WI Little Boy accidentally detonates on Tinian?

Little Boy (the atomic bomb used on Hiroshima) was a design that was EXTREMELY prone to accidental detonation. An accident could easily have driven the two pieces of uranium in the bomb together and caused a nuclear detonation, or at best a major criticality accident with absolutely massive radiation release. And that's the best-case scenario. The worst-case scenario would have been a detonation large enough to destroy the B-29 base on Tinian.

What would happen if one of the above happens? How does the USAAF cover up this humongous disaster? What airfields do they use to stage Fat Man from?
 
Little Boy (the atomic bomb used on Hiroshima) was a design that was EXTREMELY prone to accidental detonation. An accident could easily have driven the two pieces of uranium in the bomb together and caused a nuclear detonation, or at best a major criticality accident with absolutely massive radiation release. And that's the best-case scenario. The worst-case scenario would have been a detonation large enough to destroy the B-29 base on Tinian.

What would happen if one of the above happens? How does the USAAF cover up this humongous disaster? What airfields do they use to stage Fat Man from?

Little Boy was not armed until in flight (source). You could probably get a fairly nasty radiological incident, maybe even a nuclear fizzle, but I don't think you could get a full nuclear explosion without the powder charge. You might be able to get Fat Man to detonate in a crash; I don't remember if they'd worked out a way to safe the bomb against detonation. I'll see if I can find out.

Edit: Ninja'd!
 
Little Boy was not armed until in flight (source). You could probably get a fairly nasty radiological incident, maybe even a nuclear fizzle, but I don't think you could get a full nuclear explosion without the powder charge. You might be able to get Fat Man to detonate in a crash; I don't remember if they'd worked out a way to safe the bomb against detonation. I'll see if I can find out.

Edit: Ninja'd!

See my later post.
 
See my later post.

Hence my "ninja'd!" edit; I started replying before anyone else had replied to the thread.

Like I said, I don't think you could get a full detonation just from the force of gravity. I think you'd get a fizzle, fractional kiloton yield at the worst - the weapon would predetonate and disassemble itself before reaching its full output. But I'm not certain of that; I'm trying to see if I can find a source to say for sure one way or the other.
 
Hence my "ninja'd!" edit; I started replying before anyone else had replied to the thread.

Like I said, I don't think you could get a full detonation just from the force of gravity. I think you'd get a fizzle, fractional kiloton yield at the worst - the weapon would predetonate and disassemble itself before reaching its full output. But I'm not certain of that; I'm trying to see if I can find a source to say for sure one way or the other.

Actually, I've read that Little Boy probably would have detonated in the case of a violent crash, if the force of the impact was great enough.
 
Actually, I've read that Little Boy probably would have detonated in the case of a violent crash, if the force of the impact was great enough.

Where? I'm not a physicist, but it seems improbable that, at the speed imparted by a crash landing, the weapon could fully assemble itself before detonating. I've seen people talking about Fat Man going off in a crash, but the only source I've seen saying Little Boy could is wikipedia, and it's not sourced.
 
Where? I'm not a physicist, but it seems improbable that, at the speed imparted by a crash landing, the weapon could fully assemble itself before detonating. I've seen people talking about Fat Man going off in a crash, but the only source I've seen saying Little Boy could is wikipedia, and it's not sourced.

Fat Man could not have gone off in a crash. How is a crash going to set off all thirty-two explosive lenses at exactly the same time? If it doesn't, then no nuclear detonation.

Also, the "Little Boy assembling in a crash" probably depends on the fuel in the B-29 exploding.

Apparently it was only the crash of another B-29 that inspired the idea of mid-air assembly, if that B-29 didn't crash and Enola Gay did...

:eek:
 
Fat Man could not have gone off in a crash. How is a crash going to set off all thirty-two explosive lenses at exactly the same time? If it doesn't, then no nuclear detonation.

You don't need them all to go off properly to get a nasty fizzle. Probably not a full yield, but there's a good chance you could get something.

Also, the "Little Boy assembling in a crash" probably depends on the fuel in the B-29 exploding.

:confused: How would fuel explosions make it go off? I thought the idea was that the projectile would fall down the tube onto the target due to the shock of the impact.

Edit to Add: You could definitely get a fizzle from Little Boy, I don't mean it wouldn't go off at all. I'm just skeptical of getting more than a fractional kiloton.
 
You don't need them all to go off properly to get a nasty fizzle. Probably not a full yield, but there's a good chance you could get something.



:confused: How would fuel explosions make it go off? I thought the idea was that the projectile would fall down the tube onto the target due to the shock of the impact.

You wouldn't even get a fizzle. The only implosion-type weapons for which this is a danger are modern two-point implosion weapons.

By forcing the projectile down the tube? That plus the shock of the impact...

In any case, Little Boy was an extremely unsafe design due to its extreme ease of assembly. There's a reason they stopped producing them once implosion weapons came into full production.
 
You wouldn't even get a fizzle. The only implosion-type weapons for which this is a danger are modern two-point implosion weapons.

Source. Alex Wellerstein is a Real Nuclear Historian; he'd know. (He does refer to the possibility of Little Boy accidentally detonating, but I think he's talking about after it's been loaded with cordite.)

By forcing the projectile down the tube? That plus the shock of the impact...

In any case, Little Boy was an extremely unsafe design due to its extreme ease of assembly. There's a reason they stopped producing them once implosion weapons came into full production.

Oh, it's definitely unsafe. You could definitely get a fizzle out of it, no question about that, and once the cordite's loaded you have the risk of a short causing an unscheduled detonation. And I'm not certain you couldn't get a full nuclear yield without the cordite. It just seems unlikely.
 
Leaving aside the question of whether or not it could, what would happen if Little Boy did accidentally detonate?

The figures for an airburst Little Boy bomb are:

Fireball Radius: 0.06 mi
Air Blast Radius: 1.15 mi
Thermal Burns Radius: 1.33 mi

Since the most likely detonation scenario is a surface burst in a crash, the actual figures will be significantly less, but I don't know off the top of my head how to calculate that. Eyeballing a map I found on Google, it looks like one mile would take out about half the base from direct effects, plus crater at least one runway. Given the fuel and explosives about, I would guess the whole place would burn.

Using an idealized dose rate contour from Effects of Nuclear Weapons and scaling it to 16 kT, an ellipse approximately 1.6 miles long and 0.5 miles wide would be exposed to about 100 rads total dose of radiation over an 18 hour period after burst from delayed radiation. 100 rads is the point you start seeing acute radiation sickness in some people, although relatively few. In practice you won't get a nice idealized shape like that, but it should work for a ballpark of the effected area.

So, basically, North Field is destroyed. How long it takes for the radiation to die down enough to be usable depends on the standards they use. I don't know what they'd use, but IIRC their public evacuation threshold for the Trinity test was getting close to the level that would cause acute effects, i.e. crazy high even by 50s standards. I would guess a week or two, assuming they actively remediate the site, before they can start repairs.
 
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