Talk:Fat Man

An event mentioned in this article is an August 9 selected anniversary

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You put It'd be useful to explain why the bomb was dropped, and what happened after that... on the Fat Man page. Not the right place at all. The page should be purely technical, the politics of the drop should be elsewhere and link to Fat Man and Nuclear weapon for the technical details.

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Yes, maybe. But, of course, the Fat Man and Little Boy pages should link to that page (about the politics). --LMS

Re: "used in anger" is a well known expression in English, and the replacement with "used in war" whilst technically more precise doesn't have the same prose effect. Perhaps a differenct, less ambiguous (for foreign readers) expression could be substituted. Mintguy 21:53, 21 Aug 2003 (UTC)

I really think it should be anger, because that includes things like terrotist attacks. I'm not going to keep on changing it back after people who don't understand the term revert it. I feel like I'm having an edit war with myself. CGS 22:54, 21 Aug 2003 (UTC).

"Used in anger" suggests (to me) Truman got really steamed at the Japanese one day, flew off the handle and ordered the bomb dropped, i.e., "in the heat of passion", rather than the meaning you intend. Change it, i would say. Graft 13:41, 22 Aug 2003 (UTC)

I've added a little explanation for people who don't understand. CGS 19:48, 22 Aug 2003 (UTC).

cough How about "deliberately used on human beings"? That pretty much cuts through the BS euphemisms...

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found this, it needs to be fitted somewhere...too many pages for me to decide

Although the US insists it emptied its nuclear arsenal with Nagasaki, some Japanese are convinced the US had another core en route to Tinian.[1] (FWIW Nuclear Weapons Archive estimates no later than Aug 20 for another bomb to be ready.[2])

Gadget

What's "gadget"? — Matt 04:47, 19 Aug 2004 (UTC)

• "Gadget" was the code-name for the plutonium bomb tested at the Trinity Site in 1945. --Fastfission 04:09, 9 Nov 2004 (UTC)

Conflicting information?

Quote,

http://en.wikipedia.org/wiki/Atomic_bombings_of_Hiroshima_and_Nagasaki#Nagasaki

" ... It exploded 1,540 feet (469 m) above the ground almost ... "

The article states it " ... detonated at an altitude of about 1,800 feet (550 m) over the city ... "

Could someone check this out in more detail?

And more, the intro says: "An estimated 40,000 people were killed outright by the bombing at Nagasaki," - but the main text says: "According to most estimates, about 70,000 of Nagasaki's 240,000 residents were killed instantly". ?

= Redundant?

Why "second and last of two"? Don't they mean the same thing?

Well, the "last" part implies that there were no more after it. But I think it is not entirely the best way to say that. --Fastfission 17:52, 9 August 2005 (UTC)

Either way they are improvements on what was there before. The facts are it was the second nuclear bomb used in warfare and to date thankfully the last. As long as that is what is conveyed all is good. 'Second and last of two' is merely a vehicle to emphasise the fact that only 2 were used, this one being the second. I'm wasn't 100% happy with it when I wrote it to be honest. Redundant? Very possibly. I don't think my version was perfect and the version without 'and last' lacks a little impact for my liking. I think we'll all know when someone nails it though.--LiamE 09:30, 10 August 2005 (UTC)

I think the current version with "second of the two" is much better, no worries. --Fastfission 12:38, 10 August 2005 (UTC)

Drawing of Fat Man casing

I'm building a 1/48 scale model of Fat Man. The Nuclear Weapons Archive website has a dimensioned drawing of Fat Man here: [3] . However, the resolution is not high enough to read the dimensions on the drawing.

Does anyone have a larger image of the drawing, or a copy that can be scanned?

Please contact me at petero (at) metrocast (dot) net

Thanks!

65.175.224.202 19:43, 2 December 2005 (UTC)

• Let me see what I have and I'll try to get back to you on it. I might have a higher resolution copy somewhere around here. If not, I think there is likely a copy in The grand experiment at Inyokern by J.D. Gerrard-Gough (1978), if you can find a copy of that (at a library). I'll see if I can track one down.--Fastfission 00:06, 3 December 2005 (UTC)

• Also, depending on your interest, you can purchase posters of the blueprints from the National Atomic Museum online store. --Fastfission 01:55, 3 December 2005 (UTC)

Gun type

It is theoretically possible to build a plutonium gun-type device, but it would need to be 19 feet long in order to allow the sub-critical masses to be fused into a critical mass before a fizzle occurs.

