morgan@ms.uky.edu (Wes Morgan) (10/24/90)
From: Wes Morgan <morgan@ms.uky.edu> v126lm7l@ubvmsd.cc.buffalo.edu (Patrick E Montgomery) writes: > >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? The important variable in the equation is time. As I under- stand the theory, critical mass is achieved by an *exponential* increase in pressure. With a nuclear device falling into the depths, the increase in pressure is so gradual that critical mass cannot be achieved. -- | Wes Morgan, not speaking for | {any major site}!ukma!ukecc!morgan | | the University of Kentucky's | morgan@engr.uky.edu | | Engineering Computing Center | morgan%engr.uky.edu@UKCC.BITNET | Lint is the compiler's only means of dampening the programmer's ego.
v126lm7l@ubvmsd.cc.buffalo.edu (Patrick E Montgomery) (10/24/90)
From: v126lm7l@ubvmsd.cc.buffalo.edu (Patrick E Montgomery)
My question stems from the movie "the Abyiss" Sp?. In the movie a group of
navy SEALS uses special deep water diving gear to investigate the wreck of an
American ballistic missile sub. To destroy the evidence the SEALS take a
warhead off of one of the mrvs and transport it to a diving rig. 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 sea water on the warhead at deep depths
cause the warhead to ge critical? It is important when the warhead falls of a
underwater cliff and falls a unknown distance to the sea floor. Also, can
anyone recommend a book an nuclear warhead constuction/theory any that I have
seen are not at all technical. comments, ext post or email to above address.
thanks.
pat(v126lm7l)goldberg@oasys.dt.navy.mil (Mark Goldberg) (10/25/90)
From: goldberg@oasys.dt.navy.mil (Mark Goldberg) In article <1990Oct22.035642.17548@cbnews.att.com> v126lm7l@ubvmsd.cc.buffalo.edu (Patrick E Montgomery) writes: >From: v126lm7l@ubvmsd.cc.buffalo.edu (Patrick E Montgomery) >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 sea water on the warhead at deep depths cause the warhead >to get critical? It takes a strong implosive compression, as generated by a TNT explosion or even a low-level atomic explosion. I got this info from watching "Fat Man and Little Boy" plus a PBS special on the Manhattan Project. The info is consistent with my common-sense understanding of the process. So while the pressure under the sea can be great, it's probably nowhere near enough to set off the firecracker! =============================================================================== , , __ | "Everyone is entitled /|/| /| |) |/ / _. /\ | |\ |) [~ |) /~_ | to my opinion." / | /~| |\ |\ \__/ \/ |_ |/ |) [_ |\ \_/ | goldberg@oasys.dt.navy.mil
wrf@mab.ecse.rpi.edu (Wm Randolph Franklin) (10/25/90)
From: wrf@mab.ecse.rpi.edu (Wm Randolph Franklin) About the nuclear bomb in the movie "The Abyss": it would seem unlikely that it could explode far under water. 1. If the uranium (or whatever) is to be compressed very quickly, it's certainly not being compressed in a liquid, and no air or vacuum chamber would survive those depths. The problem is that as the pieces of U get closer together, the chain reaction doubling time gets smaller. All the U has to get into one small region before the chain reaction gets too big or there's a misfire. Depending on the type of fissile material, a neutron source (initiator) helps start the reaction, but still everything has to come together at a high speed in the proper sequence. In fact the easiest way to stop a booby trapped big A- or H-bomb would probably be to detonate a large explosion near it. It would spread fissile material around but couldn't detonate it. 2. You have to assume the underwater bomb would be waterlogged being so far below its design depth. So any batteries would probably be discharged and if not no high voltage circuit would operate. Related to this: what's the status of all the conventional WW2 explosives on the bottom, like the Bismark's munitions? Do they get more and more unstable until one day they go off when a sinking beer can hits the ship, or is there a gentle degradation path to more stable chemicals? -- Wm. Randolph Franklin Internet: wrf@ecse.rpi.edu (or @cs.rpi.edu) Bitnet: Wrfrankl@Rpitsmts Telephone: (518) 276-6077; Telex: 6716050 RPI TROU; Fax: (518) 276-6261 Paper: ECSE Dept., 6026 JEC, Rensselaer Polytechnic Inst, Troy NY, 12180
ntaib@silver.ucs.indiana.edu (Nur Iskandar Taib) (10/25/90)
