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

[Frank H. Bauer]

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 mount
components.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>
Subject: [amsat-bb] Re: Keep It Simple, MM
To: MM <ka1rrw at yahoo.com>, amsat-bb at amsat.org
Message-ID: <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