NavList:

As we all know by now, the small submersible with five people apparently suffered a "catastrophic implosion" on its way to the wreck of Titanic over 12,000 feet beneath the sea a few days ago. It's an instantaneous death (see my PS below). I read an account before the evidence of the implosion was reported of a case where this submersible had gotten "lost" on its way to the wreck last year. Apparently their primary means of navigation at depth was common piloting using a magnetic compass and regular communication with "traffic control". That traffic control was the mothership on the surface which could track them and tell them "go left 100 meters, then hard right... that should bring you to the bow" and such. But it got me wondering, how would you do this more generally? How would you navigate two nautical miles beneath the waves? Wouldn't it make sense to have sonar "pingers" of some sort dropped to the bottom near the wreck? Could they even have navigated by non-electronic listening if they had known sound sources like that ? What does the environment sound like down there in the deep abyss?

Frank Reed

PS: I wrote elsewhere:
"DEATH BY ANNIHILATION: An implosion at that depth is an event of shocking intensity and speed. It happens in a microsecond. The water slams in like a hammer of solid rock. The air inside the submerisible would have immediately pressurized and heated enough to burn almost anything, but then immediately the rest is annihilated by the impact. It's like flying a supersonic jet at three times the speed of sound straight into the side of a mountain. There will be no remains recovered. They probably had no warning whatsoever. And they certainly felt no pain. Annihilation. One moment you're alive and breathing and thinking. Then, an almost unmeasurable interval of time later, you no longer exist."
And later:
"  I tried to emphasize [previously] that they almost certainly would have had no hint of trouble and they would have experienced no pain or even awareness of the implosion. The speed of this was five to ten times faster than the fastest nerve impulses. This is not something that happens "really fast". It's not something that happens in the blink of an eye.. Compare with a single frame of a fast video at 100 frames per second. You can't see the individual frames when they last for 0.01 seconds. The implosion we're talking about here would have occurred roughly ten thousand times faster than that! They felt nothing. They had no "experience" of the implosion. They were annihilated instantly. To put it more vividly, and with a greater "ick" factor, they were turned from living, breathing people... into unrecognizable goo instantaneously. They ceased to exist.
"  So how does this compare with other ways to die? How does it compare with, let's say, the destruction/explosion of the Space Shuttle Challenger in 1986, or the destruction and break-up of the Space Shuttle Columbia in 2003? In both of those cases, the crew had time to realize that they were about to die. They felt the collision, the blast, the massive accelerations. They heard the horrific noises of metal torn from metal. They experienced bone-breaking injuries while conscious. Fortunately for them, and for us contemplating their torture, both crews were deprived of oxygen almost immediately and were unconscious within 30 seconds and dead soon after. Aboard Columbia, it is a consolation that at least they were not alive to suffer watching the decapitation and dismemberment of the astronauts seated next to them... Those were terrifying and horrible deaths.
"  Point being?? Yes, a catastrophic implosion in the deep ocean is quite possibly one of the best ways to die by violence. They knew nothing. They felt nothing. They disappeared. It's an intriguing way to go... Of course, for all of us, our own deaths are incomprehensible by their very nature, but there is another side to this that is, in fact, "horrible". They didn't die in a microsecond-long instant of peace, doing what they loved, exploring the deep sea. They died down there, but they also died on the front pages and the news screens of the world with their families suddenly thrust into a media frenzy. None of them wanted that. I am sure none of them wanted to die under a public microscope. That is a horrible way to die..."

I'm including these comments just as food for thought and conversation, but I'm really interested in discussing the navigation side of this here. :)