Posts Tagged ‘Fat Man’

Visions

The plutonium box

Friday, March 28th, 2014

I’ve found myself in a work crunch (somehow I’ve obligated myself to give three lectures in the next week and a half, on top of my current teaching schedule!), but I’m working on some interesting things in the near term. I have a review of Eric Schlosser’s Command and Control coming out in Physics Today pretty soon, and I’ll post some more thoughts on his book once that is available. And I have something exciting coming up for the 60th anniversary of Oppenheimer’s security hearing.

In the meantime, I wanted to share the results of one little investigation. I’ve posted a few times now (Posing with the plutoniumLittle boxes of doom, The Third Core’s Revenge) on the magnesium boxes that were used to transport the plutonium cores used for the Trinity test and the Fat Man bomb:

The magnesium cases for the world's first three plutonium cores. Left: Herb Lehr at Trinity base camp with the Gadget core. Center: Luis Alvarez at Tinian with the Fat Man core. Right: The third core's case at Los Alamos, 1946.

The magnesium cases for the world’s first three plutonium cores. Left: Herb Lehr at Trinity base camp with the Gadget core. Center: Luis Alvarez at Tinian with the Fat Man core. Right: The third core’s case at Los Alamos, 1946.

Just to recap, they were a design invented by Philip Morrison (the Powers of Ten guy, among other things), made out of magnesium with rubber bumpers made of test tube stoppers. They could hold the plutonium core pieces (two in the case of the Trinity Gadget, three in the case of Fat Man), as well as neutron initiators. Magnesium was used because it was light, dissipated heat, and did not reflect neutrons (and so wouldn’t create criticality issues). All of this information is taken from John Coster-Mullen’s Atom Bombs, an essential book if you care about these kinds of details.

But all of the photographs of the box I had seen, like those above, were in black and white. Not a big deal, right? But I find the relative lack of color photography from the 1940s one of those things that makes it hard to relate to the past. When all of Oppenheimer’s contemporaries talked about his icy blue eyes, it makes you want to see them as they saw them, doesn’t it? Maybe it’s just me.

The only place where I almost saw a color photo of the box is in a photo that the late Harold Agnew had taken of himself on Tinian. It’s one of a large series of posing-with-plutonium photos that were taken on the island of Tinian sometime before the Nagasaki raid. Only this one is in color! Except… well, I’ll let the photo speak for itself:

Harold Agnew with plutonium core redacted

Yeah. Not super helpful. This was scanned from Rachel Fermi and Esther Samra’s wonderful Picturing the Bomb book. They asked Agnew what had happened, and he told them that:

I was in Chicago after the war in 1946. The FBI came and said they believed I had some secret pictures. They went through my pictures and found nothing. Then like a fool I said, “Maybe this one is secret.” They wanted to know what that thing was. I told them and they said that it must be secret and wanted the picture. I wanted the picture so they agreed if I scratched out the “thing” I could keep the slide.

Thwarted by nuclear secrecy, once again! You can try to look extra close at the scratches and maybe just make out the color of the “thing” but it’s a tough thing to manage.

Ah, but there is a resolution to this question. Scott Carson, a retired engineer who posts interesting nuclear things onto his Twitter account, recently posted another  photo of the box — in color and unredacted! His source was a Los Alamos newsletter from a few years back. It is of Luis Alvarez, another member of the Tinian team, in the same exact pose and location as the redacted Agnew photograph… but this time, un-redacted! And the color of the box was…

Luis Alvarez with the Fat Man core, Tinian, 1945.

…yellowNot what I was expecting.

Why yellow? My guess: it might be the same yellow paint used on the Fat Man bomb. Fat Man was painted “a mustard yellow rust-preventing zinc-chromate primer” (to quote from Coster-Mullen’s book) that made them easier to spot while doing drop tests of the casings.

The box for the Trinity core doesn’t look painted yellow to me — it looks more like raw magnesium. Maybe they decided that the tropical atmosphere of Tinian, with its high humidity, required painting the box to keep it from oxidizing. Maybe they just thought a little color would spruce up the place a little bit. I don’t know.

Does it matter? In some sense this is pure trivia. If the box was blue, green, or dull metallic, history wouldn’t be changed much at all. But I find these little excursions a nice place to meditate on the fact that the past is a hard thing to know intimately. We can’t see events exactly as they were seen by those who lived them. Literally and figuratively. The difficulty of finding out even what color something was is one trivial indication of this. And the secrecy doesn’t help with that very much.

