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
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