Somewhat OT: Long term design
in [Design]
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From: Robert Baer on 14 Jan 2010 00:19 Sylvia Else 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. 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).
From: Robert Baer on 14 Jan 2010 00:20 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. * Sorry, NASA has seen whisker growth in their satellites.. > > 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 >
From: a7yvm109gf5d1 on 14 Jan 2010 00:30 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; 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. > Obviously electrolytic capacitors are a no-no, but can resistors and > capacitors be made stable enough that they'd work? Hmmm, don't know. > > Would it help to enclose the entire circuit in a vacuum tube? Again, > could the tube sustain the vacuum over such a period? 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. > > An energy source is a problem. Perhaps a cell where acid is added (how?) > at the appropriate time? > > Sylvia. 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 http://www.longnow.org/ (How long does a weight suspended in the air keeps its potential energy? Makes a good battery, no?)
From: John Larkin on 14 Jan 2010 00:41 On Wed, 13 Jan 2010 21:20:58 -0800, Robert Baer <robertbaer(a)localnet.com> wrote: >> 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. >* Sorry, NASA has seen whisker growth in their satellites.. Well, you'd have to do whatever works best. Leaded solder comes to mind! John
From: John Larkin on 14 Jan 2010 00:44
On Wed, 13 Jan 2010 21:19:12 -0800, Robert Baer <robertbaer(a)localnet.com> wrote: >Sylvia Else 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. > 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). Aluminums fail by drying out, through water vapor leakage through the rubber seals. That's a wearout mechanism. John |