Visions

Silent Nagasaki

Friday, February 7th, 2014

Teaching and other work has bogged me down, as it sometimes does, but I’m working on a pretty fun post for next week. In the meantime, here is something I put together yesterday. This is unedited (in the sense that I didn’t edit it), “raw” footage of the loading of the Fat Man bomb into the Bockscar plane on the island of Tinian, August 9th, 1945. It also features footage of the bombing of Nagasaki itself. I got this from Los Alamos historian Alan Carr a while back. I’ve added YouTube annotations to it as well, calling out various things that are not always known.

You have probably seen snippets of this in documentaries and history shows before. But I find the original footage much more haunting. It was filmed without sound, so any sound you hear added to this kind of footage is an artifact of later editing. The silent footage, however, makes it feel more “real,” more “authentic.” It removes the Hollywood aspect of it. In that way, I find this sort of thing causes people to take the events in the footage more seriously as an historical event, rather than one episode in “World War II, the Movie.”

I posted it on Reddit as well, and while there was some share of nonsense in the ~700 comments that it accrued, there was also a lot of expression of empathy and revelation, and a lot of good questions being asked (e.g. Did the people loading Fat Man into the plane know what they were loading? Probably more than the people who loaded Little Boy did, because they knew what had happened at Hiroshima). So I think some learning has happened, and I think the fact that this has gotten +100,000 views in just a day is some sign that there is quite an audience out there for this sort of stripped-down history.

There is also Hiroshima footage, but it isn’t quite as good, on the whole. It is largely concerned with the crew of the plane taking off and arriving. Which is interesting, in a sense, but visually doesn’t mean much unless you know who everybody is.

There is a lot of Trinity test footage as well which I will upload and annotate in the future as well.

Until next week!

Redactions

The Third Core’s Revenge

Friday, August 16th, 2013

By the end of August 1945, there had been a total of three plutonium cores created in the entire world. Everyone knows about the first two. The first was put into the Gadget and detonated at Trinity in July 1945. The second was put into the Fat Man and detonated over Nagasaki in August 1945. The third, however, has been largely overlooked. The third core was the one that was destined to be the Third Shot dropped on Japan, had there been a Third Shot. Instead, it has a different story — but it was still not a peaceful one.1

The magnesium cases for the world's first three plutonium cores. Left: Herb Lehr at Trinity base camp with the Gadget core. Center: Luis Alvarez at Tinian with the Fat Man core. Right: The third core's case at Los Alamos, 1946.

The magnesium cases for the world’s first three plutonium cores. Left: Herb Lehr at Trinity base camp with the Gadget core, July 1945. Center: Luis Alvarez at Tinian with the Fat Man core, August 1945. Right: The third core’s case at Los Alamos, early 1946.

One of the questions I got from people regarding the “Why Nagasaki?” post I wrote last week was “When would the Third Shot really have been ready?” The reason for the question is that since the Third Shot was unlikely to have been ready by the time Hirohito announced Japan’s acquiescence to the American surrender demands (August 15), that satisfies the question of why another one wasn’t used. In a very practical sense, it does, but it ignores the fact that Truman actually put a “stop” on all further atomic bombings on August 10 — when the effect (if any) of the bombs on Japan’s high command was yet unknown. (He did not, it is worth noting, put a stop on firebombing: huge B-29 raids continued up until the surrender announcement.)

But still, it’s an interesting question to consider. There are two components to it: when did they think the third core would be ready, and when was it actually ready? On the first question, we know that on August 10, General Groves wrote to General Marshall that:

The next bomb of the implosion type had been scheduled to be ready for delivery on the target on the first good weather after 24 August 1945 . We have gained 4 days in manufacture and expect to ship from New Mexico on 12 or 13 August the final components. Providing there are no unforeseen difficulties in manufacture, in transportation to the theatre or after arrival in the theatre, the bomb should be ready for delivery on the first suitable weather after 17 or 18 August.2

1945-Groves-to-Marshall

It was on this document that Marshall scrawled, “It is not to be released on Japan without express authority from the President” — the Truman “stop” order. But we also know, from the Seeman-Hull document I discussed in an earlier post, that Marshall was still interested in the atomic production rate on Monday, August 13, 1945. At that time, Seeman claimed that:

Seeman: There’s one ready to be shipped now — waiting on order right now. [...] The whole program is phased according to the best production. There is one of them that is ready to be shipped right now. The order was given Thursday [August 9?] and it should be ready the 19th.

Hull: If the order is given now, when can it be ready?

Seeman: Thursday [August 16] would be its readiness; the 19th it would be dropped.

Hull: In other words, three or four day advance notice before it can be shipped, and six days after that when it can be dropped.

So that’s a pretty interesting conversation — it tells us that the core was in some kind of almost-finished state by August 13. In a 2012 interview, physicist Lawrence Litz told Alexandra Levy of the Atomic Heritage Foundation that:

Levy: What was—how did—do you remember working on casting the plutonium for the third bomb?

