon Romo)
8. Re: SatPC32 Auto Doppler (Erich Eichmann)
9. PREDICT/Linux question (Rich Dailey)
10. Re: PREDICT/Linux question (Andrew Rich)
11. Satellite Thermal Lesson (Robert Bruninga)
12. Re: Satellite Thermal Lesson (Bruce)
13. Re: PREDICT/Linux question (Rich Dailey (Gmail))
14. Re: Satellite Thermal Lesson (i8cvs)
15. Re: Satellite Thermal Lesson (Idle-Tyme)
16. Re: Satellite Thermal Lesson (Rocky Jones)
17. Re: Satellite Thermal Lesson (Bill Ress)
----------------------------------------------------------------------
Message: 1
Date: Tue, 17 Nov 2009 15:01:32 -0500
From: "Alex, N3SQ" <amsat@xxxxxx.xxx>
Subject: [amsat-bb] Re: AMSAT, ITAR, More AMSAT-NA Volunteers & Such
.
To: amsat-bb@xxxxx.xxx
Message-ID: <4B03011C.2090400@xxxxxx.xxx>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Michael, W4HIJ wrote:
>Interesting stuff Alex.
> I'm currently working on an FM satellite station as that's all I can
>afford at present but I hope some of the NextGen birds will carry linear
>transponders too. At any rate, it all sounds very exciting.
>73,
>Michael W4HIJ
>
ARISSat-1 is flying a V/U Linear transponder with the 10.7MHz IF SDX board,
the NextGen bus will fly the same equipment.
I'm hoping that we can fly an L/S Linear transponder & 10.7MHz IF Matrix as
payload on the NextGen satellites.
They're not going to be the most powerful transmitters nor the largest
antennas flown, since we've got a limited power, mass, and volume budget.
Remember, we're talking about a 3kg mass budget, a 3 liter (10cm x 10cm x
30cm) volume budget and an 8w DC power budget for the spacecraft
. . . Think the size of a loaf of bread.
Alex, N3NP
------------------------------
Message: 2
Date: Tue, 17 Nov 2009 14:44:20 -0600
From: "Alan P. Biddle" <APBIDDLE@xxxxxx.xxx>
Subject: [amsat-bb] Re: AMSAT, ITAR, More AMSAT-NA Volunteers & Such .
To: "'Alex, N3SQ'" <amsat@xxxxxx.xxx>
Cc: AMSAT-BB <amsat-bb@xxxxx.xxx>
Message-ID: <7A51316B8A224D5699B5FB3C8A03601A@xxxxxx>
Content-Type: text/plain; charset="us-ascii"
Alex,
Actually, the most recent revision of the cubesat specification bumps a 1U
cubesat to 1.33 kg, or 4 kg for a 3U cubesat. See section 1.1, pg 5.
http://cubesat.atl.calpoly.edu/media/CDS_rev12.pdf
But don't go crazy with that extra mass. ;)
Alan
WA4SCA
-----Original Message-----
From: amsat-bb-bounces@xxxxx.xxx [mailto:amsat-bb-bounces@xxxxx.xxxx On
Behalf Of Alex, N3SQ
Sent: 17 November, 2009 14:02
To: amsat-bb@xxxxx.xxx
Subject: [amsat-bb] Re: AMSAT, ITAR, More AMSAT-NA Volunteers & Such .
Michael, W4HIJ wrote:
>Interesting stuff Alex.
> I'm currently working on an FM satellite station as that's all I can
>afford at present but I hope some of the NextGen birds will carry linear
>transponders too. At any rate, it all sounds very exciting.
>73,
>Michael W4HIJ
>
ARISSat-1 is flying a V/U Linear transponder with the 10.7MHz IF SDX board,
the NextGen bus will fly the same equipment.
I'm hoping that we can fly an L/S Linear transponder & 10.7MHz IF Matrix as
payload on the NextGen satellites.
They're not going to be the most powerful transmitters nor the largest
antennas flown, since we've got a limited power, mass, and volume budget.
Remember, we're talking about a 3kg mass budget, a 3 liter (10cm x 10cm x
30cm) volume budget and an 8w DC power budget for the spacecraft
. . . Think the size of a loaf of bread.
Alex, N3NP
_______________________________________________
Sent via AMSAT-BB@xxxxx.xxx. 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
------------------------------
Message: 3
Date: Tue, 17 Nov 2009 15:06:55 -0600
From: "Howard Kowall" <hkowall@xxxx.xx>
Subject: [amsat-bb] SatPC32 Auto Doppler
To: "AMSAT-BB@xxxxx.xxxx <amsat-bb@xxxxx.xxx>
Message-ID: <000801ca67c9$e54a4e20$6701a8c0@xxxxxxxxx>
Content-Type: text/plain; charset="iso-8859-1"
Hello to everyone
Is it possible to use SatPC32 12.8a without auto Doppler correction?
