Somewhat OT: Long term design
in [Design]
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From: John Larkin on 14 Jan 2010 06:57 On Thu, 14 Jan 2010 17:36:17 +1100, Sylvia Else <sylvia(a)not.at.this.address> wrote: >John Larkin wrote: >> On Thu, 14 Jan 2010 15:51:25 +1100, Sylvia Else >> <sylvia(a)not.at.this.address> wrote: >> >>> Joerg wrote: >>>> John Larkin wrote: >>>>> On Thu, 14 Jan 2010 13:31:08 +1100, Sylvia Else >>>>> <sylvia(a)not.at.this.address> wrote: >>>>> >>>>>> A recent episode of Stargate Atlantis prompted me to think about how >>>>>> would could design equipment that's intended to function far into the >>>>>> future. The episode required stuff to function 48,000 years after >>>>>> construction, but perhaps we could be less optimistic. >>>>>> >>>>>> Say 1000 years. >>>>>> >>>>>> Note, the requirement is not that the equipment function *for* 1000 >>>>>> years, but that when it is turned on, 1000 years from now, that it >>>>>> will work. >>>>>> >>>>>> It seems to me that semiconductors are out due to effects of difusion >>>>>> and radiation. >>>>>> >>>>>> But how about thermionic valves? They're not very reliable, but do >>>>>> they age when not in use? Would they hold a vacuum over that time? >>>>>> >>>>>> Obviously electrolytic capacitors are a no-no, but can resistors and >>>>>> capacitors be made stable enough that they'd work? >>>>>> >>>>>> Would it help to enclose the entire circuit in a vacuum tube? Again, >>>>>> could the tube sustain the vacuum over such a period? >>>>>> >>>>>> An energy source is a problem. Perhaps a cell where acid is added >>>>>> (how?) at the appropriate time? >>>>>> >>>>>> Sylvia. >>>>> 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. >>>>> >>>> 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. >>>> >>> 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. >> >> 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 >> >> > >However, there is a caveat that these rates apply during the design >life. That is, a part with a failure rate of one per billion hours >cannot be expected to function, on average, for one billion hours before >it fails, unless the design life is itself a billion hours. Which it >probably isn't. A billion hours is a long time, 114K years, but 1000 years is a mere 9 million hours. Unless there's a long-term wearout mechanism (diffusion, corrosion, radiation damage) I'd guess that most parts are still in the flat part of their bathtub curve at 1000 years. If one were designing a 1000 year product, you'd certainly want to look for potential wearouts. > >In the context of this thread, the issue is further complicated by the >question of whether a component is using up its design life while doing >nothing. It may, or may not, depending. That's an issue in calculating equipment MTBF. The general rule is that if you don't hit your reliability target doing straightforward calculations, then you toss in a use factor. There are old clocks and watches and scientific instruments around that work after hundreds of years, without benefit of exotic storage. I'd guess that WWII-vintage electronics, stored in military wax-sealed cardboard boxes, usually still works. What would fail in a conservatively-designed electronic gadget after 1000 years? Barring corrosion, I can't see a wearout or diffusion mechanism for thickfilm resistors or ceramic caps. Given the observable stability of bipolar transistors and ICs, there doesn't seem to be much carrier diffusion or radiation damage going on at room temperature. I'd avoid CMOS type parts where a little charge redistribution could cause problems. You could cheat and store the gear in Antartica. Most degradation mechanisms follow the Arrhenius relationship. John
From: John Larkin on 14 Jan 2010 07:03 On Thu, 14 Jan 2010 19:21:43 +1100, Sylvia Else <sylvia(a)not.at.this.address> wrote: >a7yvm109gf5d1(a)netzero.com wrote: > >> OR.... >> >> go all mechanical >> >> http://www.longnow.org/ >> >> (How long does a weight suspended in the air keeps its potential >> energy? Makes a good battery, no?) > >Yes.... > >But now you have to design a mechanism to extract the energy that will >work after 1000 years. > >Sylvia. Centuries-old weight-powered clocks still work. Surely we can do better with modern materials. I don't think 1000 years is a long time for good materials. A chemical battery with a glass-sealed electrolyte, like used in some proximity fuses, could be designed to last 1000 years. John
From: John Larkin on 14 Jan 2010 07:33 On Thu, 14 Jan 2010 06:36:27 -0500, Bitrex <bitrex(a)de.lete.earthlink.net> wrote: >John Larkin wrote: >> On Wed, 13 Jan 2010 21:54:46 -0800 (PST), a7yvm109gf5d1(a)netzero.com >> wrote: >> >>> On Jan 14, 12:45 am, John Larkin >>> <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >>>> On Wed, 13 Jan 2010 21:30:33 -0800 (PST), a7yvm109gf...(a)netzero.com >>>> wrote: >>>> >>>> >>>> >>>>> On Jan 13, 9:31 pm, Sylvia Else <syl...(a)not.at.this.address> wrote: >>>>>> A recent episode of Stargate Atlantis prompted me to think about how >>>>>> would could design equipment that's intended to function far into the >>>>>> future. The episode required stuff to function 48,000 years after >>>>>> construction, but perhaps we could be less optimistic. >>>>>> Say 1000 years. >>>>>> Note, the requirement is not that the equipment function *for* 1000 >>>>>> years, but that when it is turned on, 1000 years from now, that it will >>>>>> work. >>>>>> It seems to me that semiconductors are out due to effects of difusion >>>>>> and radiation. >>>>>> But how about thermionic valves? They're not very reliable, but do they >>>>>> age when not in use? Would they hold a vacuum over that time? >>>>> Oh, they can be made very reliable. They can be accelerated at 100Gs >>>>> and used in proximity fuzes (note the spelling), as in WWII; >>>> 20,000 Gs! >>>> >>>> John >>> Yeah, even worse! I was probably thinking of this toy >>> http://www.youtube.com/watch?v=nLpLEgAS574&feature=related >>> >>> I guess an artillery shell leaves in even bigger of a hurry, but >>> doesn't *keep* accelerating... More of a "jerk" situation? >> >> 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 am! Something more obsolete than my TTL clock! :) Try this, ftp://jjlarkin.lmi.net/Prox.zip about 2 megabytes. One of the reasons Patton blasted across Europe so fast was that the prox fuze had just been released for land use. It was a devastating and terrifying weapon against ground troops... one howitzer round going off 50 feet above the ground would basically sterilize a few acres, and foxholes weren't much help. It was also hugely effective against German bombers over Britain and against the kamakazies. It's really hard to hit a plane with a bullet. John
