Path: utzoo!attcan!uunet!lll-winken!elroy.jpl.nasa.gov!usc!ucsd!pacbell.com!att!cbnews!cbnews!military From: ccastjr@prism.gatech.edu (COOOooOoooooOOOOoOOoOOooKIE!!!!!) Newsgroups: sci.military Subject: Re: Question about Nuclear Weapons Keywords: MRVs Message-ID: <1990Oct26.021147.27271@cbnews.att.com> Date: 26 Oct 90 02:11:47 GMT References: <1990Oct23.190943.7623@cbnews.att.com> <1990Oct24.114913.4072@cbnews.att.com> <1990Oct25.151832.2153@cbnews.att.com> Sender: military@cbnews.att.com (William B. Thacker) Organization: Georgia Institute of Technology Lines: 71 Approved: military@att.att.com From: ccastjr@prism.gatech.edu (COOOooOoooooOOOOoOOoOOooKIE!!!!!) In article <1990Oct25.151832.2153@cbnews.att.com> ntaib@silver.ucs.indiana.edu (Nur Iskandar Taib) writes: > > >From: ntaib@silver.ucs.indiana.edu (Nur Iskandar Taib) >>>My question >>>is as follows: Are not nuclear weapons detinated buy compressing the core of >>>highly radioactive material until the mass is critical? If so couldn't (at >>>least theoretically) the pressure of the water on the warhead at deep depths >>>cause the warhead to ge critical? > >I always thought the fissionable material is stored in >the bomb in several sub-critical mass pieces, which are >slammed together by explosive charges. I wonder if the >explosives are really necessary: if one simply moves all >the pieces together into a big lump (do neutrons really >care if there is 0.1mm of air in the way?) won't it ex- >ceed critical mass and go off? I heard that the first >From what I know of nulcear weapons, these are both technically correct. Plutonium bombs use a sphere (or simular shape) of plutonium surrounded by an equally distributed explosive. When the Plutonium is compressed by the extremely high pressure of the explosion, it becomes critical. The second method (used in Uranium bombs), has the fissionable separated (examples usually have two masses at opposite ends of a tube..in these one of the masses is smaller, and fits as kind of a plug into the larger). To detonate, you slam the peices together. The reason you can't do the latter with Plutonium is that the reaction occurs (either too fast or too uneven), and you get a lot of small explosions while the plutonium is traveling through the tube (on it's way to the other piece of plutonium). This creates a rather small explosion (in terms of nuclear weapons), in which most of the fissionable has been blown out of the bomb, and to the winds (and thus not used). While if all you want is a small, dirty bomb (high radiation), that's great... but it's a waste of money and material... you can get the same from a good chemical weapon. The reason Uranium works with the latter is that it's reaction time is slow enough that the peices don't actually acheive critical mass reactions until they are in contact. I believe Uranium can also be used for spherical bombs too. The reason that the spherical one works is that "critical mass" means that enough neutrons are able to hit more atoms of the fissionable to perpetuate the reaction. This can be done by sheer mass, OR by density (ie. if you've got enough mass, then the peices at the center will have all of their neutrons hitting the atoms further out than them..and if you've got enough atoms, this will perpetuate the reaction.. OR.. if the atoms are extremely close together, the neutrons have a higher chance of hitting a neighboring atom). Hope that all made sence.. I'm not a physicist.... (I learned most of this when I was in NROTC, and that was just a topical overview of the systems... ) John -- Emporers Thought for the Day: | John E. Rudd jr. Only the insane have the strength to prosper; | ccastjr@prism.gatech.edu Only those who prosper judge what is sane. | (ex- kzin@ucscb.ucsc.edu) #include Send all comments, flames, and complaints to /dev/null.