Fat Man chosen to be dropped on Hiroshima...and fails to detonate

Here's a crazy idea I just thought of.

Suppose that Fat Man is chosen over Little Boy for the initial atomic bomb mission. The bomb is loaded onto Enola Gay and dropped on Hiroshima in a mission similar to OTL. However, in this mission the detonator malfunctions. No signal is sent to the conventional explosives surrounding the plutonium core and the bomb does not detonate.

If I remember correctly, this bomb would not have detonated upon contact with the ground (as LIttle Boy would have in case of malfunction). So, the bomb makes it all the way to the ground on the parachutes -- intact. If there is still a chance of the bomb going off on impact, the bomb lands in the river in the center of the city (the aiming point was a bridge) and the water softens the impact enough to not cause a detonation. It lands in shallow enough water, however, that it can be recovered.

The Japanese start wondering what they have here and immediately try to recover the object that had been dropped. It's very heavy and of a design never seen before. Not knowing what it is, but figuring it's dangerous (why would an American aircraft have dropped it on a city which hadn't been attacked yet?), the device is transferred to a secure site for scientists and army officers to investigate it.

The Enola Gay reports that the bomb failed to detonate. After five days frantically trying to figure out what went wrong (instead of the three between missions IOTL), they decide to deploy Little Boy against Hiroshima. The Japanese note the exact same mission profile. This time, however, the bomb detonates successfully with the same results as IOTL. The city is leveled.

It doesn't take a Japanese rocket scientist to realize that whatever had been dropped five days earlier had been another of these very powerful bombs. The question is: can they figure out why it didn't work and use it against the Americans in case the Americans invade? At the very least, announcing that they've got the bomb will make the Americans think twice about making further attacks on the islands. However, how many of these devices do the Americans have?

Now to be fair, the captured bomb would be best used against American troops trying to invade during an Olympic-style invasion. I can't imagine the Americans not dropping more bombs to try to forestall use of the captured bomb against invading troops: the bomb would likely be useless against aircraft and I believe the Americans had air superiority at that point so we wouldn't have the additional bombs shot down.

On the other hand, the Americans don't know what happened with the detonator. What happens if the same malfunction were to occur with one of the other bombs? 2 out of 3 isn't good enough here, and 1 out of 2 on air drops is worse. Do the Americans want to risk putting more bombs in Japanese hands in case of malfunction? If the bomb detonates, good. If the bomb doesn't detonate you have to assume it can be used against you.

Note that in the Nagasaki mission IOTL the bomber spent so much time circling over Kokura that antiaircraft fire got close and there were reports fighters were on the way. That's why they shifted to Nagasaki, the alternate target. You can bet that all remaining fighters and antiaircraft cannons will be moved to cities like Kokura and Nagasaki which haven't been attacked yet. If a bomber containing one of these devices is shot down it also leaves open the possibility of a recovery if the device fails to detonate.

Something tells me the Americans are going start focusing a lot on Little Boy style devices. And if the Japanese have subs (possibly provided by the Germans earlier) and are able to sneak one of these weapons past the American forces, however unlikely that is, and head for San Francisco...
 
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If Fat Man fails, yes the initial focus will be on Little Boy style bombs, but that won’t be a long term reaction.

They already know implosion type devices will work from the Trinity test. They just would need to figure out why Fat Man in particular failed.

In the end, gun-type uranium weapons are going to be a dead end regardless. There’s a functional limit to how much yield they can deliver.

Also, a bomb plowing into the ground at terminal velocity and then scattering all its various components over an area is not going to provide the Japanese with anything close to functional weapon, even if they can scavenge all the parts.
 
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Here's a crazy idea I just thought of.

Suppose that Fat Man is chosen over Little Boy for the initial atomic bomb mission. The bomb is loaded onto Enola Gay and dropped on Hiroshima in a mission similar to OTL. However, in this mission the detonator malfunctions. No signal is sent to the conventional explosives surrounding the plutonium core and the bomb does not detonate.

If I remember correctly, this bomb would not have detonated upon contact with the ground (as LIttle Boy would have in case of malfunction). So, the bomb makes it all the way to the ground on the parachutes -- intact. If there is still a chance of the bomb going off on impact, the bomb lands in the river in the center of the city (the aiming point was a bridge) and the water softens the impact enough to not cause a detonation. It lands in shallow enough water, however, that it can be recovered.

The Japanese start wondering what they have here and immediately try to recover the object that had been dropped. It's very heavy and of a design never seen before. Not knowing what it is, but figuring it's dangerous (why would an American aircraft have dropped it on a city which hadn't been attacked yet?), the device is transferred to a secure site for scientists and army officers to investigate it.

The Enola Gay reports that the bomb failed to detonate. After five days frantically trying to figure out what went wrong (instead of the three between missions IOTL), they decide to deploy Little Boy against Hiroshima. The Japanese note the exact same mission profile. This time, however, the bomb detonates successfully with the same results as IOTL. The city is leveled.

