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From: malloy@nprdc.navy.mil (Sean Malloy)
Newsgroups: sci.military
Subject: Re: USS Iowa
Message-ID: <5793@cbnews.ATT.COM>
Date: 21 Apr 89 03:28:36 GMT
References: <5756@cbnews.ATT.COM>
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Organization: Navy Personnel R&D Center, San Diego
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From: malloy@nprdc.navy.mil (Sean Malloy)

>My guess would be that the most likely cause was residual embers in the
>gun barrel (despite precautions, such as air blowout, to prevent such
>from occurring).  I wonder, though, if the cause may have been the old
>(WWII-vintage) powder used.  While the powder was supposedly sorted and
>rebagged before use, it's not inconceivable that some unstable powder
>may have slipped through...

>From _Principles of Naval Ordinance and Gunnery_, NAVEDTRA 10783-C,
published by the Naval Education and Training Support Command:

|    Bag Type Propelling Charge
|    
|      A complete round of bag ammunition consists of three separate
|    ammunition details as follows:
|    
|      1. A lock combination primer (so called because it fits into a firing
|    mechanism called a firing lock, and has a combination arrangement
|    which enables it to fire either on an electric firing impulse or by
|    percussion)
|      2. Two or more powder bags.
|      3. A projectile.
|    
|      Large guns must burn large quantities of propellant to develop the
|    projectile initial velocity required. In a gun as large as 16-inch,
|    several hundred pounds of propellant are needed for one full service
|    round. By dividing this into several fabric bags, each of which can be
|    handled by one man, the gun can be loaded in a relatively brief time.
|    Each bag is made of silk (because silk burns without leaving a
|    smoldering ash), has silk straps for handling and silk lacing to cinch
|    it up, and in red-dyed quilted silk pockets at one end has coarse
|    black powder to serve as the igniter in the propellant train. The bags
|    are kept in airtight steel tanks until just before use.

The normal loading procedure specifies that the primer is loaded into
the firing lock before the shell and propellant is loaded. It is
more likely that a defective primer detonated as the breech was being
closed and ignited the aftermost powder bag in the barrel than that
the propellant was unstable and spontaneously ignited.

According to the section on propellants in _Principles of Naval Ordinance
and Gunnery_, there are two types of deterioration of smokeless
powder. The first, decomposition due to ageing, simply reduces the
power of the propellant. The second, loss of volatile components
(ether and alcohol), increases the burning speed, and causes the
propellant to develop excessive pressures in the gun when fired.

If the charges in the gun had suffered from extreme loss of volatiles,
it is possible that the actual circumstance was the failure of the
breech mechanism when the gun was fired, which would blow the breech
back into the turret and allow the burning propellant to expand back
inside the turret.

[mod.note:  I stand corrected !  Thanks, Sean, for the clarification.
- Bill ]

 Sean Malloy					| "The proton absorbs a photon
 Navy Personnel Research & Development Center	| and emits two morons, a
 San Diego, CA 92152-6800			| lepton, a boson, and a
 malloy@nprdc.navy.mil				| boson's mate. Why did I ever
						| take high-energy physics?"