A Successful Japanese Atomic Bomb Test?

[pdf27]

@Rising_Sun

No doubt an overly simplistic idea based on my very limited grasp of physics, but one of the few things I recall from school is that water is incompressible.

Liquid water is incompressible. Applying a rather large amount of energy to it means you have a gas bubble at high pressure which is not incompressible.

@Rising_Sun

Does it follow that an explosion at a sufficient depth is pretty much fully contained by the water column (e.g. equivalent of a 500lb aerial bomb at 5,000 metres) but when it is nearer the surface the incompressible force is dissipated into the atmosphere by forcing the water column into the air (e.g. equivalent 500lb bomb in 3 metres of water)?

Not sure (shattered and not going to dig through The Effects of Nuclear Weapons for the answer just yet). I think it’s fairly clear that if the fireball breaches the surface you will lose quite a lot of energy which could otherwise be put into the water from the expanding steam bubble, but I’m less clear if this is actually very destructive - it might form quite a soft pulse.

@Rising_Sun

If so, would a very large explosion, be it nuclear or conventional, in shallow water such as that typically found in amphibious landings be less effective in bursting hull seams on surface ships than at deeper depths, such as 5,000 metres, where it might destroy a submarine (yes, I know crewed naval subs can’t go to 5,000 metres, but the Japanese didn’t have atomic weapons to explode in the sea or anywhere else, so this is all just speculation)?

Two separate questions here:

1. Surface ships will always need lower overpressures to burst seams than submarines - the water pressure they’re designed to face is tiny compared to that a submarine is designed for, so by and large the safety margin will be smaller too.
2. So far as how pressure wave generation and propagation goes, I have no idea. That may be in the book somewhere.

[pdf27]

@Ardee

pdf, it never even occurred to me to think of the blast blowing a ship’s seams. I thought of the blast effects of melting steel, but that’s at relatively short distances. It seems likely there’s a bunch of other things that at least this “armchair bomb expert” isn’t thinking of.

The most obvious one is the steam plant. That’s already known to be vulnerable to shock from nearby exploding bombs, and has a direct path from the seawater into it (the condensers). I would not want to be in the engine room of a steam-powered ship taking that kind of shockwave.

[burp]

Considering the geology of Japan, I suppose that pressure waves from digged atomic explosion can create several problems to the invading force (earthquakes, tsunami, and so on). With a fragile equilibrium, a small amount of telluric energy can bring serious effect.
This, ignoring the fact that on long terms, use of atomic bombs inside national borders it’s a real kamikaze tactic.

[pdf27]

@burp

Considering the geology of Japan, I suppose that pressure waves from digged atomic explosion can create several problems to the invading force (earthquakes, tsunami, and so on). With a fragile equilibrium, a small amount of telluric energy can bring serious effect.

It’s a staple of thriller-writers, but there isn’t actually any evidence to show it will happen unless you bury the bomb so deeply underground (and near a fault) that it will have no effect on the surface. Nuclear weapons are powerful, but compared to the energies involved in the earth itself they’re popguns.

@burp

This, ignoring the fact that on long terms, use of atomic bombs inside national borders it’s a real kamikaze tactic.

Not really - very little of the radiation produced by the bombs of the era was very long-lived. The overwhelming majority of radiation sickness cases (>99%) were due to exposure to the prompt radiation of the blast itself (X and Gamma rays, Neutrons) rather than to the small amount of fallout produced. It is only when they moved on to Fusion weapons and started doing groundbursts with them to take out very hard targets that fallout (mostly soil and rock that had been through the fireball and hence was very heavily irradiated and attached to bomb residue) started to become a problem. Crudely, in an airburst the small amount of fallout (basically the unreacted mass from the bomb) is spread over such a wide area that it becomes insignificant. When attached to rock and soil it falls out of the sky much closer, causing local radiation hotspots which can be lethal.

[tankgeezer]

This is a bit off the trail, but would you know about how much of the Little Boy core went as you put it, unreacted? Always been curious about that…

[burp]

@pdf27

It’s a staple of thriller-writers, but there isn’t actually any evidence to show it will happen unless you bury the bomb so deeply underground (and near a fault) that it will have no effect on the surface. Nuclear weapons are powerful, but compared to the energies involved in the earth itself they’re popguns.

For my little knowledge of geology, the deep explosions are worst, because they are near the fault lines in places like Japan. Put pressure on an instable fault lines can cause a lot of earthquake.
Considering particular conditions of Japanese island, that can bring to really destructive scenario, like partial collapse of japanese mainland.

[pdf27]

@tankgeezer

This is a bit off the trail, but would you know about how much of the Little Boy core went as you put it, unreacted? Always been curious about that…

See http://www.atomicheritage.org/index.php/component/content/article/42/146-fat-man-and-little-boy-bombs.html - about a 140lb core of which 1.38% actually fissioned. The actual amount of mass destroyed is somewhere under one gramme, the rest of the fissioned material forming decay fragments (usually highly radioactive).

[Rising_Sun]

@burp

For my little knowledge of geology, the deep explosions are worst, because they are near the fault lines in places like Japan. Put pressure on an instable fault lines can cause a lot of earthquake.
Considering particular conditions of Japanese island, that can bring to really destructive scenario, like partial collapse of japanese mainland.

Earthquakes result from the movement of tectonic plates, which are massive areas of the earth’s mantle moving at glacial pace under immense forces way beyond anything that nuclear weapons could impose.

