Atom Bombs - The ONLY Three of Them which existed in 1945

This is probably an irrelevant detail of history. But I note that even in 2012, news reports about the atomic bombs which were dropped on Japan at the end of World War II never mention what seems to me to be an important detail.

Since I was a Physics student at the University of Chicago during the 1960s, I often was given information which was probably not available to anyone other than Physicists, by some of the Professors who had participated in the Manhattan Project two decades earlier.

One story I had heard back then made me have respect for President Harry Truman as a probable excellent Poker player!

As deadly battles were happening during 1945 across the Pacific, the Japanese made clear that they would fight to absolute death, where there would be no chance of any concession or anything other than even greater bloodbaths as the battles approached Japan itself. In an effort to try to avoid the deaths of millions more of American soldiers in trying to invade the main Japanese islands with its 80 million people there, it is universally understood that President Truman decided to use the atomic bomb which had only been recently invented. President Truman had only recently become President after the death of President Franklin Roosevelt, and he had apparently never been included by Roosevelt in the secret talks about the atomic bomb. So President Truman really had very little idea what it was or how ferociously deadly it was. He had only been given second-hand and third-hand information from the scientists who were working on it.

The one and only test of whether an atomic bomb might work had been done in late July 1945, while President Truman was meeting at Potsdam with Churchill and Stalin. Just three weeks after that single test, Truman ordered an atomic bomb be dropped on Hiroshima, Japan on August 6, and then a second, entirely different atomic bomb be dropped on Nagasaki, Japan on August 9. Rather gutsy to launch two very different weapons, which each probably had a hundred ways to fail, and essentially entirely on the word of some Physicists!

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Therefore, Truman ordered one atomic bomb to be dropped on Hiroshima on August 6, 1945, and then another atomic bomb was dropped on Nagasaki three days later, on August 9, 1945.

President Truman went on television and radio to announce that he would order more and more atomic bombs to be dropped on Japan, until Japan would announce a concession and a ceasing of hostilities.

All of this is well known history. But there is a fact which was never known, and apparently not even yet today. It turned out that it was very difficult to manufacture an atomic bomb, and it took quite a while to build each one. It also took quite a bit of effort to refine the nuclear fuel for a bomb! When President Truman had made that threat, the Physicists had only manufactured a grand total of THREE atomic bombs! The first one was used for the test in Alomogordo, New Mexico which was detonated on July 16, 1945. And the second and third bombs were actually dropped on Japan.

The reality was that Truman could not have backed up his threat! There were NO more available bombs left to send to Japan. In fact, some of the scientists involved seemed to agree that it would likely take another month before another bomb could be made, and it might have actually taken two months or more, as even the U-235 fuel (for one type) or Pu-239 fuel (for the other type) was not yet even refined to be usable in another bomb.

In fact, the FOURTH atom bomb EVER detonated by America was nearly a YEAR LATER, in July 1946, in the New Mexico desert!

So President Harry Truman was actually BLUFFING with his threats to immediately and continuously be dropping more atom bombs on Japan. He couldn't have backed that threat up! So it was wonderful when the Japanese Emperor believed Truman's bluff and agreed to surrender the war. If they had not been so impressed, and might have wanted to wait for a third atomic bomb, there might have been a delay of months, where Japan might then not have been sure that they wanted to surrender.

The United States' credibility might have been really hurt if Japan had not surrendered then, as there would have seemed no good explanation for a delay of months before dropping another bomb. So a significant fact of the end of World War II in the Pacific is never mentioned, that it was highly dependent on President Harry Truman seeming really believable during his bluffing.

On a different matter, no one seems to notice that the two atom bombs dropped on Japan were ENTIRELY DIFFERENT devices, which worked on different basic ideas and even used entirely different nuclear fuels! The bomb which was tested in New Mexico about three weeks earlier, and the SECOND bomb dropped, on Nagasaki, called Fat Man, used an idea where amounts of the nuclear fuel were IMPLODED at each other by a lot of high explosives, inside the bomb, to try to cause a super-critical mass of nuclear fuel, which was then capable of creating a self-sustaining chain reaction.

The testing of that SINGLE TEST in New Mexico did not really go very smoothly! In order to obtain the needed Pu-239, they started with the U-238 which they had large quantities of from the purification of U-235. The scientists discovered that it was possible to bombard a neutron into a U-238 atom without causing any chain reaction. Instead, they created U-239. This was an extremely unstable (radioactive) isotope which quickly Beta-decayed into Np-239 and then into Pu-239. However, this process also sometimes created another isotope of Plutonium, which sometimes would spontaneously fission, which might have catastrophic consequences!

This problem actually resulted in the idea of IMPLOSION, to enable a Plutonium bomb to be detonated without any catastrophic side effects first! So the one and only test done in New Mexico was of the Plutonium bomb, partly because they were still not really sure they could make the Implosion process occur as necessary.

As a Physics student, I was taught that individual chunks of U-235 which were about the size of golf balls were not massive enough to create a self-sustaining chain-reaction individually, as the surface area of each was too large and they allowed too many neutrons to excape. But when two or more of the chunks could be jammed together with great power, the small chunks could be fused together into a larger baseball size piece of the nuclear fuel. Now that the surface area was relatively less than with the smaller chunks, and if the explosive or implosive blasts could force the pieces together for about a millionth of a second, that could then can start the self-sustaining chain-reaction.

Interestingly, the Implosion method (the Plutonium bomb) which was used for the ONE test detonation (on July 16, 1945), was NOT the method used for the first atomic bomb ever dropped, the one on Hiroshima! That bomb, was a U-235 bomb, called Little Boy, and it was a much smaller bomb. The thing that amazes me is the amazing arrogance of the Physicists, who clearly ASSUMED that they could not make any mistakes!

