That’s for sure!
The whole reason? Isn’t there anything to qualifying for submarine duty involving, you know… the ability to not go completely bonkers when underwater in a confined space for long periods of time?
Suprisingly very little! Funny story… I didn’t want Subs when I enlisted but the training program I wanted required that I volunteer for Sub duty. My recruiter said to tell the Medical people in bootcamp that I was claustrophobic. I did exactly that. They took me to a little room with a chair and table in it and said “Wait here, a doctor will be in momentarily” …I sat down and waited. I soon fell asleep. (It was bootcamp…I was tired! :rolleyes: ) They opened the door after 30 minutes and said “You are not claustrophibic, sign here!” THAT was how I “Volunteered” for Submarine duty.
It’s possible that the titanium hull may have made the submarine less detectable by magnetic anomaly detectors.
In any case who really knows what submarines can do? Maybe they visit the Marianas Trench regularly, and just don’t tell the public about it.
Damn Russkies, leaving their caviar cans and vodka bottle down here!
Naw, as said upthread no non-bathyscape (an underwater balloon with gondola basically) submersible can dive beyond the point where it would have to have a hull heavier than can float in seawater. Unless someone’s secretly invented a superstrong lightweight material that can be produced in thousands of tons and formed into structural members several meters long, there aren’t any warboats below 1500 meters, and probably not that deep.
Unless I am misunderstanding what you are saying, this can’t be true. Submarines sink, usually deliberately while submerging, and sometimes due to accidents. Submarines can be made negatively buoyant, and will sink without any impetus, though they may be screwed if they lose power while in this condition. Submarines can be negatively buoyant and still climb if they have sufficient power to overcome it and sufficient control surface to orient their propeller in the right direction.
I don’t think limits on depth have much of anything to do with buoyancy. My guess is that there is there is a complex strength to size ration involving the surface area of the hull related to the volume within the hull that is compressible. Buoyancy can be overcome by power, but more power means a larger power plant, and more compressible volume within the hull. And similarly, with issues like personnel and weapons, this same trade off comes into play. Ultimately, the law of diminishing returns makes it impractical, though perhaps not impossible, to have a really deep-diving operational armed and operational submarine.
I do recall reading some years ago of work being done to split the air ahead of an aircraft which would allow it to travel much faster. Your idea sounds similar. I suspect the difficulty is the generator required to beam microwaves, X-rays or whatever would add significant weight and fuel.
Quite unrelated but I also remember 30 years ago scientists knew how to create a cone of silence a la Get Smart by projecting soundwaves to cancel out surrounding noise. Quiet cafeterias and bars. I’m still waiting… 
There are enough things that can go wrong that you don’t want a loss of propulsion to be fatal.
x2! That’s what happened to the Thresher in the 60’s!
Yes, I understand that, but people in this thread are talking as if this is some kind of physical limitation that makes a deep diving sub impossible. I would agree that it is a legitimate safety concern.
I remember a techno-thriller I read in my teens (though the term hadn’t been invented yet), written by Martin Caidin, I think, about a revolutionary submarine. It referenced the performance advancement gained when zeppelins were replaced by winged aircraft, which were supposedly much more dangerous because they too would “sinK” if they lost power. His point was that current submarines are still in the zeppelin stage of development, and his conceptual sub was the first to abandon that concept.
The key difference is that in both cases, the “safe” level is the surface, but while an airplane will glide (more or less gently) back to the surface, a negatively buoyant sub
will just sink to the seafloor. This is the equivalent of an airplane drifting off into space when it loses power.
Now, a sub which is positively buoyant but uses wings instead of ballast is equivalent to an airplane, and in fact Virgin Oceanic’s sub works just that way.
Well…kinda. A submarine will normally surface by pumping out some ballast and just “driving there”. Three types of other ways to get to the surface are called “Blows”. LP blow…used sometimes to keep ballast tanks clear when surfacing in rough weather. Normal (HP) Blow, and Emergency blow.
It’s been so long since I read Caidin’s book that I can’t recall why the sub was built with negative buoyancy, but it was repeatedly mentioned that if there was ever a failure of the propulsion system in dep water, the crew were dead men. Really, they point I wanted to make was that this is a safety feature (and an important one, no doubt), but there is nothing about the laws of physics that make a negatively buoyant submarine impossible, given sufficient power and adequate control surfaces to counteract it.
I am not an expert, so please correct me if I’m wrong and explain how.
I understand what I was describing is not the routine because the routine does involve filling and emptying ballast tanks. But it is possible. And I guess, though I don’t know, that if the ballast tanks are filled to the maximum (I dunno if that ever even happens) that many subs would not have enough power to drive themselves up to the surface. I wouldn’t think diesel-electric subs, at the least, would have that kind of submerged power.
Agreed.
Well, that and the uncontrolled flooding, of course. 
Isn’t there a surveillance scenario for bad guy-tracking by looking down at them, in which case bottom-of-the-sea maneuvering would be contraindicated?
No, that’s all true (and actually something I suggested upthread). And maybe for a military vehicle, that level of risk could be reasonable (certainly it’s reasonable for something unmanned). I was just pointing out that there’s a key safety difference here as compared to airplanes.
At any rate, there are modern materials, such as syntactic foam, which has very high compressive strength and low density, and therefore makes achieving positive buoyancy much easier.
…and thats when the chocolate bar got stuck in the peanut butter…
No uncontrolled flooding in the “Thresher” sinking. From what I’ve been told/read about Thresher she had minor flooding that caused electrical problems. This…in turn caused a reactor scram (loss of propulsion). Her ballast tank blow lines were too small and froze when an emergency blow was attempted.
“After shallow dives on April 9, 1963, over the continental shelf of the Atlantic Ocean, where the waters are no deeper than 600 feet, the decision was made to take the USS Thresher to deeper waters and make another dive to her test depth of 1,300 feet.”
"When she sank, Thresher had notified her surface escort (men remembered different things after the fact, but Polmar believes this statement of the ship’s last report makes the most sense): “Experiencing minor problems… have positive up angle… attempting to blow up…”
[…] Bob Ballard’s book “Explorations” […] begins with an account of the loss of the Thresher. According to him, they were at a depth of about 1000’ (if I recall correctly) and were moving very slowly (a couple of knots) when the fitting blew. This caused a reactor scram and subsequent loss of power. At such a depth, blowing ballast tanks does not work, since the pressure causes the blowing ports to ice over. The only way for the sub to reach the surface is to “power” its way up. Ordinarily you’d just trim the bow planes up and apply power, but in this case, they had to hope that they could trim up the bow with just their momentum, since it would be some fifteen minutes before they could get the reactor back on line. The bow planes were trimmed up, but it caused the sub to stall, just like an airplane. The bow went up a little, but forward momentum was lost. With no power, the sub slowly slipped backwards and down until it passed its crush depth of 1500’, then […] she imploded and quickly drifted to the bottom in 8000’ (I think) depth. [Tauxe]
Little info on them-they are built in Iran, and have a 10 man crew. With limited range, weapons, diving capability.
What are they good for?
Suicide attacks or just crew suicide?