It is not clear whether this applies for the purest plutonium (probably), or the kind that was available.--Patrick 01:19, 3 December 2005 (UTC)

• Hmm, I don't know, but the added length would, I imagine, serve to allow the pieces to pick up speed. If they were fast enough, I assume they would be able to combine reasonably well before the reaction completed. --Fastfission 02:00, 3 December 2005 (UTC)

Considering that the spontaneous fission rate depends very much on the purity of the plutonium, giving a precise figure like 19 feet without mentioning the purity is odd. The sentence by itself would suggest that what is meant is "for the purest possible plutonium", but in context it is suggested that it applies for the impure kind that was available. Any sources?--Patrick 08:47, 3 December 2005 (UTC)

After writing this I noticed that very pure plutonium was available (and used later), only not as pure as produced at Berkeley.--Patrick 03:02, 5 December 2005 (UTC)

It was me that made that contribution. I don't have a source for the purity of the plutonium, but I can easily ask the guy who told me about the 19 ft length (and who worked in nuclear targetting research and therefore knows what he is talking about). I'll come back to you when I have the answer. David Newton 09:10, 3 December 2005 (UTC)

19 ft sounds to me like the right number for what they calculated during the war based on the Hanford plutonium, but I can check on that. --Fastfission 18:23, 3 December 2005 (UTC)

I added a calculation, which would suggest that the last few centimeters would have to be travelled in preferably much less than 40 microseconds, i.e. a speed of "much" more than ca. 1000 m/s. Considering that muzzle velocity can be up to 1,800 m/s, it may indeed just be possible.--Patrick 00:46, 4 December 2005 (UTC)

I've got a preliminary answer. The exact values are classified (for good reason), although I would imagine that anyone with much of a background in nuclear physics could come up with a ballpark figure based on things like neutron cross-section fairly easily. The guy's going to find a public domain figure. Beyond that, he said that assuming that the grade of plutonium used in this hypothetical massive gun-type device would be the same as the grade used in an implosion-type device. David Newton 18:31, 4 December 2005 (UTC)

No hilly terrain but US flight crew incompetence!

>Because of Nagasaki's hilly terrain, the damage was somewhat less extensive than that in relatively flat Hiroshima

This is bullshit. The reduced damage was because the B-29 crew badly messed up the targetting, they were in fact lucky to find Nagasaki at all. Eventually they dropped the A-bomb using radar aiming, not visuals due to clouds. They were a full nine kilometers (six miles) off course and pretty much dropped their nuke onto no-man's land! But the 21 kiloton bomb was so powerful it still managed to destroy much of Nagasaki and kill a hundred thousand people or more to this day. 195.70.32.136 10:18, 19 January 2006 (UTC)

It's true that the mission was practically botched, but the terrain did definitely play the primary factor in the focusing of the blast. --Fastfission 23:18, 14 July 2006 (UTC)

The mission was fortuitously "botched". When the crew reached Okinawa, the first thing Ashworth, the weaponeer, did was to go to Gen. Doolittle's HQ to request to make a strike report. He was advised by Doolittle that "I'm sure that Gen. Spaatz (waiting on Tinian) will be happier that you dropped the bomb on the valley and not the city". The mission achieved its end, which was to detonate a second weapon on a Japanese city. The mistakes encountered--a malfunctioning fuel transfer pump, a change in cruising altitude, the forty minute wait for Hopkins, the three runs at Kokura--all conspired to create the fuel consumption crisis aboard Bockscar and were the grist of flying in combat. Things beak down and you adjust. They adjusted. Ashworth's decision to initiate a radar bomb run (in violation of the field order) instead of dropping Fat Man into the sea is to me one of the more unsung but critical decisions of the war.--Buckboard 02:49, 27 July 2006 (UTC)

The crew of bocks car were not incompetant, and they did not botch the drop of fat man. Nagasaki is located amid mountians, and there was 100% cloud cover over nagasaki on August 9 th 1945. Targeting was done by instruments only when fat man was dropped. The mountians tended to contain the blast wave, and reduced its effectiveness. Likewise the cloud cover restricted the effectiveness of the thermal pulse from the firball.— Preceding unsigned comment added by Tmayes1999 (talk • contribs)

two pictures

Is it really necessary to have two pictures describing the interior of the bomb? --Jontsang 19:53, 23 May 2006 (UTC)

• One illustrates the concept. The other illustrates how these sorts of things work out in practice. I think they have sufficiently different goals, and as a consequence look pretty different from one another at a functional level. --Fastfission 20:13, 23 May 2006 (UTC)

Picture of drop?