They sent an absolutely untested type of atom bomb in the Enola Gay to be dropped on Hiroshima on August 6, 1945! That was a gun-type system, which actually had many more ways that it could have failed to detonate! Especially since it had never even been tested prior to that morning over Hiroshima.

Essentially, the scientists were still experimenting! Once the test detonation worked in mid-July in New Mexico, (which was actually the Implosion type of atom bomb, fueled with Plutonium, like the second bomb dropped on Nagasaki) it really would have made the most sense to simply make both of the other two bombs which were to be used to be the same type weapons, the type that had been experimentally proven in the single test detonation, since it had PROVEN itself to work. But the physicists sent the ABSOLUTELY UNTESTED Little Boy gun-type bomb to be dropped on Hiroshima! The bomb dropped on Hiroshima WAS actually the very FIRST test detonation of that U-235 type of device! What if it had not gone off? Of that FIRST atom bomb ever simply dropping like a rock and thudding into the city, instead of detonating several hundred feet above the ground? Imagine the United States having to try to explain the total failure of the first atom bomb ever! But I guess that since no one had any idea just what it was supposed to be or do, maybe they might have gotten away with a failure of some sort.

It was my impression during being around those Physicists at the University of Chicago that there just had not been enough refined muclear fuel of either U-235 or of Pu-239 for the three bombs, so they may have had to use Uranium-235 as the fuel in the Hiroshima bomb and use Plutonion-239 as the fuel in the Nagasaki bomb. (That is a supposition on my part as all information about that stuff is still Top Secret!)

Medical Issues

I have always been mystified during my career in Physics why researchers never seemed to consider the possibility that different Medical effects might have occurred due to the Uranium weapon as to the Plutonium weapon. I reviewed many Research Reports on the effects of those two bombs, and never noticed where anyone ever considered looking for different Medical issues in patients of the two very different types of atom bombs. Later (1953 and after) that same poor thinking seemed to also apply to the Medical and destructive effects of the far more powerful Hydrogen bombs. It seems that everyone assumed that death is death, but good science would be much more thorough than that! (There were several variants of Hydrogen bombs, too.)

On another matter, the atomic bombs were actually VERY INEFFICIENT in their operation! Consider that using Einstein's well-known formula easily shows that ONE kilogram of matter would create the equivalent to 22 Megatons of TNT if entirely converted from matter to energy. Yet, the two atom bombs both needed to contain SEVERAL kilograms of nuclear fuel (whether U-235 or Pu-239) to detonate, and that to create explosions which were equivalent to 15 Kilotons (Hiroshima) and 20 Kilotons (Nagasaki). In other words, only about 1/5000 of the nuclear fuel put into each of those two bombs actually got converted from matter into energy! The other 4999/5000 of the atoms of the nuclear fuel did NOT get converted and simply remained as matter.

My naturally curious mind also has always wondered if anyone considered the two very different types of nuclear fuel regarding explaining the known facts that the Hiroshima bomb had an equivalent power of about 15,000 tons of TNT, and instantly killed around 70,000 people, while the Nagasaki bomb had an equivalent power of 20,000 tons of TNT, and instantly only killed around 40,000 people. Both were detonated at the proper altitude above major cities. Shouldn't the one that had nearly twice as much power, and also contained the Plutonium-239 which was later learned to be EXTREMELY deadly as a chemical, have killed MORE people rather than a lot less? None of the Physics Professors would ever answer my questions on issues such as that!

Again, as a Physics student at the University of Chicago, a Physics Professor once said that Plutonium is the most dangerous chemical that exists, and he said that only three atoms of Plutonium is enough to immediately kill a person. I immediately wondered how he could have known that! But the point here is that if we had just won a War for having detonated a Plutonium atomic bomb over a large city, AND if only 1/5000 of it actually disappeared in the Fission process, doesn't that imply that a large Japanese city was left with the remaining 4999/5000 of that bomb, in other words, astounding numbers of atoms of Plutonium? As far as I can find in research, no one seems to have ever tried to clean up either of those Japanese cities for innumerable particles of either U-235 or Pu-239! Shouldn't someone have done that?

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Around that same time, when I was just 17 years old and a Physics student at the University of Chicago, the professors all seemed to assume that all the students already knew massive amounts of Physics, such as how and why atomic weapons work as they do. Since I was ignorant of that knowledge, I had to study a lot at the world-class Library that the University of Chicago has, and so I quickly learned those things (many of which were only discovered twenty years earlier in the Manhattan Project when the atomic bomb was invented. As an unusually creative kid with a very active mind, and now access to amazing amounts of information from Nobel Prize winners and other geniuses, I obviously thought I saw some possible improvements that seemed possible. So, at 17 years old, I designed my own atomic bomb (in 1963). And then I got intrigued at the possibility of testing whether my idea had any merit. So I found a really desolate area of western Utah, a long public dirt road which happened to pass between two military Test Ranges. I briefly started thinking about building my bomb in the back of an old pickup truck, and taking a bicycle and road barricades out to Utah. It turned out that as a student of U of C, I was allowed to go to Argonne National Laboratory to submit requests for small amounts of U-235. I never really thought that anyone would give a kid any U-235, but the presence of my Student ID apparently was sufficient (for the VERY small amount that I requested). When the guy put the very heavy lead container on the counter and shoved a paper toward me to sign, I chickened out! I also clearly had NOOOO idea how our government would have reacted if a kid detonated a nuclear weapon in desolate Utah! I probably would STILL be in some Federal Prison if it had worked as I had expected! I don't think they would have seen much value in the fact that I made sure that no one could possibly get hurt by my experiment.


This presentation was first placed on the Internet in April 2012.

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C Johnson, Theoretical Physicist, Physics Degree from Univ of Chicago