I use 2 separate transceiver one for uplink the other for downlink,all I
want to do is be able to change the downlink freq. and let the uplink follow
according to the Doppler sqf file.I want no automatic Doppler correction
just transparent tuning.
Thanks to all who read this
Howard
VE4ISP
------------------------------
Message: 4
Date: Tue, 17 Nov 2009 15:16:09 -0600
From: "Howard Kowall" <hkowall@xxxx.xx>
Subject: [amsat-bb] Re: SatPC32 Auto Doppler
To: "AMSAT-BB@xxxxx.xxxx <amsat-bb@xxxxx.xxx>
Message-ID: <002101ca67cb$2f2227b0$6701a8c0@xxxxxxxxx>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
Follow up to my last post
So really what I want to do is to make 2 tranceiver,to act like a
FT847,FT736,IC910,etc.
Thanks again
Howard
VE4ISP
----- Original Message -----
From: "Howard Kowall" <hkowall@xxxx.xx>
To: "AMSAT-BB@xxxxx.xxxx <amsat-bb@xxxxx.xxx>
Sent: Tuesday, November 17, 2009 3:06 PM
Subject: [amsat-bb] SatPC32 Auto Doppler
> Hello to everyone
> Is it possible to use SatPC32 12.8a without auto Doppler correction?
> I use 2 separate transceiver one for uplink the other for downlink,all I
> want to do is be able to change the downlink freq. and let the uplink
> follow according to the Doppler sqf file.I want no automatic Doppler
> correction just transparent tuning.
> Thanks to all who read this
> Howard
> VE4ISP
>
> _______________________________________________
> Sent via AMSAT-BB@xxxxx.xxx. 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
------------------------------
Message: 5
Date: Tue, 17 Nov 2009 20:20:00 -0500
From: "Mark L. Hammond" <marklhammond@xxxxx.xxx>
Subject: [amsat-bb] Re: Problem with Basic Stamp based tracker box
serial display
To: amsat-bb@xxxxx.xxxx mat_62@xxxxxxxxxxxx.xxx
Message-ID:
<5d8cecfe0911171720u379d1b5eh47c7910dbaa6e2b9@xxxx.xxxxx.xxx>
Content-Type: text/plain; charset=ISO-8859-1
Hi Michael,
Greg has given you sound advice about checking the voltage to the LCD.
The only problem I've ever had with the LCD was related to a BAD
CONNECTION to the pins on the LCD. It exhibited similar symptoms as
what you describe. I found that it lost good contact and would cause
the display to go dim or OFF. Took me a little checking to figure
that one out. Other than, I've had no issue with my SAEBRTrack
box..but then again, I helped design it ;)
Glad to see your return to the birds!!
73,
Mark N8MH (formerly KC4EBR, and thus the EBR in SAEBRTrack)
_______________
Hi Michael,
When the display dies, does the rest of the box keep working? If the whole
thing dies, then I'd suspect the 7805 (5v) power supply. Does the 7805 get
hot? If so, that's the problem; they have a built-in thermal shutdown for
over-temp and/or over-current. What sort of heat sink do you have on it?
If the problem is limited to the display, then I'd take a look at what's
feeding it, power-wise, if it's different than the rest of the board. Again,
I'd first look for things that are running too warm.
If there's no heat problem, I'd next look for RF problems, or other things
that
can be cured with better shielding or grounding. My controller (also
Stamp-based) was extremely sensitive to the electric glitches created when the
motors were turned off. Kept losing its mind; I fixed it by adding more
bypass
caps around the board.
Good luck,
Greg KO6TH
> Date: Mon, 16 Nov 2009 19:23:08 -0500
> From: mat_62@xxxxxxxxxxxx.xxx
> To: amsat-bb@xxxxx.xxx
> Subject: [amsat-bb] Problem with Basic Stamp based tracker box serial
display
>
> I have a a homebrew tracking box designed around a Basic Stamp. It's
> known as the SaebrTrack, I built it from an article on the web. The
> circuit uses an LED display with a serial "backpack" attached from
> Scott Edwards electronics to display the Azimuth and Elevation readings.
> The information is fed to it from the Basic Stamp.
> Lately the display light will start flickering at times and then the
> letters will fade out completely as well. It takes turning the box off
> and back on to bring them back up. This seems to be a sporadic
> occurrence and can happen when the box is turning the rotators or
> sitting idle. There is no rotator control box, the entire operation is
> handled by this unit.
> I just basically read the schematic and built this thing and then
> loaded the Stamp with the software. I'm not well versed in this
> technology. Could this be something as simple as voltage regulation?
> There is a 12V transformer that runs the DC rotator motors and a
> separate 6V transformer that takes care of the display and indicator
> lights as well as feeding voltage to the position pots on the rotators.
