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 Question for The Mad Scientist

 Author:  Topic:  Posted:
Sep 10, 2002
 Comments:
In current news reports, claims have been made by an influential London think-tank that Saddam Hussein could build a nuclear weapon within six months, if he is able to acquire the necessary nuclear materials. How far are you from completing your own weapon of mass destruction, and what level of threat do you feel you pose to democracy? How long should the United States hesitate before responding to your arms manufacturing efforts?
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That's what I said to myself! (none / 0) (#1)
by because it isnt on Tue Sep 10th, 2002 at 01:43:37 AM PST
I'm close to building a nuclear weapon, too! I'm just as close as Saddam is. All I need is, uh, nuclear materials. Everybody else in the world is "close" to building a nuclear weapon, if only they could get some plutonium, which is THE WHOLE FUCKING POINT. Meanwhile, Dubya has a crate of millions upon millions of nuclear weapons. Plus, America has already asserted it's willingness to use nuclear weapons in anger at what it perceives as its "enemies".

I say we launch a pre-emptive attack against these American warmongers, because if we don't, they will hold the world to ransom with their indescriminate bombing campaigns.
adequacy.org -- because it isn't

Not so (none / 0) (#2)
by T Reginald Gibbons on Tue Sep 10th, 2002 at 01:55:23 AM PST
As I'm sure El Cient�fico Enojado will hasten to point out, one needs more than a ready pair of hands and 20 kilograms of Uranium. A spryton is, I believe, quite necessary, although I haven't a clue what it might be for. Indeed, if your attitude to weapons research were true, it would have been sufficient for the Manhattan Project to send J. Robert Oppenheimer to Hiroshima with ten kilograms of Plutonium in one and and ten kilograms of Plutonium in the other. Upon arriving in Japan, he could yell something spooky about becoming death and smash his hands together, causing destruction and chaos.


Actually... (none / 0) (#3)
by gordonjcp on Tue Sep 10th, 2002 at 02:52:04 AM PST
... that would pretty much work.


In principle, yes. (none / 0) (#4)
by The Mad Scientist on Tue Sep 10th, 2002 at 04:06:33 AM PST
Practically, no.

At the moment the subcritical masses start forming a critical one, they start to strongly repulse each other.

So it would technically work, you would get decent chain reaction, and before releasing enough of energy to be worth of the effort, disperse around much like a crude dirty bomb.

In fact, in case of plutonium bombs, if you don't manage to synchronize all the explosive lenses to fire at exactly the same moment or have nonhomogenities in them that could disrupt the pressure waves, the compression of the core will not be symmetrical which will lead to dramatical lowering of the bomb's yield. Actually, asynchronous detonation of the charges is used in real-life bomb assemblies in case the bomb's electronics detects tampering and decides to self-destruct.


Oh, yeah, it wouldn't be a very good bomb (none / 0) (#5)
by gordonjcp on Tue Sep 10th, 2002 at 05:29:53 AM PST
But it would make quite a mess. Some of the early bombs tested were crude "gun"-type devices, which were large and difficult to make, for a given yield. They worked in much the same way.


Nitpicking and construction hints (none / 0) (#8)
by The Mad Scientist on Tue Sep 10th, 2002 at 06:21:25 AM PST
The only known-to-me gun type device ever detonated was Little Boy.

Similar configurations were routinely used for research of criticality issues, when ie. a slug of 235U was free-falling through a ring of 235U, temporarily forming critical mass for few milliseconds. The resulting neutron flux was measured. Sharp spike meant critical amount was reached.

A gun-type device is very simple to construct. The only problematic thing is the fissile core itself, and maybe the 238-U shields and neutron mirrors around it. (Indium-doped steel does its job too.)

There are drastical limitations of gun-assembly device performance, though. The yield is limited to about 20-25 kilotons at most; the speed of insertion is limited, and the assembly will vaporize before the assembly is finished, thus wasting alot of energy. The trick of high yields from the primary stage (we aren't talking thermonuclear now) is to release as much of energy at the first nanoseconds; once the device turns to plasma and starts to expand, the density of the fissile core dramatically decreases, thus becoming subcritical rather quickly.

Another problem of gun assembly is the fissile material. Uranium comes as a mixture of isotopes 235 and 238 (and some 233 and traces of others), which are difficult to separate. Plutonium is easier; comes as 239 and 240, both are fissile, and can be manufactured by irradiating of 238-U by neutrons (a commercial power plant reactor is enough). The problem here is that 240 is fissile, but doesn't release neutrons, thus doesn't contribute to the chain reaction and decreases the neutron population. 239 is the primary product here, but when it stays in the reactor for too long, it becomes 240 easily. In a common VVER-based power plant, where you exchange typically a 1/4 of the fuel quarterly and total stay-in time is one year, you get plutonium unusably contaminated with 240 - too much for a decent bomb. Thus you want to shorten the fuel cycles, which will require more frequent shutdowns of the plant, which will attract the intelligence services. (Guess what revealed nuclear program of North Korea couple years ago.)

