On Thu, 23 Feb 2012 23:53:17 -0500, Ed Huntress
wrote:

On Thu, 23 Feb 2012 20:37:59 -0800, Paul Drahn
wrote:

On 2/23/2012 8:08 PM, Richard wrote:
Like most of us (baby boomers) I grew up in a world that already had
nuclear weapons. We did "Duck and Cover" drills in school, and I
thought I had a fair notion about how these things worked.

But this photo (second one on this page) of the PU core of the
"Fat Man" implosion device - it's so small...fit's in your hand.




http://simplethinking.com/home/nuclear_weapons.htm

The majority of the energy release is nearly instantaneous, the mean
time from neutron release to fission can be of the order of 10
nanoseconds, and the chain reaction builds exponentially. The result is
that greater than 99% of the very considerable energy released in an
atomic explosion is generated in the last few (typically 4-5)
generations of fission -- less than a tenth of a microsecond.*

This tremendous energy release in a small space over fantastically short
periods of time creates some unusual phenomena -- physical conditions
that have no equal on earth, no matter how much TNT is stacked up.


A fascinating collection of high speed photos...

http://simplethinking.com/home/rapat...hotographs.htm

http://simplethinking.com/home/rapatronic_2.shtml

and the "rope tricks"...
http://simplethinking.com/home/rapatronic_3.shtml
Very impressive photos. I don't recall seeing them before.

Still the critical component is not described. It is the mechanism to
trigger the conventional explosive segments all at the identical time.
The key word being - identical. The failure of these devices in the last
North Korea test probably caused the dud. Until Iran is able manufacture
the devices and get them to work properly, all the uranium in the world
will not get them the bomb.

Paul

Well, that *is* really a problem. All of the plutonium in the world
won't get them a bomb, but the gun trigger for Little Man

That should be "Little Boy," the Hiroshima bomb. We had never tested a
gun-tirgger bomb before we dropped Little Boy.

--
Ed Huntress

could
probably have been made in a good basement shop. That's why it's a lot
scarier for them to have enriched uranium than plutonium. Any goof can
make a gun-trigger uranium bomb, if they have a plan that gives them
useable dimensions.

The US made a few gun-trigger bombs, and the Brits made a few, and
then we both scrapped them. They're dangerous as hell: anything that
will set off the explosive charge, like lightening or a big spark,
can, theoretically, make them go "boom."

Gun triggers won't work with plutonium because the bomb will
self-destruct before the chain reaction is more than a fizzle. BTW. it
takes a much larger uranium pit than a plutonium pit to make a bomb.