> I believe there is a 7805 regulator in the 6V circuit if memory serves.
> Any thoughts or ideas? I've checked for loose connections. Could the
> serial backpack display itself be causing this?
> Any help would be appreciated. It gets kind of annoying when it happens.
> Tnx and 73,
> Michael, W4HIJ
--
Mark L. Hammond [N8MH]
------------------------------
Message: 6
Date: Tue, 17 Nov 2009 20:34:35 -0500
From: "Mark L. Hammond" <marklhammond@xxxxx.xxx>
Subject: [amsat-bb] Re: SatPC32 Auto Doppler
To: hkowall@xxxx.xxx amsat-bb@xxxxx.xxx
Message-ID:
<5d8cecfe0911171734u28e0b1c2n817b31e630fa896@xxxx.xxxxx.xxx>
Content-Type: text/plain; charset=ISO-8859-1
Hi Howard,
I think the answer is "yes" you can do what you want to do. SatPC32
12.8a is really good with 2 radios. I've had it running a TS-2000x
and an IC-910H at the same time, in both directions, meaning one radio
xmit, the other receive--and flip flopped from that, too. It works!
Oh, I tried the IC-910H with a FT-817, too. Worked fine.
What 2 radios are you trying to configure, and which one do you want
to Xmit and which one receive?
The configuration is under the Radio setup window. You need to setup
both radios. Try one radio as Radio 1, then the other as Radio 2. If
you have the xmit/receive setup backwards, just set them up the other
way.
73,
Mark N8MH
---------
Follow up to my last post
So really what I want to do is to make 2 tranceiver,to act like a
FT847,FT736,IC910,etc.
Thanks again
Howard
VE4ISP
----- Original Message -----
From: "Howard Kowall" <hkowall@xxxx.xx>
To: "AMSAT-BB@xxxxx.xxxx <amsat-bb@xxxxx.xxx>
Sent: Tuesday, November 17, 2009 3:06 PM
Subject: [amsat-bb] SatPC32 Auto Doppler
> Hello to everyone
> Is it possible to use SatPC32 12.8a without auto Doppler correction?
> I use 2 separate transceiver one for uplink the other for downlink,all I
> want to do is be able to change the downlink freq. and let the uplink
> follow according to the Doppler sqf file.I want no automatic Doppler
> correction just transparent tuning.
> Thanks to all who read this
> Howard
> VE4ISP
--
Mark L. Hammond [N8MH]
------------------------------
Message: 7
Date: Tue, 17 Nov 2009 19:52:21 -0600
From: Alvaro de Leon Romo <xe2at@xxxxxxx.xxx>
Subject: [amsat-bb] EK19 activation !!
To: <sat-xe@xxxxxxxxxxx.xxx>
Cc: amsat-bb@xxxxx.xxx
Message-ID: <BAY108-W415507235E415D77572CBBF5A30@xxx.xxx>
Content-Type: text/plain; charset="iso-8859-1"
Hi I will fly to Veracruz and I will activate EK19 the 18th in SO50 at 2055
and 2236 UTC pass, I will try AO27 at 2006 pass the 18th also....
GL all
Ps all depend of weather..
Al XE2AT
_________________________________________________________________
Tlike a
> FT847,FT736,IC910,etc.
> Thanks again
> Howard
> VE4ISP
>
> ----- Original Message -----
> From: "Howard Kowall" <hkowall@xxxx.xx>
> To: "AMSAT-BB@xxxxx.xxxx <amsat-bb@xxxxx.xxx>
> Sent: Tuesday, November 17, 2009 3:06 PM
> Subject: [amsat-bb] SatPC32 Auto Doppler
>
>
>> Hello to everyone
>> Is it possible to use SatPC32 12.8a without auto Doppler correction?
>> I use 2 separate transceiver one for uplink the other for downlink,all I
>> want to do is be able to change the downlink freq. and let the uplink
>> follow according to the Doppler sqf file.I want no automatic Doppler
>> correction just transparent tuning.
>> Thanks to all who read this
>> Howard
>> VE4ISP
>>
>> _______________________________________________
>> Sent via AMSAT-BB@xxxxx.xxx. 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
>
> _______________________________________________
> Sent via AMSAT-BB@xxxxx.xxx. 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
>
------------------------------
Message: 9
Date: Wed, 18 Nov 2009 08:49:47 -0500
From: Rich Dailey <richdailey@xxxxxxxxxx.xxx>
Subject: [amsat-bb] PREDICT/Linux question
To: amsat-bb@xxxxx.xxx
Message-ID: <7.0.0.16.2.20091118084248.02411320@xxxxxxxxxx.xxx>
Content-Type: text/plain; charset="us-ascii"
After a Linux hiatus of a few years, I setup an spare pc with Linux Mint, an
offshoot of Ubuntu. Through the software manager (gee, thing have become
easier since
my last Linux adventure) I was able to install the latest Predict software.
