Michael Perry asked:
What happens when a bomb explodes underwater?
Dave - Well when any bomb explodes the first thing you're going to get is a lot of high-pressure gas because you've taken a load of solid and turned it into gas. It wants to expand. Water isn't going to move away nearly as quickly as air does. The pressure's going to remain very high, pushing water away. The fastest the water can move away is roughly the speed of sound in water. That's 1400m/s. You're going to form a bubble. As that water is pushed away very fast you're going to get a second powerful sound wave or pressure wave moving away from it. If the water doesn't compress that's going to have a very high pressure and do a lot of damage which is why depth charges can destroy strong things like submarines, even 10-20m away. Apparently it's way that there's a theory of how you might be able to blow up safes. If you fill a safe with water an drop a small charge in then because the pressure change is so much greater it might blow the door off.
Chris - That's because all the pressure is being exerted on the safe. If you were to just stack a load or dynamite at the front of the safe, some of it would hit the safe but a lot of that pressure would go out.
Dave - The gas that's produced, all that extra volume that's produced is pushed on the side of the safe. Normally you can just compress the air inside the room.
Kat - It would be more explosive if you fart in the bath as well.
Michael Perry asked the Naked Scientists: Naked scientists, I'm wondering, if a bomb or a similar explosion went off underwater, would the water amplify or dampen the blast? What do you think? mike2niner4, Sat, 7th Mar 2009
I didn't find any good references on this, but my guess is that the concussion would amplify in the inelastic water so that the blast would be felt stronger to objects in the water. But the water would be somewhat of a shield for things outside the water.
I remember reading somewhere that if you want to blow up a concrete dam it's best to place the bomb underwater as it has more effect. DoctorBeaver, Sun, 8th Mar 2009
Wouldn't the effect be twofold?
I suspect that in space you would be subject only to the ejecta from the explosive device. Vern, Sun, 8th Mar 2009
Yep, that's what I think too :) Whatever molecules there might be will probably belong to the device exploding, and they will disperse quite near the explosion without finding anything to propagate it further with. yor_on, Mon, 9th Mar 2009
since water cant be easily compressed the force of an explosion underwater transfers far more of the energy of a greater distance tony6789, Mon, 9th Mar 2009
Tony that was mighty mystical :)
ok not completely understanding wat ur saying...are u asking if a bomb was encased in a large diamond?? if so (assuming the bomb is powerful enough to explode the diamond) then yea it will likely weaken the bombs power. so yea i agree to an extent tony6789, Tue, 10th Mar 2009