You can theoretically use plutonium for a gun-assembly device, but the yield will be even lower - and plutonium has some more undesirable characteristics, like higher neutron production in subcritical state, which poses alot of secondary problems.

If I'd have enough of weapon-grade 235-U (about 25 kilograms - it should be possible to build a nuke with less, but it requires more hightech magic), and a smaller sponsor (a typical sponsored regional sport event would eat about as much money than I'd need for this project, except for the uranium), a gun-type nuke would be well-within my capabilities.

The resulting device would be rather large and heavy and crude, unsuitable for delivery by anything other than a middle-to-large aircraft or a truck (forget about grenades, forget about missiles), but hey - it'd be a nuke.


A note about reactors (none / 0) (#9)
by The Mad Scientist on Tue Sep 10th, 2002 at 06:25:21 AM PST
Thus you want to shorten the fuel cycles, which will require more frequent shutdowns of the plant, which will attract the intelligence services.

Or you could use a different kind of reactors, like Canadian CANDU or Russian RBMK, which don't have to be shut down for exchanging the fuel.


 
or... (none / 0) (#14)
by PotatoError on Tue Sep 10th, 2002 at 10:03:26 AM PST
you could just take a visit to the former soviet union. ALthough I am sure it isn't as easy to purchase nuclear material as some in the media say, I'm sure that if you have the money there will be someone willing to sell.

What about making it yourself though? Pakistan and India use Uranium mined from their own countries. Of course the tricky bit is to separate the 235. I know there are two methods to do this (gas diffusion and mass spectography or both), there may be more I don't know of. But the devices to do this require quite a lot of land area in order to separate enough 235. Although I suppose you could just set up smaller systems which had a slower production time if you were trying to be covert about it.

Just imagine if there was a really fast and simple means of splitting U235 and 238. That would be crazy! Everyone in the world would have Uranium stockpiles in their back garden...imagine the fun!
<<JUMP! POGO POGO POGO BOUNCE! POGO POGO POGO>>

 
Now wait a minute. (none / 0) (#15)
by RobotSlave on Tue Sep 10th, 2002 at 10:04:05 AM PST
If you go with a gun assembly, where are you going to use your shiny, useless laser contraption? All that hypothetical bullshit for nothing!

Now, be a good boy, and thank the nice Mr. gordonjcp for introducing you to a simple design that wasn't in your copy of The Way Things Work, or whatever.

Credit where credit is due, Bad Cientist.


© 2002, RobotSlave. You may not reproduce this material, in whole or in part, without written permission of the owner.

'Slave striking again, part 2 (5.00 / 1) (#18)
by The Mad Scientist on Tue Sep 10th, 2002 at 10:42:36 AM PST
If you go with a gun assembly, where are you going to use your shiny, useless laser contraption? All that hypothetical bullshit for nothing!

This is a gun assembly, 'Slave. No synchronous ignition of explosives is necessary.

However, synchronous laser initiation of explosives is a sexy thing, even if not useful for this particular case.


Um, yes. (5.00 / 1) (#19)
by RobotSlave on Tue Sep 10th, 2002 at 11:13:15 AM PST
It must be lots of fun pretending you're so foreign that you can't understand a rhetorical question.

The game, I'm afraid, is over.


© 2002, RobotSlave. You may not reproduce this material, in whole or in part, without written permission of the owner.

The comeback king (none / 0) (#23)
by because it isnt on Tue Sep 10th, 2002 at 12:22:47 PM PST
has made yet another dumb question secretly ironic.
adequacy.org -- because it isn't

personally I just enjoy (5.00 / 3) (#25)
by nathan on Tue Sep 10th, 2002 at 12:45:05 PM PST
RobotSlave vs RobotSlav.

Nathan
--
Li'l Sis: Yo, that's a real grey area. Even by my lax standards.

+5, Puntastic [n/t] (none / 0) (#26)
by because it isnt on Tue Sep 10th, 2002 at 12:53:54 PM PST

adequacy.org -- because it isn't

 
oh...ugggggggggggggghhhhhhhhhh (none / 0) (#27)
by derek3000 on Tue Sep 10th, 2002 at 01:07:40 PM PST
fucking brilliant you cocksmoker


----------------
"Feel me when I bring it!" --Gay Jamie

 
Refresh my memory. (none / 0) (#6)
by derek3000 on Tue Sep 10th, 2002 at 05:57:05 AM PST
Is that from the Tibetan Book of the Dead, or some other weird text?


----------------
"Feel me when I bring it!" --Gay Jamie

different brown-people book (none / 0) (#7)
by nathan on Tue Sep 10th, 2002 at 06:13:04 AM PST
Bhagavad Gita.

Nathan
--
Li'l Sis: Yo, that's a real grey area. Even by my lax standards.

