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From: eachus@aries.mitre.org (Robert I. Eachus)
Newsgroups: sci.military
Subject: Re: FAE/BACKLU-82
Message-ID: <1991Mar15.035113.8170@cbnews.att.com>
Date: 15 Mar 91 03:51:13 GMT
References: <1991Mar6.040610.24007@cbnews.att.com>
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From: eachus@aries.mitre.org (Robert I. Eachus)

     Yes the Daisy Cutter is an FAE, but not the usual type.  Finely
divided aluminum is hypergolic in air (no ignition necessary) if it is
either warm enough or does not have an oxide coating.  (Aluminum in
air quickly forms a protective coating of AlO3).  If you disperse a
cloud of aluminum in air, when it reaches the "right" proportions it
explodes.  Since aluminum is happy to form the nitride if no oxygen is
handy, all the aluminum is consumed.

     The ammonium nitrate is set off by the fuse, and oxidizes the
polystrene.  This exposes the fresh aluminum surfaces, and when the
cloud has sufficiently mixed with air the second explosion occurs.
You only hear one explosion (assuming that you are far enough away),
because the second explosion starts at the edge of the first
explosion's wavefront, and propagates faster than the speed of sound
(in the external medium) through the internal cloud.  Think of it as
two separate fluids, the hot gasses having a higher speed of sound,
and you will realize that almost all the energy winds up in the
explosion wavefront.  This is what makes it a concussion type weapon.
--

					Robert I. Eachus