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CUBESAT easy rides to space...



On Fri, 23 Aug 2002, G. Beat (W9GB) wrote:

> This is encouraging.  Some type of adapter (ESPA) was going to be built -
> since many of the future military and commercial proposals are using mini or
> microsatellites designs (from Surrey, DoD contractors, others).

Having attended the AIAA/USU Small Satellite Conference this year, 30% of
the papers presented had to do with small NANO, PICO and the TINY CUBESATS
(4" on a side).  Since the cubesats give a standard size all expense and
integration costs included in a single price of $60K, it is a great way to
get into space and since this was mostly a governemnet, university and
commercial conference, the message was clear that there is LOTS of
interest here..

Interestingly, of the 30 or so small 4" cubesats under design and
construction, I have heard that about 18 of them are student built and
will be launched as amateur satellites conducting a variety of
experiments having loosely to do with the radio art.  Interestingly,
however, I dont know of any of them that are being built from the ground
up to serve the primary mission of general two-way comm transponders.  I
have personally encouraged all of the ones with AX.25 uplink and downlink
telemetry and command  to add UI digipeating as one of their mission
obejctives..

When you realize that many of these are schools just looking for an idea
to build a satellite around, its a shame that they dont have more contact
with HAM radio operators that can help guide them towards missions and
payloads that would be more popular with the large worldwide amateur
satllite community.

Of course, with a 1 Watt average power budget, (on a 4" satellite) its
hard to do much, but if you consider that the HAM population of the world
only covers about 10% of the area of the globe, and if you turn the
transmitter off over the other 90% of the globe, three is actually quite a
bit of transponder power available for short passes.

The big advantage of these cubesats is that they are launched 3 at a time
from a standard "P-POD" spring loaded tube, and as many as 6 to 15 of
these tubes can be affixed to a launch vehicle.  Thus each builder of a
CUBESAT only has to deliver a 4" working cube, and does not have to worry
one bit about any othere launcher integration isues...  And the Launcher
only has ONE interface to deal with to launch as many of these as the
rocket can hoist...

I would suggest that if  you have any ties with a university EE or
AEROSPACE program that you inquire around and see if they are working on a
CUBESAT or are interested in building one.  And then GET YOUR AMATEUR
COMMUNICATIONS ideas in there early...  They would love to have a mission
that their students could get excited about...

Going to the CUBESAT web site is probably too late to get in on the ground
floor, because by the time a school shows up there, they already have
their student ideas in place.  Find a school that hasn't thought of it
yet.  An MIT research prof was just touring my lab yesterday looking for
ideas on student projects.  He was not aware of CUBESATS, but said that
getting $50K together to launch one would not be a problem...  ANyone live
in Boston and has HAM radio ties to MIT?

I can think of MANY cubesat ideas that could work with the 1W power
budget:

1) FM voice mode B transponder
2) 3 to 5 Channel linear Mode B transponder
3) PCsat packet transponder
4) 10m PSK-31 ==> 2mFM transponder (20+ simultaneous users)

Ways to save power are:
1) Turn off transmitter and have receiver go to sleep mode when not in
view of serious HAM populatinos
2) Only operate it in the sun (daytime for school kids, weekends)
3) CUBESAT with popout solar panels to double power budget
4) Purchase a double or triple cube launch so you can have twice or
   3 times the power.
etc...

With modern electronics, SIZE is not an issue.  There were Magnetometers,
Magnitorquers, gravity booms, and even tiny grain-of-rice sized thrusters
being commercially produced for these 4" cubesats... all on show at the
conference.  At first I chuckled at the thought of thrusters, but then
when the satellite only weighs 1 Kg, a micro newton thruster can do a lot.
Not that they have any value for us, but the demonstrate that many
satellite system scale down to small size quite easily.

One thruster concept was simply a wire sticking out the side of the cube.
Every time you can charge up enough power to trigger a spark to the
aluminum case of the cubesat, you generate thrust!  The spark breaks the
bond of an aluminum atom and you get a tremendous specific impulse (but at
a microscopic scale).  In effect, you are using your aluminum frame for
fuel...  THink of the fun figuring out how high you can go with that
one...

de WB4APR@amsat.org, Bob

old (not current) CUBESAT Design ideas:
http://www.ew.usna.edu/~bruninga/cubesat.html

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