Why The slow subs ?

I was just curious as too why there are no super fast subs or attack type subs that
go really fast ? I mean in the air we have bombers (subs) but know attack subs (like a
yf-22 equivalant).

Is this not possible under water because its so thick and friction?

Im talking at least above 70 knots.

Right, unlike in Air, Water is much denser, put it this way, which is easier, for you to run, or swim? Which goes faster? Which covers more distance?

Shattered OUT...

I bet it would be hard to get a few report or any evidence at all, i mean most oceans are very deep and complicated to investigate. Considering the ammount of water on our planet just think about an flying and submersive type of vehicule, drool Q___.

One could go 50 feet under your boat and never have any clue as i assume they would be stealth too .. i guess.

I just watched the abyss, hence the inquirey. It made me think abit.

The faster you go underwater, the more noise you make, so the less stealthy you are. The Los Angeles SSNs were capable of 30+ knots, but only below 700 feet. At high speed you get bubbles off the prop, and as those bubbles burst, you get noise. It's called cavitation. The new generation propulsors are supposed to be ultra quiet and give higher speeds.

Is there a need for subs to go any faster than what they do now? Remember they are running blind under the water except for sonar. Remember the sub that hit the underwater mountain a few years ago?

The biggest enemy of a sub is noise. The faster you go the more noise you generate. Over 20 knots the water passing over the hull startes to generate noise. Over 30 knots that noise is easily detectable. With aircraft and rocket boosted torpedoes speed is not that big of an advantage if the noise it generates tells the enemy where the sub is.

i dont now that much about subs, but what is the US top sub and how far away can it detect on enemy sub, and what effectve range can it fire a torpedo?

Originally posted by zakattack
i dont now that much about subs, but what is the US top sub and how far away can it detect on enemy sub, and what effectve range can it fire a torpedo?

My info might be a little dated.

Torpedo range can be upwards of 20,000 yards.

Detection range depends on ocean conditions. Figure 60-70 miles max range for detection.

Stealth is more important then speed for subs.

But also like ShatteredSkies mentioned going fast under water is much harder it might take a few thousands HP to move a jet the speed of sound, under water that same mass would require more like a million HP to hit the speed of sound.

Originally posted by ShadowXIX
Stealth is more important then speed for subs.

But also like ShatteredSkies mentioned going fast under water is much harder it might take a few thousands HP to move a jet the speed of sound, under water that same mass would require more like a million HP to hit the speed of sound.

With current propellor technology you wouldn't get speeds over 100 knots no matter how much horsepower you had. One of the previous posts here addressed the issue of cavitation. Cavitation is the slippage that a propellor has in water. As your speed increases so does cavitation. At a certain point cavitation would consume any increase of power that you have, like spinning your tires on pavement.

Who said you had to use propellors

Thrust above and below water could be created in many ways. Ive seen prototypes that use magnetohydrodynamics, thrust in water without any moving parts.

As was said, stealth is better than speed.

But...

DARPA is working on a cool project called the Underwater Express that is for a controllable underwater craft at speeds in excess of 100 knots.

Looks like DARPA is trying to build a sub based off of supercavitation technology, the same as that Russian torpedo. I just wonder how it is going to see where it is going?

The top two US subs are the Seawolf Class, and the Virginia Class. However, only three Seawolfs have been built and that's all that ARE going to be built, and there are currently only two active Virginia subs, because they're brand new. The abilities of all US sub classes is still highly classified, but under the right conditions you could hear something happening several hundred miles away. The EFFECTIVE detection range is under 100 miles though.

Who say you have to use a propelor.
I would assume that to avoid slippage you could use some
sort of compressor, and the use pumps to jet the water out.
Like a jet ski or something.

So...

This is a limitation of the propulsion systems or the friction on the
skin of a sub ?

The Virginia and Seawolf use a propulsor. But again you get the same problem of power and noise. Even with them using the propulsor you get noise at some point.

Running Fast = Running Blind

Dont get all enamoured of speed underwater.

Most of the posters are correct about speed and then the application to the noise threshold. The faster you go at some point you begin to make noise. The trick is to increase the speed at which you can move quietly. This "low noise speed Threshold" has been moving up over the years with new designs and new applications. Newer designs/applications are on the drawing boards right now...and some in the testing phases.

It is also important to note and I have posted in other places...that the faster you go...you must make absolutely sure the equipment you use for depth control is very ...very accurate and dependable. At high speeds one mistake in depth control and you are very very quickly below crush depth. A fatal mistake. This also means good crew training. While I wont take the liberty of quoting speeds this is also a tell tale indicator that they can go very fast if need be. However ..many of the posters are correct in that they prefer stealth to speed when operating. No big secret here.
What is classified is of course the precise speeds , the depth capabilitys, and the techniques used to maintain stealth.
Nevertheless dont get all enamoured of speed ..it is not all that it is made out to be in this buisness. It can be two edged sword..it can cut you as well as the enemy...if not properly controlled/diciplined.

Good question you posted.
Thanks,
Orangetom

Originally posted by Zaphod58
The faster you go underwater, the more noise you make, so the less stealthy you are. The Los Angeles SSNs were capable of 30+ knots, but only below 700 feet.

Untrue. At flank speeds, noise is not the concern.
The submerged operating envelope is what you're worried about.

I would guess the Seawolf and Virginia probably max out around 40 knots.
We won't see 70 knot nuclear subs for a loooong time. Maybe by 2050.

Much depends on the tactical situation . For example if you want an presence in a region you could fly or ship in modern min submarines. The subs themselvs dont have to be that quick if the means of delivery is fast.