Talk:Gun-type fission weapon

Plutonium gun

Does Plutonium really rule out the gun method alltogether or does it just mean the gun would have to be prohibitively long (extra length giving it extra time to gain more speed)? I recall reading somewhere that the reason that the Plutonium gun program was abandoned during the Manhattan Project was because the bomb would have to be so long that it would require both bomb bays on the B29 to open at the same time, which was technically very difficult to accomplish. I know a plutonium bomb would be inefficient, but would it be impossible? --Fastfission 15:01, 20 January 2006 (UTC)

I believe plutonium totally ruled out the gun method although I am not sure of this. The main problem with the thin man concept wasnt with the bomb bays opening at the same time. The B-29 could open both fairly quickly and wasnt much of a problem at all. The problem with thin man was that it was shackled at two locations. Getting these two shackles to release simultaneously was difficult and plenty of testing went towards this problem. The simultaneous release was never worked out and the USAAF settled on using a British designed single shackle (Type F I believe) that closely resembled the single point shackle used to drop Tall Boys and Grand Slams from the Lancaster.

It is not impossible for Pu-239 or U-233 to be used in a gun-type weapon. However, production of these isotopes yields impurities (Pu-240 and U-232) which would require an extremely high gun-tube velocity. This would itself require either impractical explosive design, high-strength tube design, and/or an impractically-long gun-tube. Plus, there is the issue of pre-detonation (again, the gun-tube velocity issue) which would make the weapon very inefficient. The impurities are much less of an issue in a sphere-design weapon. But, since Pu-239 and U-233 production is fundamentally easier than U-235 production, and since gun-type bombs are fundamentally easy to build, some parties might be willing to go this route despite the inefficiencies involved. 147.145.40.44 23:32, 30 November 2006 (UTC)

I wonder what the critical lengths and velocities for tube weapons are for the various isotopes are. We can probably guess what it is for U-235 from historical photographs. 147.145.40.44 23:32, 30 November 2006 (UTC)

As well as I know, and I will get out the book soon, U235 needs 1000ft/s, and Pu needs 3000ft/s. It isn't a longer gun that is needed, but a faster one. I will have to check if the 3000ft/s is with or without reactor U240 in it, with the high spontaneous fission rate. Gah4 (talk) 07:00, 14 June 2019 (UTC)

OK, from The Los Alamos Primer, the 3000ft/s was expected to work for the first samples of Pu that were low in Pu240. When they started getting reactor produced Pu, with more Pu-240, the spontaneous fission rate was high enough that a 3000ft/s gun wouldn't work. It seems that 3000ft/s is high, but reasonable, for a gun. Much more is not possible. Gah4 (talk) 07:13, 12 July 2019 (UTC)

References

Cordite

The article says it was powered by a "cordite" charge. That is doubtful. The U.S. didn't use cordite (Check cordite article.) —Preceding unsigned comment added by 65.100.6.149 (talk) 20:00, 16 May 2008 (UTC)

The US used during this period a nitrocellulose propellant for the guns only -because it was safer. If one had a hang fire, one could throw the shell out (or over-board) with much less chance of it exploding. Unlike a British cordite shell, where a dud was more inclined to go off before it could be safely deposed of. However, cordite was a ruddy more powerful and so for Little Boy, cordite was used. After the big drop, there was no chance for the bombardier of Enola Gay to do anything about a hang-fire so this issue didn’t count. What did count however, was driving the slug into the core as fast as possible – hence the decision to use cordite (manufactured in Canada if I remember right). It is all documented the history books. Hope this explanation helps. --Aspro (talk) 21:38, 22 June 2012 (UTC)

Teflon-lined gun barrel?

See Polytetrafluoroethylene. Teflon is a Dupont trademark for polytetrafluoroethylene (PTFE), among other fluorocarbon polymers. It was not invented by them, nor does its use in the Manhattan Project appear to be obscure. It would be interesting if the gun barrel was lined with PTFE but is this more than an educated guess?Moletrouser (talk) 13:58, 15 June 2008 (UTC)

Ah, darn it. That entire section was false information, there was no barrel liner on the Little Boy weapon. I removed the section and left the person who added it a warning. Georgewilliamherbert (talk) 22:03, 16 June 2008 (UTC)

Hollow Projectile...?

