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From:
gherbert@gw.retro.com (George William Herbert)
Newsgroups: sci.military.moderated
Subject: Re: Unexploded ordnance
Date: 24 Jan 2002 17:31:30 -0800
Organization: Retro Aerospace
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Karl M. Syring wrote:
>"Carey Sublette" schrieb
>> Don't use a primary explosive.
>> An electrical detonator doesn't need to use a hot wire/primary explosive
>> detonator. It can use a slapper detonator to initiate a booster or main
>> charge explosive directly - PETN, which is safely used in primacord
>> among other applications, is very easy to initiate this way for example.
>> I know slapper detonators for bomblets have already been developed and
>> tested, though I don't know if they are in service.
>
>Could you explain to us, how a slapper detonator works? Google reveals 1998
>patent (http://www.llnl.gov/str/Pat698.html), but I am not clear about the
>exact mode of action.
There are a whole family of types of detonators using variants on the
same idea: rather than heat something up to detonate a sensitive
explosive, you pump electrical energy into the system in sufficient
quantity to cause a mechanical shockwave and thus detonate relatively
insensitive explosives.
The first variants were "exploding bridgewire" detonators, first used
in the US nuclear weapons program as far as I can tell. These have a
thin bridge wire between two posts surrounded by secondary HE
such as PETN. Enough current is passed through the bridgewire in
short enough time to vaporize it and cause a mechanical shockwave
in the surrounding PETN.
EBW and variants are relatively safe from heat (the HE doesn't have
to be sensitive to / initiate by heating), stray electrical currents
(anything other than sufficient voltage/current fast enough may
melt the wire, but won't cause the detonating shockwave to form),
and physical shock and such.
Other early variants include "exploding foil initiators", where a
similar arrangement is manufactured using conductive foils on
a substrate of some sort, and thin-necked pinches in the foil
conduction layer shapes. EFI are somewhat easier to manufacture
and more reliable (the foil is less vulnerable to damage than
a EBW wire is).
There are also systems which use an intermediate mechanical
transfer device on top of a foil or bridge wire, such as a
plastic pellet which is accellerated by the exploding bridge
and then impacts an area of explosive.
One commercial manufacturer is RISI, with their website at:
http://www.risi-usa.com/0products/index.html
They make and provide info on classic EBW and EFI initiatiors.
-george william herbert
gherbert@retro.com