The page for Little Boy has a picture of its drop and subsequent mushroom cloud. There exists a similar picture for Fat Man (found here[4]). Is there any specific reason it's not on this page? Vicious Blayd 08:45, 6 August 2006 (UTC)

Probably because there isn't a lot of room for it. We'd have to remove the Bockscar image, I suppose. Personally I'm not opposed to it — a picture of an bomber is not as interesting to me. --Fastfission 13:04, 10 August 2006 (UTC)

I'm curious about why there's an image of a model of the bomb? It's not the real thing which exploded in Nagasaki. 84.230.251.132 03:16, 9 August 2006 (UTC)

I think you're misinterpretting what "model" means here. It doesn't mean "miniature scale" or "false version", it means it is another "Fat Man" bomb produced postwar (they made a number of them). But yes, as it indicates it is not the same Fat Man which was dropped on Nagasaki (and has some slight design differences, i.e. it does not have contact fuses). In any case, this picture is the most classic of the bomb (it was the first released to the press in the 1960s), and is the best one we have on the Wiki at the moment. While there are some pictures of the actual Nagasaki Fat Man itself out there (i.e. [5]) most of them either have lots of half-naked guys running around them (which I find visually distracting) or are of a lower resolution (or have washed-out lighting). But I don't personally care too much, if others feel otherwise. --Fastfission 13:04, 10 August 2006 (UTC)

The design of the Fat man type atomic bomb and the lens implosion system presented here in this article is not the exact & specific design of the device that exploded at Trinity on July 16, 1945 , nor is it the actual & specific design of the atomic bomb that destroyed Nagasaki.It does however do a fairly good job of showing the general principles, and concepts of solid core implosion type atomic weapon designs .*** The device in the picture is some what more like such later designs as the MK 4, the MK 5, & MK 6 then it is the design of the Origional Fat Man of history.Many post war varients , and improved re-designs of the Origional Fat man of history were made post war beginning in 1947-1948. Only a general & short summary version of the design of the 1945 Fat Man device of history is available from verifiable public sources , and not a specific, totally complete , & detailed version of it .tmayes1999

re: section "Physics package"

Would someone please (gently) color code the explanations to match each parts of the diagram above? It would look ever so purty and would be a lot easier to read :) --geekyßroad^{. meow?} 06:13, 10 August 2006 (UTC)

• No problem. --Fastfission 13:54, 10 August 2006 (UTC)

Name

I remember being told as a child that Fat Man was named after Churchill and Little Boy after Truman, or that people associated the names with those two. The article lists a book as saying where the names really came from (which I can't access as I'm not in the States). Was this story just something an adult made up to satisfy a WhywhyWhywhyWhy kid, or is this a common misconception? Any info'd be great. Gaviidae 07:39, 1 December 2006 (UTC)

• It is something which is sometimes said but I've never seen any good evidence of it (and am not sure where it originated from). Serber's book definitely says that is not the case, and as he was actually very close to the building of these bombs and to the project administration itself. --24.147.86.187 01:34, 8 May 2007 (UTC)

It is not certian that the "soccor ball" high explosive configuration was actually used in the Fat Man Atomic Bomb .I have seen the actual Blue prints of the Fat Man Device. They show a hollow steel metal sphere filled with up to 2500 kg of preparation B being used to trigger the Fat Man. The instructions given to the technicians for assembly of the gadget:on July 16,1945 specificly instructed, the technicians to place a hypodermic needle in the dome cap and inject liquid high explosive (preparation B) into the 60 inch diameter steel hollow sphere.This was done to assemble the high explosive trigger.These Instructions also specificly instructed the technicians to place 32 high explosive detonators symmetricaly, on the outside of the steel sphere, and raise it on top of the 100 foot tower.This was done with a crane.The steel sphere had a handle on it for this. The steel sphere was assembled by bolting steel sections together at the tower before injecting the high explosive into it.