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 atomic bomb scientists determined the critical mass for ^235 U by dropping various size spheres through donuts, and watching for neutrons. This was supposedly very risky.. if the two together exceeded critical mass, the whole thing could have gone off. Now, whether or not deep sea pressures are enough to squeeze the pieces of Pu together depends on many things: 1) How strong is the case 2) does it leak 3) will the pieces fit together even if forced together, or are they made so that they do not interlock, and one would need high explosive to force it into a spherical shape? If the case is too strong, the pressures will not crush it. If it leaks, the pressure inside will be the same as outside, so the pieces stay stationary. If the pieces don't fit together, it may end up with a big empty space in the middle. I don't think pressures even six miles down match what is produced by the triggering high explosives in the bomb. ------------------------------------------------------------------------------- Iskandar Taib | The only thing worse than Peach ala Internet: NTAIB@AQUA.UCS.INDIANA.EDU | Frog is Frog ala Peach Bitnet: NTAIB@IUBACS !
cr2r+@andrew.cmu.edu (Christian M. Restifo) (10/26/90)
From: "Christian M. Restifo" <cr2r+@andrew.cmu.edu> First, let's just say that although "The Abyss" was a good movie (in my opinion), the parts dealing with nuclear weapons were a little hard to believe. Warheads are not exposed like that. Secondly, no ballistic submarine goes chasing after unknown targets. It'll track and record them, but it really wants to remain undetected. Anyway, I'm sure if some rocket scientist sat down, he could calculate the theoretical depth at which the material would go critical. Most nuclear weapons, nowadays, are actually two nuclear weapons in one. A fission explosion causes the radioactive material to go critical and start a fusion reaction. I don't think any known depth could implode the material enough (at the same level of a fission explosion) to initiate a fusion reaction. Then again, I'm not a rocket scientist. Chris Restifo cr2r@andrew.cmu.edu
) (10/26/90)
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<std.disclaim> Send all comments, flames, and complaints to /dev/null.
jwm@stdc.jhuapl.edu (Jim Meritt ) (10/26/90)
From: jwm@stdc.jhuapl.edu (Jim Meritt ) >From: v126lm7l@ubvmsd.cc.buffalo.edu (Patrick E Montgomery) >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 sea water on the warhead at deep depths cause the warhead >to get critical? I would be terribly suprised if ocean water pressure got high enough to squeeze stronger than an implosion. However, getting squeezed is only part of the problem. The blast has to be contained in its supercritical state long enough for a significant amount of the fissionable to fission. Otherwise it fizzles. I REALLY doubt that ocean pressure (that had been slowly equalizing throughout the descent) could contain it. As a demo. We HAVE dropped the suckers into the ocean. No boom. The Soviets lost LOT of them (missle warheads on sunk SSBN) deep. No boom. Jim Meritt
fiddler%concertina@Sun.COM (Steve Hix) (10/29/90)
From: fiddler%concertina@Sun.COM (Steve Hix) In article <1990Oct25.151832.2153@cbnews.att.com>, ntaib@silver.ucs.indiana.edu (Nur Iskandar Taib) writes: > > I always thought the fissionable material is stored in > the bomb in several sub-critical mass pieces, which are > slammed together by explosive charges. That's one way to do it. > 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? Doing that might get you a "squib" explosion. Very little of the mass would fission, but the generated heat would blow the mass apart and scatter pieces around. You have to slam it together very quickly, and in just the right shape, or you don't get full yield. This was one of the tricky technical problems solved by the Manhatten project team; getting the explosives to all go off at the right time in the right direction(s) to properly implode the reactive mass. Just in case, they developed a second approach that fired a piece of (darn...one used Pu, the other used U) stuff at a just-less-than-critical mass. Both were used. Both worked. > I heard that the first > atomic bomb scientists determined the critical mass for > ^235 U by dropping various size spheres through donuts, > and watching for neutrons. This was supposedly very risky.. "Tickling the dragon's tail". At least one researcher (Louis Slotin) died after one such experiment went wrong. > if the two together exceeded critical mass, the whole > thing could have gone off. The problem was not so much one of an explosion killing you, as it was getting fried by the resulting high neutron flux. -- ------------ The only drawback with morning is that it comes at such an inconvenient time of day. ------------
