Can submarines go faster, fully submerged? How?

[Bandit]

I worked at Scott Polar Research Institute during the Falklands War. One memory I have of that war was the MoD coming to us to get copies of the most up-to-date maps of the Falklands from our library! You'd have thought that the MoD would have had its own resources rather than having to scrape around University libraries. The resulting military maps are simply photo-enlargements of the maps they borrowed from us. If they'd asked us to help - and perhaps provided a few resources - we could have provided much better intelligence for them, as the existing maps were (and still are) of relatively poor quality.

There was a programme on the box recently about the Vulcan raid on Stanley airport where they tried to bomb the runway. The RAF did not have the maps so they had to use north hmisphere maps and draw on the relevant details themselves?

I assume that mapping using aircraft sonars, radars etc is much easier in this digital age than it was in the 80's which i assumed required a theodolite and a tape measure on the ground.

 

[davidej]

Sonar signal coming through...

That's pretty poor!

Surely you could have found us a topless pic!

 

[AntarcticPilot]

There was a programme on the box recently about the Vulcan raid on Stanley airport where they tried to bomb the runway. The RAF did not have the maps so they had to use north hmisphere maps and draw on the relevant details themselves?

I assume that mapping using aircraft sonars, radars etc is much easier in this digital age than it was in the 80's which i assumed required a theodolite and a tape measure on the ground.

Yes, it is much easier, but the technologies used are high resolution satellite images and GPS. Sonar, radar, SAR etc, have some rather severe problems as mapping tools, and so are not used as primary sources - though they may be used as backups. LIDAR from aircraft is also widely used to measure topographic height. We also have other satellite based means of measuring topographic elevations (SRTM, for example).

High resolution mapping is still best done using photogrammetry, but we now have much better semi-automatic means of analyzing stereoscopic surveys than were available in the 1980s.

The story about the RAF maps of Stanley sounds apocryphal; there were certainly maps good enough for locating the airstrip available!

 

[Greenheart]

Sorry gentlemen, I'm fascinated by the serious discussion here, but my low humorous side has control of the keyboard...

Flatulent blondes or spying Bonds, I suppose hot-tub sonar detection could actually have some basis in reality, nowadays...

 

[maxi77]

There was a programme on the box recently about the Vulcan raid on Stanley airport where they tried to bomb the runway. The RAF did not have the maps so they had to use north hmisphere maps and draw on the relevant details themselves?

I assume that mapping using aircraft sonars, radars etc is much easier in this digital age than it was in the 80's which i assumed required a theodolite and a tape measure on the ground.

I suspect the problem was not so much the availability of maps but that the map display system in the Vulcan was orientated more around the USSR than the Falklands involving drawing new maps for the system. In those days map display systems in aircraft were very custom hence the problems.

 

[alant]

Yes, it is much easier, but the technologies used are high resolution satellite images and GPS. Sonar, radar, SAR etc, have some rather severe problems as mapping tools, and so are not used as primary sources - though they may be used as backups. LIDAR from aircraft is also widely used to measure topographic height. We also have other satellite based means of measuring topographic elevations (SRTM, for example).

High resolution mapping is still best done using photogrammetry, but we now have much better semi-automatic means of analyzing stereoscopic surveys than were available in the 1980s.

The story about the RAF maps of Stanley sounds apocryphal; there were certainly maps good enough for locating the airstrip available!

They weren't talking about "RAF maps of Stanley", they were talking about South Atlantic Charts, which the RAF didn't have. On the TV programme (Channel More 4 last night), they explained that their navigator turned a North Atlantic paper Chart upside down, relabelled the Azores as the Falklands, just to get down there from Ascension. Watched it last night & excellent prog.

 

[alant]

Sorry gentlemen, I'm fascinated by the serious discussion here, but my low humorous side has control of the keyboard...

Flatulent blondes or spying Bonds, I suppose hot-tub sonar detection could actually have some basis in reality, nowadays...

The way he's stroking that tiller, mmmm methinks a closet....................................














































raggie!

 

[alant]

I suspect the problem was not so much the availability of maps but that the map display system in the Vulcan was orientated more around the USSR than the Falklands involving drawing new maps for the system. In those days map display systems in aircraft were very custom hence the problems.

One of the guys said - if it was a choice between bombing Leningrad, or Port Stanley, it was a no-brainer.

 

[whiteoaks7]

Some numbers

First - every Admiral I've met (quite a few) has always impressed me with his detailed knowledge (and not just reiteration of his brief either!) Likewise every submarine CPO and every submariner too come to think of it. I have the greatest regard for them.

