Why didn't we focus on a gun-type nuclear weapon only?

Why is it in WW2, the Manhattan Project had focused on creating a gun-type and an implosion type weapon. Almost everyone was confident of the gun-type weapon, that no test was carried out for it and went dropped as planned. However, the Fat Man implosion type had a previous Trinity implosion type test to see whether it could work or not.

What if the Manhattan Project had focused on creating a gun-type only weapon? Do we get nukes faster than the OTL since we focus on producing one type instead of two types? I understand to make the material necessary for it is difficult, but this shouldn't be a problem considering that the US industrial output could make it.
 
My understanding was that it used much more 140 lb (64 kg) v 6.2 kilograms (14 lb) so it may be easier but you need more uranium (and I don't think it works with PU?)?
 
because they also looked ahead i guess, the guntype cannot be easily scaled up, the implosion type can.
 

CalBear

Moderator
Donor
Monthly Donor
The Gun type, as noted, was extremely limited, both in potential numbers and, perhaps more importantly, in yield.

It was more or less a math problem. If the U.S. had been forced to wage an actual campaign with nuclear weapons, instead of simply using them to finish off an opponent that was ready for a knockout blow (which actually was a combination of two nuclear jabs and Soviet invasion uppercut), it would not have been possible using urainium weapons exclusively.
 
Gun types are also extremely dangerous. An implosion type requires a very precisely calculated set of circumstances to get anything to happen.They're safe and not easily tampered with without rendering them inoperative.

A gun type, by contrast, only requires that the two subcritical elements be physically brought together to reach critical mass. The faster this happens, the more powerful and efficient your explosion. But simply dropping the bomb wrong could cause, at the very least, a very dangerous criticality accident that would kill everyone in a city block sized area by lethal radiation bombardment.
 
The Gun type, as noted, was extremely limited, both in potential numbers and, perhaps more importantly, in yield.

It was more or less a math problem. If the U.S. had been forced to wage an actual campaign with nuclear weapons, instead of simply using them to finish off an opponent that was ready for a knockout blow (which actually was a combination of two nuclear jabs and Soviet invasion uppercut), it would not have been possible using urainium weapons exclusively.

So basically, if the US wanted to focus on the quantity of nuclear weapons, then implosion types would have only been possible.
 
If trinity was a bust then no bomb would ever have been dropped on japan. It was plutonium or bust.

You can implode U-235, but that's the reason for gun assembly, it was 'simple' with fewer things to cause a failure.

Postwar many US nuclear weapons were composite core, with both elements. US produced far more HEU than Pu-238 after the war
 

Delta Force

Banned
Why is it in WW2, the Manhattan Project had focused on creating a gun-type and an implosion type weapon. Almost everyone was confident of the gun-type weapon, that no test was carried out for it and went dropped as planned. However, the Fat Man implosion type had a previous Trinity implosion type test to see whether it could work or not.

What if the Manhattan Project had focused on creating a gun-type only weapon? Do we get nukes faster than the OTL since we focus on producing one type instead of two types? I understand to make the material necessary for it is difficult, but this shouldn't be a problem considering that the US industrial output could make it.

Implosion bombs are far more efficient than gun type bombs. Little Boy achieved an efficiency of around 1.38%, while Fat Man achieved an efficiency of around 13%. Gun type bombs also present packaging challenges because they are giant guns, while an implosion bomb can take the shape of a sphere or egg.

Implosion bombs can also use a greater variety of material. Gun type bombs take much longer to assemble a critical mass than implosion bombs, which would cause plutonium to undergo an incomplete fizzle and blow the device apart while the plutonium bullet is still speeding down the barrel. The same thing probably happens with the uranium as well due to the inefficiency of the gun type mechanism, but it's still enough for uranium to achieve a critical mass and multi-kiloton detonation instead of a fizzle of a few hundred or maybe thousand pounds of TNT.

The advantages of implosion bombs are thus greater efficiency, easier packaging, and the ability to use more material types. Implosion bombs can also be used to help develop thermonuclear weapons.

From a program perspective moving towards plutonium type implosion bombs has advantages as well. Plutonium is produced as a byproduct of nuclear reactor operations, so it's possible to attach a secondary loop to the unit and produce power as well. If the production pile is a heavy water or graphite moderated design then it doesn't even need enriched uranium to operate. In contrast, uranium has to be enriched to be suitable for weapons use. Uranium can't be enriched in a reactor and has to be produced using energy intensive processes.

