Using Radar to Search for Submarines

[SeaQueen]

Originally Posted by bottomcrawler

I could easily imagine a hull-conformal mine storage. I don't know the size of a typical mine, but I'm certain a fair number could be hauled along outside the pressure hull. But it would make for a slightly noisier sub, and a slower one.

Actually, one of the things people in engineering circles are looking at for future submarine designs is weapons storage external to the hull.

[bottomcrawler]

Ah!

Well, as I said, my main interest is aircraft and aviation in general, and conformal fuel tanks and sensor packages are becoming more common there. It just made sense to me to have something similar under water.

Carefully designed, CFTs only add around half the wetted area compared to a pylon-mounted drop tank of the same volume. In addition to that, they free up pylons for missiles and bombs.

For a sub, I figure faster reloading and an increased load capacity would be the main advantage. Having torps in long tubes that are already flooded, outside the pressure hull, would make for quieter launches. I don't know if it's possible, but gently pushing a torpedo out, then have it "hover" silently until the launching boat quietly swims away to a safe distance, would allow very stealthy engagements.

[SeaQueen]

My understanding is that with future 774 class flights you'll see more experimentation with various ideas. Rickover did a lot for the nuclear Navy in terms of safety, but at the expense of quashing innovation with weapons systems and sail designs in particular. There's all kinds of things on the books for future versions.

Originally Posted by bottomcrawler

For a sub, I figure faster reloading and an increased load capacity would be the main advantage. Having torps in long tubes that are already flooded, outside the pressure hull, would make for quieter launches. I don't know if it's possible, but gently pushing a torpedo out, then have it "hover" silently until the launching boat quietly swims away to a safe distance, would allow very stealthy engagements.

[LoBlo]

Originally Posted by bottomcrawler

Ah!

Well, as I said, my main interest is aircraft and aviation in general, and conformal fuel tanks and sensor packages are becoming more common there. It just made sense to me to have something similar under water.

Carefully designed, CFTs only add around half the wetted area compared to a pylon-mounted drop tank of the same volume. In addition to that, they free up pylons for missiles and bombs.

For a sub, I figure faster reloading and an increased load capacity would be the main advantage. Having torps in long tubes that are already flooded, outside the pressure hull, would make for quieter launches. I don't know if it's possible, but gently pushing a torpedo out, then have it "hover" silently until the launching boat quietly swims away to a safe distance, would allow very stealthy engagements.

Sounds like your thinking along the lines of the the Navy's "Tango Bravo" research project http://www.darpa.mil/STO/maritime/tango.html

I love speculating about future designs as well.

Conformal would make sense if it looked similar to the Ohio Class subs fairwater area [above the missile tubes]. That would be the only way to make them conviently reloaded otherwise the weapons would need be loaded underwater [awkward at pierside and with a 1 ton torp]. Not sure how many torps you could fit at a 'read to launch' position in such a small space though. I say, storage in the ballast tanks would be better.

[bottomcrawler]

I'm not so sure. The easiest way to load them would be through the ports, and all that's required is something to align the loading tube with the storage tube, make the connection and gently push the torp over. Surely that would be possible underwater, and fully automated as well.

If torps are made to swim out, then you could have a rail system inside the storage tube, so that when the first torp is away, the next in line is moved forward to the launch position. If the sub itself is 400 ft long, for example, the storage tubes could maybe be 250 ft, and that's eight torps in line. Imagine three such tubes stacked vertically on each side... 48 extra torps. Not sure how that would work with regards to buoyancy, though.

Added a simple illustration. The big black circle is the pressure hull, and the grey is the outer hull, with the six black circles as torp tubes. This would be for a new hull design, though.

[Dr.Sid]

Launched torpedoes would be replaced by sea-water, same as with VLS, so there should be no problem with buoyancy.
Also VLS is in fact such system. It's not accessible from inside, though I'm not sure if it's inside pressure hull or outside.
Problem I see is that no maintenance would be possible. But then VLS missiles don't need any, or it is done by wire (I guess).
Then there is problem that you have explosives outside your hull, and they do not work as good bumper.
Which reminds me .. hey ! Russians use external tubes for some time now. All problems solved.

[TLAM Strike]

Originally Posted by Dr.Sid

Which reminds me .. hey ! Russians use external tubes for some time now. All problems solved.

Yes and the US Did it in WWII. Between the world wars it was trendy to have a set of external tubes that were trainable like the mounts on destroyers.


^USS Stingray with two external tube mounts.

[LoBlo]

Originally Posted by bottomcrawler

I'm not so sure. The easiest way to load them would be through the ports, and all that's required is something to align the loading tube with the storage tube, make the connection and gently push the torp over. Surely that would be possible underwater, and fully automated as well.

If torps are made to swim out, then you could have a rail system inside the storage tube, so that when the first torp is away, the next in line is moved forward to the launch position. If the sub itself is 400 ft long, for example, the storage tubes could maybe be 250 ft, and that's eight torps in line. Imagine three such tubes stacked vertically on each side... 48 extra torps. Not sure how that would work with regards to buoyancy, though.