Litz: The particular day that remembers—that remains in my memory was the day that we cast the plutonium for the third bomb because we weren’t sure that the Japanese would surrender even after the second bomb was dropped. We had to cast the atmospheres for the third, and because time was short we had to cast the two hemispheres at the same time. But it was dangerous to cast them in the same laboratory at the same time so we set up two adjacent laboratories with the high vacuum apparatus and the—so we could cast one hemisphere in each one of the two labs.

Levy: How long did that take to cast?

Litz: About twenty-four hours and we had to work straight through.

Which gives some indication of the tenor of the day, and the fact that Truman’s “stop” order didn’t mean that they weren’t expecting to potentially keep atomic bombing. (As does the Seeman-Hull conversation.)

How much plutonium was on hand in August 1945? I’ve been hunting around for anything that would give me some hard numbers on this, and finally, basically when I’d given up on the effort, I was surprised to stumbled across a document that did:

1945-08-30 - Los Alamos plutonium inventory

“49 Interim Processing Program No. 24,” dated August 30, 1945, indicates that by that date that Los Alamos had, by their assessment, received 26.136 kg of plutonium from Hanford.3  Figuring out what was done with all of that requires a little decoding of the terminology. 12.292 kg of the material is listed as having been transferred to the US Army with the notation “HS-1, 2, 3, 4; R-1″ after it. I haven’t seen this notation before, but I think it’s almost certain that “HS” means “hemisphere,” i.e. half of a sphere of plutonium. So two full spheres worth were transferred to the Army and were at that time “non-usable,” along with “R-1.” R-1 is almost certainly an “anti-jet” ring developed for use in the Fat Man core (and not present in Trinity’s core).4 So HS-1+HS-2 were the Trinity core components, and HS-3+HS-4+R-1 was the Fat Man core. The first two cores were “non-usable” because they had been detonated.

So we can see from the document that HS-5, HS-6, and R-2 had already been cast and were in the hands of Quality Control at the lab (QC). HS-7 and R-3 had been already cast by then, but still needed hot pressing and nickel coating. HS-8 was scheduled to be pressed on August 31, and finished by September 5. Which is the finest-grain look at the early nuclear production schedule that I’ve ever seen. (And as you can tell I’m quite proud of myself for finding it and deciphering it!)

But the story of the third core doesn’t end there. 

The core was cast sometime around August 13th, but still likely needed to be pressed and coated, ergo the need to take until August 16th to finalize. By August 15th, it became clear that it wasn’t going to be needed in the war. So it was kept at Los Alamos.

A mockup of the third core's experimental setup, August 21, 1945. (Source: Los Alamos)

A mockup of the third core’s experimental setup, August 21, 1945. (Source: Los Alamos)

What it was doing between August 15th and August 21st, I don’t know. But I do know that on August 21st it was being used for critical mass experiments — “tickling the dragon’s tail.” The experiments in question involved surrounding a full 6.2 kg core with tungsten carbide, getting information about the effect that different tamper arrangements had on criticality. (The tamper reflects neutrons back into the core, thus increasing the overall neutron economy and thus lowering the effective critical mass.)

The experimenter in question was 24-year-old physicist Harry Daghlian, Jr. To quote from a report on the experiment:

[Daghlian] was carrying one brick [of tungsten carbide] in his left hand over the assembly, to place it in the center of the fifth layer. While he had this brick suspended over the assembly, he noticed (from the instruments) that the addition of this brick would have made the assembly supercritical if placed on top of the assembly. Having realized this, he was withdrawing his left hand and the brick from over the assembly and while doing so the brick slipped out of his hand and fell immediately onto the center of the assembly. Knowing that this brick would made the assembly dangerous, he instinctively and immediately pushed this brick off the assembly with his right hand. While doing this, he stated that he felt a tingling sensation in his right hand and at the same time noticed a blue glow surrounding the assembly, the depth of the blue glow being estimated to be about two inches.5

Daghlian was estimated to have received a 510 rem dose of ionizing radiation — a usually lethal dose. He died after an agonizing month. This, incidentally, appears to have been why at the time of the August 30 audit, the core was in Quality Control: they were checking to make sure it had not undergone any “dimensional changes” as a result.

One might think that someone involved with the investigation of the Daghlian accident would be especially cautious around using such a core in further critical mass experiments, even if only for superstitious reasons.

