nuclear Submarines

Hey

What is the top speed for NuclearSumbmarines????
My Dad knew Radar operators from the Navy and they said that
SSNs(attack submarines) can cruise at 60 knots and tracked one at 60knots.
Does anyone else have storys like this???
Do you think this is true???
And other things regarding the top speed of NuclearSubmarines.

Ta!

Originally posted by JimmyCarterIsSmarter
Hey

What is the top speed for NuclearSumbmarines????
My Dad knew Radar operators from the Navy and they said that
SSNs(attack submarines) can cruise at 60 knots and tracked one at 60knots.
Does anyone else have storys like this???
Do you think this is true???
And other things regarding the top speed of NuclearSubmarines.

Ta!

Top speeds for nuclear subs are classified but as a practicing naval architect i can tell you they are extreamly unlikely to be at 60knots

yeah thats what i thought

www.subsim.com... - Interesting article on submarine speeds/future of this.

Edit:
www.mod.uk...
"The United States introduced the first nuclear-powered vessel in 1955. It had an environmental regeneration plant, and high-performance navigation and communications systems and could remain submerged for weeks, reaching speeds of up to 30 knots, if required. This class of vessel evolved into the strategic missile-carrying submarine (SSBN) such as the UK’s Vanguard class. "

[edit on 16-3-2005 by Odium]

Originally posted by JimmyCarterIsSmarter
Hey

What is the top speed for NuclearSumbmarines????
My Dad knew Radar operators from the Navy and they said that
SSNs(attack submarines) can cruise at 60 knots and tracked one at 60knots.
Does anyone else have storys like this???
Do you think this is true???
And other things regarding the top speed of NuclearSubmarines.

Ta!

How did Radar operators track a sub doing 60 knots???

SSNs go faster under the water than on the water.

they go faster beacause they are no longer generating waves as they did on the surface so the only resistance is frictional drag from the surface. You can calculate estimates for this quite easily and from the data a quick search on the net provides it would suggest nothing above 35 knots is likely. This does not include any high tech methods for reducing drag that they may have developed in secret.

The article on supercavitation is interesting and has been discussed many times on this board. To date nothing bigger than a torpedo has been fielded. The US are developing a system for mine clearance that uses supercavitating projectiles (think phalanx underwater). A few years ago they broke the sound barrier underwater using this research!!!!

Other countries looking into it are the Uk, france, russia, india and propably china as well.

Subs that use it will not be around for a while due to massive technical challanges in developing control systems and cavity maintainance.



Ps. I have a large folder of technical papers on this subject sitting on my desk at this very moment - makes interesting reading!!!!

The fastest ' official ' speed of any SSN was the Soviet ' Alpha ' Class, with a speed of 45kts.

I couldn't imagine what sort of powersource would be needed to propel a submarine fast enough to form a 'supercavity'. The propulsion source for torpedos using supercavitation involves rocket motors.

An intersting design feature of known supercavitating technology is the use of a flat nose which allows the cavity to be formed.

Pareplane talks about the ' Phalanx ' version of a a mine clearing gun based on supercavitaion. The rounds used also have a flat nose allowing them to penetrate the water and form a supercavity. I think the effective depths achieved so far are around 20m. There ae some papers on the National Defence Indsutry Asscociation (?) website with high speed photos of the gatling gun test, you can see the bullet evolped in a bubble just before it penetrates a dummy mine.

Originally posted by rogue1
The fastest ' official ' speed of any SSN was the Soviet ' Alpha ' Class, with a speed of 45kts.

I couldn't imagine what sort of powersource would be needed to propel a submarine fast enough to form a 'supercavity'. The propulsion source for torpedos using supercavitation involves rocket motors.

An intersting design feature of known supercavitating technology is the use of a flat nose which allows the cavity to be formed.

Pareplane talks about the ' Phalanx ' version of a a mine clearing gun based on supercavitaion. The rounds used also have a flat nose allowing them to penetrate the water and form a supercavity. I think the effective depths achieved so far are around 20m. There ae some papers on the National Defence Indsutry Asscociation (?) website with high speed photos of the gatling gun test, you can see the bullet evolped in a bubble just before it penetrates a dummy mine.

The info i saw on it was in the warship technology magazine a few years back and the were horizontal tests in a long water tank (David Taylor model basin i think?). They were fired underwater so did not have to penetrate the surface (they are looking into a helicopter mounted version and also one for the bottom of ships hulls)

One Los Angeles class submarine was said to be tracked at 92 km/h. I don't know how much exactly it is in knots, but I think it was 55-56 knots. So it is NOT impossible to reach 60 knots.
This sub was tracked by Japanesse sonar operator during US-Japan naval excersizes. This operator has sworn that the sub was moving that fast. It is not official and maybe it is not true, but I have read about it from various sources.
Also the recent sub crasch near Guam? (I think) happened when the LA class submarine was moving a lot faster than is it's official speed. I don't know the exact number, so maybe someone would help...
Now the US Navy has Seawolf and Virginia that are more advanced and could be also faster (although they probably rely more on stealth than speed...).