Thank you. (none / 0) (#10)
by derek3000 on Tue Sep 10th, 2002 at 07:12:32 AM PST
Fuckin' darkies.


----------------
"Feel me when I bring it!" --Gay Jamie

 
Perhaps you meant a krytron? (none / 0) (#11)
by Adam Rightmann on Tue Sep 10th, 2002 at 08:33:23 AM PST
A kyrtron is used to very quickly switch high currents. In conjunction with Mad Scientists' detailed explanations, I think they are used to ensure critical timing in nuclear and thermonuclear explosions, so we get megaton explosions instead of kiloton fizzles. One could say, that without the kryton, Europe would be a communist controlled hellhole where possession of a Bible is illegal, instead of Europe being a communist controlled hellhole where possession of a Bible is distasteful.


A. Rightmann

Krytron vs sprytron (none / 0) (#12)
by The Mad Scientist on Tue Sep 10th, 2002 at 08:55:18 AM PST
There is small difference between these two. Krytrons are filled with low-pressure gas, while sprytrons contain vacuum.

Early models of nuclear arms were using krytrons. Development of sprytrons was caused by the fact krytrons tended to be susceptible to fire not only with the trigger pulse, but also if they were hit by a flash of ionizing radiation, common for nearby nuke detonations. (Which was a necessary condition to survive intact for the planned full-blown nuclear war.) Sprytrons are also less sensitive to the ionizing radiation from the bomb's core itself (and other parts, like the tritium gas reservoirs), which increases reliability.

I personally think that all the fuzz with embargoing krytrons (and making problems to my university friends who use them for triggering their laser experiments) would be eliminated if someone would test synchronous detonating of several charges using a laser beam. (Which is in rudimentary not-so-accurately synchronized version used for detonating some kinds of explosives in mines; optical fiber is then used instead of a wire.) My idea involves a strong (ie. Nd:YAG) laser pulse, fed to appropriate number of optical fibers and led to the appropriate explosive charges around the bomb's core, instead of using the common "exploding wire" priming method. Deploying this design would make some of the embargoed parts (like low-inductance capacitors and fast high-current switching elements) irrelevant (and possibly available on an open market), so my EMP weapon project wouldn't need so much of man-hours on mere construction of basic parts. (Though the triggered spark-gap results were encouraging.)


We've been over this. (none / 0) (#13)
by RobotSlave on Tue Sep 10th, 2002 at 10:00:29 AM PST
Now you have to trigger your laser.


© 2002, RobotSlave. You may not reproduce this material, in whole or in part, without written permission of the owner.

Solution: (none / 0) (#16)
by The Mad Scientist on Tue Sep 10th, 2002 at 10:14:17 AM PST
Now you have to trigger your laser.

Triggered spark gap.

Very short rise time. The hard to predict delay before switching on doesn't matter here, as we are switching only one laser and don't need to synchronize it with any other one.


Won't work. (none / 0) (#20)
by RobotSlave on Tue Sep 10th, 2002 at 11:49:50 AM PST
Get back to us when you're done burning up splitters and fibers. You don't explode foil with communications-grade lasers, doofus.

The big boys aren't using sprytrons just for the hell of it, which you'd realize if you weren't just cutting and pasting from university web sites and old issues of Popular Mechanics.


© 2002, RobotSlave. You may not reproduce this material, in whole or in part, without written permission of the owner.

Tested, works. (none / 0) (#21)
by The Mad Scientist on Tue Sep 10th, 2002 at 12:10:01 PM PST
You don't explode foil with communications-grade lasers, doofus.

Nd:YAG isn't used (at least not commonly) as a communication-grade laser, ummm - 'Slave.

The technology is in use, and is called "laser slapper". I even guessed the suitable laser type well.

The big boys aren't using sprytrons just for the hell of it, which you'd realize if you weren't just cutting and pasting from university web sites and old issues of Popular Mechanics.

I rarely cut/paste. When I take the pains of looking it up, instead of relying on memory, I refer to the sources.


Thank you. (none / 0) (#24)
by RobotSlave on Tue Sep 10th, 2002 at 12:27:38 PM PST
I like this new trick you have where you take what I've said and pretend it was the opposite.

So droll.

At least you've admitted this isn't something you thought up on your own.

(Yes, I can copy press releases onto a web page and pretend I wrote it all ten years ago, too).

Incidentally, your subject should have been "Is being tested, doesn't work well enough for nukes yet, nowhere near deployment."

The weak link is the foil, of course. Manufacturing that stuff to the tolerances necessary is harder than building a sprytron from scratch.


© 2002, RobotSlave. You may not reproduce this material, in whole or in part, without written permission of the owner.

 
Very funny (none / 0) (#22)
by Ortho Normal on Tue Sep 10th, 2002 at 12:17:53 PM PST
Funniest thing I've seen in a while.


 

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