From: Martin Brown on 14 Jan 2010 07:40 John Larkin wrote: > On Thu, 14 Jan 2010 17:36:17 +1100, Sylvia Else > <sylvia(a)not.at.this.address> wrote: > >> John Larkin wrote: >>> 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. >> However, there is a caveat that these rates apply during the design >> life. That is, a part with a failure rate of one per billion hours >> cannot be expected to function, on average, for one billion hours before >> it fails, unless the design life is itself a billion hours. Which it >> probably isn't. > > A billion hours is a long time, 114K years, but 1000 years is a mere 9 > million hours. Unless there's a long-term wearout mechanism > (diffusion, corrosion, radiation damage) I'd guess that most parts are > still in the flat part of their bathtub curve at 1000 years. If one > were designing a 1000 year product, you'd certainly want to look for > potential wearouts. You also have to be fairly cunning to weed out infant mortality in any components that might be vulnerable early on. It would be really annoying to wait 1000 years to find that bad handling had wrecked or weakened a component that failed at switch on. I am fairly sceptical of anything with wet chemistry inside surviving on these timescales. Electrolytic capacitors have a bad habit of drying out or otherwise developing defective internal behaviour when left alone for a long time. Or for that matter anything using tin, zinc, cadmium or other metals inclined to form whiskers. http://www.aciusa.org/leadfree/leadfree_verdi-11-5-04.htm Aluminium chassis and heatsinks might not be all that good longer term either. The metal is just too reactive for its own good even if the oxide coat is inert. Copper coated with gold ought to be OK though. > >> In the context of this thread, the issue is further complicated by the >> question of whether a component is using up its design life while doing >> nothing. It may, or may not, depending. > > That's an issue in calculating equipment MTBF. The general rule is > that if you don't hit your reliability target doing straightforward > calculations, then you toss in a use factor. > > There are old clocks and watches and scientific instruments around > that work after hundreds of years, without benefit of exotic storage. > I'd guess that WWII-vintage electronics, stored in military wax-sealed > cardboard boxes, usually still works. Depends how many bites the rodents have taken out of it. Inductors and galvanometers survive remarkably well - the mirrors may tarnish though and that is over mere couple of hundred years. Clocks that are not well looked after seem to have a half life of about fifty years. I reckon Zambonni piles might be OK as a maintainence free power source (for tiny currents). The oldest one at the Clarendon lab is still going strong after 170 years running the Oxford Electric bell. http://en.wikipedia.org/wiki/Oxford_Electric_Bell I have one somewhere ex WWII image intensifier. And I am pretty sure there is (or was) something similar at Leiden with a ball of sulphur that is gradually wearing away as it rings. But a quick search failed to find it. > > What would fail in a conservatively-designed electronic gadget after > 1000 years? Barring corrosion, I can't see a wearout or diffusion > mechanism for thickfilm resistors or ceramic caps. Given the > observable stability of bipolar transistors and ICs, there doesn't > seem to be much carrier diffusion or radiation damage going on at room > temperature. I'd avoid CMOS type parts where a little charge > redistribution could cause problems. > > You could cheat and store the gear in Antartica. Most degradation > mechanisms follow the Arrhenius relationship. A salt mine is a pretty safe location provided you hermetically seal the kit in dry nitrogen before it is taken down. Steady temperatures also help longevity just as thermal shock accelerate decrepitude. One of the advances neutrino detector experiments is down our local potash mine. Regards, Martin Brown
From: baron on 14 Jan 2010 08:00
George Herold Inscribed thus: > On Jan 13, 9:31 pm, Sylvia Else <syl...(a)not.at.this.address> wrote: >> A recent episode of Stargate Atlantis prompted me to think about how >> would could design equipment that's intended to function far into the >> future. The episode required stuff to function 48,000 years after >> construction, but perhaps we could be less optimistic. >> >> Say 1000 years. >> >> Note, the requirement is not that the equipment function *for* 1000 >> years, but that when it is turned on, 1000 years from now, that it >> will work. >> >> It seems to me that semiconductors are out due to effects of difusion >> and radiation. >> >> But how about thermionic valves? They're not very reliable, but do >> they age when not in use? Would they hold a vacuum over that time? >> >> Obviously electrolytic capacitors are a no-no, but can resistors and >> capacitors be made stable enough that they'd work? >> >> Would it help to enclose the entire circuit in a vacuum tube? Again, >> could the tube sustain the vacuum over such a period? >> >> An energy source is a problem. Perhaps a cell where acid is added >> (how?) at the appropriate time? >> >> Sylvia. > > 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. The Ancients created mechanical traps in the pyramids. AFAIA they still worked after how many years 4500 or so. -- Best Regards: Baron. |