John, Juan, Bob D., & Bob M.:
I have been preparing for my presentation to the Space Symposium on the subject of internal module heat sinks. As a concurrent subject, not in my paper, I have been preparing to discuss the temperatures that modules can achieve during a solar eclipse of the Eagle satellite. In this vein, things do get interesting and pretty darned chilly. I am showing the outboard, deployed solar panels getting down to the -117°C to -125°C! I also show body-mounted solar panels getting down to -81°C and other body sheet metal in the -60°C range.
This analytic effort has pretty heavily exercised this new, high speed computer with some runs taking from 40 to 70 minutes, that is a lot of number crunching!
The spaceframe temperatures for the start of the analysis was set at +10°C and modules at +20°C.
For the modules I have analyzed both power off and with modest power dissipation in some modules. Some modules, with the necessary coatings to be able to handle 3.5W dissipation (e.eg. the URx in full operation), show a considerably deeper cooling than those with only the lowest emittance of a low-power module. Unpowered, or those with very low dissipation, show temperatures near to zero Celsius after three hours of eclipse while those of the higher emittance, for higher power operation, can get down to -30° to -38°C in that same time. This clearly illustrates why I have been pushing, wherever possible, to keep the module emittance low and to keep the module thermally decoupled from the spacecraft to the greatest extent possible. It also reinforces my high degree of upset with our German friends who painted not only the inside of their P3E modules black, but did me a favor by painting the outside black as well, failing to follow my instructions. The P3E situation will have to be dealt with as another issue.
In eclipse, modules with low emittance and modest power dissipation show temperatures of +10° to +20°C. But the modules with the necessarily higher emittances, and dissipating a modest 1.0W of power, are only 10°C warmer than the unpowered condition, running at -25° to -28°C.
I need to further refine this analytic model and to try different power dissipation situations. I felt, however, that it was necessary for me to report the results of these analyses to you at this time. These results are in line with the AO-10 telemetry for an eclipse condition, that was reported to me many years ago.
73,
Dick Jansson, KD1K
kd1k@amsat.org
kd1k@arrl.net
I'm planning on cutting power dissipation in the U-band receiver to 3 W maximum in the next version. The SAW filters should then remain above -35 C under any conditions.
73,
John KD6OZH ----- Original Message ----- From: Dick Jansson-rr To: AMSAT Eagle Sent: Saturday, September 15, 2007 20:16 UTC Subject: [eagle] Module Temperatures & Eclipse
John, Juan, Bob D., & Bob M.:
I have been preparing for my presentation to the Space Symposium on the subject of internal module heat sinks. As a concurrent subject, not in my paper, I have been preparing to discuss the temperatures that modules can achieve during a solar eclipse of the Eagle satellite. In this vein, things do get interesting and pretty darned chilly. I am showing the outboard, deployed solar panels getting down to the -117°C to -125°C! I also show body-mounted solar panels getting down to -81°C and other body sheet metal in the -60°C range.
This analytic effort has pretty heavily exercised this new, high speed computer with some runs taking from 40 to 70 minutes, that is a lot of number crunching!
The spaceframe temperatures for the start of the analysis was set at +10°C and modules at +20°C.
For the modules I have analyzed both power off and with modest power dissipation in some modules. Some modules, with the necessary coatings to be able to handle 3.5W dissipation (e.eg. the URx in full operation), show a considerably deeper cooling than those with only the lowest emittance of a low-power module. Unpowered, or those with very low dissipation, show temperatures near to zero Celsius after three hours of eclipse while those of the higher emittance, for higher power operation, can get down to -30° to -38°C in that same time. This clearly illustrates why I have been pushing, wherever possible, to keep the module emittance low and to keep the module thermally decoupled from the spacecraft to the greatest extent possible. It also reinforces my high degree of upset with our German friends who painted not only the inside of their P3E modules black, but did me a "favor" by painting the outside black as well, failing to follow my instructions. The P3E situation will have to be dealt with as another issue.
In eclipse, modules with low emittance and modest power dissipation show temperatures of +10° to +20°C. But the modules with the necessarily higher emittances, and dissipating a modest 1.0W of power, are only 10°C warmer than the unpowered condition, running at -25° to -28°C.
I need to further refine this analytic model and to try different power dissipation situations. I felt, however, that it was necessary for me to report the results of these analyses to you at this time. These results are in line with the AO-10 telemetry for an eclipse condition, that was reported to me many years ago.
'73,
Dick Jansson, KD1K
kd1k@amsat.org
kd1k@arrl.net
------------------------------------------------------------------------------
_______________________________________________ Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
John and group,
This is even better that trying to warm the filters with heaters! Have you receiver the SAW filters yet?
Juan
_____
From: eagle-bounces@amsat.org [mailto:eagle-bounces@amsat.org] On Behalf Of John B. Stephensen Sent: Saturday, September 15, 2007 3:54 PM To: Dick Jansson-rr; AMSAT Eagle Subject: [eagle] Re: Module Temperatures & Eclipse
I'm planning on cutting power dissipation in the U-band receiver to 3 W maximum in the next version. The SAW filters should then remain above -35 C under any conditions.
