Enemy sub, scramble our u-fighters! (why not, really?)

Safe-Keeper

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Since my "why trains" thread turned out so well, I decided to start another thread to ask another question I've been thinking about a lot lately.

OK, so we all know what fighter jets are - from the early WWI designs to the F-22, these fast planes patrol the skies, deliver bombs and missiles at ground targets, carry out recon missions, act as forward observers for ground troops and artillery, and so on and so forth. They've proven themselves quite useful, which is why there are so many of them in the world today. This much is common knowledge.

What I'm wondering is - why haven't anyone taken a similar path underwater, other than in fiction books (X-Com Terror from the Deep comes most readily to mind)? It sounds simple enough to me - build small, fast and agile subs, give them crews of one or two people, arm them with torpedoes suitable for their size, and give them pretty much the same missions fighter jets get in the sky. Even if the enemy sees them coming, there won't be much they can do with their big and bulky subs designed to attack surface ships and other big and bulky subs. I know several powers have employed mini-subs and kaiten torpedoes or whatever they were called, but why haven't they progressed past that level?

Obviously, since there aren't too many 'sub fighters' in the world's navies, there's got to be some sort of serious drawback I haven't though of. So... what is it? Would they run out of fuel to fast? Wouldn't they be able to follow the conventional subs into the high pressure depths of the ocean? Would they have trouble finding targets somehow?

In short, why don't Russian subs in Norwegian waters risk running into flight groups of Barracudas on patrol;)?
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Safe-Keeper said:
Obviously, since there aren't too many 'sub fighters' in the world's navies, there's got to be some sort of serious drawback I haven't though of. So... what is it? Would they run out of fuel to fast? Wouldn't they be able to follow the conventional subs into the high pressure depths of the ocean? Would they have trouble finding targets somehow?
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They tend not to exist during peacetime simply because they are too risky. At least that is the generaly accepted reason for britian getting rid of it's stickleback class.

Still during wartime such boats have been built:

http://en.wikipedia.org/wiki/Biber_(submarine)

One prototype rather faster sub has been built:

http://en.wikipedia.org/wiki/Schwertwal

Now for the problems. First is there is simply too much for one person to do. Keeping trim, finding and tracking targets, navigateing and the various other things that need to be done on a sub. Two man or more midget subs have a better record.

Speed is another problem. Even at the 20 knots the Schwertwal could suposedly reach the thing is going to be rather slower than destroyers. Even so there is a significant risk that the pilot will lose control and dive below crush depth.

Next up weaponry. See small subs tend to have very limited reserve buoyancy which means that if you want to use torpedeos they have to have neutral buoyancy.

Then you have range issues. Modern naval combat takes place at a distance of 100s of miles. One man subs don't really have the range. A few two man ones do but by they had traveled between the two fleets the battle would be over. Still the japanese Ko-hyoteki class were designed to operate during a clash at fleets but the design assumed that such a clash would take place at gunnery range rather than aircraft carriers.


Midget submarines have been built but in the modern naval enviroment about the only roll left to them is espionage. even the harbour assalt role could probably be done better through a couple of patrol boats packed with anti-anti ship missiles. Still it's not incovivable that a war betweenn thrid class powers could result in the reappeared of things like the german Seehund and the british X-craft.
 
I agree with all of geni's points; the propulsion system alone is large and bulky.

However, we may be doing something rather similar with underwater "UAV" craft. I see that the Navy is playing with remotely-controlled small reconnaissance craft now.... Not much of a step up to add a bit of armament, or just make the whole thing into a "smart bomb".
 
Bikewer said:
I agree with all of geni's points; the propulsion system alone is large and bulky.

However, we may be doing something rather similar with underwater "UAV" craft. I see that the Navy is playing with remotely-controlled small reconnaissance craft now.... Not much of a step up to add a bit of armament, or just make the whole thing into a "smart bomb".
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Thats pretty much what torpedoes do already.
 
Safe-Keeper said:
OK, so we all know what fighter jets are - from the early WWI designs to the F-22,

build small, fast and agile subs, give them crews of one or two people, arm them with torpedoes suitable for their size, and give them pretty much the same missions fighter jets get in the sky. Even if the enemy sees them coming, there won't be much they can do with their big and bulky subs designed to attack surface ships and other big and bulky subs. I know several powers have employed mini-subs and kaiten torpedoes or whatever they were called, but why haven't they progressed past that level?

Obviously, since there aren't too many 'sub fighters' in the world's navies, there's got to be some sort of serious drawback I haven't though of. So... what is it? Would they run out of fuel to fast? Wouldn't they be able to follow the conventional subs into the high pressure depths of the ocean? Would they have trouble finding targets somehow?
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Manned jets have been flying since WWII to the present, not WWI.

Submerged missions tend to be measured in days or months unlike those hours long missions in aircraft. So you will need more than 1-2 guys in the sub. Even a small sub will need a large battery and some means of charging it while away from base (or a tender such as a larger SSN or SSBN/SSGN). This adds bulk and noise. If you want to carry a decent torpedo or two, then this is much more bulk. A Mk-48 is 21" wide and 19 feet long, the launch tubes are even bigger. Some electric torpedoes are smaller, but not much. A missile could be used, but the launch would be noisy enough to be heard miles away.