Re-creation of Slotin's fatal experiment with the third core. (Source: Los Alamos)

Re-creation of Slotin’s fatal experiment with the third core. (Source: Los Alamos)

But exactly 9 months later, one of the co-authors of the above-cited report, Louis Slotin, would himself receive a lethal radiation dose from the exact same core in the process of yet another (different) critical mass experiment. Slotin knew the experiment in question was dangerous, and had been told by Enrico Fermi that he would be “dead within a year” if he continued to work with such bravado. Like Daghlian, his hand faltered at a literally critical juncture: he was holding a neutron reflector above the core with a screw driver when his fatal slip occurred, lowering the reflector just a fraction of an inch, releasing a stream of neutrons and the characteristic blue glow. Slotin died 9 days later.

The third core, by now nicknamed the “demon core” for having taken two lives, would not go out with a whimper. By some accounts, it found its final disposition in the first postwar nuclear test, shot “Able” of Operation Crossroads, on July 1, 1946,  just under a year after it had been first cast, in that all-night session, in the closing days of World War II. Encased in a “Fat Man” assembly with “GILDA” stenciled on its hull, it was finally dropped from a B-29, as it was originally intended to be, and it detonated over a fleet of empty ships in the Bikini atoll, with a yield of 21 kilotons. Alas, the journalists who saw it, with perhaps higher expectations for their first atomic bomb test, incorrectly dubbed it a flop.

The final use of the third core: the Crossroads "Able" shot, July 1, 1946.

The final use of the third core: the Crossroads “Able” shot, July 1, 1946.

That a single plutonium core could go through so much may seem remarkable. But it is a reflection of a time when such cores were extremely rare commodities. And so a single core could simultaneously be the one originally destined for the “third shot,” and also be the subject of two fatal criticality accidents, and also still be the first core consumed by postwar nuclear testing. It is a potent reminder of how paltry the American nuclear arsenal once was — when there were less than a dozen pieces of cores, much less cores themselves.

Notes
  1. Since a few people have gotten confused, I think I should say somewhere explicitly: the Hiroshima bomb, Little Boy, used a 64 kg highly-enriched uranium core. I’m only talking about plutonium here, in part because it was only plutonium cores that were being manufactured at this point, since the Little Boy design was considered more or less instantly obsolete. []
  2. Leslie R. Groves to George C. Marshall (10 August 1945), copy in the Nuclear Testing Archive, document NV0137881. []
  3. C.S. Garner, “49 Interim Processing Program No. 24,” (30 August 1945), DOE OpenNet Document ALLAOSTI126018. It is interesting, as well, that the Hanford (W) and Los Alamos (Y) assays were off by 1.376 kg, which is quite a lot in this context (22% of a bomb core, or 44% of a single hemisphere). There are indications in the files that they did quite a lot of sniffing around trying to figure out what each site was doing that led to these different assessments. The problem of Material Unaccounted For never really goes away, but it’s interesting that it shows up this early in the game. []
  4. I discussed the fact that the Trinity and Nagasaki cores were slightly different in a very old blog post; Trinity was just two hemispheres, whereas Fat Man also included the ring. []
  5. Paul Aebersold, Louis Hempelmann, and Louis Slotin, “Report on Accident of August 21, 1945 at Omega Site,” (26 August 1945), LAMD-120, copy reprinted in John Coster-Mullen, Atom bombs: The Top Secret inside story of Little Boy and Fat Man, rev. 2007. []
Meditations

Why Nagasaki?

Friday, August 9th, 2013

Today is the 68th anniversary of the atomic bombing of Nagasaki. Everyone knows that Nagasaki came three days after Hiroshima — but Nagasaki doesn’t get talked about nearly as much. The reason Nagasaki gets “overlooked” is pretty obvious: being the second atomic bombing attack is a lot less momentous than the first, even if the total number of such attacks has so far been two.

The bombing of Nagasaki. Original source. Slightly edited to improve foreground/background distinction.

A temple destroyed by the bombing of Nagasaki. Original source. Slightly edited to improve foreground/background distinction.

We all know, or think we know, why Hiroshima was bombed. This is because the bombing of Hiroshima is synonymous with the use of the atomic bomb in general. But why was Nagasaki bombed?

I don’t mean, why the city of Nagasaki as opposed to another city. That is well-known. Nagasaki only made it on the list after Kyoto was removed for being too much of an important cultural center. The initial target on August 9 was Kokura, but there was too much cloud cover for visual targeting, so the Bockscar moved on to the backup target, nearby Nagasaki, instead. Bad luck for Nagasaki, twice compounded.

What I mean is: Why was a second atomic bomb used at all, and so soon after the first one? Why wasn’t there more of a wait, to see what the Japanese response was? Was less than three days enough time for the Japanese to assess what had happened to Hiroshima and to have the meetings necessary to decide whether they were going to change their position on unconditional surrender? What was the intent?

