Questions for Submariners

[Steadman Uhlich]

I know that several CF Members are also submariners, so I am asking these question here. My questions are sincere and asked in a friendly tone. I am just curious.

I saw this photo shared today on Facebook (by the builder) and thought it was interesting.

Serious question for submariners and others who may know:
Please explain the function of the multiple layered “pagoda” shaped caps on those “periscope” like tubes sticking up above the sail. What are they?

Are those “pagodas” ventilators or snorkels or what?

Are those the sub’s periscopes?

Are they only periscopes (only for optics), or do they have multiple functions?

Also, is it normal for the lookouts and captain to stand up that high? Or do they normally stand lower with only their head and shoulders up above the sail (and protected by the windscreen)?

[Don C L]

Can I also ask, can submarine sonar see sailboats at the surface? I've always wondered just how much, and how small a keel, they can spot reliably and up to what sea conditions.

[a64pilot]

I am not Submariner, nor even been near one really.
However it’s my assumption that a sub could detect phenomenally small things at significant distances, however to do so would may mean active Sonar?
That I assume is roughly analogous to an infantryman sneaking around at night looking for the enemy with a spotlight?

I have actually heard some incredible things about sub hunters.
You can find a sub from the small disturbance of the surface water? You can find one by finding the silent hole on the water, which is the sub?
Of course they have been found for decades due to the interference of the Earths magnetic field a large ferrous metal obj causes.

What I want to know is how fast is an attack sub?
Nearly unlimited power, if very deep the pressure is so high that a prop won’t cavitate, even with nearly unlimited power?
Was the Soviet Alpha really faster than our torpedoes? Was it so fast that it was deaf and blind at high speeds?

Subs have fascinated me since I was a kid, but I think you have to be a special form of insane to crew one.

[Tillsbury]

I'm pretty sure they can. One of the most freaky things I ever experienced was sailing in towards Portsmouth harbour and having a Vanguard surface about 50m from us on our starboard side and continue in on the surface. Those things are massive close-up! Yacht traffic is very busy there, and they'd need to be able to see everything to safely surface.

[sailorboy1]

lots of different periscopes on a sub (periscope being anything you could raise higher up the sail)
some are just exhaust or intake and have have ball valves to prevent down flooding
the sonar may or may not see a sailboat or any other boat, which is why it comes to periscope depth and looks before surfacing

an attack sub can go more than 20 knots (depends on the prop as one than may could do 30 might only do 20 with a quiet prop)
a prop can pretty much always cavitate depending on how fast you try to accelerate
no an Alpha could was not faster than a Mark 48 torpedo, but so close to the speed you needed to be right on their ass for any hope to hit one before the torpedo ran out of fuel (it didn't really matter as the Alpha was so noisy you knew where it was and it never could hear you over itself)

[a64pilot]

I have heard Captain has a vote in which prop the sub has?
Are they called props, or propulsers?

[CaptNemoO2]

Originally Posted by Steadman Uhlich

I know that several CF Members are also submariners, so I am asking these question here. My questions are sincere and asked in a friendly tone. I am just curious.

I saw this photo shared today on Facebook (by the builder) and thought it was interesting.

Serious question for submariners and others who may know:
Please explain the function of the multiple layered “pagoda” shaped caps on those “periscope” like tubes sticking up above the sail. What are they?

Are those “pagodas” ventilators or snorkels or what?

Are those the sub’s periscopes?

Are they only periscopes (only for optics), or do they have multiple functions?

Also, is it normal for the lookouts and captain to stand up that high? Or do they normally stand lower with only their head and shoulders up above the sail (and protected by the windscreen)?

That's the AN/BVS-1 periscope on the newer Virginia class subs. Its not optical like periscope on the other classes, it uses cameras. That pic was taken just off of GDEB's yard in Groton. I'm surprised the Cross Sound Ferry was allowed to depart at the same time.

[socaldmax]

I'm most familiar with SSN 594 class and 688 class US Navy fast attack subs. That photo looks like a Virginia class, much newer. Those are photonics masts, which replaced traditional periscopes beginning with the Virgina class. A regular periscope is a thick metal tube that runs to the bottom of the sub when lowered, and sticks out about that height when raised. It had a few very small antennas in it for ESM, GPS and early warning receivers.

The photonics mast has more ESM antennas in it, as well as a suite of high res cameras, infrared, thermal, laser rangefinding, etc. It also telescopes into the sail and does not penetrate the pressure hull, which is safer in case of collision.

Normally, the lookout and officer stand inside the sail and are protected up to the waist, with a short windshield to break the wind. In this case, they are in the channel posing for pics, so they have a lot more people crowded up there than usual.

[socaldmax]

Originally Posted by Don C L

Can I also ask, can submarine sonar see sailboats at the surface? I've always wondered just how much, and how small a keel, they can spot reliably and up to what sea conditions.

If the sailboat is not running any engines or generator, chances are sonar won't be able to pick them up. A sailboat is virtually silent unless there is an engine running on it somewhere.

[JohnT]

I love the Raymarine radar dome on the sail.

[Shrew]

That picture looks like it is the Thames River in Ct. That sub looks like it is heading outbound from the Groton, Ct sub base. That sub would have been close to right in front of my old marina when the pic was taken.

[Steadman Uhlich]

To ALL: Thanks for the answers to my questions.

I still find the pagoda shapes interesting.

[socaldmax]

Originally Posted by a64pilot

I am not Submariner, nor even been near one really.
However it’s my assumption that a sub could detect phenomenally small things at significant distances, however to do so would may mean active Sonar?
That I assume is roughly analogous to an infantryman sneaking around at night looking for the enemy with a spotlight?

