The Hiroshima Bomb Fails to Detonate... done right!

No, I am not going to pull an Eleven11, mainly because I don't have a backup plan.

Anyhow, lets say for mechanical reasons, the altimeter that triggered the detonation fuses fails. So the B-29 pilots are dissapointed... for about 5-10 seconds.

The Little Boy gun-type bomb design is a highly dangerous one. It is the only nuclear bomb design I know of that can go off by itself. So when the bomb drives itself into the ground, the uranium 'bullet' is driven into the sphere and we get a critical mass.

And the bomb goes off.

Now, in OTL the bomb left no crater cause the fireball never touched the ground, but here the fireball digs a 500 yard (457 meters for you foreigners) diameter crater into the ground.

Now, the initial damage is going to be less then OTL, because the thermal pulse and shockwave is semi-blocked by the ground. There is still significant damage and a massive firestorm, but that's not the problem.

The problem is all that dirt that was vaporised has been turned into radioactive particulate matter and is now being blown over Hiroshima. Thus, the result is a significantly more 'dirty' then explosion then OTL.

Mainly, I am interested in how this effects the local ecology. How much longer does it take before Hiroshima can be rebuilt? Or do the Allies decide to ignore the pesky radiation and force reconstruction forward? Or what?
 
wow. that's a scary though.

I'l think this is a perfect opertunity to examin the damage radiation would do, and we'ld have a lot more hibakusha, not to mention the death toll.

and if they figure out how dangerous Radiation is, i don't see them rebuilding any time soon.

and....maybe, this is a big maybe, Japan will surender earlier, so no nagasaki bomb.
 
No, I am not going to pull an Eleven11, mainly because I don't have a backup plan.

Anyhow, lets say for mechanical reasons, the altimeter that triggered the detonation fuses fails. So the B-29 pilots are dissapointed... for about 5-10 seconds.

The Little Boy gun-type bomb design is a highly dangerous one. It is the only nuclear bomb design I know of that can go off by itself. So when the bomb drives itself into the ground, the uranium 'bullet' is driven into the sphere and we get a critical mass.

And the bomb goes off.
(snip)

Possibly not; the critical mass has to be assembled very rapidly to explode properly (hence the gun) the velocity of the bomb through the air may not be enough. Also the squashing/disintegrating effect of the sphere (and more particularly the the neutron-reflecting tungsten carbide tamper) hitting the ground might prevent the correct formation of the critical mass.

On the other hand, I've a feeling that there was a backup plan in the form of more than one trigger mechanism. Edit: Actually no, I just checked and the fuse had three stages: a timer, then a barometric stage and then quadruply redundant radar altimeters.
 
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Possibly not; the critical mass has to be assembled very rapidly to explode properly (hence the gun) the velocity of the bomb through the air may not be enough. Also the squashing/disintegrating effect of the sphere (and more particularly the the neutron-reflecting tungsten carbide tamper) hitting the ground might prevent the correct formation of the critical mass.

There was actually a fairly decent chance that if the Enola Gay had lost an engine on takeoff and crashed that the bomb would have detonated, so far as I remember reading.
 
I seem to recall the bomb was armed in the air to prevent an accident that would have destroyed Tinian.

Now if Fat man and Little Boy were failures, we'd have the specter of implementing Operation Coronet and perhaps a Russian invasion in the north which has been discussed at length before.
 
i know from from several sources
that the Hiroshima A-bomb was installe without the detonation fuses in B-29 bombbay
after liftoff one of crew had go in bombbay and screw the detonation fuses in to the bomb
he had allot of problems to get the fuses into the bomb

here you nice POD

A ground explosion of Hirshima Nuke had made massive Fallout

the link show a 10 kt groundblast on Washington D.C. in case of a terrorist nuclear blast
http://www.washingtonpost.com/wp-dyn/content/graphic/2005/05/03/GR2005050300035.html

GR2005050300035.gif
 
The first bomb doesn't work? They try again, and the second bomb works. The third too. The Japanese surrender.

As others have said, the bomb can't go off on a take-off accident. It was fully armed only once airborne, with crewmen working in the unheated and unpressurized bomb bay. A take-off crash will make a tricky situation, but not a nuclear explosion in Tinian.

As others have said, it's also virtually impossible that the bomb doesn't go off in the air. It came with _four_ radar altimeter fuses, more than one barometric altimeter fuses, and a timer.

Assuming the extremely unlikely event that all of that doesn't work, the impact with the ground will _not_ have the time to wreck alignments and shapes, because the bomb also comes with old-fashioned impact fuses in the nose. It doesn't go off on impact just because of the sudden deceleration, it goes off also because the impact activates the conventional explosive designed to fire the "bullet" into the core.
 
There was actually a fairly decent chance that if the Enola Gay had lost an engine on takeoff and crashed that the bomb would have detonated, so far as I remember reading.
Yes, but although there would be a large release of radiation it would probably not be a full on explosion.

The first bomb doesn't work? They try again, and the second bomb works. The third too. The Japanese surrender.
Yep.
As others have said, it's also virtually impossible that the bomb doesn't go off in the air. It came with _four_ radar altimeter fuses, more than one barometric altimeter fuses, and a timer.
The three types of fuse are in series though not independent. For the explosion to occur all three fuses types have to work not any of the three. Still highly unlikely to fail though IMO, the clockwork timer and the barometric device are both extremely simple and there are four radar altimeters.
Assuming the extremely unlikely event that all of that doesn't work, the impact with the ground will _not_ have the time to wreck alignments and shapes, because the bomb also comes with old-fashioned impact fuses in the nose. It doesn't go off on impact just because of the sudden deceleration, it goes off also because the impact activates the conventional explosive designed to fire the "bullet" into the core.
Are you sure about that http://en.wikipedia.org/wiki/File:Little_Boy_Internal_Components.png for example doesn't show an impact fuse.

BTW, as shown in that diagram above, the arrangement wasn't a bullet and a core but in fact rings and a spike.
 
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