When I run it, it
first asks for my station info. I enter this, and at the last <cr> it kicks
me back out to the terminal
prompt.
Anyone else had this issue?
Thanks,
Rich, N8UX
------------------------------
Message: 10
Date: Thu, 19 Nov 2009 00:11:37 +1000
From: "Andrew Rich" <vk4tec@xxxxxxxxxxxxx.xxx>
Subject: [amsat-bb] Re: PREDICT/Linux question
To: <amsat-bb@xxxxx.xxx>, "Rich Dailey" <richdailey@xxxxxxxxxx.xxx>
Message-ID: <015397B9270C40E8A349151F0041FC74@xxxxxxxxxx>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
Yes several times
You can edit /root/.predict/predict.qth
VK4TEC
-27.300
-153.10
25
I am -27.300 S 153.10 E
Yes predict is backwards
Andrew
----- Original Message -----
From: "Rich Dailey" <richdailey@xxxxxxxxxx.xxx>
To: <amsat-bb@xxxxx.xxx>
Sent: Wednesday, November 18, 2009 11:49 PM
Subject: [amsat-bb] PREDICT/Linux question
> After a Linux hiatus of a few years, I setup an spare pc with Linux Mint,
> an
> offshous found in this incoming message.
Checked by AVG - www.avg.com
Version: 8.5.425 / Virus Database: 270.14.71/2510 - Release Date: 11/17/09
19:26:00
------------------------------
Message: 11
Date: Wed, 18 Nov 2009 09:34:18 -0500
From: "Robert Bruninga" <bruninga@xxxx.xxx>
Subject: [amsat-bb] Satellite Thermal Lesson
To: <amsat-bb@xxxxx.xxx>
Message-ID: <4875C9F79EA0422B930AEA05C8493550@xxxxx.xxxx.xxx>
Content-Type: text/plain; charset="us-ascii"
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
------------------------------
Message: 12
Date: Wed, 18 Nov 2009 08:46:11 -0600
From: Bruce <kk5do@xxxxx.xxx>
Subject: [amsat-bb] Re: Satellite Thermal Lesson
To: bruninga@xxxx.xxx
Cc: amsat-bb@xxxxx.xxx
Message-ID: <4B0408B3.1030302@xxxxx.xxx>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
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...
------------------------------
Message: 13
Date: Wed, 18 Nov 2009 10:39:55 -0500
From: "Rich Dailey (Gmail)" <redailey1@xxxxx.xxx>
Subject: [amsat-bb] Re: PREDICT/Linux question
To: Andrew Rich <vk4tec@xxxxxxxxxxxxx.xxx>
Cc: amsat-bb@xxxxx.xxx
Message-ID: <7.0.0.16.2.20091118103909.0493b018@xxxxx.xxx>
Content-Type: text/plain; charset="us-ascii"
Thanks! Got it working... Rich, N8UX
At 09:11 AM 11/18/2009, you wrote:
>Yes several times
>
>You can edit /root/.predict/predict.qth
------------------------------
Message: 14
Date: Wed, 18 Nov 2009 16:50:37 +0100
From: "i8cvs" <domenico.i8cvs@xxx.xx>
Subject: [amsat-bb] Re: Satellite Thermal Lesson
To: "Bob Bruninga" <bruninga@xxxx.xxx>, "AMSAT-BB"
<amsat-bb@xxxxx.xxx>
Message-ID: <002701ca6866$df7637a0$0201a8c0@xxx.xx>
Content-Type: text/plain; charset="iso-8859-1"
Hi Bob
> 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@xxxxx.xxx. 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
------------------------------
Message: 15
Date: Wed, 18 Nov 2009 10:33:06 -0600
From: Idle-Tyme <nss@xxx.xxx>
Subject: [amsat-bb] Re: Satellite Thermal Lesson
To: kk5do@xxxxx.xxx
Cc: amsat-bb@xxxxx.xxx
Message-ID: <4B0421C2.5060707@xxx.xxx>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
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 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...
>
>
>
>
>
> _______________________________________________
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> 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
>
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------------------------------
Message: 17
Date: Wed, 18 Nov 2009 08:52:42 -0800
From: Bill Ress <bill@xxxxxxxxxxx.xxx>
Subject: [amsat-bb] Re: Satellite Thermal Lesson
To: bruninga@xxxx.xxx
Cc: amsat-bb@xxxxx.xxx
Message-ID: <4B04265A.2080707@xxxxxxxxxxx.xxx>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
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 acecraft 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@xxxxx.xxx. 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
>
------------------------------
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Sent via amsat-bb@xxxxx.xxx. Opinions expressed are those of the author.
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End of AMSAT-BB Digest, Vol 4, Issue 612
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