# Talk:Thin Man (nuclear bomb)

I know there are some pictures out there of the "Thin Man" casings, but I don't seem to recall exactly where they are. If anybody has a ref I'm happy to dig it up and scan it. Google Images suggests nobody else has scanned them yet. --Fastfission 15:56, 11 April 2006 (UTC)
Never mind, found them! --Fastfission 01:03, 19 April 2006 (UTC)
Bueno!  Good spot.  Georgewilliamherbert 02:22, 19 April 2006 (UTC)

I was reading over Swords of Armageddon a few weeks ago and I recall Hansen noting that there was some confusion over which bombs were designated as Mk1, Mk2, and Mk3, since the Mark designations didn't occur until after the war. I'm wondering if it makes more sense to rename this to just "Thin Man nuclear bomb" or something like that, which I think is a better known name, if Mark 2 is potentially inaccurate. --Fastfission 04:29, 5 August 2006 (UTC)

The 'Thin Man' Gun type bomb used U235 not Pu.
So those Gun barrels were for U235.
Due to the quick fission time of impurities in the Pu,
it was necessary to assemble critical mass far quicker
than could be assembled with the 'Gun'.  Thus the
implosion technique was developed.
Kent Britain
kent@jts.net  — Preceding unsigned comment added by 75.9.46.68 (talk) 02:59, 21 March 2014 (UTC) 

Thin Man used Pu, not U235. Due to the quick fission time of impurities in the Pu, the design was impractical. Hawkeye7 (talk) 11:26, 21 March 2014 (UTC)
...and the gun barrels were steel, supplied by the Navy. See the design depicted in Little Boy. SkoreKeep (talk) 02:42, 24 January 2015 (UTC)

Chuck Hanson (in US Nuclear Weapons - the Secret History") says: "The MK II was an early Fat Man low-efficiency implosion bomb design configured to use either plutonium or uranium-235. The design was discarded as being "too theoretical" (the geometry of the high explosives shell could not provide the required implosion symmetry to guarantee a reasonable nuclear efficiency). A postwar version (the MK 4 with a composite levitated pit) proved to be highly efficient."  Is this a garble version of the story in this article, or is he referring to something else?  The part about "high explosives shell" leaves me wondering; perhaps an AEC red herring? SkoreKeep (talk) 02:48, 24 January 2015 (UTC)

In Swords of Armageddon, vol. 5, p. 105, Chucks says: "Some sources claim that the designations MK I and MK II were used for early FAT MAN designs; a September 24, 1946 letter to Col. George F. Smith, Chief, Service Engineering Subdivision, Air Materiel Command, Wright Field, refers to the LITTLE BOY as the MK II (presumably the THIN MAN was the MK I). For the purposes of this volume, the LITTLE BOY will be referred to as the MK I." Hawkeye7 (talk) 04:44, 24 January 2015 (UTC)
Well, I guess he learned more between the two, then. SkoreKeep (talk) 05:00, 24 January 2015 (UTC)

Hi Hawkeye7; I can see we aren't agreeing about the derivation of "Thin Man" etc. As I said, Rhodes' book quotes Ramsey directly (presumably from his 1946 text) that the codenames were used by USAF representatives so that their phone conversations could be interpreted as referring to Churchill and Roosevelt in the context of adapting a plane. I also saw Bowen's 1959 history where he says that Wilson and Putt used the Los Alamos codenames to refer to modification of a Pullman rail car. Robert Serber's account of his choice of names - from Dashiel Hammet's book and the Maltese Falcon film - doesn't appear in Rhodes' book, as far as I can see.
It sounds like the names were first chosen by Serber, but persisted, in part, because the USAF found them useful, because the codenames fitted neatly into their inventive cover story. I wouldn't say the Churchill/Roosevelt explanation was wrong, although probably it wasn't the initial reason for the names being chosen. It was, however, a reason why the codenames persisted and is an interesting little story in itself. Ewen (talk) 08:35, 22 May 2020 (UTC)

(interpolated heading removed)
Rhodes (p. 481) (quoting Ramsay) says: For security reasons, these were called by the Air Force representatives the Thin Man and the Fat Man respectively; the Air Force officers tried to make their phone conversations sound as though they were modifying a plane to carry Roosevelt (the Thin Man) and Churchill (the Fat Man)...
This does not refer to the derivation of the names. The USAAF history makes it plain that Los Alamos's Thin Man and Fat Man code names were adopted by the USAAF for the weapons, and from the names a  cover story was devised that Silverplate was about modifying a Pullman car for use by President Franklin Roosevelt (Thin Man) and United Kingdom Prime Minister Winston Churchill (Fat Man) on a secret tour of the United States. (Bowen, p. 96)  Hawkeye7 (discuss) 08:41, 22 May 2020 (UTC)

Yes, so Rhodes doesn't mention Serber's version of the choice of names at all, just Ramsey's explanation. Bowen mentions that the USAAF found the Los Alamos names "served excellently" because they fitted into a neat cover story. I think both stories are valid and worth mentioning: Serber's explanation of how he invented the names, and the Ramsey/Bowen account of why the USAAF adopted the names. Ewen (talk) 11:04, 22 May 2020 (UTC)