Talk:Gun-type fission weapon

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Plutonium gun[edit]

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. 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. 23:32, 30 November 2006 (UTC)


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 (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?[edit]

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...?[edit]

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[edit]

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[edit]

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)

Gun-type fission weapon
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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