[eagle] Cool Model

Dick Jansson-rr rjansson at cfl.rr.com
Sun Jun 17 14:11:58 PDT 2007


Bob:
 
I have done some experimental work with a satellite in the eclipse mode of
cooling using the currently active P3E files. The results are a little bit
tongue in cheek, but I shall report them nonetheless as these results may
help the Eagle team. The reason for my caution is that some of the results
are a bit uncertain in my mind, but useful to others.
 
The P3E model had the sun "turned off" for a 2 hour period and pretty well
powered down save for a command receiver, a beacon transmitter, and the IHU.
The geometry of these modules, and their placement in the P3E spaceframe,
bears no resemblance to the Eagle modules, which certainly is a point of
caution.
 
The results of these analyses, one with propellant (a very substantial
thermal mass) and one without the propellant. I shall report two
temperatures, one for the model with propellant and the other without the
propellant. Solar panels really get chilly, as expected, as do the internal
equipment panels. So here goes, all temperatures in degrees Celsius:
 
Solar Panels:                 -45.7/-51.6
Equipment Panels  :     -22.6/-29.5
Top & Bottom Panels:  -30.0/-36.6
Central Cylinder:           -10.7/-26.7
L Receiver:                       0.0/-2.0
U-V Transmitter:           -12.2/-14.2
 
I shall not report the IHU temperatures as I don't believe them and have not
yet been able to understand them. The LRx was dissipating 2.0W while mounted
on top of a box dissipating 0.4W, the U-V Tx dissipating only 2.0W, with a
total dissipation of only 6.2W. The power dissipation is modest but so to is
the P3E battery energy. 
 
What these numbers tell me is that there is hope that the Eagle equipment
would not even see -20°C, but I feel that  -30°C should be used as a bottom
limit number. This caution is based on the fact that the Eagle geometry is
not nearly as closely packed as is P3E.
 
Dick Jansson, KD1K
 <mailto:kd1k at amsat.org> kd1k at amsat.org 
 <mailto:kd1k at arrl.net> kd1k at arrl.net 
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