I have actually heard some incredible things about sub hunters.
You can find a sub from the small disturbance of the surface water? You can find one by finding the silent hole on the water, which is the sub?
Of course they have been found for decades due to the interference of the Earths magnetic field a large ferrous metal obj causes.

What I want to know is how fast is an attack sub?
Nearly unlimited power, if very deep the pressure is so high that a prop won’t cavitate, even with nearly unlimited power?
Was the Soviet Alpha really faster than our torpedoes? Was it so fast that it was deaf and blind at high speeds?

Subs have fascinated me since I was a kid, but I think you have to be a special form of insane to crew one.

Unless the boat is fairly close to the surface, they're pretty hard to detect via surface disturbance or even mag detection. Subs get demagnetized whenever they start showing a magnetic signature and if you're down deep, the salt water can mask whatever is left. In my 10 yrs on fast attacks, we did a lot of cat and mouse exercises with surface and airborne assets and we never got detected. The surface ships make too much noise when moving to pick up anything. The only thing that is deadly to even a well commanded sub is dipping sonar on a helicopter. They can hover, drop a mic down as far as they want and listen without any noise. At about 400 ft, there is a thermocline that acts like an acoustic mirror, the only way to get past it is to drop a mic down below it. Helicopters have the speed and hovering ability to drop the mic 3 times and get a good triangulation on you - if you're making any noise.

The actual top speed is still considered TS, but if you look it up in Jane's, it's probably not too far off. Even with a nuclear power plant, I remember we gained about 3 knots when we got the hull cleaned.

There was a long time period where US subs were using CNC machined and polished screws (sub term for propeller) and the other guys were unaware. Between the lack of screw noise, covering the hull in rubber, sound isolating all sources of noise, extensive crew training, etc a typical US sub was quieter than background biologics (mostly shrimp and whales) so the typical sonar tech looking for a noise source would never find it. We were jokingly referred to as "the hole in the water" because we absorbed a lot of ambient noise, so a sonar display would show a quiet spot where the sub was. Eventually, the Soviets also bought the same Toshiba-Kongsberg CNC milling machine that was forbidden for export, those 2 companies were slapped with a 7 or 8 yr sanction, IIRC.

The older boats had screws, the new Virginia class has a propulsor, like a jet drive, it cuts down on cavitation closer to the surface. Like you stated, at deeper depths, cavitation is not as much of an issue.

I don't believe any naval force has any surface or subsurface vessels that can outrun a Mk 48 ADCAP torpedo. The story I heard was the original Mk 48 was designed to go down to XXXX ft because no sub could go any deeper. Then the Soviets came up with a sub that could go something like 200 ft deeper, so they did some minor changes to the Mk 48 and greatly increased it's depth capability. About the only 3 ways to escape a torpedo is to:
1. Outrun it as soon as you hear it launch, it only has a certain amount of range. A well launched torpedo should be launched as close as possible, making that very unlikely.

2. Head for the nearest enemy surface contact and try to get the torpedo to lock onto it. Depending on if they're also looking for you, they might be ready to drop depth charges, so that might not be a good option.

3. Crank up the speed and immediately do a high speed turn, called a "knuckle in the water." It's a large cloud of cavitation, then you launch "noisemaker" countermeasures as you exit the cloud and head off quietly in a different direction. The countermeasures should trick the torpedo into detonating.

We all went through psychological screening to ensure that we were the kind of guys that society wanted locked up in a long steel tube away from polite society for long periods of time. OTOH, they gave us plenty of food, water and nuclear weapons, so it wasn't all bad.

[socaldmax]

Originally Posted by Tillsbury

I'm pretty sure they can. One of the most freaky things I ever experienced was sailing in towards Portsmouth harbour and having a Vanguard surface about 50m from us on our starboard side and continue in on the surface. Those things are massive close-up! Yacht traffic is very busy there, and they'd need to be able to see everything to safely surface.

They might not have known you were there. Normal procedure is to give several hundred yards of distance from any contact, especially sailboats, since they have limited maneuverability compared to motor vessels. Sailboats are nearly impossible to detect unless they have an engine running.

[Nicholson58]

Originally Posted by Steadman Uhlich

I know that several CF Members are also submariners, so I am asking these question here. My questions are sincere and asked in a friendly tone. I am just curious.

I saw this photo shared today on Facebook (by the builder) and thought it was interesting.

Serious question for submariners and others who may know:
Please explain the function of the multiple layered “pagoda” shaped caps on those “periscope” like tubes sticking up above the sail. What are they?

Are those “pagodas” ventilators or snorkels or what?

Are those the sub’s periscopes?



Are they only periscopes (only for optics), or do they have multiple functions?

Also, is it normal for the lookouts and captain to stand up that high? Or do they normally stand lower with only their head and shoulders up above the sail (and protected by the windscreen)?

Not a submariner so I can’t identify. On a sub, It’s all about noise. I suspect odd looking things either quiet turbulence or change the frequency to make it less detectable. Under way, these things are withdrawn to flush with the tower. Active sonar is seldom used as it reveals a sub’s position. The passive array towed behind the sub can detect noises at great distance, especially low frequency stuff. Our boats and other surface craft are wildly noisy from the sub’s perspective. We are not likely to see one except near their port.

I just read
Submarine : A Guided Tour Inside a Nuclear Warship, Tom Clancy & John Gresham

A good factual history and state of affairs such as the navy will permit.