The 2011 Japanese earthquake / tsunami occurred at a depth of about 24 kilometres. http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=49621 , which is about two and a half times the altitude above earth of the 1945 American nuclear bombers.

I expect that placing an atomic bomb in the Japan Trench to affect the tectonic plates would have been a very much hit and miss operation when allowing for currents and water densities through about 24 km, not to mention many other technical challenges.

As pdf 27 said, on my commonsense rather than scientifically educated basis, I’m inclined to think that even if the most powerful nuclear weapon could be delivered at the optimum point above the tectonic plates it would still be a popgun.

If not, there should be evidence that the earth has shifted on its axis due to the many atmospheric and underground nuclear tests over the past 60 or so years.

[burp]

Thank you for the corrections :).

[pdf27]

@Rising_Sun

Earthquakes result from the movement of tectonic plates, which are massive areas of the earth’s mantle moving at glacial pace under immense forces way beyond anything that nuclear weapons could impose.

The 2011 Japanese earthquake / tsunami occurred at a depth of about 24 kilometres. http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=49621 , which is about two and a half times the altitude above earth of the 1945 American nuclear bombers.

I expect that placing an atomic bomb in the Japan Trench to affect the tectonic plates would have been a very much hit and miss operation when allowing for currents and water densities through about 24 km, not to mention many other technical challenges.

Enough nuclear weapons in the right place could no doubt cause enormous earth movements (if nothing else, if you suddenly vapourise half the rock along the fault line it’s going to break free and move). Problem is getting to the right place. As of 1974 the deepest hole in the world was the Bertha Rogers hole in Oklahoma, which reached just under 10km in depth and really challenged the drilling technology of the day. The best I can find for 1945 is the record for the British Empire & Commonwealth, at 3.8km. That just isn’t deep enough to get anywhere close to the depths required in the crust to cause this sort of earthquake.

[herman2]

Could an underground atomic bomb test in todays age cause enough disruption to put the earth off its rotation? I understand North Korea is undertaking another test (them bastards), so if they were to make the test so powerful could it do this? Also, what about the ground water run off? Does it not contain radiation…or what about the enzymes, worms etc that get radiated…dont they cause harm to the birds or fish that eat them. I was wondering about this and worried at the same time!!

[Rising_Sun]

@herman2

Could an underground atomic bomb test in todays age cause enough disruption to put the earth off its rotation?

No. http://www.livescience.com/32120-can-a-nuclear-blast-alter-earths-rotation.html

Disrupting the planet’s rotation is a different issue to my earlier comment about shifting the earth off its axis, as the angle of rotation is different to the speed of rotation.

[pdf27]

@herman2

Could an underground atomic bomb test in todays age cause enough disruption to put the earth off its rotation?

By how much? It’s simple Newtonian Mechanics - to stop the earth’s rotation outright you need to transfer the angular momentum currently possessed by the earth to some other body. Essentially, that means chucking enormous amounts of rock out into space at massive speeds - given the engineering involved, you’re probably looking at maybe 1% of the speed of light as the optimum (!). Possible, maybe, but no point. The other way of doing it is to hit the earth with a very large rock - basically a small planet - arriving at the right angle and speed. I don’t much fancy that option, as it would probably lead to the extinction of life on earth.
To change the rotation of the earth is very easy. As an example, spin yourself around on a swivel chair and then move your legs in and out. You’ll speed up when you pull your legs in, and slow down when you move them out. The same with the earth - moving weight upwards (e.g. building dams or mining) slows down the rotation of the earth by a tiny amount.

@herman2

I understand North Korea is undertaking another test (them bastards), so if they were to make the test so powerful could it do this? Also, what about the ground water run off? Does it not contain radiation…or what about the enzymes, worms etc that get radiated…dont they cause harm to the birds or fish that eat them. I was wondering about this and worried at the same time!!

I wouldn’t worry about it - unless you happen to live right next to the test site, your equivalent dose will be less than you’d get from eating a banana.

[herman2]

Where does North Korea get its fusion material? From China? NK has been doing too many underground tests, and I don’t like it. I sometimes think the reason we have such strange weather is because of these atomic explosions. How can this isolated country be so advanced? I think china is involved and I don’t understand how we let China get away with this. I know China on the surface condemns NK for doing its tests but at the same time, I bet they are supplying NK with fusion material. Maybe it is time that Japan get the Atomic bomb, so it can defend itself from NK.

[pdf27]

Note:
Fusion = banging light atoms together to make heavier ones. It’s what I do for a living, and how Hydrogen bombs work.
Fission = breaking up heavy atoms to make lighter ones. This is how bog-standard nuclear bombs work, and is what the North Koreans are up to.

So far as the Chinese supplying the North Koreans with fissile material, no chance at all. They want a nice, pliant client state that will do what it is told to. If they had nuclear weapons, they might start getting ideas above their station.

[herman2]

Are you saying YOU do the same stuff that Oppenheimer did? Have you ever been to Los Alamo’s? Are you doing second generation Manhattan Project stuff we don’t know about?
I think its really cool what you do.

[pdf27]

Not exactly, no. At the risk of outing myself, I work on this machine.

[tankgeezer]

@pdf27

Not exactly, no. At the risk of outing myself, I work on this machine.

I’ve heard that this machine operates on highly enriched Haggis…

[flamethrowerguy]

@pdf27

Not exactly, no. At the risk of outing myself, I work on this machine.

The link doesn’t work for me. I only see red dots and colorful lines.

[tankgeezer]

Shhh, thats just what they want you to see…