# "Battlefield nukes", "bunker-busting nukes" -- don't exist yet? **URL:** \ **Category:** Factual Questions\ **Created:** [April 19, 2006, 6:38pm UTC](https://boards.straightdope.com/t/battlefield-nukes-bunker-busting-nukes-dont-exist-yet/353340 "2006-04-19T18:38:38Z")\ **Posts on this page:** 10\ **Page:** 2
**Author:** ![The\_Hamster\_King](https://avatars.discourse-cdn.com/v4/letter/t/8edcca/32.png) [@The\_Hamster\_King](https://boards.straightdope.com/u/The_Hamster_King)\ **Post date:** [April 20, 2006, 7:20pm UTC](https://boards.straightdope.com/t/battlefield-nukes-bunker-busting-nukes-dont-exist-yet/353340/21 "2006-04-20T19:20:29Z")
> [@Enola Straight](#): > > If the outer casing of a bunker-buster nuke were armored with depleted…or enriched…uranium, would that add to the nuke’s punch? No. In order to get a significant nuclear reaction in a bomb you have to maintain critical mass for a non-trivial amount of time. It’s not enough to just assemble the critical mass and squirt some neutrons into it to start the chain reaction. You have to hold the reaction mass together long enough for a substantial fraction of the atoms to take part in the cascading fissile chain. Without some sort of confinement the bomb will blow itself apart with most of the atoms unsplit – a fizzle. Modern weapons use inertial confinement. They create a spherical shockwave with conventional explosives to compress the reaction mass and hold it together long enough for a long chain reaction to occur. That’s why a uranium outer casing won’t make much difference in a bomb’s yield. Because the outer casing doesn’t have any sort of confinement the moment a nuclear reaction begins in the casing it will blow itself apart, terminating the chain. In fact it’s unlikely a chain reaction would begin in the casing at all. The initial conventional explosive blast would probably disintegrate the casing long before any neutrons from the bomb’s core could reach it. Shouldn’t someone named \*\*Enola Straight \*\* already know all this? 😉 ---
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [April 20, 2006, 8:22pm UTC](https://boards.straightdope.com/t/battlefield-nukes-bunker-busting-nukes-dont-exist-yet/353340/22 "2006-04-20T20:22:40Z")
> [@Pochacco](#): > > No. In order to get a significant nuclear reaction in a bomb you have to maintain critical mass for a non-trivial amount of time. It’s not enough to just assemble the critical mass and squirt some neutrons into it to start the chain reaction. You have to hold the reaction mass together long enough for a substantial fraction of the atoms to take part in the cascading fissile chain. Without some sort of confinement the bomb will blow itself apart with most of the atoms unsplit – a fizzle. > > Modern weapons use inertial confinement. They create a spherical shockwave with conventional explosives to compress the reaction mass and hold it together long enough for a long chain reaction to occur. > > That’s why a uranium outer casing won’t make much difference in a bomb’s yield. Because the outer casing doesn’t have any sort of confinement the moment a nuclear reaction begins in the casing it will blow itself apart, terminating the chain. In fact it’s unlikely a chain reaction would begin in the casing at all. The initial conventional explosive blast would probably disintegrate the casing long before any neutrons from the bomb’s core could reach it. > > Shouldn’t someone named \*\*Enola Straight \*\* already know all this? 😉 I half-remembered from an old Time/Life educational book using a Uranium bomb casing around an H-Bomb was a cheap, albeit dirty, way of boosting the power of said nuke. ---
**Author:** ![LiveOnAPlane](https://avatars.discourse-cdn.com/v4/letter/l/3d9bf3/32.png) [@LiveOnAPlane](https://boards.straightdope.com/u/LiveOnAPlane)\ **Post date:** [April 20, 2006, 8:31pm UTC](https://boards.straightdope.com/t/battlefield-nukes-bunker-busting-nukes-dont-exist-yet/353340/23 "2006-04-20T20:31:37Z")
> [@Enola Straight](#): > > I half-remembered from an old Time/Life educational book using a Uranium bomb casing around an H-Bomb was a cheap, albeit dirty, way of boosting the power of said nuke. I’m not sure, but you may be remembering something about two-stage and three-stage devices(if I remember the terminology correctly). These, though, do not use **depleted** uranium. They use weapons grade uranium. ---
**Author:** ![LiveOnAPlane](https://avatars.discourse-cdn.com/v4/letter/l/3d9bf3/32.png) [@LiveOnAPlane](https://boards.straightdope.com/u/LiveOnAPlane)\ **Post date:** [April 20, 2006, 8:38pm UTC](https://boards.straightdope.com/t/battlefield-nukes-bunker-busting-nukes-dont-exist-yet/353340/24 "2006-04-20T20:38:11Z")
Oops. Looks like my bad. [According to this source](http://nuclearweaponarchive.org/Nwfaq/Nfaq1.html) depleted uranium can also be used. Shoulda checked first. > [@](#): > > The fast fission of the secondary jacket in a fission-fusion-fission bomb is sometimes thought of, or referred to, as a “third stage” in the bomb, and it is in a sense. But care must be taken not to confuse this with the true three-stage thermonuclear design in which there is another complete tertiary fusion stage. > > Bombs that are billed as “clean” bombs (a relative term) obtain a large majority of their total yield from fusion. The last and largest stage of these bombs is always a pure fusion stage (not counting the spark plug), substituting a non-fissionable material for the jacket. The fusion-fraction of these designs as demonstrated in tests has been as high as 97% (this was the Tsar Bomba, see below). > > Fission-fusion-fission bomb are dirty, but they have superior “bang for the buck” and “pow per pound”. They generate a large amount of fission fallout since fission accounts for most of their yield. The 5 Mt Redwing Tewa test (20 July 1956 GMT, Bikini Atoll) had a fission fraction of 85%. If the emphasis is on cheapness depleted or natural uranium is usually used for the jacket. If the emphasis is on yield per weight (like nearly all modern strategic weapons) enriched uranium is used. