QUOTE (sranderson @ Dec 18 2005, 06:46 PM)
Actually, in my experience over the past 20 years dealing with aging systems that are still in use but were built in the late 1960's through late 1980's, I have seen that even for electronics there is a right side wall to the bathtub curve.
I think that for most electronics systems the end-of-life increase in failures is not seen because the systems are usually discarded upon first failure.
The failure curve starts with initial infant mortality, followed by constant fairly low failure rates, and then a significant increase in failures (that at first appears random), with finally a rather catastrophic increase in failures caused by specific issues that affect large numbers of parts. These final failures are traced to things like internal bonding material failures, bimetallic formation leading to bond-wire and other connection failures, migrations of materials (flow), crystal growth, the formation and movement of conductive particulates, seal failures leading to leakage of electrolytes, epoxy degradation with age, shrinkage and hardening of soft goods (in connectors and shock mounts), etc. Most of these processes are greatly exacerbated by environmental extremes and low pressures.
So really what we see are materials and mechanical failures within the electronics components. I have seen the oddest things happen.
I have also become much more concerned about corrosion on Mars lately.
Scott
That does not fit well with my experience. We had quite a lot of 50’s and 60’s vintage avionics flying until quite recently (some still do) and while we have had a few issues about particular brands of insulation materials deteriorating, there have been no massive reliability problems.
In my experience aging electronics go out of service because:
a spares are no longer obtainable
b operating and maintaining them has become a lost art
c integrating digital and analog systems can be
very difficult
Perhaps living up here in the cool and fairly dry north has something to do with it. One thing we have learned in recent years is that dehumidifiers, even if only used intermittently, dramatically improves the reliability of electronics (and almost everything else).
In this respect at least Mars should be a very favorable environment though that still leaves extreme temperature cycles, dust, low pressure and perhaps corrosive chemicals.
tty