dcn@cbnewsd.ATT.COM (david.c.newkirk) (10/28/89)
From: dcn@cbnewsd.ATT.COM (david.c.newkirk) I have seen a reference to a linear implosion technique using conventional explosives to trigger a fission or fusion explosion. Does anyone know if any such weapons were ever successfully tested? The basic idea is the same as spherical implosion, except in a cylindrical shape. A rod of fissionable material surrounded by a hollow cylinder of high explosives might work, but I'm skeptical about the fusion version. This design is more adaptable to fitting into small artillery shells and rockets. -- Dave Newkirk, att!ihlpm!dcn
gwh%typhoon.Berkeley.EDU@ucbvax.Berkeley.EDU (George William Herbert) (10/30/89)
From: gwh%typhoon.Berkeley.EDU@ucbvax.Berkeley.EDU (George William Herbert) Well, this is a possible method, but it _still_ gives larger weapons than gun-type bombs. Despite advances, from what i can tell most nukes are still the gun type, colliding two pieces. **************************************** George William Herbert UCB Naval Architecture Dpt. (my god, even on schedule!) maniac@garnet.berkeley.edu gwh@ocf.berkeley.edu ----------------------------------------
smb@ulysses.homer.nj.att.com (Steven M. Bellovin) (10/30/89)
In article <10711@cbnews.ATT.COM>, dcn@cbnewsd.ATT.COM (david.c.newkirk) writes: > I have seen a reference to a linear implosion technique using conventional > explosives to trigger a fission or fusion explosion.... The basic idea > is the same as spherical implosion, except in a cylindrical shape. I've never heard of a linear implosion technique based on conventional explosives (which isn't to say it doesn't exist, of course); however, H-bombs do use a linear implosion as a crucial part of their design. (The following explanation is taken from Richard Rhodes' ``The Making of the Atomic Bomb'', which I highly commend to anyone interested in the subject.) If you use a straight-forward fission bomb to set off a thermonuclear explosion, it doesn't work; the shockwave starts to ignite the fusion reaction, but blows it apart too soon. Instead, H-bombs depend on the fact that X-rays from the fission explosion propagate much faster than the shockwave. Imagine the following configuration. At one end of a cylinder, you have a spherical implosion-based fission bomb. The case of the cylinder is made from U-238; a bit away from the fission trigger, you have several cylindrical layers. The outermost one is a dense plastic foam; the next layer in is more U-238, followed by lithium-6 deuteride, followed by a central core of plutonium. ** **** <--- fission trigger ** |||||| |||||| |||||| |||||| |||||| |||||| <--- nested cylinders |||||| |||||| |||||| |||||| |||||| |||||| |||||| When the fission trigger detonates, it produces X-rays. The outer shell of U-238 helps reflect these back into the plastic foam. The foam is instantly heated by the X-rays; it immediately expands explosively as a plasma. This causes an implosion in the inner layers, compressing the Li-6 D mixture and the Pu core. Several things start happening now. The plutonium is compressed to critical mass as well, causing another fission reaction. The flux of neutrons from it (and from the original trigger reaction) causes the Li-6 to produce tritium (and, I assume helium, which is unimportant here); under the pressure of the imploding plastic and exploding plutonium, the tritium and deuterium fuse, liberating vast amounts of heat and more neutrons. And these neutrons in turn initiate more fission in the normally-inert U-238. The whole thing is known as a fission-fusion-fission bomb. The idea of using the plastic foam in that way is apparently due to Ulam; Teller's original designs just wouldn't work. He did, however, come up with the concept of the central plutonium core. >From the picture in the book, the whole thing is shaped to fit very well into a bomb. The presence of more tritium would presumably speed up the fusion reaction; modern weapons do in fact use tritium. In fact, some of them can be ``tuned''; by varying the amount of tritium actually in the bomb, the yield can be varied in the field. --Steve Bellovin smb@ulysses.att.com att!ulysses!smb
mamba@csd4.csd.uwm.edu (Paul A Deisinger) (11/01/89)
From: mamba@csd4.csd.uwm.edu (Paul A Deisinger) In article <10744@cbnews.ATT.COM> smb@ulysses.homer.nj.att.com (Steven M. Bellovin) writes: > >In article <10711@cbnews.ATT.COM>, dcn@cbnewsd.ATT.COM (david.c.newkirk) writes: >>From the picture in the book, the whole thing is shaped to fit very >well into a bomb. The presence of more tritium would presumably speed >up the fusion reaction; modern weapons do in fact use tritium. In >fact, some of them can be ``tuned''; by varying the amount of tritium >actually in the bomb, the yield can be varied in the field. > --Steve Bellovin > smb@ulysses.att.com > att!ulysses!smb That reminds me, take a look at this story off of the AP newswire: "An Energy Department laboratory in Tennesee lost a significant amount of radioactive tritium in a test shipment between two lab buildings, raising the possibility of foul play, governmental records show. Ironically, the secret test was done as a part of an internal investigation into troubling discrepancies in the amount of tritium shipped from the Oak Ridge National Laboratory at Oak Ridge, Tenn., to commercial buyers. Tritium supplies are classified by teh government. The material is produced in Energy Department reactors in South Carolina for use in nuclear warheads, although small amounts are sold to domestic and foreign companies. No explanation could be found for the tritium lost in the test shipment, according to a report Wednesday." Wonderful, just wonderful. Paul Deisinger -- My other .sig is a porche. Boongawa.