Is there some sort of official (or even quasi-official) reference source for the "hollow bullet" projectile design concept. This is somewhat new to me and, while it makes sense, I've been wondering where it came from. Some recent authoritative sources (most notibly Rhodes "Making of the Atomic Bomb") continue to describe the old-school "hollow-target" configuration for LITTLE BOY. Is it possible that LB used the more conservative approach and later gun-design weapons the better, but more advanced system?

Basesurge (talk) 05:24, 1 June 2011 (UTC)

Article title

Should this article title not be in the plural (with an s) as there are several types of device based on this principle?--Aspro (talk) 21:10, 22 June 2012 (UTC)

File:Gun-type fission weapon en-labels thin lines.svg

Hello! This is a note to let the editors of this article know that File:Gun-type fission weapon en-labels thin lines.svg will be appearing as picture of the day on April 30, 2014. You can view and edit the POTD blurb at Template:POTD/2014-04-30. If this article needs any attention or maintenance, it would be preferable if that could be done before its appearance on the Main Page. Thanks! — Crisco 1492 (talk) 01:00, 15 April 2014 (UTC)

Picture of the day

Gun-type fission weapons are fission-based nuclear weapons whose design assembles their fissile material into a supercritical mass by the use of the "gun" method: shooting one piece of subcritical material into another. This design is rather inefficient owing to the slowness of the process and the amount of uranium required, and has fallen out of use. The bomb Little Boy, which was detonated over Hiroshima on August 6, 1945, was of this type.Diagram: Dake, Papa Lima Whiskey, Mfield

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excessive significant figures

The article says 984ft/s for little boy, not 985 or 983. Note the excessive significant figures. It is convenient that it rounds to 300m/s. It is pretty obvious that someone rounded to 300m/s, and then converted to 984ft/s. The sources I remember, which I will dig out soon, say 1000ft/s. It needs to be fast, there is no reason to work on it until it comes out exactly 300m/s. Gah4 (talk) 07:14, 14 June 2019 (UTC)

Also see false precision. Gah4 (talk) 07:18, 14 June 2019 (UTC)

Operation Nougat

What does the source actually state?

“ Although this was still the "era of atmospheric testing", Nougat was actually the first underground test series. ” — https://nuclearweaponarchive.org/Usa/Tests/Nougat.html

So, not an unspecified tunnel (which could be situated near the ground, underwater, or anywhere else), but an underground tunnel. Incnis Mrsi (talk) 19:06, 13 October 2019 (UTC)

Sounds like you are in agreement with me. There is no specific mention of "underground tunnel" and you're making an inference, which is akin to original research. Assuming that your premise is correct, the context is established in that sentence and does not need to be repeated because it's been established. Repeating it gains nothing for the article. Leitmotiv (talk) 19:17, 13 October 2019 (UTC)

In agreement with what? The paragraph explains that one test was performed. Where did it happen? The answer “underground tunnel” is specific enough, whereas simply “tunnel” leaves some room for guesses. Incnis Mrsi (talk) 19:43, 13 October 2019 (UTC)

You're looking to insert a defining characteristic of the tunnel. Either way you cut it, your source doesn't explicitly say the tunnel is underground, and if your source is indirectly implying that underground refers to the tunnel, then it is redundant two ways. The test series was underground - great, no need to repeat the fact that it's underground again. Regardless, your source doesn't come out and directly say it. The source you provided seems to realize that calling a tunnel underground was also redundant and skipped that step. I'd recommend perhaps to follow their lead. If you don't want to follow the people in the know (the source you provided), then my recommendation would be to find another source the states it outright. Leitmotiv (talk) 22:55, 13 October 2019 (UTC)