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Author Topic: What causes the initial flash in an underwater explosion?  (Read 15500 times)

Offline LeeE

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What causes the initial flash in an underwater explosion?
« Reply #25 on: 29/11/2008 19:43:52 »
Although the initial flash would be very quick, being an explosion, I think the resulting fireball, where the heated gases are still producing light, lasts long enough to illuminate the expanding shockwave.
 

lyner

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What causes the initial flash in an underwater explosion?
« Reply #26 on: 29/11/2008 19:57:45 »
Very possibly.
You'd have to be there! to see it. Keep your eyes open for films in the near future. Then we can resurrect this thread and speak from an informed position> (Now that would be novel).
 

Offline LeeE

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What causes the initial flash in an underwater explosion?
« Reply #27 on: 29/11/2008 20:51:01 »
No TV here, so films are out, and film FX explosions use petrol/gasoline anyway, which aren't really proper explosions - too slow.  Explosion vids on youtube are probably a better bet.  This one is interesting because you can see the shockwave.

http://uk.youtube.com/watch?v=Q_y7JLJGX_w
 

lyner

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What causes the initial flash in an underwater explosion?
« Reply #28 on: 30/11/2008 00:06:12 »
This is good, too:
http://www.youtube.com/watch?v=16heorrfsgY&feature=related

The shock wave is very impressive but there is no visible fireball. I am surprised, considering that it is blinding in atmospheric tests.
 

Offline LeeE

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What causes the initial flash in an underwater explosion?
« Reply #29 on: 30/11/2008 11:27:30 »
If you look very carefully - by clicking quickly on the play button I was almost able to step through it frame by frame - you can just see the fireball emerging from the surface of the water before it's obscured by spray and debris.

 

lyner

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What causes the initial flash in an underwater explosion?
« Reply #30 on: 30/11/2008 11:31:38 »
Well spotted.
It must have been very brief (if you needed to step frame) compared with surface explosions which last for a long time on films. Film is better for showing this because eyes / tv can flare for a long time, whatever the period of the actual flash.
 

Offline LeeE

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What causes the initial flash in an underwater explosion?
« Reply #31 on: 30/11/2008 11:42:57 »
Have a look at the pics of the Redwing Seminole test - you'll need to scroll down a bit.

http://nuclearweaponarchive.org/Usa/Tests/Redwing.html

The Wilson Effect cloud is interesting.  On that sequence of pics you can see the fireball but it's quickly obscured by the cloud, even though the tank it was in was relatively small.
 

Offline yor_on

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What causes the initial flash in an underwater explosion?
« Reply #32 on: 02/12/2008 13:54:57 »
Light slows down in 'matter' right.
So how much would light slow down in 'bubbles?

Under all the time the device explodes there should be light produced, shouldn't it?
From the 'blasting cap' to the burnables driving the 'explosion'.

So how fast will those bubbles be created.
If they are there before the explosion 'burnt through' 
Wouldn't it be possible for light to be 'reflected' in that foam and so keep light confined for some moment?
Also, light from above reflected back from foams surfaces will give a white effect I believe?
As the bubbles will spread the reflective spectrum, much the same as colored glass becomes 'white' when crushed.
 

lyner

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What causes the initial flash in an underwater explosion?
« Reply #33 on: 02/12/2008 23:12:17 »
YES
Except for the 'light slowing down in the bubbles' bit. It would go faster through the air in the bubbles than through the water. Lots of internal reflections would diffuse the light.
I am surprised that there is so much absorption, though. The Wilson Effect Cloud, apparently.
 

Offline DoctorBeaver

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What causes the initial flash in an underwater explosion?
« Reply #34 on: 04/12/2008 13:43:41 »
This thread has got a lot more interesting than I thought it would. Thank you all.
 

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What causes the initial flash in an underwater explosion?
« Reply #34 on: 04/12/2008 13:43:41 »

 

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