[edit on 16-3-2005 by longbow]

Originally posted by paperplane_uk
Top speeds for nuclear subs are classified but as a practicing naval architect i can tell you they are extreamly unlikely to be at 60knots

Without getting too technical could you please explain why a sub couldn't go 60 knots underwater? I have often wondered about the top speeds, and heard allk the rumors. I don't see a reason why with a strong enough hull, and enough power a sub could achieve a speed of 60knots or maybe even better? Thanks

[
Without getting too technical could you please explain why a sub couldn't go 60 knots underwater? I have often wondered about the top speeds, and heard allk the rumors. I don't see a reason why with a strong enough hull, and enough power a sub could achieve a speed of 60knots or maybe even better? Thanks

If you simply the shape of an LA class submarine to a cylinder with a halfsphere at each end (is valid for an estimate). The size would be 109.73m X 10m raidus (length x diameter from www.fas.org website). The frictional resistance coefficient of this shape can be calculated using standard formula.

Multiplying Cf by 0.5*density*speed(m/s)^2 * surface area give the resistance of the shape. Multiply this by the speed gives the power needed to move the shape at a given speed.

If you assume the efficiency of the propulsor to be 70% could be prop or pumpjet, still 70% would be a very high efficiency for both. Then assuming a shaft efficiency of 98% gives the power the engine needs to send down the shaft to run at a given speed. On top of this you need to add a hotel load to power pumps and all the electrics etc. say add an extra 30% (is probably higher) to the curve to give the total power the sub needs to generate.

I worked this out and it gives a curve with the following exponetial formula

Power (mega watts) = 0.0010858492*(speed in knots ^ 2.8772851590)

if you plot this for a range of speeds you will get an estimate of the power curve of an LA class sub

The FAS website states that the LA class sub has a S6G reactor delivering 35,000 horsepower or 26.0995 Mega watts.

Putting this value into the power formula gives a maximum speed of 33.3knots. To do 60knots the LA class would need at least 142 MW of power generated.

It has to be remembered that this is an esimate using published data and a very simplified hullform. with better information this can be estimated more accuratly.

Hope this helps

WOW,
thanks for all the fast reply guys, even 45knots for the Alpha is
fast.

paper plane is correct about speeds being classified on nuclear submarines. Lots of gimicks have been tried over the years from better steam engines..to electric motors..to different nuclear plants to get the performance where they want it, also different propellers. From the begining of a series of submarines constructed to the end ..many changes are done before the series runs its construction course. Also many changes are done in the repair yards incorporating newer equipment and modifications in the areas discussed.

I worked on the USS San Francisco when it was under construction. It is a shame to see the damage photos in the dry dock and at the pier in Guam. I can tell you from personal knowlege of how they are constructed...that is a very lucky crew.. very lucky. The hull is damaged heavily ..almost up to the forward eliptical bulkhead...where the crew space is..the watertight portion of the boat. They were within a foot or two of rupturing this part of the hull. I wonder if they are going to bother with the funds necessary to rebuild her or just scrap her as she is one of the older designs with fairwater planes on the sail instead of the retractable dive planes .on the later boats. She took a hard...hard hit. One of the worst I've ever seen. I am sure the outer torpedo doors lost its seat or seal...leaving only the inner torpedo door..to stop the water...at least on the side visible. The damage appears to be that close to disasterous.

Orangetom

Dimples in a golf ball will make it go further, faster and with less energy.

I say we put dimples in the submarines.

And now you know why I am not a marine designer.

Love and light,

Wupy

I don't believe that there are current subs that go 60 knots, but I think the current seed of 35knots on most subs is false info by the military, the subs probably go a bit faster.
And I don't see why a sub couldn't do 60 knots if you put a powerful enough reactor on it and made the shape more efficient.

Originally posted by mrwupy
Dimples in a golf ball will make it go further, faster and with less energy.

I say we put dimples in the submarines.

And now you know why I am not a marine designer.

Love and light,

Wupy

A golf ball also spins rapidly which is why the dimples work, cant see a sub doing that! There have been persistant rumours that speed for nuclear sunbmarines have been exagerated since the cold war days. Each new class of sub developed was said to outdo the previous ones, so nowadays we get unrealistic claims of super-fast subs. On the other hand there have been rumours about polymer aditives being injected into the stream near the nose of the sub to reduce the drag by about half (they are known to exist and the drag reduction effect is proven, just nobody has ever developed it to that scale as far as i know). The simple truth is anyone in a position to know the exact speed of modern SSN's isnt telling.

Originally posted by WestPoint23

And I don't see why a sub couldn't do 60 knots if you put a powerful enough reactor on it and made the shape more efficient.

As paperplanes calculations have deduced, the power needed is too high to build into a compact reactor.

Originally posted by WestPoint23

And I don't see why a sub couldn't do 60 knots if you put a powerful enough reactor on it and made the shape more efficient.

Because power required is proportional to the speed cubed so if to do 40 knots you need 64000 units of energy (40 x 40 x 40) to do 60 you would need 216000 (60 x 60 x 60). Also using the same brief method going from 40 to 41 knots increases the power needed by 4921 units (41 x 41 x 41=68921, 68921-64000 =4921). to go from 60 to 61 knots you need an extra 10981 units (61 x61 x 61 =226981, 226981-216000 = 10981 units). From this you can see that to add an extra knot takes more and more energy the faster you go. Eventuly it is just too uneconomical to go any faster.

I ain't telling!!!

Orangetom

I used to know an American guy that worked as a contractor on carriers and subs etc he said that US subs could travel at 60knts too, even that they could circle an aircraft carrier as it was moving. I dont know if this is BS or not but thats what he said.