There are, unsurprisingly, a number of theories about this amongst historians. There are some that think Nagasaki was justified and necessary. There are also many who agree with the historian Barton Bernstein, who argued that: “Whatever one thinks about the necessity of the first A-bomb, the second — dropped on Nagasaki on August 9 — was almost certainly unnecessary.”1 And there are those, like Tsuyoshi Hasegawa, who don’t think either of the atomic bombings had much effect on the final Japanese decision to unconditionally surrender when they did. (I will be writing a much longer post on the Hasegawa thesis in the near future — it deserves its own, separate assessment.)

The following images are screens taken from footage taken of the Fat Man preparations on Tinian, courtesy of Los Alamos National Laboratory. Above, preparing the final weapon, sealing the ballistic case joints with red Pliobond and blue Glyptol (plastic film). The different colors made it clear that they were properly applied and overlapped.

The following images are screens taken from footage taken of the Fat Man preparations on Tinian, courtesy of Los Alamos National Laboratory. Above, preparing the final weapon, sealing the ballistic case joints with red Pliobond and blue Glyptol (plastic film). The different colors made it clear that they were properly applied and overlapped.

The first is the standard, “official” version — the second bomb was necessary to prove that the United States could manufacture atomic weapons in quantity. That is, the first atomic bomb proved it could be done, the second proved it wasn’t just a one-time thing. One wonders, of course, why anyone would think the Japanese would think the atomic bomb was a one-off thing, or that the Americans wouldn’t have the resolve to use it again. They had, after all, shown no flinching from mass destruction so far — they had firebombed 67 Japanese cities already — and while making an atomic bomb was indeed a big effort, the notion that they would be able to make one and no more seems somewhat far-fetched. The idea that the US would have a slow production line isn’t far-fetched, of course.

What did the participants in the decision to bomb have to say about the use of specifically two bombs? General Groves told an interviewer in 1967 that:

…it was not until December of 1944 that I came to the opinion that two bombs would end the war. Before that we had always considered more as being more likely. Then I was convinced in a series a discussions I had with Admiral Purnell.2

Which, if true, would peg this decision fairly early in the process. In his memoirs, Groves also has this little exchange from just after the “Trinity” test:

Shortly after the explosion, [Brig. General Thomas] Farrell and Oppenheimer returned by jeep to the base camp, with a number of others who had been at the dugout. When Farrell came up to me, his first words were, “The war is over.” My reply was, “Yes, after we drop two bombs on Japan.”3

Both of these, of course, are recollections made long after the fact. And Groves is known to have “smoothed” his memories in order to present him in the best possible light to posterity. The actual instructions for the use of the bomb, from late July 1945, only give detailed information about the first bomb:

1. The 509 Composite Group, 20th Air Force will deliver its first special bomb as soon as weather will permit visual bombing after about 3 August 1945 on one of the targets: Hiroshima, Kokura, Niigata and Nagasaki. [...]

2. Additional bombs will be delivered on the above targets as soon as made ready by the project staff. Further instructions will be issued concerning targets other than those listed above.4

President Truman, in his diary entry, referred to the impending use of the atomic bomb as a singular thing. In his public statements after Hiroshima (which he probably did not write), he claimed that many more atomic bombs would be used until the Japanese surrendered. That being said, he did put a “stop” on any further bombing on August 10th, to wait for a response. This didn’t have any immediate consequences on Tinian, since the next, third bomb wouldn’t have been ready for a few more weeks, and even then, it wasn’t clear whether it would have been immediately dropped or “saved” for a multi-bomb raid.

The bomb prepared, it was then sheathed in canvas and towed out to the loading bay. I find the shot on the right particularly ominous — the second bomb, still a secret, its size and probable importance not quite masked by its shroud.

The bomb prepared, it was then sheathed in canvas and towed out to the loading bay. I find the shot on the right particularly ominous — the second bomb, still a secret, its size and probable importance not quite masked by its shroud.

Oppenheimer, for his part, seems to have expected that both “Little Boy” and “Fat Man” units would be used in combat. In a memo sent on July 23, 1945, Oppenheimer explicitly discussed the expected performance of “the first Little Boy and the first plutonium Fat Man.” Notably, he expressed near complete confidence in the untested Little Boy:

The possibilities of a less than optimal performance of the Little Boy are quite small and should be ignored. The possibility that the first combat plutonium Fat Man will give a less than optimal performance is about twelve percent. There is about a six percent chance that the energy release will be under five thousand tons, and about a two percent chance that it will be under one thousand tons. It should not be much less than one thousand tons unless there is an actual malfunctioning of some of the components.5

Which raises the interesting secondary question of why Little Boy went first and Fat Man went second. Was it because Little Boy was the more predictable of the two? There’s very little about this that I’ve seen in the archives — it seems like it was taken for granted that the gun-type would be the first one. Groves claimed later that the order was just an issue of when things ended up ready to be used on the island, but the components for both were available on Tinian by August 2, 1945, in any event.6