If they want to find something, they need a good periscope, secure communication equipment and good sonar. Sight is limited to line of sight. They could receive radio traffic, but this requires an antenna that floats in the water or is raised from the sub. Good sonar requires a long trailing array and a good computer, both of which need electrical power. For get about active pinging. The enemy can hear it twice as far as your sub can get a return. It would be like broadcasting your name and address underwater.

The subs best defense is a low noise level. The newest attack subs are very good at detecting any machine noise, even electric motors with the sonar arrays they trail hundreds of yards behind them. Any attempt at a fast closing speed will result in lots of prop noise and a good source for a MK48 torpedo to home in on. While a little sub might make an ambush platform, this is already done by the existing nuclear and diesel-electric subs.

I was reminded of the movie "Escape from LA" The silly little sub that Snake Plisken used to travel to LA was a noisy little thing that would not last long in open water as a good SSN would have just sent a fish (with a warhead on it) to say hello; and goodbye. :)

Ranb
 
geni said:
Next up weaponry. See small subs tend to have very limited reserve buoyancy which means that if you want to use torpedeos they have to have neutral buoyancy.
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I recall seeing somewhere that the Japanese midget subs would pop up to the surface when they fired their torpedoes because of the sudden lack of weight.

Steve S.
 
Ranb said:
Manned jets have been flying since WWII to the present, not WWI.
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The first ever air reactive propelled aircraft flew in 1910. I think the OP just
meant fighter aeroplanes in general, not necessarily jets.
 
Displacement ship's speed and efficiency is a factor of size- the bigger the ship, the faster it can go. Square root of the water line length in feet, times 1.3-1.5. And it takes one horsepower for every 500 pounds. Hydroplaning boats are different, but they are not submarines. Different formula for subs, but... So a little sub can't go as fast as a bigger ship? Aaand, today's huge subs go well over 30 knots- (I don't think even Tom Clancy knows- I could tell you, but then I'd have to kill you :) )
 
Small fast boats are going to be loud. Just no way around it. You'll hear them coming. And when you do; Well, torpedos can be programmed to home in on any source.

What you really want (and we have) are boats that can run silent at speeds of several knots while passive sound ranging assisted by computer processing gives situation awareness to the skipper.

Our boats are not very silent, however, compared to some of the modern German electric boats; There is a limit to how quiet a running reactor can be, even when all the equipment floats in mercury.
 
I have read of rocket proppeled torpedoes using supercavitation to reduce drag and achieve misile speed underwater.
Guess you could build something similiar for a small submarine.

I don´t see it as very practical through.

You would be better off with a pack of torpedo boats with a datalink between their sonar systems. Or some good diesel subs.
 
There are hunter-killer subs in service tasked to find and kill the enemy.
ISTR maybe one of ours at least has run afoul of a potential enemy and been sunk!
 
Ranb said:
Sounds interesting, got a link?

Ranb
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I think he must be referring to Coanda's effort. It was interesting, but didn't work in the same was as a jet engine as we'd think of it today. Perhaps if the design was developed we might have seen some useful stuff sooner, but as it was it didn't offer real benefits over contemporary piston engines and it wasn't pursued.
 
Safe-Keeper said:
What I'm wondering is - why haven't anyone taken a similar path underwater, other than in fiction books (X-Com Terror from the Deep comes most readily to mind)? It sounds simple enough to me - build small, fast and agile subs, give them crews of one or two people, arm them with torpedoes suitable for their size, and give them pretty much the same missions fighter jets get in the sky.
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I've managed to get hold of a top secret government film suggesting that exactly this sort of project has been operating covertly for over 40 years.

Yuri
 
It's a bad idea because the fighter-subs would be traversing the same medium as the carrier sub. It would be like a surface carrier that launches speed boats. They can't do anything the big ship couldn't be built to do better, the combined cost of a bunch of them would be exorbitant, and because their endurance would be so limited, you'd need the carrier around anyway.

With supercavitating bullets and torpedoes, though, it would at least be pretty cool to watch.
 
Lynx2174 said:
It's a bad idea because the fighter-subs would be traversing the same medium as the carrier sub. It would be like a surface carrier that launches speed boats. They can't do anything the big ship couldn't be built to do better, the combined cost of a bunch of them would be exorbitant, and because their endurance would be so limited, you'd need the carrier around anyway.
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With the increaseing effectiveness and falling cost of anti-ship missiles thats not a completely unreasonable tactic on the surface.
 
Another factor is the human one: people get squirrelly enough being underwater in a confined space for extended periods when they have room to move around and company.
 
It all comes down to the density of air vs. the density of water, I think.
 
jj said:
It all comes down to the density of air vs. the density of water, I think.
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But what JWideman was inferring was the density of bubbleheads.

And that film clip of Stingray outrunning the big fish brings up the Sewerpipe sailor's worst enemy- The Sperm whale. They've been know to bite off the end of a submarine and suck out all the seamen.
 
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