henry@zoo.toronto.edu (Henry Spencer) (10/29/90)
From: henry@zoo.toronto.edu (Henry Spencer) >From: ntaib@silver.ucs.indiana.edu (Nur Iskandar Taib) >... I wonder if the >explosives are really necessary: if one simply moves all >the pieces together into a big lump ... won't it ex- >ceed critical mass and go off? ... No, because timing is critical. The chain reaction is not all or nothing. It starts to happen as the pieces *approach* each other (or as a single piece's density increases, which is actually what most modern bombs do). The graph of activity versus distance is not a step function at zero; it gradually rises in a near-asymptotic increase as distance drops. The significance of this is that if you move the pieces together slowly, the beginnings of the chain reaction will melt them down into radioactive slag (in the process generating enough radiation to kill you) long before they can come into contact. Move them together rather more quickly, and you will actually get an explosion equivalent to a modest charge of TNT, just enough to splatter radioactive debris around the immediate vicinity. If you want them to go "bang" instead of "splut", they have to go from separate pieces to one big lump ***QUICKLY***. In fact, the problems don't end when you get them together, because the critical mass will still tend to blow itself apart before it can react fully. Modern bombs have a massive casing that is imploded inward at very high speed, striking the fissionable core, compressing it almost instantaneously to very high densities, and delaying its expansion by sheer inertia to give it more time to fission. (The above is all public information, by the way.) -- The type syntax for C is essentially | Henry Spencer at U of Toronto Zoology unparsable. --Rob Pike | henry@zoo.toronto.edu utzoo!henry
jtchew@csa3.lbl.gov (JOSEPH T CHEW) (10/29/90)
From: jtchew@csa3.lbl.gov (JOSEPH T CHEW) In article <1990Oct26.021043.27122@cbnews.att.com>, cr2r+@andrew.cmu.edu (Christian M. Restifo) writes... >Most nuclear weapons, nowadays, are actually two nuclear weapons in one. >Afission explosion causes the radioactive material to go critical and >start a fusion reaction. I don't think any known depth could implode >the material enough (at the same level of a fission explosion) to >initiate a fusion reaction. Hmm. This seems to confuse three issues. A fission device is triggered by a conventional explosion. Mr. Restifo is probably thinking specifically of how a plutonium fission device works: conventional explosion compresses a sphere of fissile material. The resulting fission chain reaction does not involve fusion. A fusion device is triggered by a fission device. X-rays from the fission compress the tritium in a small target capsule. This was, I believe, the key idea contributed by Dr. Teller: radiative compression. An excellent beginner's introduction to fission weapons is John McPhee, "The Curve of Binding Energy" (Farrar Strauss Giroux, NY, 1976). The technical details of fusion weapons are harder to come by. I learned the above stuff (a subset of the nonclassified information, simplified for reasons of space) in the context of inertial-confinement fusion. --Joe "Just another personal opinion from the People's Republic of Berkeley"
military@cbnews.att.com (William B. Thacker) (10/29/90)
From: p14.f7.n391.z8.fidonet.org!Dan.Daetwyler (Dan Daetwyler) PE> least theoretically) the pressure of the sea water on the warhead at PE> deep depths PE> cause the warhead to ge critical? It is PE> important when the warhead falls of a PE> underwater cliff and falls a unknown PE> distance to the sea floor. Also, can PE> anyone recommend a book an nuclear PE> warhead constuction/theory any that I have PE> seen are not at all technical. comments, PE> ext post or email to above address. Compression of the fission materials is a typical technique, however the compression must occur in micro (maybe milli) seconds. A slow compression