Oppenheimer had, interestingly, earlier suggested to Groves that perhaps they ought to disassemble the 64 kg enriched-uranium core of Little Boy and use it to create a half-dozen enriched-uranium Fat Man bombs. Groves rejected this:

Factors beyond our control prevent us from considering any decision other than to proceed according to existing schedules for the time being. It is necessary to drop the first Little Boy and the first Fat Man and probably a second one in accordance with our original plan. It may be that as many as three of the latter in their best present condition may have to be dropped to conform with the planned strategic operations.7

All of which is to say that the Los Alamos people seemed to assume without question that at least two bombs would be necessary and would be used. At the higher levels, while Truman did publicly proclaim that further atomic bombings were follow, it isn’t terribly clear he was clued in on the actual schedule of those which followed the first. I wonder if his order to stop bombing, issued immediately after Nagasaki (and the Soviet declaration of war on Japan) wasn’t partially a reaction to the fact that he suddenly felt out of control of the military situation over there.

On the left, the bomb being unshrouded, just before loading into the B-29, Bockscar. On the right, the results: the fireball and mushroom cloud, seen through the window of one of the B-29s on the Nagasaki raid, just a few seconds after detonation, roiling and rapidly rising.

On the left, the bomb being unshrouded, just before loading into the B-29, Bockscar. On the right, the results: the fireball and mushroom cloud, seen through the window of one of the B-29s on the Nagasaki raid, just a few seconds after detonation, roiling and rapidly rising.

The historian Stanley Goldberg proposed another theory: that two bombs were necessary in order to justify the decision to pursue both the uranium and plutonium routes.8 That is, Little Boy would justify the (enormous) expense of Oak Ridge, and Fat Man would justify Hanford. To support this argument, Goldberg points out that during the war Groves was completely afraid of being audited by Congress in the postwar. Groves knew he was engaged in a huge gamble, and he also knew he had made a lot of enemies in the process. This is one of the reasons that he meticulously documented nearly every decision made during the Manhattan Project — he wanted “evidence” in case he spent the rest of his years being subpoenaed.9 It’s a clever argument, though it relies heavily on supposition.

Michael Gordin has argued that this entire question revolves around a false notion: that it was known ahead of time that two and only two bombs were to be used. That is, instead of asking, why were two, and not one, used, Gordin instead looks into why were two, and not three, four, and etc. usedGordin’s book, Five Days in August, argues that it was assumed by Groves and the other planners (but not necessarily Truman) that many more than two bombs were going to be necessary to compel Japan to surrender — that the surprising thing is not that the bombing cycle continued on August 9, but that Truman stopped the bombing cycle on August 10.10

Of these options, I tend to lead towards Gordin’s interpretation. The decision-making process regarding the atomic bomb, once the Army took over the production side of things, was that they would be used. That is, not that it would be used, though the importance of the first one, and all of the import that was meant to be attached to it, was certainly appreciated by the people who were planning it. But it was never intended to be a one-off, once-used, anomalous event. It was meant to be the first of many, as the atomic bomb became yet another weapon in the US arsenal to use against Japan. The use of the bomb, and continued bombings after it, was taken by Groves et al. to be the “natural” case. To stop the atomic bombing would have been the unusual position. Go back to that original target order: the only distinction is between the “first special bomb” and the “additional bombs,” not a singular second special bomb.

So “Why did they bomb Nagasaki?” might not be the right question at all. The real question to ask might be: “Why did they stop with Nagasaki?” Which, in a somewhat twisted way, is actually a more hopeful question. It is not a question about why we chose to bomb again, but a question about why we chose not to.

