pretty cool, shooting underwater @ 27000 frames per second

[chrish]

http://www.youtube.com/watch?v=OubvTOHWTms

This is pretty neat to watch.

[downtownv]

That WAS cool! Like an acid trip in the 60's!:hippie::hippie::hippie:
Right Jocko?

[CJB]

I didn't watch the whole video, but.. I'll hand out a gold star to anyone who correctly states what causes the linear trail of "bubbles" behind the bullet. Hint, it aint the propellant gasses.

[chrish]

I didn't watch the whole video, but.. I'll hand out a gold star to anyone who correctly states what causes the linear trail of "bubbles" behind the bullet. Hint, it aint the propellant gasses.

Initially, I'd have said heat boiling the water instantly, but after thinking about that...bullet starting out underwater...less friction therefore unlikely. Thinking maybe same concept as submarine/boat propeller? Whatever physics term goes w/ that? I'm an ex-mathematician/statistician, physics is for the REALLY smart people.

What I really found cool too (again, no idea what the physics is behind it) was the implosion and expansion of the water around the bubble groupings. That was pretty neat looking.

I can't find the link now, but as I was watching a bunch of those guys' videos, I ran across another guy that enlisted 'theslowmoguys' to help him shoot an AK underwater. Much more pronounced/cleaner looking than what the 9mm produced.

[CJB]

close enough for the gold star.... its cavitation....which is water boiling at low temperature due to low pressure caused by movement of some object in the water - be that object sub propeller, bullet, or pump impeller. The "wake" of the object creates localized low pressure and because of that, the water boils. And as we know - and unlike that which has been falsely mentioned - the cavitation is not water becoming distinct hydrogen and oxygen gasses, but instead it is water changing state from liquid to vapor.

Thought I'd add the science class in there... I deal with this crap all day long....

[chrish]

So the pressure change allows the water to boil, vs just the bullet being hot from being fired? Cool. Who knew. I need to read more!

I didn't realize the boat propeller was actually causing the water to turn to vapor. Again, amazing. Figured it was something else at play, but then again, it's always temperature, pressure, energy...when you get right down to it, there are only a couple of variable to consider.

Thanks for the science lesson! Stuff for me to go look up now.

[Tinman507]

https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcTCiA3X-E3qF-WehoWSNqR1cDR1dZ-QJoK8IYW0HIdXZlZcUHj6

[Ikeo74]

How is a camera able to split 1 second into 27,000 picture frames? Sounds impossible to me.

[chrish]

How is a camera able to split 1 second into 27,000 picture frames? Sounds impossible to me.

The power of digital technology. They had film 'way up there' years and years ago, before digital photography. Nothing like this however. But 'putters have made all the difference.

I've got a Nikon 1 series camera (pretty cheap) that can do 1/16000 electronic shutter speeds. It can do this kind of stuff, but at an extremely low res and only up to 1200fps. The effect is still cool, but not nearly fast enough to slow down a bullet (or something faster). Not sure how much the stuff these guys use costs, but I'm sure it's not inexpensive.

[chrish]

https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcTCiA3X-E3qF-WehoWSNqR1cDR1dZ-QJoK8IYW0HIdXZlZcUHj6

Cavitation man...not flatulation.

[Longitude Zero]

Slo Mo films like that are fascinating. IIRC Lawrence Livermore Labs has the capacity to get up to an over 1 million frames per second in their synchrotron.

[nuke]

Cavitation man...not flatulation.

+1

Stick something in there to stop her... flatulation.

[wyntrout]

I think the answer to Ljutic's explosive flashes in the clear ballistic gelatin are answered in that explanation.

I thought the noise would be more intense underwater and the pressure waves would be "unpleasant"!

Wynn:D