Juan & John:
I have finally been able to achieve some analytical results for projecting
the temperatures of Eagle modules after two hour and three hour eclipse
periods of no-solar heating. This has taken some time as I was struggling
with the proper use of the SINDA software and had to call for some help
which is why we pay money for the license, it comes with help when needed.
(I should also note that with modern versions of this software and a pricey,
but fast and capable, Dell computer, these analytic runs only required 18
seconds of real run time!)
Nevertheless, I have been able to get some believable modeling results. The
spacecraft model used is what I now call Small Eagle, the formerly
proposed, but rejected 600x600x435mm spaceframe structure. While this is not
as large as our currently planned hexagonal structure, the equipment bays
are just about the same size as the larger spaceframe. I ran the model with
one of the E05 20, 125x180mm, modules with coatings with an effective
emittance of about 0.45, rather than 0.04, as would have to be done for the
URx module. There was essentially no power dissipations in any module, at
the most about 20mW in a few modules. This is granted to be an abnormal
situation, but I wanted to see what happens. A later run was made with only
a total spacecraft power dissipation of only 7mW were only lower by 0.1°C to
0.2°C lower temperatures.
Modules started out at temperatures of +20°C and the spaceframe core
structure at +10°C. The propellant tank was empty so it did not contribute
any large thermal mass to delaying the cool-down. After two hours of eclipse
the module temperatures were -5.2°C to -5.4°C (with the high emittance
module being cooler), and after three hours of eclipse the module
temperatures were -15.9°C to -16.2°C. The spaceframe core structure
(equipment panels) were down to -10.2°C and -19.4°C respectively. For these
cooling periods, the spacecraft outer skin temperatures ranged from -35°C
down to -55°C. The deployed solar panels became a bit chilly, down to
A subsequent SINDA run was made with some kind of useful power dissipations
in modules 0.5W to 1.0W not large but supposedly enough to keep things
from getting out of hand, and with a total spacecraft dissipation of 16.5W.
The two hour eclipse temperatures ran from -3.4°C (1.0W) to -3.9°C. In three
hours of eclipse the module temperatures were at -13.3°C down to -14.0°C. In
other words, these levels of power dissipation did not significantly warm
the modules. The spaceframe core temperatures were at -8.0°C and -16.3°C
respectively., just a few degrees warmer.
What this data tells me is that specifying the cold temperature of a
module does not have to be much lower than -20°C, and if it is operating at
all they can be only a little higher. Cold module temperatures certainly do
not need to be in the -60°C range. Beyond these statements, I shall not
presume to be a specification writer.
Dick Jansson, KD1K
Sooner or later, we need to publish more. Publishing in QST would bring
our efforts to widespread attention, which could help many things.
Well, we may have our chance:
* QST Wants You!: Have you ever thought of writing an article for QST?
The official journal of ARRL, the national association for Amateur
Radio, QST is always on the lookout for articles that explore all the
possibilities of ham radio. We are looking for stories and articles that
present a project or idea that is useful and engaging to most hams. The
story you have had brewing in your head for months might be perfect for
QST or the ARRLWeb. For the Web, we're looking for short (1500 words
maximum), general-interest articles that tell a particularly interesting
story. At least one photo to accompany the story is mandatory. Send your
submissions to QST Managing Editor Joel Kleinman, N1BKE <qst(a)arrl.org>.
If you've something to submit, go for it. I'll be happy to help as a
reviewer or whatever, but I will not get in the way as a gatekeeper. If
you want to write for QST, PLEASE DO!!
It is that time of year again. I need to compose my report of things
accomplished, things projected to be accomplished next year, and
projections of funds required to accomplish those things. Your
unexpended funding requests from this year will NOT be rolled in to next
yea -- we start over.
I need your input (or negatives) on progress, projections, funds
expended, and funds projected to be expended in 08.
I need this information by 15 Sep 07 so that I can formulate my report
to the BoD in Oct.
Questions: Please contact me asap.
Thanks & 73,
I've posted the schematic and assembly drawing for the U-band receiver test
fixture on the U-band receiver page in EaglePedia just above the receiver
fabrication section. This PCB was made to test a way to tune the matching
networks for the narrow-band SAW filters. I also added a new second mixer
and IF amplifier so that changes to reduce thermal dissipation in revision B
of the receiver can be tested. Note that the average DC power consumed by
first IF amplifier, second mixer and second IF amplifier drops from 870 mW
to 370 mW. The circuit should exceed the specifications in the
recently-revised U-band receiver requiremnts document.
Since there has been a lot of discussion on the CAN-DO power supply
considerations, I thought I would pass on what the Suitsat-2 people are
They seem to have settled on using the Newport NMV series of COTS
isolated supply modules. I've attached 2 PDF files that describe the
units for your information.
Sorry I had to bail, but it was a REALLY URGENT phone call. You were
all long gone before I got off the phone. Gould, pls send me a synopsis
of the discussion after I left.
Thanks & 73,.