Notes
  1. Barton J. Bernstein, “The Atomic Bombings Reconsidered,” Foreign Affairs 74, no. 1 (1995), 135-152, on 150. []
  2. Quoted in Robert S. Norris, Racing for the Bomb: General Leslie R. Groves, the Manhattan Project’s Indispensable Man (Steerforth, 2003), 655 fn. 29. []
  3. Leslie R. Groves, Now it Can be Told (Harper, 1962), 298. []
  4. General Thomas Handy to General Carl Spaatz (25 July 1945),  U.S. National Archives, Record Group 77, Records of the Office of the Chief of Engineers, Manhattan Engineer District, TS Manhattan Project File ’42 to ’46, Folder 5B. Copy online here. []
  5. J. Robert Oppenheimer to Thomas Farrell (23 July 1945), copy in the Nuclear Testing Archive, Las Vegas, NV, document NV0103571. []
  6. Groves, Now it Can be Told, 308. All of the Little Boy components were on the island by July 28. The Fat Man core and initiator were on Tinian by July 28, and the HE pre-assemblies arrived on August 2. []
  7. Leslie Groves to J. Robert Oppenheimer (19 July 1945), copy reproduced in John Coster-Mullen, Atom Bombs: The Top Secret Inside Story of Little Boy and Fat Man. []
  8. Stanley Goldberg, “General Groves and the atomic West: The making and meaning of Hanford,” in Bruce Hevly and John Findlay, eds., The atomic West (University of Washington Press, 1998),  39-89. []
  9. And, in fact, he did end up needing some of those records when he was asked to testify at various times. But the scandals weren’t what Groves had guessed they would be: they weren’t about waste, but about people. Groves ended up drawing on his classified Manhattan Project History file when testifying about Klaus Fuchs and, later, J. Robert Oppenheimer. []
  10. Michael Gordin, Five Days in August: How World War II Became a Nuclear War (Princeton University Press, 2007). []
Redactions | Visions

Soviet drawings of an American bomb

Friday, November 30th, 2012

The United States government is pretty gun-shy on publishing drawings of nuclear weapon designs, even very crude ones. When it comes to implosion bombs, this is about all that’s allowed to come out of official sources:

From the 1977 edition of Glasstone and Dolan’s The Effects of Nuclear Weapons. “Then explodes” puts it a little mildly, I think.

Not extremely informative — a ball-within-a-ball — and a heck of a lot less information than you can find from other sources. The reasons for this are ostensibly based in security — terrorists, enemy powers, etc. — though I tend to suspect they are based in the fear of scandal more than anything else. Congressional oversight gets itchy when they see something that looks like a “bomb-making guide,” even when it is well-within the limits of security.1 (The basic implosion idea was declassified in 1951 as part of the Rosenberg trial, though there were knowledgable people arguing for it as early as 1945.)

I find the level of abstraction allowed in such drawings to be a little ridiculous, especially when far more detailed technical information is actually declassified. For reasons that I suspect are deeper than mere policy considerations alone, you can write a lot of things down that you can’t draw, if you’re someone with an actual security clearance. This isn’t totally nonsensical: drawings can make immediately clear lots of things that can otherwise hide in technical descriptions, which is one of the reasons that putative drawings of nuclear weapons are one of the topics that originally drew me to the topic of nuclear secrecy.

We aren’t really talking about blueprints here — these things aren’t usually to scale, they aren’t designed for engineers to use. Even if we were talking about blueprints, there are still quite a few steps in between a drawing of a thing and the thing itself. Drawings of this sort could certainly help an incipient nuclear program, but only in the sense that they can guide research questions or general directions. A drawing of an atomic bomb is not an atomic bomb.

But even though the US is fairly tetchy about its bowdlerized bomb drawings, it does better than most other nuclear states. The United States actually publishes things about their nuclear programs. Though the US has a well-deserved reputation for secrecy, they also have put out tons and tons of technical and non-technical information about how their bombs work(ed), how bombs in general work, technical details about the weapons themselves, and so on. Why? It’s a legacy, perhaps, of the Smyth Report, Atoms for Peace, and other gestures towards the positive role that nuclear information can play in the public sphere.

Ah, but there is one exception: post-Soviet Russia. The people working at Rosatom, the Russian state nuclear agency/corporation, have been publishing impressive amounts of raw historical documents information about the Soviet bomb project, as part of their on-going series Atomnyi proekt SSSR/Атомный проект СССР/USSR atomic project. The series started in 1998, and the early volumes have gotten a lot of good scholarly attention by folks like Alexei Kojevnikov and Michael Gordin, but only very recently did I find that they’ve been still publishing them, and from what I can tell, the newer volumes have not been used too much. The most recent volume that I’ve heard of — volume 3 — was published in 2009. Getting ahold of them is another matter altogether; in the United States, anyway, they’re devilishly hard to find to purchase, and even on Russian websites they are pretty rare. The Library of Congress has the first two volumes in their entirety, and I think I’ve found a source for purchasing the third (supposedly it is on its way), but not without some effort.

Here, for example, is the sort of drawing that the Russians declassified and published in one of the 2007 volumes:

Nuke aficionados will recognize immediately that this is a pretty good drawing of an implosion bomb, especially when compared to the ball-within-a-ball. The labels are pretty straightforward: A– detonator; B– explosive lens (1–Comp. B outer lens, 2–Baratol cone, 3–Comp. B inner lens); C–cork lining; D–aluminum pusher; E–uranium tamper; F–boron plastic shell; G–the Po-Be initiator. The only weird part is that they didn’t label the actual plutonium core itself (the cross-hatched sphere that surrounded the G sphere), but I guess it went without saying. Note also that they’ve indicated how the core can be added in after-the-fact with the removable “trap door” pusher. That’s one of those nice little touches that says, “I am not merely trying to explain an abstract concept, I’m trying to tell you how we might build one of these things.”

