Newsgroups: sci.military
From: John De Armond <jgd@dixie.com>
Subject: Re: Neutron bomb
Date: Wed, 29 Jun 1994 16:30:15 GMT

Andrew Weitzman <aweitz@cam.org> writes:

>       Which is more difficult for your typical Third World nuclear-club
>aspirant--producing a fission "city-buster" strategic nuke, or a tactical 
>neutron bomb/enhanced radiation warhead.  For my money, I'd rather go for 
>a neutron bomb than a city buster.  In most third-world conflicts, there 
>usually are only one or two cities large enough to warrant a nuclear 
>attack.   Why bother making the one or two devices, which are guaranteed 
>to be countered by your enemy?

>         Neutron bombs are a touch more versatile.  You can use them in 
>conventional conflicts--especially useful if your opponent has large tank 
>or infantry forces.  And in a pinch, they *can* be used strategically, 
>although not very well.
>          So, technically speaking, which is easier to make--neutron or 
>fission?

Apples and oranges.  First to define an enhanced radiation weapon (mis-
named the neutron bomb).  This is any weapon which uses fusion to
enhance the production of radiation beyond that which is "normal".
The most common type is a modification the single stage fission-fusion-fission 
thermo-nuclear bomb.  In this device, an implosion fission device, typically
in the yield range of 20kt, initiates a fusion reaction in a "secondary"
typically composed of lithium-6 deteuride.  The fusion reaction produces
energy and copious high energy neutrons.  In a conventional thermonuclear
weapon, these neutrons would initiate fast fission in a U-238 blanket 
or casing surrounding the rest of the mechanism.  As much as half the yield
of the weapon is derived from this secondary fission reaction.  The 
fusion stage serves as a "booster" (not to be confused with boosted fission 
weapons in which tritium is injected into the pit to enhance the yield.).

In an enhanced radiation device, the fissile casing is simply replaced
with an atomically inert material such as steel.  The energy yield is as
little as half that of a similar conventional device while the radiation
produced is only slightly less.

The mistake many people make, based on the media hype, is to think
of enhanced radiation weapons as little pip-squeak bombs that emit
a lot of radiation.  The device is still a thermonuclear bomb with
yield in the tens or hundreds of kiloton range.  In a civilian setting,
the difference in effects would be small.  This is because the blast and
thermal effects do not scale linearly with yield (which is why really
large bombs are pretty useless except in instances where they can
be detonated against fortified targets) and because the blast and thermal
effects do damage much further out than the prompt radiation does.  
Civilian structures just don't take much blast to destroy them.
The true purpose of the enhanced radiation weapon is for use against
armor.  Armor isn't affected by either thermal or blast unless extremely
close to ground zero.  Armor, and its inhabitants, IS harmed by 
intense radiation.

In the context of your question, it is important to realize that an advanced
implosion fission device is the trigger for thermonuclear bomb.

It is simply not possible for a third world country to make a strategic
bomb.  While pure fission yields in the vicinity of a megaton have been
demonstrated by the superpowers, the technology is very advanced and
is the culmination of decades of research.  Even if say, a 100 kt
fission bomb could be built and delivered, it would not be a "city
buster", at least not in a major city.  The pictures of Hiroshima
and Nagasaki distort the effects of a bomb because both cities were
essentially matchboxes just waiting to be blown over.  Telling is
the relative integrity of "modern" buildings even close to ground zero.

Consulting the bomb blast calculator from ye olde "The Effects of Nuclear
Weapons", a 100 kt bomb produces a 5 psi overpressure out only to 
about 3/4 mile and that is if the device is detonated at the optimum 
altitude.  While a 5 psi overpressure will destroy a frame house, it
does little more than blow out the windows of a re-enforced building
typical of office buildings.  If such a bomb were detonated on the 
ground in the center of a large city, the buildings close in would 
absorb much of the blast, shielding buildings further out.

If a country can build and test an implosion weapon, it still faces the
daunting task of building and testing the secondary.

John
-- 
John De Armond, WD4OQC, Marietta, GA    jgd@dixie.com 
Performance Engineering Magazine.  Email to me published at my sole discretion
Clinton at Normandy for D-day is worse than Hitler presiding over the 
Holocaust Museum.