US Navy underwater laser development "changes everything" | Hacker News Reader

US Navy underwater laser development "changes everything"

strategypage.com

20 pointscwan6 comments

I remember reading about the importance of sub-millisecond shutters in underwater photography. Apparently, if you time the flash and shutter just right, you can get the light bouncing back from the target into the camera, but block all the light from in front of and behind the target, as well as ambient water particles . This apparently increases your visible distance underwater by twofold.

Note that here the laser is used to generate an _acoustic_ pulse, so the light is not used as a carrier, sound is.

Research in using lasers underwater for 40 years with the same result: little use other than for very short distances. Water absorbs the energy too much for lasers to be of use at long distances. And high power emissions only make you look like a searchlight, hardly something you want to do if you're in a submarine.

I cannot see that this "changes everything".

>> To do this, the sub releases a similar buoy through its garbage chute.

This is technically incorrect. The garbage shoot is for weighted trash that gets flushed vertically downward. If the sub were going to launch a buoy it would send it upward via one of its 3" signal launchers (used for flares, other buoys, etc.)

Though they did note that the buoy hovers for a while so the sub isn't below it when it rises to the surface. Considering the delay it could be deployed above or below the sub, but below may make more sense because it won't float up on its own.

I wonder if this technolgy will provide an alternative to communicating with satelites in space. I think using this underwater laser system is great because it provide security from signals being intercepted.

I don't believe this is relevant to ground-to-space communications. The way I read the article the laser pulse has a short range, ionising the water in the vicinity of the buoy, which creates sound waves which emanate out to wherever the sub is. The laser isn't bouncing back and forth from sub to buoy.

As the communication is via sound and not laser it also means that anyone else in the vicinity could intercept the message. Strong encryption and authentication would still be required.

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