It doesn't take a Japanese rocket scientist to realize that whatever had been dropped five days earlier had been another of these very powerful bombs. The question is: can they figure out why it didn't work and use it against the Americans in case the Americans invade? At the very least, announcing that they've got the bomb will make the Americans think twice about making further attacks on the islands. However, how many of these devices do the Americans have?

Now to be fair, the captured bomb would be best used against American troops trying to invade during an Olympic-style invasion. I can't imagine the Americans not dropping more bombs to try to forestall use of the captured bomb against invading troops: the bomb would likely be useless against aircraft and I believe the Americans had air superiority at that point so we wouldn't have the additional bombs shot down.

On the other hand, the Americans don't know what happened with the detonator. What happens if the same malfunction were to occur with one of the other bombs? 2 out of 3 isn't good enough here, and 1 out of 2 on air drops is worse. Do the Americans want to risk putting more bombs in Japanese hands in case of malfunction? If the bomb detonates, good. If the bomb doesn't detonate you have to assume it can be used against you.

Note that in the Nagasaki mission IOTL the bomber spent so much time circling over Kokura that antiaircraft fire got close and there were reports fighters were on the way. That's why they shifted to Nagasaki, the alternate target. You can bet that all remaining fighters and antiaircraft cannons will be moved to cities like Kokura and Nagasaki which haven't been attacked yet. If a bomber containing one of these devices is shot down it also leaves open the possibility of a recovery if the device fails to detonate.

Something tells me the Americans are going start focusing a lot on Little Boy style devices. And if the Japanese have subs (possibly provided by the Germans earlier) and are able to sneak one of these weapons past the American forces, however unlikely that is, and head for San Francisco...
Given all the triggers , partly to stop your scenario happening, it might fail to go critical but it would go boom ie scatter Pu over a small area, like a dirty bomb. People were not stupid , they did know , given the timings needed , it might misfire and planned and double planned to make sure it would not be intact after a failure.
 
Given all the triggers , partly to stop your scenario happening, it might fail to go critical but it would go boom ie scatter Pu over a small area, like a dirty bomb. People were not stupid , they did know , given the timings needed , it might misfire and planned and double planned to make sure it would not be intact after a failure.

There is no scenario in which is it intact and potentially usable again. Either the explosives detonate and the physics package fails to go off, which means it’s functionally a dirty bomb, or the explosives fail to detonate and it’s hits the ground at terminal velocity, reducing it to nothing but scattered components and radioactive material.
 
We've had a thread about one of the bombs failing not even a month ago:

Fat Man was discussed there too.
 
How do the Japanese manage to detonate it against invading American troops?

They don’t. There is no way that Fat Man will provide the Japanese with anything close to a usable weapon if it fails to detonate.

At best, they might be able to scrape together the fragments of its plutonium core and use them as a dirty bomb.
 
They don’t. There is no way that Fat Man will provide the Japanese with anything close to a usable weapon if it fails to detonate.

At best, they might be able to scrape together the fragments of its plutonium core and use them as a dirty bomb.
One dirty bomb used in the beaches for the American invasion would mean America retaliates with more nukes.
 
Another thing to consider is this.

If the first bomb does not detonate and there is a long investigation into why it fails to detonate, the Soviets can get much further into Japan by the time the Japanese do surrender (if the Emperor does so).
 
Given all the triggers , partly to stop your scenario happening, it might fail to go critical but it would go boom ie scatter Pu over a small area, like a dirty bomb. People were not stupid , they did know , given the timings needed , it might misfire and planned and double planned to make sure it would not be intact after a failure.

Three trigger systems, plus redundant components within those systems. Parsons was determined to ensure then would work. The electrical circuits were repeatedly tested after assembly, the last time being when Lt Cmdr Parsons installed the detonators on the compression charges aboard the aircraft.

Also, this was not a heavy steel case like a ordinary iron bomb. Not a fuze stuck on a heavy steel case. It was of relatively light weight frame and sheet metal construction. A precision instrument. Hitting the ground even wi the parachute will wreck the device
 
Depending on how much it stays together, the core could turn into a form of the Demon Core event. Besides the intense radiation being put out of the by core, you should have it heating itself up to the point it melts the case and even itself.
 
One dirty bomb used in the beaches for the American invasion would mean America retaliates with more nukes.
Not like they would hold back on using nukes anyways. The Americans were planning to use the bombs on the beaches themselves and then to land there. They had no real idea about how dangerous the radiation was back then.
 
Not like they would hold back on using nukes anyways. The Americans were planning to use the bombs on the beaches themselves and then to land there. They had no real idea about how dangerous the radiation was back then.
I guess the Japanese didn't either, so there'd be little incentive for them to make a dirty bomb.
 

marathag

Banned
Fat_Man_Internal_Components.png
Now even one detonator going off from impact (very likely) will set off most of those thousands of pounds of High Explosive lenses.
You wouldn't get implosion, or even a fizzle, but that heavy Uranium tamper with the Plutonium inside, gets shot off like a seed from a squeezed grape.
If the Japanese even find that weird metal medicine ball sized lump, they have no idea what they are looking at.
 

Capbeetle61

Banned
A massive embarassment that could just have butterflied away the foundation of an independent United States Air Force branch.
 
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