The British and French nuclear programs were built around dual purpose Magnox and UNGG reactors, respectively, which used natural uranium fuel to produce military plutonium and civilian power. Magnox was even given the codename PIPPA (Pressurised Pile Producing Power and Plutonium) during its development by the United Kingdom Atomic Energy Authority.
 
They knew that a gun-type bomb with uranium would WORK--but they did NOT know how long it would take to get enough weapns-grade uranium to make it.
 
As an aside - this doesn't answer your question, because it wasn't discovered until well after the decision to go ahead with both programs, but the plutonium being made at the Oak Ridge reactor turned out not to be suitable for gun-type devices due to impurities in the plutonium (impurities of Pu 240 in the Pu 238, necessitating the same procedures to purify it as enriching uranium, but way more, since uranium doesn't have to be 100% enriched to work in a bomb (indeed, it almost never is), but even a tiny amount of Pu 240 causes predetonation in gun-type devices). The implosion device, which "blew up faster", was less affected by this problem.
 

Cook

Banned
Why is it in WW2, the Manhattan Project had focused on creating a gun-type and an implosion type weapon.

Actually they examined every conceivable design imaginable, and several inconceivable designs and developed the most promising concepts in parallel because on-one was quite certain which design held the most promise, would be quickest, or would even work. For example, it was only quite late in the project that it was realised that a gun-type Plutonium device (Thin Man) would pre-detonate and therefore was unworkable (not because the theory was flawed, but because of impurities in the Plutonium that affected the characteristics of the reaction); a similarly unforseen problem could have shown up with either the enriched uranium gun-type device (Little Boy) or plutonium implosion (Fat Man) methods; no method could be the sole focus of the project because no-one could be sure what would or wouldn't work.

If trinity was a bust then no bomb would ever have been dropped on japan. It was plutonium or bust.

Trinity was a Plutonium implosion device, Hiroshima was an Enriched Uranium gun-type device; the two had no design commonality whatsoever.
 
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There was not enough uranium to build more than one bomb. If trinity failed then japan would have to be invaded. It was that simple. It was plutonium or bust.
 

Cook

Banned
There was not enough uranium to build more than one bomb. If trinity failed then japan would have to be invaded. It was that simple. It was plutonium or bust.

I feel obliged here to point out what should be obvious; where did the plutonium come from?
 
The Gun type, as noted, was extremely limited, both in potential numbers and, perhaps more importantly, in yield.

It was more or less a math problem. If the U.S. had been forced to wage an actual campaign with nuclear weapons, instead of simply using them to finish off an opponent that was ready for a knockout blow (which actually was a combination of two nuclear jabs and Soviet invasion uppercut), it would not have been possible using urainium weapons exclusively.
This. Gun-barrel weapons were (and are) inefficient in their use of fissionable material, can't use plutonium unless it's extremely isotopically pure (i.e. basically no Pu240) which reduces the efficiency of the breeding process.
Historically the Manhattan project produced sufficient uranium for two MK1 bombs by the end of 1945 but enough plutonium for eighteen MK3 bombs.
Of course in 1947 the later MODs of the MK3 and the MK4 bombs used composite core pits with a mix of plutonium and HEU; this reduced the amount of plutonium needed to <2.5kg
 
I feel obliged here to point out what should be obvious; where did the plutonium come from?
Hanford.
Specifically the breeder reactors and plutinium separation facilities at the complex.
Even more specifically the B Reactor (aka 105-B) there which was the world's first plutonium production reactor; it used 180 tonnes of natural uranium, graphite moderation and water cooling and ran at 250MW thermal. It was constructed between AUG1943 and SEP1944, went critical that month and produced the first plutonium in November. Two more reactors ("D" and "F") were operating by FEB1945. The first plutonium was shipped to the Los Almos complex on 05FEB1945.

More fundamentally the plutonium is produced by nuclear transmutation of uranium; U238 atoms absorb a neutron each and then successively emit two beta particles becoming plutonium 239 (and an occasional atom of Pu240 much to people's irritation when a second neutron is absorbed). After a period in the reactor the fuel tubes are removed and very carefully chopped up, the fissionable material dissolved in nitric acid and the plutonium separated chemically. At Hanford this was done in the 221-T building.
 

Cook

Banned

You, and he, seem to have missed my point. Had the atomic bomb program focused entirely on enriched uranium there would have been more available because none would have been diverted to the manufacture of plutonium.
 
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