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From: rainer@boulder.Colorado.EDU (Rainer Malzbender)
Newsgroups: sci.electronics
Subject: Re: What are some typical characteristics of mechanical relays?
Message-ID: <1991Apr1.004857.17286@colorado.edu>
Date: 1 Apr 91 00:48:57 GMT
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In article <2640@sun13.scri.fsu.edu> murray@sun13.scri.fsu.edu (John Murray) writes:
>
>Application: High-current (peaks may be around 40V, 20A or more) switching
>of the magnetics on a coil gun... :-)
>

Hmm...will that be enough ? (Don't feel like doing a Jackson problem
right now :-). For reference, the power requirements of the second
Princeton-MIT mass driver design (a = 5000 m/s^2, vmax = 112 m/s, bucket
mass = 1kg)) were V = 668 volts, Imax = 6315 amps, di/dt =
58.6 amps/microsecond. Run that through your average mechanical relay!
In contrast the first one had an acceleration of 33 g's and used mechanical
switches to trigger the coils, so maybe it's doable. I know there's been
a magnetic-weapon discussion here before, and I don't want to reopen it,
but the Germans had trouble with electromagnetic cannon during
WWII due to melting projectiles. I don't know anything about coil guns,
but their efficiency must be a lot worse than mass drivers, which have
pretty good coupling between drive and bucket coils.

Maybe you could write a Popular Electronics article for the DIY crowd
once you build it ??
--
Rainer Malzbender                                Save a dinosaur - buy DEC.
Dept. of Physics (303)492-6829
U. of Colorado, Boulder         rainer@boulder.colorado.edu 128.138.240.246