73,
John
KD6OZH
----- Original Message -----
From: Dick Jansson-rr mailto:rjansson@cfl.rr.com
To: AMSAT Eagle mailto:eagle@amsat.org
Sent: Saturday, September 15, 2007 20:16 UTC
Subject: [eagle] Module Temperatures & Eclipse
John, Juan, Bob D., & Bob M.:
I have been preparing for my presentation to the Space Symposium on the subject of internal module heat sinks. As a concurrent subject, not in my paper, I have been preparing to discuss the temperatures that modules can achieve during a solar eclipse of the Eagle satellite. In this vein, things do get interesting and pretty darned chilly. I am showing the outboard, deployed solar panels getting down to the -117°C to -125°C! I also show body-mounted solar panels getting down to -81°C and other body sheet metal in the -60°C range.
This analytic effort has pretty heavily exercised this new, high speed computer with some runs taking from 40 to 70 minutes, that is a lot of number crunching!
The spaceframe temperatures for the start of the analysis was set at +10°C and modules at +20°C.
For the modules I have analyzed both power off and with modest power dissipation in some modules. Some modules, with the necessary coatings to be able to handle 3.5W dissipation (e.eg. the URx in full operation), show a considerably deeper cooling than those with only the lowest emittance of a low-power module. Unpowered, or those with very low dissipation, show temperatures near to zero Celsius after three hours of eclipse while those of the higher emittance, for higher power operation, can get down to -30° to -38°C in that same time. This clearly illustrates why I have been pushing, wherever possible, to keep the module emittance low and to keep the module thermally decoupled from the spacecraft to the greatest extent possible. It also reinforces my high degree of upset with our German friends who painted not only the inside of their P3E modules black, but did me a favor by painting the outside black as well, failing to follow my instructions. The P3E situation will have to be dealt with as another issue.
In eclipse, modules with low emittance and modest power dissipation show temperatures of +10° to +20°C. But the modules with the necessarily higher emittances, and dissipating a modest 1.0W of power, are only 10°C warmer than the unpowered condition, running at -25° to -28°C.
I need to further refine this analytic model and to try different power dissipation situations. I felt, however, that it was necessary for me to report the results of these analyses to you at this time. These results are in line with the AO-10 telemetry for an eclipse condition, that was reported to me many years ago.
73,
Dick Jansson, KD1K
kd1k@amsat.org
kd1k@arrl.net
_____
_______________________________________________ Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Hi Dick,
Thanks for the information. As you know, the SAW filters are rated for a minimum operating temperature of -35C and storage of -40C. We might need to get creative and attach miniature strip heaters to those to keep them warm. As soon as John gets his IF test board running and tuned up I want to do a temp run to see how they behave over temperature. They appear to be very touchy in terms of matching. The matching appears to be the cause of the passband ripple weve been fighting. With luck well have some information to share at the symposium
73,
Juan
_____
From: eagle-bounces@amsat.org [mailto:eagle-bounces@amsat.org] On Behalf Of Dick Jansson-rr Sent: Saturday, September 15, 2007 1:17 PM To: AMSAT Eagle Subject: [eagle] Module Temperatures & Eclipse
John, Juan, Bob D., & Bob M.:
I have been preparing for my presentation to the Space Symposium on the subject of internal module heat sinks. As a concurrent subject, not in my paper, I have been preparing to discuss the temperatures that modules can achieve during a solar eclipse of the Eagle satellite. In this vein, things do get interesting and pretty darned chilly. I am showing the outboard, deployed solar panels getting down to the -117°C to -125°C! I also show body-mounted solar panels getting down to -81°C and other body sheet metal in the -60°C range.
This analytic effort has pretty heavily exercised this new, high speed computer with some runs taking from 40 to 70 minutes, that is a lot of number crunching!
The spaceframe temperatures for the start of the analysis was set at +10°C and modules at +20°C.
For the modules I have analyzed both power off and with modest power dissipation in some modules. Some modules, with the necessary coatings to be able to handle 3.5W dissipation (e.eg. the URx in full operation), show a considerably deeper cooling than those with only the lowest emittance of a low-power module. Unpowered, or those with very low dissipation, show temperatures near to zero Celsius after three hours of eclipse while those of the higher emittance, for higher power operation, can get down to -30° to -38°C in that same time. This clearly illustrates why I have been pushing, wherever possible, to keep the module emittance low and to keep the module thermally decoupled from the spacecraft to the greatest extent possible. It also reinforces my high degree of upset with our German friends who painted not only the inside of their P3E modules black, but did me a favor by painting the outside black as well, failing to follow my instructions. The P3E situation will have to be dealt with as another issue.
In eclipse, modules with low emittance and modest power dissipation show temperatures of +10° to +20°C. But the modules with the necessarily higher emittances, and dissipating a modest 1.0W of power, are only 10°C warmer than the unpowered condition, running at -25° to -28°C.
I need to further refine this analytic model and to try different power dissipation situations. I felt, however, that it was necessary for me to report the results of these analyses to you at this time. These results are in line with the AO-10 telemetry for an eclipse condition, that was reported to me many years ago.
73,
Dick Jansson, KD1K
kd1k@amsat.org
kd1k@arrl.net
participants (3)
-
Dick Jansson-rr -
John B. Stephensen -
Juan Rivera