[amsat-bb] Re: Keep It Simple, MM

Thu Oct 4 07:22:14 PDT 2007

All,

I plan to give two presentations at the AMSAT Symposium and one will focus
almost exclusively on zero defect surface mount technology (SMT.)  As Frank
points out, SMT has been used extensively in space for many years.
Unfortunately, many people believe they can transfer their previous
thru-hole PCB experience to surface mount.  This is a recipe for disaster.
The two technologies are totally different.  SMT requires a completely new
way of thinking.  The margin between high reliability and disaster is very
thin.  A firm understanding of the unique issues associated with SMT coupled
with attention to small details is essential if you want to avoid early
failure.

The other huge issue that is often not fully appreciated is the impact of
radiation on modern components.  As I'll show at the Symposium, the old
familiar 14 and 16-pin plastic DIP devices were quite robust and could
tolerate fairly high doses of radiation.  This is not necessarily true
anymore.  This is why commercial and military payloads use rad-hardened,
space-rated, and screened components.  Commercial Off-The-Shelf (COTS)
devices are manufactured for use in a benign environment where failures can
be corrected by replacement or repair.  They are not designed for space.
They are not tested for space, and you must accept a higher degree of risk
it you use them.

73,

Juan - WA6HTP

On 10/3/07, Jim Sanford <wb4gcs at amsat.org> wrote:
>
> Frank:
> Have you seen Juan Rivera's work on the UHF RX?  He's learned and
> published a bunch about surface mount for our purposes.  Your validation
> and/or commentary would be very valuable and appreciated.
>
> Thanks & 73,
> Jim
> wb4gcs at amsat.org
>
>
> Frank H. Bauer wrote:
>
> I feel compelled to comment on one specific item that Dave questions in this
> thread---surface mounted components in space.
>
> I have worked at NASA for 32+years and have led or guided avionics teams
> throughout NASA for a large part of that time (15+ years).  For many years
> we have used surface mount technology in our avionics products.  I was quite
> proud of our (Goddard) surface mount capabilities.  One of our techs was an
> expert on the installation, removal and replacement of surface mountcomponents.an expertise that is highly sought after.  This technology is a
> mainstream capability within the space community.
>
> So I need to say that this myth is "busted"
>
> 73,  Frank, KA3HDO
>
>
>
> Date: Mon, 01 Oct 2007 22:20:55 -0400
> From: "David B. Toth" <ve3gyq at amsat.org> <ve3gyq at amsat.org>
> Subject: [amsat-bb] Re: Keep It Simple, MM
> To: MM <ka1rrw at yahoo.com> <ka1rrw at yahoo.com>, amsat-bb at amsat.org
> Message-ID: <6.2.3.4.2.20071001220931.03f3beb0 at pop3.wcoil.com> <6.2.3.4.2.20071001220931.03f3beb0 at pop3.wcoil.com>
> Content-Type: text/plain; charset="us-ascii"; format=flowed
>
> At 08:06 AM 10/1/2007, MM wrote:
>
>
> Keep It Simple Silly KISS
> By Miles WF1F
>
> The direction of this tread is caution.  I am not suggesting that we do
> not use digital technology for satellites, just that we need to be
> careful of the technology.  The Space environment is not kind to
> digital circuits.  Digital circuits are easily corrupted by solar
> radiation and thermal stresses.  A digital circuit designed for use on
> Earth many not survive the rigors of outer space.  This is partially
> because of the Size of a transistor inside a modern CPU.
>
> In 1978 a computer transistor was made up of wires 3 microns in size.
> Today's CPU Itanium, uses wires 0.18 microns in size.  The new DSP
> chips used on Digital radio will be some where in-between.  With the
> wire sizes in the 0.20-micron range, it's much easier for solar
> radiation to cause temporary shorts, which can cause system crashes.
>
>
> The SDX is a software-defined radio ... it does not necessarily, and
> probably does not, use a DSP chip.
>
>
>
>
> Keep It simple.  A small satellite that does one or
> two features is better than one big satellite that
> does 10 big features.
>
>
> At the cost of launches and satellites, i think this point is easily
> disputable.
> I am sure that the engineers are looking at an overall systems approach, AND
> they've done this before. The difference is the addition of a
> software-defined approach, which WILL be space-tested in SuitSat2 anyway
>
>
>
>
>
> Axle lead Resistor and through-hole mounting of
> components are much more resilient in space than
> surface mount components.
>
>
> Miles, do you have any data to support this statement because right
> off-hand, I can't see why this would be true.
>
>
>
>
> Hardware is not your only problem; you also need to
> Extensively Test the software that runs the satellite
> project.
>
>
> This is not the first satellite these guys have built - I think they
> had this somewhere on their "To-Do List" ...
>
>
>
>
>
> The Analog satellites AO-7 (launched Nov 1974) and
> AO-10 (June 1983) are still there when the sun is
> shining.
>
>
> Well, that is actually a bug, not a feature. We need to have a way
> that we can guarantee that when a satellite dies, it STAYS dead. That
> was a real sticking point with Larry Kayser when he was still alive.
> These things pop up, un-controlled, and if we had enough of them,
> they'd be an interference problem.
>
>
> Dave
>
>
>
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