gary@gatech.edu (Gary Coffman) (10/29/90)
From: ke4zv!gary@gatech.edu (Gary Coffman) In article <1990Oct26.021043.27122@cbnews.att.com> cr2r+@andrew.cmu.edu (Christian M. Restifo) writes: > > >From: "Christian M. Restifo" <cr2r+@andrew.cmu.edu> > >Anyway, I'm sure if some rocket scientist sat down, he could calculate >the theoretical depth at which the material would go critical. Most >nuclear weapons, nowadays, are actually two nuclear weapons in one. A >fission explosion causes the radioactive material to go critical and >start a fusion reaction. I don't think any known depth could implode >the material enough (at the same level of a fission explosion) to >initiate a fusion reaction. I'm not a rocket scientist, but I play one on the net. :-) The basic problem with detonating a fission bomb to to achieve super criticality quickly enough to prevent the weapon from "squibbing" when it becomes merely critical. If everything is not done just right, the weapon squibs and blows the nuclear material apart before a significant reaction takes place. When everything is done just right, the inertia of the pieces holds the core together in super critical conditions long enough to let the nuclear reaction really heat up. Even then the weapon explodes long before fission reaches completion. One of the quests of nuclear bomb designers is to find ways to hold the core super critical longer thus getting more yield from a given size device. The very deepest ocean trenches have insufficent pressure to prevent squib fire. Gary
henry@zoo.toronto.edu (Henry Spencer) (10/30/90)
From: henry@zoo.toronto.edu (Henry Spencer) >From: jtchew@csa3.lbl.gov (JOSEPH T CHEW) >An excellent beginner's introduction to fission weapons is John McPhee, "The >Curve of Binding Energy" (Farrar Strauss Giroux, NY, 1976). The technical >details of fusion weapons are harder to come by... A book that is worth reading is Howard Morland's "The Secret That Exploded". Morland was the author of the Progressive article that spilled the basic design principle of the fusion bomb. Morland worked exclusively from public material and unclassified interviews, so his deductions have to be taken with a grain of salt, but there is reason to believe he's close to the truth in many respects. -- "I don't *want* to be normal!" | Henry Spencer at U of Toronto Zoology "Not to worry." | henry@zoo.toronto.edu utzoo!henry
ntaib@silver.ucs.indiana.edu (Nur Iskandar Taib) (11/01/90)
From: ntaib@silver.ucs.indiana.edu (Nur Iskandar Taib) *>In fact the easiest way to stop a booby trapped big A- or H-bomb would *>probably be to detonate a large explosion near it. It would spread *>fissile material around but couldn't detonate it. Speaking of which, how many times have you seen, on TV or in movies, someone disarming a nuclear bomb by removing a piece of it out of a hole in such a way "that this here thing better not touch the sides or we'll be crispy critters...." Makes for great drama, but how accurate is it?? 8-) ------------------------------------------------------------------------------- Iskandar Taib | The only thing worse than Peach ala Internet: NTAIB@AQUA.UCS.INDIANA.EDU | Frog is Frog ala Peach Bitnet: NTAIB@IUBACS !
ntaib@silver.ucs.indiana.edu (Nur Iskandar Taib) (11/01/90)
From: ntaib@silver.ucs.indiana.edu (Nur Iskandar Taib) >A fusion device is triggered by a fission device. X-rays from the fission >compress the tritium in a small target capsule. This was, I believe, the >key idea contributed by Dr. Teller: radiative compression. I remeber seeing a diagram of a contemporary fission bomb. An interesting detail was an added jacket of U-238, which normally doesn't spontaneously fission, but which does when bombarded by fast neutrons from the primary U-235 core. Another diagram showed a hydrogen bomb. It contained a fission bomb, and Lithium Hydride or Deuteride (a solid) as the fuel for the fusion reaction. I thionk this was in one of the Time-Life illustrated books. ------------------------------------------------------------------------------- Iskandar Taib | The only thing worse than Peach ala Internet: NTAIB@AQUA.UCS.INDIANA.EDU | Frog is Frog ala Peach Bitnet: NTAIB@IUBACS !