But more awesome than the drawing itself — which you can, incidentally, get on a T-shirt, if you’re interested and go for that sort of thing — is its source. It’s from the Soviet archives, part of a report dated January 28, 1946, titled “Notes on the design of the atomic bomb: Description of the construction of the ‘explosion inside‘ type bomb.”2 Get it, “explosion inside”? They hadn’t even formalized their terminology for “implosion” yet and were using a scare-quoted, made-up word in the meantime. As the report makes clear, this is a Soviet description of the American atomic bomb detonated at “Trinity,” based on intelligence received from Soviet spies at Los Alamos. (Other reports refer to Klaus Fuchs directly by name, though I’m not sure if the people drawing up this particular report knew he was the source.)

There is no way in heck that the American government would ever allow the release of so “detailed” a drawing from any source that had access to classified information. Granted, it’s a long way from being a “blueprint” — something the drawing itself acknowledges; the text at the bottom reads “schematic drawing, not to scale” — but it’s still the sort of thing that no weapons lab would want a Congressperson to see them handing out, much less publishing widely. But apparently Rosatom is not as burdened by this — when it comes to publishing pictures of American bombs, anyway!3

Here’s another fan-favorite — a series of drawings breaking the final assembled “Fat Man” bomb into its constituent parts, showing how they call go together, IKEA-style (click any of them to zoom):

The outer casing and the placement of the bomb within it. The caption at bottom says, “Bomb used on Nagasaki (Total weight 10,500 pounds – 4,650 kilograms).” I’m having trouble making out the “note” at the top left but it is seems to be saying something is tentative about the drawing.

The first four “spheres”: 1–initiator, 2–plutonium, 3–tamper, 4–aluminum pusher. Note that the publishers have omitted the exact measurements and replaced them with ellipses. It seems to indicate that the plutonium core is in “3 parts,” which jibes with an earlier post of mine (and indicates that the intelligence source really knew what he was talking about, not that we didn’t already know that). Actually, as is pointed out in the comments, if I had continued translating, I’d see that it says the plutonium must have impurities of only 3 parts per million. Still, a nice little detail.

Spheres 5 and 6: a layer of 32 blocks of chemical explosives, and then a layer of 32 blocks of explosive lenses. The detonator is labeled as a “booster” in English, oddly enough.

Sphere 7: the duraluminum casing, with “holes for detonators.” Comrade Beria likes his details! Compared with the Trinity Gadget.

Lastly, the overall arrangement of the bombs within the casing itself, with its electrical and detonating systems indicated. (You’ll perhaps recognize the first and last images here from another post I did, awhile back, as they are reprinted in a tiny form in another source.)

It’s a veritable nuclear Matryoshka doll, is it not? I wish I could make this stuff up, but I can’t. My favorite part about this document, though, is the fact that so much of the captions are in English — again, as if any indication were needed about where this information was coming from. The document itself was written by Igor Kurchatov for Lavrenty Beria, dated June 4, 1946.

There isn’t anything remotely like a security threat here — you can get better drawings on Wikipedia these days, without the numbers redacted — but to have stuff like this published by an actual nuclear power, based on data they derived in the course of making their own atomic bomb, data taken from a source working in a weapons lab… well, let’s just say, I don’t think it’s going to happen over here anytime soon.

Still, the drawings do have a talismanic power, and the Mandala-like quality of the implosion design doesn’t hurt that. It’s the bomb, right? And yet, it’s really not. It’s a drawing. A technically crude one, albeit more detailed than the other “official” releases. It’s no surprise, I suppose, how easily we get sucked in by the superficially technical — whether it carries any real power or not.

Notes
  1. See, for example, page 70 of chapter 2 of the Cox Report, which criticized Los Alamos for releasing exactly this kind of heavily-sanitized information. []
  2. Заметки о конструкции атомной бомбы. Описание конструкции бомбы типа “взрыва вовнутрь.” []
  3. This reminds me of a joke from the Brezhnev-era USSR that a Russian teacher of mine told me: During a visit to the United States, Premier Brezhnev and President Carter happen to see a protest. “No Carter, No Reagan!” the protesters shouted. “You see,” said Carter, “in our country we have freedom of expression, something you don’t have over in your country.” “Ah, Comrade,” says Brezhnev, “you are wrong! Come over and see!” So they go to Red Square, and indeed, there is a mob of protesters forming, shouting, “Nyet Carter, nyet Reagan!” []