Do they need to?
Or are they physically unable to do this?
What if everything goes wrong and they just sink to the bottom?
Submarines have a maximum depth, so most of them can’t explore the abyss. If it’s in shallow enough water, then it might be able to sit on the bottom.
There’s a few problems with sitting on the bottom for a sub. Some of them have vents underneath that you wouldn’t want to get clogged with sediment. If it’s muddy at the bottom, a sub could sink into it and get stuck. Also, they tend to be top heavy, and I would think they’d tend to roll over, but I’m not sure about this.
I’d think if subs were top-heavy enough to roll over then that would be a problem at all times and not just on the ocean floor.
Not really, the conning tower could act as a “keel” when it’s moving to prevent rollover. I admit, I’m guessing a bit here, and this is GQ, so I shall withdraw the comment.
I went googling and found this article from 2004, discussing diesel-electric subs made in other countries:
From here:
http://www.nationaldefensemagazine.org/archive/2004/August/Pages/Diesel_Submarines3451.aspx
So apparently at least some modern diesel-electric subs can sit on the ocean bottom.
Do you mean military submarines, or just submarines in general? Because James Cameron just went to the bottom of the Marianas Trench a couple years ago. Pretty sure it was the bottom bottom, not just hovering there a few feet up. The wiki page mentions “touchdown”.
For at least one non-military sub the answer is a qualified yes.
Atlantis Submarines operates a tourist submarine for relatively shallow excursions around the coral reefs in several tourist destinations. WE have one here in Cayman and they most definitely set it down on the bottom. I’ve been scuba diving in the area where they do their tours and seen it happen.
However, as a safety measure they set their buoyancy tanks with a slight amount of positive buoyancy. There are electrically driven propellers that push the sub down. These propellers would have to stay in operation for the sub to stay on the bottom. Turn off the power and the sub floats back to the surface on its own.
Like in the movies, like Destination Tokyo (1943), when the sub sits on the bottom so they can operate on a guy.
Yeah about that keel thing. I don’t think it would work as a keel if the sub were floating at the surface. But that’s just a land lubbers stab at it.
Mostly answered here, but I can confirm that military submarines are in no way “top-heavy.” For one thing, submarines have fixed lead ballast in the bottom of the boat to provide a righting moment and ensure they stay right-side up. (They do tend to have a reduced righting moment due to their circular cross section, but that is a separate consideration.)
Incidentally, sailing boats don’t stay right-side up due to the hydrodynamic forces on their keel, either. Again, they have lead ballast in the bottom of the boat or in the keel itself. (The reason for the hydrodynamic keel is to convert the sideways motion of the wind when it is abeam into forward motion.)
I seem to recall a Tom Clancy bit about some subs outfitted for special ops having fittings installed to allow them to sit on the bottom.
I know WWII subs could sit on the bottom, although it was not always deliberate. I remember the German sub in Das Boot sat on the bottom – I think it was in the Mediterranean – while they worked on the batteries. I am having a hard time finding anything on the internet about modern subs sitting on the bottom. Is it classified or something? I read about boomers on patrol “sitting” but I’ve never been clear on if they actually sit on the bottom or just hover. I know we have some former submariners here. I hope they’ll chime in.
As in robby just above?
Clearly there’s lots of ocean where it’s deep enough that only wreckage is going to be sitting on the bottom. Only a relatively small area of the ocean is shallow enough where the bottom is reachable. OTOH, for a lot of submarine missions, that relatively shallow inshore water is where you want to be.
Nuke boats have coolant circulation going on constantly. I assume it’s pumped, but perhaps there’s an especially low-power stealth mode where they can rely on convective flow. Either way they probably don’t want very much sediment in their heat exchangers.
So I’m going to speculate that bottom-sitting by nukes is real rare unless they have some sort of stilt-like “landing gear” ref BrotherCadfael’s fictional reference.
But robby didn’t say anything about sitting on the bottom.
The USS Jimmy Carter allegedly has the equipment necessary to tap undersea fiber optic cables. I’m not sure if it actually sits on the floor in the sense that it’s putting a significant amount of weight on it, but the cable is on the floor and obviously the sub has to get pretty damn close if it’s going to work on a cable. Maybe they have a work chamber that extends a bit from the hull, but this would still be on the order of a few meters at most.
LSLGuy has covered most of the salient points.
Nuclear-powered submarines do indeed need a constant flow of seawater for their heat exchangers and turbine condensers, and clogging up the intakes with sediment would be detrimental. This is less of a issue with diesel-electric subs, but their endurance is only a small fraction of that of the nuke boats.
Another consideration that the ocean bottom is not a featureless, smooth surface as is commonly imagined. Instead, it has topography just like dry land (which is typically covered with sediment). This mean that a potential bottom-sitting operation would have to conducted very carefully, to avoid striking an outcropping or ending up in a precarious orientation.
Boomers on patrol don’t sit on the bottom, nor do they routinely hover. Instead, they proceed at a fast enough speed to maintain steerageway so that their rudder and planes work. (Hence the unofficial boomer slogan of “three knots to nowhere.”)
P.S. Just noticed that this will be my 5,000th post! (And it’s only taken me 16 years…)
Isnt there a US sub which could navigate underwater up a river?
The NR-1 nuclear submarine was specifically designed to sit on the bottom and even had wheels to drive it across the ocean floor. It had a test depth of 3,000 feet. It had water thrusters which allowed it to hover above the ocean floor or gently descend and make contact. However even the NR-1 sometimes got stuck on the floor.
There is a book about the history and use of this submarine:
Re regular nuclear submarines, the average ocean depth is 12,000 feet. The test depth of a Los Angeles-class nuclear submarine is about 950 feet. A nuclear sub is usually operating in water so deep that if everything went wrong and it sank, it would implode long before reaching the bottom. There would be no reason to make specific design tradeoffs (such as repositioning bottom-mounted water intakes) for a scenario which almost never happens and is not survivable when it does.
IIRC some Russkie titanium hulled subs, like the Alpha class could go pretty deep, circa 4000 feet?