Path: utzoo!utgpu!water!watmath!clyde!rutgers!rochester!PT.CS.CMU.EDU!SPEECH1.CS.CMU.EDU!phd
From: phd@SPEECH1.CS.CMU.EDU (Paul Dietz)
Newsgroups: sci.electronics
Subject: Re: electronic time capsule
Keywords: Space, the final frontier...
Message-ID: <888@PT.CS.CMU.EDU>
Date: 17 Feb 88 20:14:25 GMT
References: <3a56593d.44e6@apollo.uucp>
Sender: netnews@PT.CS.CMU.EDU
Organization: Carnegie-Mellon University, CS/RI
Lines: 35

In article <3a56593d.44e6@apollo.uucp> nelson_p@apollo.uucp writes:
>  I had in mind an 'electronic time capsule', i.e., a small box
>  perhaps set in a remote location where it wouldn't be accidentally
>  disturbed, that would remain in a dormant state for decades or 
>  even centuries at the end of which time it would begin transmitting 
>  a radio signal to call attention to itself (at least during the
>  day when solar power could provide a current source).

Probably the hardest part would be finding a place to put it. If
you're using solar power, you need to make sure that the cells will
remain exposed. There is a simple, if somewhat expensive solution:
put it in orbit! You can be pretty sure that the cells will remain exposed,
and you can probably rule out external corrosion as a failure
mechanism.

As for earth-bound techniques, you might want to consider putting the
beast under the ocean. For energy, you could harness the currents or
even the thermals. Then, when the time had come, it could release itself
to the surface, throwing out an array of solar cells to power its
transmissions.

You have to be pretty careful these days about what IC's you use.
Channel lengths are getting awfully short, and gate oxides are getting
pretty thin. For long term reliability, you'd probably want to use
some low-tech stuff. Any experts out there on long term reliability
of sub-micron devices?

(So, what do you transmit; old sci.electronics posts? :^O )

Paul H. Dietz                                        ____          ____
Dept. of Electrical and Computer Engineering        / oo \        <_<\\\
Carnegie Mellon University                        /|  \/  |\        \\ \\
--------------------------------------------     | | (  ) | |       | ||\\
"If God had meant for penguins to fly,             -->--<--        / / |\\\  /
he would have given them wings."            _________^__^_________/ / / \\\\-