What effect does a nuke have underwater?

[MHrtz]

So I was watching Abyss the other day and got to the part where Ed Harris drops down an underwater cliff to disable a nuke which lies at the bottom. I think the distance was two miles underwater. If the nuke were to have exploded what kind of damage would be done and would it have even been worth the trouble to disarm it in the first place (assuming the way he got down there was actually plausible)?

 

[Danger]

That would depend upon the yield. I'll leave it up to some experts to give you definitive answers.
My first thoughts turn toward tsunamis (as in 500-metre waves), massive clouds of radioactive steam, probable earthquakes... not pretty.

 

[Dr Lots-o'watts]

Some were detonated underwater, albeit near the surface, in the mid 20th century. It surely depends on the yield, but since tsunamis are caused by earthquakes, and devices are not known to cause earthquakes, I'm not sure.

 

[MHrtz]

I can see the radioactive steam but earthquakes? Tsunamis? I don't know exactly how much energy water can absorb but a nuclear blast is the equivalent of 13000 million tons of TNT.

 

[MHrtz]

Also, let's say radioactive steam was produced. Is even worth the trouble to disarm the nuke in the first place.

 

[cjl]

I can see the radioactive steam but earthquakes? Tsunamis? I don't know exactly how much energy water can absorb but a nuclear blast is the equivalent of 13000 million tons of TNT.

Not any nuke that we've ever produced. 13,000 million tons of TNT would be 260 times more powerful than the most powerful nuclear device ever detonated (and closer to a thousand times more powerful than the most powerful US device ever detonated). Typical nuclear blasts are more in the neighborhood of a few hundred kilotons, the equivalent of a few hundred thousand tons of TNT.

 

[stereobot]

The nuke, not factoring its yield, if detonated very deep underwater would still create its fireball and massive amounts of heat. From that it would vaporize water in and outside the blast zone. The resulting massive steam bubble(s) would make their way to the top.

The shock wave from the nuke would move faster through the water than it would the air since water is denser. Regarding fallout, I'm not sure how that would work since the nuke would likely not be sending as many dirt/debris particles into the atmosphere, although the water vapor from the ocean water would probably be radioactive.

The nuke would certainly not cause a tsunami or anything like that. I'd say the only real purpose for detonating a nuke underwater during wartime would be to eliminate one or more enemy submarines with an indefinite location that pose a serious threat. Seems like it would be overkill, but if an enemy nuclear sub is threatening the country, no chances would be taken.

 

[Dr Lots-o'watts]

In the effects of an underwater accident was too catastrophic, perhaps the concept of nuclear subs carrying nuclear warheads wouldn't have left the design table.

 

[stereobot]

Not any nuke that we've ever produced. 13,000 million tons of TNT would be 260 times more powerful than the most powerful nuclear device ever detonated (and closer to a thousand times more powerful than the most powerful US device ever detonated). Typical nuclear blasts are more in the neighborhood of a few hundred kilotons, the equivalent of a few hundred thousand tons of TNT.

The largest nuke ever detonated was the http://en.wikipedia.org/wiki/Tsar_Bomba" by the Soviets in 1961. 50 Megatons. In comparison the bomb the US dropped on Hiroshima in WWII was 10 - 15 kilotons and wasn't a very efficient bomb.

 

[Lsos]

50 x 260 = 13000

Had me going for a few minutes as well...

 

[stereobot]

50 x 260 = 13000

Had me going for a few minutes as well...

Yeah I totally misread the post. Thanks for clearing that up!

 

[cjl]

The largest nuke ever detonated was the http://en.wikipedia.org/wiki/Tsar_Bomba" by the Soviets in 1961. 50 Megatons. In comparison the bomb the US dropped on Hiroshima in WWII was 10 - 15 kilotons and wasn't a very efficient bomb.

Yep. The most powerful US device was the Castle Bravo test, which was around 15 megatons.

 

[Vanadium 50]

You might want to Google "nuclear depth charge".

 

[Meatbot]

Here's a hypothetical. What if you took about 1,000 nukes and buried some in the ocean floor, then strung the rest evenly up a cable all the way to the surface. When set off, you create a huge tube of air from surface to seafloor. Ocean collpases into the tube --> Mega Tsunami? Anyone here who can do a simulation?

 

[jumpjack]

So I was watching Abyss the other day and got to the part where Ed Harris drops down an underwater cliff to disable a nuke which lies at the bottom. I think the distance was two miles underwater. If the nuke were to have exploded what kind of damage would be done and would it have even been worth the trouble to disarm it in the first place (assuming the way he got down there was actually plausible)?

I think by sure it will create a tsunami, as you can't compress water, and the explosion produces a huge amount of steam, which requires much more space tha liquid water, hence water must go "somewhere".

But there is an additional effect nobody mentioned: fishes!
Thousands of dead fishes!
I always wondered how many thousands/millions of fishes old underwater nuclear tests killed! And where did they go once dead?!?