"Soccor ball" configurations of interlocking plastic bonded explosives connected together by adhesives are used to trigger many modern nuclear weapons fission primarys.I think the "soccor ball", high explosive configuration was not used until the first PBXs were invented & used to trigger nuclear weapons after the year 1956.***In 1945 PBXS had not been invented yet & high explosive shaped charges using castable explosives were in fact only newly invented to make anti-tank shells as of the year 1942 . Timothy J Mayes

Sorry I don't think you know what the hell you are talking about! And judging by your talk page others agree with me! Take a look at any of the real historical sources (i.e. Hoddeson et als Critical Assembly) and you'll see that your proposed model not only has no historical records to back it up, but it doesn't even make any goddamn sense. In any case, on Wikipedia you have real sources, not supposed claims to have seen secret documents. --24.147.86.187 01:34, 8 May 2007 (UTC)

Seconded. There are actual published photos of Fat Man devices being assembled - they show the various segments being mounted into the geometric metal frame, inside the spherical aluminum casing (before the casing was bolted over the segments). See for example John Coster-Mullen's book "Atom Bombs: The Top Secret Inside Story of Little Boy and Fat Man", which has quite detailed photos and plans, including photos he took of the inside the casing of a (disarmed) post-war stockpiled Fat Man casing (explosives and fissile pit removed, but the framework is all there). Georgewilliamherbert 02:20, 8 May 2007 (UTC)

Also... castable high explosives go back to WW I (artillery shell fillings); plain TNT is perfectly usable, just lower energy than Composition B. TNT was in use in shells from 1902, see TNT. The sphere isn't steel, it's aluminum, as is documented all over the place. Liquid explosives can't be used for precision implosion under most circumstances because any bubbles or density variation will cause uneven implosion. Nor would a purely hollow sphere filled with homogenous explosive implode in an even manner; there's a reason the explosive lens assemblies were used. You clearly haven't seen any of the real blueprints which are out there, or you wouldn't have said any of the above.

Your wrong about that: so long as it is simultaneously detonated at 32 to 100 or more symmetrical points on its outer surface . A hollow sphere is a spherical wave mirror that reflects all shock waves impinging on it to the central focus of the hollow sphere where the pit is . Its simply basic college physics in the way it works .

I have verified this fact with 25 years of careful research .*** — Preceding unsigned comment added by Tmayes1999 (talk • contribs)

Please knock it off. You keep wasting everyone's time on these issues, and you haven't done a bit of homework on any of them. Georgewilliamherbert 02:29, 8 May 2007 (UTC)

My information source is the origional records of the manhattan project which I obtained from the Los Alamos scientific laboratory in the past.**************************************

I said that shaped charges were not invented until world war 2 . I was not talking about castable high explosives. The first castable high explosives in U. S. were actually introduced by the union army during the cival war .I never said anything about liquid explosives at all .*

A castable explosive is a liquid explosive that hardens into a putty like solid mass of explosive when it cools after being poured into a mold .******************************* — Preceding unsigned comment added by Tmayes1999 (talk • contribs)

Tim... Please stop this. The blueprints for Fat Man are available. Pictures of Fat Man are availible. You clearly haven't bothered to look at them. You clearly haven't worked with explosives, or even studied an explosives engineering textbook. Basic college physics does not teach you what you say it does, and doesn't explain explosives engineering's actual technology and science either; they're more advanced and specialized. You're making yourself look foolish. Do your homework or go away. Georgewilliamherbert 00:34, 9 August 2007 (UTC)

ALL kinds of waves in the universe including high explosive shock waves obey the same universal physical laws that describe the refraction,behavior , and reflection of all other kinds of waves in the universe . **

I know exactly how high explosive shaped charges work , and I understand their principles. I have seen the fat man blue prints that have been published . These are scketchy and incomplete . They do however show a spherical lense implosion , system . and a design for the 32 detonators that were used to trigger it . The 1946 Smith report to congress on the other hand showed a 3 layer hexagonal-conical lens implosion design for the fat man . The published fat man blue prints are not complete enough, and detailed enough to decisively show what the lens implosion design actually used was . The truth is no one in the public realm actually knows for sure and certian what it was.

That is why Wickipedia can not correctly state for sure and certian what configuration of high explosives was used to trigger Fat Man. There are multiple contradictory accounts of the fat man high explosive lense design out there that have variable credibility . There are reasonable speculations out there but no decisive detailed information about this . — Preceding unsigned comment added by Tmayes1999 (talk • contribs)

Who thought of using explosive lenses?

The article states that John von Neumann thought of explosive lenses, and some sources agree. Other sources say James Tuck thought of it. Man with two legs 08:03, 3 June 2007 (UTC)

The Los Alamos site contradicts itself saying here [6] that Von Neumann thought of it and here [7] that it was Tuck. My guess (I have no evidence) would be that Tuck thought of it in principle and Von Neumann figured out exactly what shape the lenses should be. Man with two legs 08:23, 3 June 2007 (UTC)