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 20, 2006, 8:38pm UTC](https://boards.straightdope.com/t/battlefield-nukes-bunker-busting-nukes-dont-exist-yet/353340/25 "2006-04-20T20:38:16Z")
> [@](#): > > Bolding mine. No, depleted uranium has nothing to do with nuclear weapons; it’s just a dense metal. Well, it does have _something_ to do with nuclear weapons, in so far as it’s a by-product of bomb making (which we would do anyway), which makes it cheap enough to be practical for use in armor, shells, etc. But it’s exactly the wrong kind of uranium to try to make a bomb out of: You’d have much better luck with pitchblend dug straight out of the earth. While I don’t think that a 10-kiloton conventional explosive has ever been used as a weapon, there probably have been conventional explosions that big before. I think that the explosion of the Soviet N-1 rocket might have been up in that range. But we do have (or at least, had) nukes weaker than 10 ktons, though. What does “kip” stand for, incidentally? ---
**Author:** ![The\_Hamster\_King](https://avatars.discourse-cdn.com/v4/letter/t/8edcca/32.png) [@The\_Hamster\_King](https://boards.straightdope.com/u/The_Hamster_King)\ **Post date:** [April 20, 2006, 8:47pm UTC](https://boards.straightdope.com/t/battlefield-nukes-bunker-busting-nukes-dont-exist-yet/353340/26 "2006-04-20T20:47:50Z")
> [@Enola Straight](#): > > I half-remembered from an old Time/Life educational book using a Uranium bomb casing around an H-Bomb was a cheap, albeit dirty, way of boosting the power of said nuke. Ah, if you’re talking H-bombs it’s an entirely different story. The dynamics of a fusion reaction are very different than the dynamics of a fission reaction. However, as far as I am aware the low-yield “battlefield nukes” are all purely fission devices. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [April 20, 2006, 8:59pm UTC](https://boards.straightdope.com/t/battlefield-nukes-bunker-busting-nukes-dont-exist-yet/353340/27 "2006-04-20T20:59:07Z")
> [@MEBuckner](#): > > **Stranger** , you’re talking about a 20 kip = 20,000 pound = 0.01 kiloton nuclear device (like the “Davy Crockett”) being comparable to a large conventional bomb (such as the 18,700 pound MOAB), right? Kips, kTs…it’s only a two and a half magnitude difference. :rolleyes: That’ll teach me to deal with units after half a bottle of wine. My egregious lapse of attention to units aside, the effects of a nuclear weapon will be more extensive and certainly have greater long-term impact than comperable yield conventional device. Stranger ---
**Author:** ![ralph124c](https://avatars.discourse-cdn.com/v4/letter/r/8797f3/32.png) [@ralph124c](https://boards.straightdope.com/u/ralph124c)\ **Post date:** [April 20, 2006, 10:13pm UTC](https://boards.straightdope.com/t/battlefield-nukes-bunker-busting-nukes-dont-exist-yet/353340/28 "2006-04-20T22:13:00Z")
I read that the British developed a very heavy (conventional) bomb in WWII-it was a 2 ton monster designed to penetrate abut 20 foot into the earth, before exploding. The idea was to knock buildings down. Was it very effective at this? And, was it cost-effective? I can’t imagine that carrying just one bomb was a good way to empliy a Lancaster! ---
**Author:** ![LiveOnAPlane](https://avatars.discourse-cdn.com/v4/letter/l/3d9bf3/32.png) [@LiveOnAPlane](https://boards.straightdope.com/u/LiveOnAPlane)\ **Post date:** [April 21, 2006, 12:42am UTC](https://boards.straightdope.com/t/battlefield-nukes-bunker-busting-nukes-dont-exist-yet/353340/29 "2006-04-21T00:42:22Z")
> [@ralph124c](#): > > I read that the British developed a very heavy (conventional) bomb in WWII-it was a 2 ton monster designed to penetrate abut 20 foot into the earth, before exploding. The idea was to knock buildings down. Was it very effective at this? And, was it cost-effective? I can’t imagine that carrying just one bomb was a good way to empliy a Lancaster! More info on [that bomb here.](http://www.bismarck-class.dk/tirpitz/miscellaneous/tallboy/tallboy.html) ---
**Author:** ![matt](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@matt](https://boards.straightdope.com/u/matt)\ **Post date:** [April 21, 2006, 7:18am UTC](https://boards.straightdope.com/t/battlefield-nukes-bunker-busting-nukes-dont-exist-yet/353340/30 "2006-04-21T07:18:00Z")
And [here](http://home.aol.com/nukeinfo2/). Lots of history, photos, required plane modifications, and the outcomes of various bombing raids… [Previous page](https://boards.straightdope.com/t/battlefield-nukes-bunker-busting-nukes-dont-exist-yet/353340.md?page=1)