[Ground-station] Yes, you can buy a cubesat, but...

[Douglas Quagliana]

Phil writes:
> Most LEO AMSAT satellites eventually succumb to battery wearout because
> of the constant day/night cycles (typically 14).

Well, many, but not all, succumb to battery failures.

In particular, UO-11 (and most of the Microsats) flew with batteries that
Larry Kayser,
VE3LK, now a silent key, selected and "matched" from a large set of
commercial grade
batteries.  UO-11 was launched in 1984(!) after a rather hasty development
effort.
However, those batteries have survived many tens of thousands of charge
discharge
cycles. UO-11 is still heard when the watchdog timer switches the
transmitter "ON".

Unfortunately, I cannot find the low level details describing exactly how
Larry did
his battery matching. I am pretty sure that if his process could be
re-discovered that
people would line up to have a battery pack for their satellite that was
likely to last a
long time. I'm also pretty sure it's more tedious than complicated because
he didn't
have all that much time before the launch in order to develop and execute
his matching
process.

Anyway, if anybody know *ANY* of the details of Larry's battery matching,
please
share them.  I'd like to reproduce his results one day.

Douglas KA2UPW/5



On Tue, Apr 24, 2018 at 12:00 AM, Phil Karn via Ground-Station <
ground-station at lists.openresearch.institute> wrote:

> On 4/23/18 21:34, Mark Whittington via Ground-Station wrote:
>
> > On the open research side of things, testing mechanical components to
> > failure and publishing the results sounds like fun.  Are there other
> > general categories of parts that would be useful to characterize in
> > similar ways?
>
> The AMSAT practice and experience has been to just fly good commercial
> grade parts but only after all the standard pre-launch tests, primarily
> thermal vacuum and vibration (or "shake and bake"). After a while you
> begin to see patterns in what works and what doesn't. I think
> electrolytic capacitors can be problematic, and so can crystals (which
> may not oscillate at low temperature). Connectors should be minimized or
> eliminated.
>
> Jan King, W3GEY, has said for a long time that if you survive the
> launch, space (especially low earth orbit) is actually a pretty benign
> environment. There's no gravity, no vibration, no rain and no hams
> tinkering with the hardware. There will be day/night thermal cycling,
> but if you do your thermal design properly this is a manageable problem.
>
> Even radiation is fairly benign in LEO, though it does get much worse as
> you go up. The inner Van Allen belt around 1/2 - 1 earth radii is full
> of energetic protons and is best avoided. Nevertheless, AMSAT Oscar 10
> got into an elliptical orbit with a perigee around 4000 km, and despite
> using 16kx1 MOSTEK dynamic RAM, about the most rad-sensitive stuff out
> there, it survived about 3 years before succumbing to total dose. It had
> mechanical shielding and used ECC ram with scrubbing, and we could see
> the error counts go up on each perigee pass.
>
> Most LEO AMSAT satellites eventually succumb to battery wearout because
> of the constant day/night cycles (typically 14). One (Oscar-7, launched
> 1974) actually came back years later when the batteries finally went
> open-circuit and let the electronics run when the panels were in sunlight.
>
> More recently, many of our satellites have worked fine right up to
> orbital decay. AO-13 was in a resonant orbit that took the perigee into
> the atmosphere after about 8 years. Our most common LEO destination used
> to be 850-1400 km, which is very long lived, but more recent LEO
> opportunities are in the 400-600 km range (particularly 400 km, since
> some are launched from the ISS and that's where it flies). Orbital
> lifetimes here are much more limited; ARISSat-1, deployed from the ISS
> in August 2011, decayed in early January 2012. So again, it's common for
> these satellites to operate right up until they decay. And that's
> actually OK with me, because space debris is becoming a real problem and
> we're much less likely to encounter pushback when we go into the lower
> orbits.
>
> Phil
>
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