annala%neuro.usc.edu@usc.edu (A J Annala) (11/11/89)
From: annala%neuro.usc.edu@usc.edu (A J Annala) The idea that fusion weapons depend on xrays or styrofoam/plastic is totally FUBAR. The fact is that when the fission device used as the trigger is detonated a whole lot of neutrons is released. The next stage of the device (the actual fusion weapon) consists of a uranium wrapper around a lithium6-deuteride core. The initial neutrons make the Li6D convert to tritium-deuterium (T-D) and cause fast fissions in the uranium wrapper. The fast fissions generate heat causing the uranium wrapper to expand (both away from and toward the Li6D core). The expansion toward the core compresses the T-D to fusion pressure and temperature. The T-D burns releasing additional fast neutrons. These new neutrons cause additional fast fissions in the uranium wrapper. The cycle repeats and the wrapper holds the core together until the fuel in the core is completely burned. xrays and styrofoam/plastic are more or less irrelevant to the process.
jgd@gatech.edu (John G. De Armond) (11/14/89)
From: rsiatl!jgd@gatech.edu (John G. De Armond) In article <11336@cbnews.ATT.COM> annala%neuro.usc.edu@usc.edu (A J Annala) writes: > > >From: annala%neuro.usc.edu@usc.edu (A J Annala) > >The idea that fusion weapons depend on xrays or styrofoam/plastic is >totally FUBAR. The fact is that when the fission device used as the >trigger is detonated a whole lot of neutrons is released. The next >stage of the device (the actual fusion weapon) consists of a uranium >wrapper around a lithium6-deuteride core. The initial neutrons make >the Li6D convert to tritium-deuterium (T-D) and cause fast fissions >in the uranium wrapper. The fast fissions generate heat causing the >uranium wrapper to expand (both away from and toward the Li6D core). >The expansion toward the core compresses the T-D to fusion pressure >and temperature. The T-D burns releasing additional fast neutrons. >These new neutrons cause additional fast fissions in the uranium >wrapper. The cycle repeats and the wrapper holds the core together >until the fuel in the core is completely burned. > >xrays and styrofoam/plastic are more or less irrelevant to the process. This is a joke, right? Just in case it is not. Sir, would you care to explain how the neutrons in your scenario would reach the fusionable fuel before the gamma/X/thermal radiation destroy it considering that fast neutrons are not relativistic? Or how elastic collisions between the neutrons (which can approach the density of molecules in the structure) and the resultant disruptive heating is going to be controlled long enough to allow the fusion reaction to start? Or could you explain how uniform ignition along a rod of fusionable material is going to be accomplished (remember neutron transit time)? Magic? Perhaps you have access to much more highly classified material than I and therefore know some secret that I don't. I doubt it. If you do, you could probably explain why most of the weapons in the arsenal contain this big FUBAR? Or why a large facility exists for the express purpose of fabricating X-ray mirrors? Or why the government continues intense research into improving the efficiency of X-ray mirrors? You could probably save all us taxpayers a lot of money. Tell us more. -- John De Armond, WD4OQC | Manual? ... What manual ?!? Radiation Systems, Inc. Atlanta, GA | This is Unix, My son, You emory!rsiatl!jgd **I am the NRA** | just GOTTA Know!!!