Care for some debate/critique? In the spirit of debate, I see a few issues with that design.

1) One is that it would be cumbersome to load front hatches/ports while they are underwater. Even the Akula had its external tubes on the dorsal surface to allow easy loading.



You would either need divers to ease the torps into their ports (awkward for a floating diver manipulating a 1 ton torp being supported by a crane and having to repeat it 48 times), or special support platforms to load the torps; meaning only ports with the special support platforms can load torps whereas currently any port with a simple crane will do (good for wartime improvising).

2) that profile would make the boat non-axissymetric, meaning more drag and all the pitfalls of more drag. If its made to be axis symetric, its now essentially a double hull a.k.a increased building expense, whereas most Navy's are looking at ways to build things cheaper.

3) The launch needs not only to gently push, but also needs be able to forcibly eject the weapons outward while the sub is a flank speed, meaning that the system would need a the same load and latch systm currently in all subs now. They would then be outside the boat chronically exposured to seawater at months at a time, unavailable for diagnosis and repair of any malfunctions unless returning to port/pier. Remember that seawater is the most corrosion medium on the planet and anything chronically exposed will have an increase risk of malfunction (relative to being in air). When you think about it, we've essentially taken the loading/rail/hatch system of any current sub, moved it outside the hullr, exposed it to seawater for months at a time, and made it completely off limits to maintenence for months at a time as well.

All and all, not sure we're getting much bang for the buck there with all that's required in the name of having a few more torps in the loadouts.

A simple solution would be to replicate a 'VLS' approach for torps. Preload the torp into their launch tubes off the boat. Drop the preloaded tubes from the top into the ballast tank horizonally and secure them to the correct angle. Ready and done. No extra moving parts to break, malfunction, or matain. I would probably go with a 'quad-canister' arranagements (like used by the harpoon missiles) at the 4 quadrants of the ballast tanks angled forward. Just open the door and shoot when needed. Simple, easy, reliable.

[Dr.Sid]

I like the 'not for public use' watermark

[bottomcrawler]

Originally Posted by LoBlo

1) One is that it would be cumbersome to load front hatches/ports while they are underwater. Even the Akula had its external tubes on the dorsal surface to allow easy loading.

You would either need divers to ease the torps into their ports (awkward for a floating diver manipulating a 1 ton torp being supported by a crane and having to repeat it 48 times), or special support platforms to load the torps; meaning only ports with the special support platforms can load torps whereas currently any port with a simple crane will do (good for wartime improvising).

We live in the 21st century. An automated loading system with self-alignment would be an easy matter to design and build. You start with a crane and then add a rigid lift mechanism that lowers the loading tube (carrying the torp) into position. A docking mechanism then engages the edge of the storage tube inside the port, aligning and securing the loading tube. A rail system would then push the torp into the storage tube, where it transfers to the internal rail. Done!

Originally Posted by LoBlo

2) that profile would make the boat non-axissymetric, meaning more drag and all the pitfalls of more drag. If its made to be axis symetric, its now essentially a double hull a.k.a increased building expense, whereas most Navy's are looking at ways to build things cheaper.

When you say more drag, do you simply refer to the increase in wetter area (surface friction drag) and the slight increase in frontal area (form drag)? Or is the another factor that comes into play?

Originally Posted by LoBlo

3) The launch needs not only to gently push, but also needs be able to forcibly eject the weapons outward while the sub is a flank speed, meaning that the system would need a the same load and latch systm currently in all subs now. They would then be outside the boat chronically exposured to seawater at months at a time, unavailable for diagnosis and repair of any malfunctions unless returning to port/pier. Remember that seawater is the most corrosion medium on the planet and anything chronically exposed will have an increase risk of malfunction (relative to being in air). When you think about it, we've essentially taken the loading/rail/hatch system of any current sub, moved it outside the hullr, exposed it to seawater for months at a time, and made it completely off limits to maintenence for months at a time as well.

Well, there are several ways to solve that problem. One is to simply evacuate the tubes (which would require pressure-resistant storage tubes, i.e. a bit heavier) and only slowly flood them right before hostilities are expected. They could then be flushed with fresh water at a later time, to prevent large-scale corrosion.

Or, the tubes could be flooded with fresh water permanently and then flushed again (like above) after "use".
I'm not sure what the realistic production capacity for fresh water is in a modern sub, though.

Or, have encapsulated torps, where they each have their own, snug, storage capsule that is jettisoned at launch (this capsule could also have an ejection mechanism to solve the high-speed ejection issue).

My mind is always looking for problems to solve and imperfections to improve on. Some ideas are good, others, not so great...

