Re: Apollo 8 and a LM
- From: fairwater@xxxxxxxxx (Derek Lyons)
- Date: Sun, 03 May 2009 15:49:25 GMT
derek_c@xxxxxxxxxxxxxxxxxxx wrote:
*From:* Joe Pfeiffer <pfeiffer@xxxxxxxxxxx>
*Date:* Sun, 26 Apr 2009 14:22:21 EDT
Something I find interesting is just how late the daebate over
analog/digital lasted. As a CS undergrad in the late 1970s, analog
computers seemed just unbearably quaint. And the first generation
of
automotive engine computers was analog, in exactly that time frame!
To a die hard engineer, using a digital computer to solve an analogue
computer problem would be a waste of parts.
Analogue computers are really quite simple, just using a few op-amps ,
capacitors inductors and resistors. Solving the same problem with a
digital computer requires a lot more electronics, *and* all that nasty
software stuff!
I was producing the software for a power station in the late 70's. The
main control system was digital, but the customer used a custom analogue
computer to simulate the turbines to test it.
That analogue computer was just a few parts on a plugboard.
That depends on the nature of the problem and the nature of the analog
computer being used to solve it. An analog gun fire control system is
much more than 'a few parts on a plugboard' for example.
The class 'analog computers', even limiting to the subclass of
electronic analog computers, also includes synchros, resolvers, and
other such partially mechanical components. (As opposed to fully
mechanical analog computing devices like Vannevar Bush's differential
analyzer.[1])
The digital system occupied several 19" racks, with the computers
themselves (there were two per turbine set, each less powerful than the
later Zilog Z80) occupying 10U each plus another 10U for the hard drives.
Until the late 1980's/early 1990's the USN used analog computers
(strictly electronic with no mechanical components) in it's submarine
"dive and drive" simulators. The computer took the various input
elements (trim tank levels, ships speed, control surface angles) and
then drove the platform the simulator was mounted on to the
appropriate angle and produced the appropriate readings on the control
panel.
The analog simulators for the SSBN 726 class, which dated from the
same era as you discuss (the late 1970's), was a commercial unit and
filled the equivalent of two 19" racks.
The control system installed on the submarine (of the same era), which
could not only dive and drive the ship but do other things at the same
time, consisted of a pair on AN/UYK-7 computers - which took up
(roughly) the equivalent of four 19" racks.
[1] http://web.mit.edu/klund/www/analyzer/
D.
--
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http://derekl1963.livejournal.com/
-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL
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