Somewhat OT: Long term design

What does the machine have to do? Mechanical stuff (gears, cams, punch cards) lasts a long time. It could be powered by gravity.

George H.

I'd expect that most semiconductors and passives would last 1000 years, given a conservative design. There's not much radiation around at sea level. The gadget could be stored in vacuum or dry nitrogen to prevent corrosion and wiskers and such.

It shouldn't be hard to keep a vacuum tight for 1000 years. A decent flange-sealed vacuum vessel hardly leaks at all. If it can do 1e-12 torr for a minute, it leaks to atmosphere in (linear extrapolation) 2 billion years.

I think solar cells would stand up well. I bet that a Casio solar calculator will work 1000 years from now if properly stored. The biggest hazard would probably be polymerization of the plastics in the keypad, or maybe leakage from a poorly sealed LCD.

I still use my original HP35 calculator, purchased in 1972.

John

HP11C over here. I still use my grandpa's drill from around the 1920's. Works fine. You just have to keep the grease reservoirs packed by tightening the caps once in a while and refilling when at the peg.

Oh, and the church we were married at goes back about 1200 years, the organ in there is probably well past 500 years. I guess a pipe organ fulfills the definition of "equipment". It can be done.

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Well, I'm not sure the organ qualifies, even if it reaches 1000 years. Has it never been repaired?

The requirement is that the equipment be built, be left untouched for

1000 years, and then work.

Sylvia.

It could do that if not played, except for the bellows which are leather. Of course, nowadays you could make those from some newfangled material. Also, this organ only needed the bellows when there was no wind so technically it would still qualify as operational with cracked leather. Unless you say the rules don't allow wind :-)

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Thermionic valves are very reliable if used well within specifications. Running the filaments at 90 percent of spec increases apparent lifetime by a factor of 100 (or so it seems).

Electrolytic capacitors are also quite reliable; i have seen the old wet electrolytics working near spec up to 30 years later even without addition of electrolyte. As far as the most "modern" reliable aluminum electrolytics go, the Sprague TE series outperform anything else i have seen.

Film and wirewound resistors have a similar long life reliability, as long as they are used within ratings.

** Expect possible 30 to 100-year continuous reliable use if these parts are made with high quality production methods using high grade materials, and if run well within specifications. ** Expect your possible "immediate" usability 1000 years from now with the caveat that aluminum electrolytics (even of the Sprague TE series quality) would need "forming" (which could be designed in the circuit).

• Sorry, NASA has seen whisker growth in their satellites..

Oh, they can be made very reliable. They can be accelerated at 100Gs and used in proximity fuzes (note the spelling), as in WWII; the first submarine cable repeaters used tubes and they were reliable.

1) By using very pure cathode materials, preventing known lifetime issues such as cathode interface crystal growth (barium orthosilicate, remove all silicon from cathode materials.) 2) A lot of stress on tubes apparently comes from the high enveloppe temperature. So if they're not running, the glass should prevent diffusion since it'll be cold. When running, it's not an issue unless you are dealing with high temperatures (260C), or expect to run a long time. 3) Glass to Kovar seals are very reliable, having decades of empirical knowledge to build proper ones helps, it's all in musty old books somewhere 4) Use more getter to capture errant gas molecules.

You can also use Nuvistors, all metal/ceramic construction.

Hmmm, don't know.

But then you'd need materials that are made to resist vacuum for 1000 years, and then work in the vacuum, so sound is out.

Yes, like air-to-air missiles. They can lie around for decades and spring into 100% action in milliseconds thanks to the miracle of the thermal battery.

OR....

go all mechanical

(How long does a weight suspended in the air keeps its potential energy? Makes a good battery, no?)

Well, you'd have to do whatever works best. Leaded solder comes to mind!

John

Aluminums fail by drying out, through water vapor leakage through the rubber seals. That's a wearout mechanism.

John

20,000 Gs!

John

What about 1960s-style welded flatpacks? No solder at all!

Al Po's?

Generally considered as good as tantalum and fairly indestructible, aren't they? Kind of new to use for millenium hardware though.

Tim

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Reliability folks generally assign component failure rates in FITs, namely one failure per billion hours. Most passives have numbers near

1 FIT, and lots of semiconductors are in the single digits.

So a 100-part gadget that uses average 1 FIT parts will have an MTBF of 1e7 hours, a bit over 1000 years. That assumes the parts have no wearout mechanism. In practise, field failure rates can be quite a bit better than specs like MIL-HBK-217 or Bellcore predict, ie better than

1 FIT average per part.

John

Yeah, even worse! I was probably thinking of this toy

I guess an artillery shell leaves in even bigger of a hurry, but doesn't *keep* accelerating... More of a "jerk" situation?

They are kind of new, so it's hard to tell. Apparently one failure mechanism is water vapor leaking *in* and wrecking the polymer.

If it ain't one thing, it's something else.

I've been using polymers lately and they seem fine. ESR is low, leakage is low. They seem to fail suddenly at ballpark 2x rated voltage or so with no "warning" leakage or anything like you'd see in a tantalum or regular 'lytic. They don't detonate like tantalums.

John

In Europe the problem with much of the Roman stuff was that there were usually 5-10 fierce wars over a period of 1000 years. That kind of puts a crimp into the MTBF.

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Artillery shells accelerate *very* rapidly and then spin at insane rates.

Good book: The Deadly Fuze by Baldwin.

I have a few tube-type prox fuze schematics if anybody is interested.

John

I have a hammer that must be 400 years old. The handle has been replaced a dozen times, and the head maybe 6 times. ;-)

Best regards, Spehro Pefhany

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