From: jim bell <jimbell@pacifier.com>
Date: Sun, 25 Feb 1996 07:36:52 +0800
To: Black Unicorn <unicorn@schloss.li>
Subject: Re: [Off topic] Re: Easy Nuclear Detonator
Message-ID: <m0tqAvX-000958C@pacifier.com>
MIME-Version: 1.0
Content-Type: text/plain




At 08:05 PM 2/22/96 -0500, Black Unicorn wrote:

>Actually, your design still is vulnerable to my objection, as my 
>objection was specifically to your intermediary chamber concept.
>
>Your intermediary chamber, if surrounding the blasting cap, is likely to 
>detonate to one side first, at a right angle to the axis of the chamber 
>to the explosive assembly. 

What I anticipated, to tell you the truth, was a long intermediary thin tube 
(again, 1 mm diameter for concreteness, just as an example) BETWEEN a 
chamber surrounding the cap, and the secondary chamber.  (the secondary 
chamber would be carefully designed to spread the shock front evenly)   I 
fully intended to avoid all of the possible consequences of weird explosive 
modes in common blasting caps.

What really mystifies me is that you would think somebody who was 
intelligent enough to be capable of building a bomb could possibly be 
unaware of the strange behavior of common blasting caps?  Do you think we're 
all stupid out here?!?

Last time I talked to Dr. Edgerton in his lab (You _do_ know about Dr. 
Edgerton, don't you?!?  EG+G?), in about 1978 or so, he showed me some 
interesting pictures he had taken of blasting caps exploding, and the weird 
patterns they made.  Believe me, from that moment onwards I had no illusions 
about the predictability of the common blasting cap.  

BTW, the reason Edgerton paid a bit of attention to ME, as opposed to 
every other lowly undergrad at MIT, was the fact that I did something he had 
tried many times and failed to do:  For my strobe laboratory project, I decided 
that I was going to photograph a popcorn kernel opening up at 10,000 frames 
per second.  He called it "impossible": I called it a challenge.  That is 
why I did the  project.  I showed him 11 frames taken a few weeks later.

Dr. Edgerton was suitably impressed.

>> >1>  Interference from the milling shape and accuracy o
f the openings to 
>> >the tubes containing the liquid explosive.
>> 
>> Quantify, quantify.  How much of a problem?
>
>Clever question given that I am without any information as to the exact 
>shape of your tubes, if they are bowled down towards the explosive 
>assembly, or what their exact width (excepting your vague 1mm figure) 
>might be.  You make some guesses as to material, but these two are fairly 
>flimsy even by your own admission.

I don't expect you to be able to "use ESP" and anticipate all the exact 
mistakes somebody could make.  Rather, you should be willing to accept the 
principle, and explain how much inaccuracy is "too much," and try to give an 
example of an error that would produce an inaccuracy of this magnitude.  So 
far you've done none of this.  I have to conclude you were simply trolling, 
or intentionally spreading FUD (Fear, Uncertainty, and Doubt) without 
genuinely trying to get involved in an interesting hypthetical idea.

BTW, while I do indeed consider this as purely hypothetical, on the 
offchance you're a FUDmeister from the government, you should be aware that 
_I'm_ fully aware that while the main form of radioactive emanation from 
Pu-239 is alphas which can be stopped by a piece of paper or a few inches of 
air, I am also fully aware that the decay produces a substantial quantity of 
gamma radiation (whose exact wavelengths and energies I can easily look up 
in my trusty CRC Handbook).   So don't bother flying an airplane equipped 
with a gamma ray detector over my house; while I haven't the inclination to 
do the calculations, were it important to do so I'd calculate the minimum 
thickness of lead required to reduce the gamma intensity to below-background 
levels (using gamma-ray cross section tables and the appropriate equations), 
double or triple it, _and_ ensure that anything I did manage to acquire would 
be invisible to even a secretly-placed nearby detector at all times.

And I'm also fully aware of ground-penetrating SAR (and the possibility of 
mobile variants) and JSTARS and terahertz radar, etc, so don't bother scanning.

>All you need to realize to appreciate the problem is that if you do not 
>have a precisely milled end, with a precise depth into the compressing high 
>explosive outer face, you have differences in how and when the various 
>faces of the explosive assembly are going to initiate.  If you make your 
>tubes narrow, it becomes very hard to mill the ends of your tubes, and if 
>you widen the tubes, it exagerates the distortive effect of 
>irregularities in the tube ends.

But you should be able to estimate the magnitude of the errors.  Given a 
certain detonation velocity, for example, and assuming some sort of 
localized slowdown/speedup to to this velocity, you should be able to 
estimate (even if only accurate to a factor of 2-3) the amount of error 
present at that particular junction.  Again, the fact that you have never 
done even this rudimentary analysis is quite telling.  You've revealed 
nothing that I wasn't aware of, and that was apparently quite intentional.

>I'm not in the business of designing nuclear initiators.  I expose poorly 
>thought out explosive engineering as a hobby.  Your best solution is to 
>mill each tube exactly alike, right down the the degree of bend and slope 
>of arc as well as shape of either end.  But you could have figured that 
>out without me spelling it our for you.

More likely, I would have velocity-tested sample configurations down to 10 
nsec accuracy, which would have revealed any unexpected error sources from 
temperature and/or pressure variation, as well as mechanical considerations 
such as bent tubing, etc... 

[stuff deleted]

>But they don't.  The timing problem is quite significant.  Why do you 
>think high speed and superaccurate switches are so well guarded?  There 
>isn't an easy grassroots substitute, if there were, the switches would be 
>fairly useless.

Maybe that's the secret.  I already anticipated this.  If it's the 
government's motivation to keep "terrorists" from trying to build a bomb, 
then their first line of defense might be to make it appear more difficult 
than it really is.  They also know that secrets which are actually turned 
into running, installed hardware eventually leak to the public, meaning that 
it might actually be better to keep THEIR bombs complicated, and to not use 
simplifying hardware. 


>> >Remember, kryonic switiches are necessary even when dealing with the 
>> >speeds of electric conductivity.  The velocities of even hydrazine based 
>> >explosives are signigicantly lower.  The margin for error is similarly 
lower.
>> 
>> How low?  Be specific.
>
>Again, I don't know what your dimentions are.  Hydrazine explosives tend 
>to detonate around 8500-10000 m/s.  The speed of transmission of electric 
>impulses through a given conductive medium is certainly much higher.

Why do you keep mentioning "hydrazine explosives" when I didn't?  Are you 
some sort of "one-trick pony"?

>
>> >Plutonium gun is still the easiest method for the home grown nuclear 
>> >device, even if it requires more fissile material.
>> 
>> The "gun" design wasn't used with the plutonium, because IT WOULD NOT HAVE 
>> WORKED! "Fat Man," the bomb dropped on Nagasaki, used the implosion 
method.  
>> "Little Boy," the gun-method bomb, used U-235.   Plutonium detonates far 
too 
>> rapidly to use the "gun" method.   The 
>> scientists knew that in 1945.  You seem to be at least 50 years behind the 
>> times.
>
>You are correct this time.  My fault.  Uranium should have been in there.  
>Typo on my part. 

Finally!  He's able to admit a MISTAKE!  


>Hey, be my guest.  If you had a critical mass worth of plutonium you're 
>playing around with the wrong list, and, I might add, wasting your time 
>with anything but the black market for the material.

If I had some, or for that matter if I even wanted some, would I be 
advertising the fact on an "NSA-required-reading" list BEFORE I'd done 
all this work?