Way off topic, still.... On Wed, 21 Feb 1996, jim bell wrote:
At 10:56 PM 2/21/96 -0500, Black Unicorn wrote:
On Sun, 18 Feb 1996, jim bell wrote:
[easy nuclear initiation device described, key in design are:]
"Multiple very thin flexible hollow tubes (1 mm ID? teflon?) filled with a homogenous liquid explosive (for example, pure nitromethane)
To which I reply:
This method is so dependent on the uniformity of the initiator (the cap in this instance) as to be nearly useless. Normal blasting caps do not detonate with the uniformity required to initiate each of the tube paths at the same time. In the off chance that you contemplated surrounding the cap with liquid explosive of a sufficent type, (which still wouldn't assure proper uniformity with any certainty as the liquid explosive is as likely to detonate slightly off left to right as up to down) you still have extremely difficult problems to overcome.
Re-read my whole statement. I copy the relevant commentary that you sloppily forgot to read:
Detonated from a single cap, with an intermediary chamber of liquid explosive to stabilize the shock front,
You, quite inadvertantly I am sure, managed to ignore the following:
In the off chance that you contemplated surrounding the cap with liquid explosive of a sufficent type, (which still wouldn't assure proper uniformity with any certainty as the liquid explosive is as likely to detonate slightly off left to right as up to down) you still have extremely difficult problems to overcome.
And thus boast:
I already entirely anticipated your objection. And destroyed it.
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. Blasting caps tend to rupture their casings on one side before the other. In this case you will have a left to right detonation in the intermediary chamber, as I indicated. If you have your tubes spun off the chamber like a starfish, your initiation times will vary, probably significantly. In the worst case, the duration determined by diameter of chamber/velocity of detonation. In the event your chamber is 1/5 of the length of the tubes themselves, you will have one side of your explosive assembly detonating when another tube has 1/5 a length to go. As you have not specified any of the dimentions of your chamber or tubes, or the exact liquid explosive you intend to use, the delay is impossible to quantify exactly. Attempting to mitigate the delay by shortening the tubes brings the explosive assembly closer to the intermediary chamber, with associated hazards. Most problematic, disruption of the reflector orientations. Also note, that if starfished, the worst possible timing error will occur, that being, the tubes with the most extreme difference in initiation time will be those at opposite poles of the quasi-sphere of the explosive assembly. Bad news for uniform compression. If you intend to run the intermediary chamber into a funnel before seperating into your individual tubes, you have the same problem as if you never had a chamber at all, namely the initiation of one or the other tubes before the rest. While the funnel may limit the effect of radial differences in initiation timing, it complicates things by requiring very precise milling of the connections of the tubes to the intermediary chamber as well as such milling at the ends which meet your explosive assembly.
1> Interference from the milling shape and accuracy of 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. 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. It's very simple, if you don't have a precisely flat end of tube, you have a shaped charge in effect. On the other end, you have problems with easy of initiation. (Hint: If you seriously
believed there was a problem with this idea, you would be able to give a few examples on how to avoid them. Reading your commentary, you did none of this.
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.
2> Mild to obscure impurities in the liquid explosives causing differences in velocity with respect to other tubes.
All the tubes can be filled at the last minute by pulling a vacuum on the system and letting atmospheric pressure fill all the tubes. No impurities, or at least it's a perfectly homogeneous mixture.
Hard to prevent with a hydrazine explosive. Hydrazine based explosives may vary as much as 10-15% in velocity of detonation with mere .1% changes in pressure and 1% changes in temp. I don't know how impurity comes into play exactly, but I suspect they are very sensitive to such changes as well.
Even small changes in pressures within the tubes might cause enough timing problems to make uniform initiation of the primary high explosive assembly impossible.
"might"? Well, could you be more specific? How many nanoseconds would be too many?
What is the mass of your subcritial material? What shape are you using? Simple sphere or multifaceted polygon? What is the thickness of your compressive explosive? What kind of explosive is it? How deep are the initiators inserted into the compressive explosive? What is the material of your tubes? Glass or metalic? (Metalic will be force conductive before failure, glass will merely shatter, the difference in initiation points in the compressive explosive will be equal to the depth of the tubes when comparing glass and metalic tubes. Glass is likely to initiatite at the surface, metalic tubes at the point of tube terminus.
3> Interference from the milling shape and accuracy of the terminus of the tubes containing the liquid explosive.
So what's your point?
You might have signifincantly different characteristics in the initiation of your compressive explosive. As I said before, anything but a precisely milled flat end on your tubes will effectively be a shaped charge. The effects of various shapes at the ends of tubes are left as an exercise for the reader.
4> Overpressure in the device causing premature detonation of the near portion of the high explosive assembly.
Sure about that?
Quite. It was a big problem in the first compressive devices. Some early experimentation produced mushroom like shapes in the compressed material (inert for experimentation) because one side of the compressive explosive was initiated by presure of the impact of the casing itself. Supercriticality would not have been achieved in these instances of failure. Further experimentation attempted to rectify the problem by placing the entire inner chamber at .25 of an atmosphere. I think their eventual solution got around overpressure initiation in a simplier way, but I don't recall what it was. (Might have been new explosives for the compression phase)
All of these might cause enough timing error to prevent uniform pressure and thus prevent uniform compression and make supercriticality impossible.
Pigs might fly.
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.
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.
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. Doesn't change the fact that it's much easier as an initiator.
Sheesh! I guess we now know what field YOU don't know about, huh? Or, perhaps more likely, this is a specific DIS-information campaign. You want someone to waste a critical-mass worth of plutonium.
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. --- My prefered and soon to be permanent e-mail address: unicorn@schloss.li "In fact, had Bancroft not existed, potestas scientiae in usu est Franklin might have had to invent him." in nihilum nil posse reverti 00B9289C28DC0E55 E16D5378B81E1C96 - Finger for Current Key Information