[LoBlo]

Originally Posted by bottomcrawler

We live in the 21st century. An automated loading system with self-alignment would be an easy matter to design and build. You start with a crane and then add a rigid lift mechanism that lowers the loading tube (carrying the torp) into position. A docking mechanism then engages the edge of the storage tube inside the port, aligning and securing the loading tube. A rail system would then push the torp into the storage tube, where it transfers to the internal rail. Done!
When you say more drag, do you simply refer to the increase in wetter area (surface friction drag) and the slight increase in frontal area (form drag)? Or is the another factor that comes into play?
Well, there are several ways to solve that problem. One is to simply evacuate the tubes (which would require pressure-resistant storage tubes, i.e. a bit heavier) and only slowly flood them right before hostilities are expected. They could then be flushed with fresh water at a later time, to prevent large-scale corrosion.
Or, the tubes could be flooded with fresh water permanently and then flushed again (like above) after "use".
I'm not sure what the realistic production capacity for fresh water is in a modern sub, though.
Or, have encapsulated torps, where they each have their own, snug, storage capsule that is jettisoned at launch (this capsule could also have an ejection mechanism to solve the high-speed ejection issue).

Sure, those things are achievable, but are they efficient? My impression, is that the rail system itself would be the maintenance headache [as oppose to the torp], meaning that all the moving parts of the rail would need to be 100% malfunction proof, be able to sit in seawater for months between maintenance cycles without any malfunctions, and be able to sit in seawater for years before dry dock/dry maintenence (even in port they would be in the seawater and the maintence would have to be done in the water by divers, unless its expected that the sub would be in dry dock quite often). Is that doable? Yes. But is it worth it in terms of capability/maintenence/reliability/and cost? That's the tough question.

Hm... I'm not sure how often submariners haul the subs into dry dock or go into the ballast tank for maintence. I'll ask in the RL submariner's thread.

In terms of drag, I believe an elipsoid form have a higher coeffient of dray than a cylindrical form, meaning higher drag coeffience = higher drag per surface area.

My mind is always looking for problems to solve and imperfections to improve on. Some ideas are good, others, not so great...

Here's a challenge then. How would you solve these problems? http://www.darpa.mil/STO/Solicitatio.../proposers.htm

 The Defense Advanced Research Projects Agency's (DARPA) Advanced Technology
Office (ATO) announces the joint DARPA/United States Navy TANGO BRAVO 
program. The intent of this effort is to overcome selected technological 
barriers that are judged to have a significant impact on submarine platform 
infrastructure and cost. DARPA and the US Navy together plan to execute a 
technology demonstration program to enable design options for reduced-size 
affordable submarines with full nominal capability, while simultaneously
decreasing platform infrastructure and the cost of future design and 
production. Five technical areas will be solicited under a Broad Agency 
Announcement anticipated to be published in the forthcoming weeks: 
 
1. shaftless propulsion,
2. external weapons stow and launch,
3. hull adaptable sonar array,
4. radical ship infrastructure reduction, and
5. reduced crew/automated attack center.
 
A classified Proposers' Day Conference will be held on 8 November 2004
at the Executive Conference Center, One Virginia Square, Suite 600,
Arlington, VA 22203. A Proposers?Day Conference announcement will be 
forthcoming with details on registration.

[bottomcrawler]

Well, the easiest way to avoid corrosion, is to use materials that aren't much affected by seawater. Plastics, for example. My idea was to use a system where moving parts are made of a suitable plastic material (also good for reducing mass and overall density), and actuate them using pressurised water (the pumps could be housed externally in an easily accessible compartment). Teflon-coated sliding plates/rollers work fine when wear is low. After all, such a system would not see much action (only during loading and launch, and how often does that happen?).

[LoBlo]

Well, according to the RLBTDT (Real Life Been There, Done That's), on the RL Submarine thread, guess 'in-water' equipment isn't as maintenence intensive as I thought... so what do I know (diddly squat!)

Of course one could always go with the SSN 23 Jimmy Carter's Wasp Waist design combined with a rotary stowage to store torps. I believe the rotary idea was pioneered by a British engineer, Harold Armstrong by Babcock Defense Systems, according to a book I read. For a 40foot sub, you could probably hold about 30 torps on the rototary and could be loading from the top. If the sub sail was getting in the way it could always be moved to aft of the reactor compartment since subs are going for nonpenetrating mast now anway. Here's a pic. Critique?

[bottomcrawler]

Another idea I have is for a recoverable mobile sensor platform. It could hold a passive 360-degree sonar array, optics ("remote periscope"), simple ESM and a comms system. A larger "spine" or a longer sail could house a couple of units.

This would probably be more useful for a smaller AIP/diesel-electric sub. It could lie in wait at the bottom, with a wire-connected mobile sensor bobbing at the surface, effectively giving the sub nearly the same situational awareness as if it had been at periscope depth with a couple of masts extended.

In an emergency, the wire would simply be cut and the "drone" left to its own. It could of course be programmed to quietly swim to a predetermined safe resting location, to be recovered later by a surface unit.