Second - the fastest submarine in the sea when I was working (eight years ago) was the Russian Alpha attack vessel which was made of titanium did 40knots and was capable of diving to 1000m. Thankfully they are very noisy and pretty much blind when travelling fast but still caused the UK MoD to rethink it's weapons policy of the time. Marconi had to come up with Spearfish torpedo which does ** knots and the air dropped Stingray in response. Spearfish has a thermal engine to generate the power to force it through the water. I remember the top speed of the weapon being classified Secret in all our documents then one day Weinstock (who headed Marconi at the time) gave an interview to (I think) the Guardian and quoted the numbers. Next day it was secret again (and no, I won't quote them here but now you know the target speed you can guess). The wireguided Spearfish range is also staggering, and also classified.

Third - can submarines 'see' across the Atlantic. I believe so though it requires towed sonar and the right conditions.

Forth - 80 knots? Don't think so, not for a weapon platform anyway.

Fifth - 'O' boats - wonderful things. Loved every minute I spent on them especially the beer from the stern tubes I did once catch the 'pilot' on one boat using a GPS from the local chandlery to fix his position, something, he said, that was quite common amongst crews at that time when SatNav was still a bit cumbersome.

BTW this is all public domain info so please don't come knocking...

David Berry

 

[Greenheart]

No wish to further dilute the theme, but what is a thermal engine?

 

[maxi77]

No wish to further dilute the theme, but what is a thermal engine?

One which depends on hot stuff to run. A steam engine for example or a gas turbine, or in this case an engine using an exotic fuel to produce steam

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

The current alternative to such propulsion systems is batteries and electric motors, for example the Tigerfish used a very interesting silver based primary battery

 

[catmandoo]

compresible water

Water is incompressible, so can't get denser.

Not quite true If that is the case then I wouldn't have been able to test pressure vessels to 4000 psi and more and calculate loads on each part by calculating the respective deflections

In fact all things are compressible its just the degree of volume change that is different depending on the material . for example if I put a weight on a piece of steel then it supports the weight by exerting an upward pressure . This pressure is possible because the weight compresses the steel by deflecting it downwards in proportion to its elasticity . In fact both item compress until the opposing forces are equal etc but not to the same amount of deflection unless they are of the same material

 

[billskip]

Not quite true If that is the case then I wouldn't have been able to test pressure vessels to 4000 psi and more and calculate loads on each part by calculating the respective deflections

In fact all things are compressible its just the degree of volume change that is different depending on the material . for example if I put a weight on a piece of steel then it supports the weight by exerting an upward pressure . This pressure is possible because the weight compresses the steel by deflecting it downwards in proportion to its elasticity . In fact both item compress until the opposing forces are equal etc but not to the same amount of deflection unless they are of the same material

Errr if it cant be seen it cant be true and if you cant prove it in your shed, its also doubtful see god thread can you read it in the daily mail?

 

[maxi77]

Not quite true If that is the case then I wouldn't have been able to test pressure vessels to 4000 psi and more and calculate loads on each part by calculating the respective deflections

In fact all things are compressible its just the degree of volume change that is different depending on the material . for example if I put a weight on a piece of steel then it supports the weight by exerting an upward pressure . This pressure is possible because the weight compresses the steel by deflecting it downwards in proportion to its elasticity . In fact both item compress until the opposing forces are equal etc but not to the same amount of deflection unless they are of the same material

I seem to remember the phrase, 'for practical purposes incompressible', now metal vessels do change shape and size when compressed or expanded with internal pressure. As an OOW on a submarine I used to have to remove considerable amounts of water ballast as we increased our depth to compensate for the compression of the hull. When we did a full diving depth dive the sailors would often stretch a wire across the inside of the hull and watch it sag as the hull compressed

 

[Greenheart]

I seem to remember the phrase, 'for practical purposes incompressible', now metal vessels do change shape and size when compressed or expanded with internal pressure. As an OOW on a submarine I used to have to remove considerable amounts of water ballast as we increased our depth to compensate for the compression of the hull. When we did a full diving depth dive the sailors would often stretch a wire across the inside of the hull and watch it sag as the hull compressed

Rather different when the 'solid material' isn't solid at all, isn't it? It's an alarming thought, that submarines squish a bit when they go deep, but it's easier to imagine a steel submarine full of air squeezing slightly, than to picture compressing the same displacement of H2O.

Spoken without an inkling of knowledge of physics...

 

[maxi77]

Rather different when the 'solid material' isn't solid at all, isn't it? It's an alarming thought, that submarines squish a bit when they go deep, but it's easier to imagine a steel submarine full of air squeezing slightly, than to picture compressing the same displacement of H2O.

Spoken without an inkling of knowledge of physics...

And remember the reverse also happens increase the pressure within a hollow container and it expands proportionately to the increase in internal pressure

 

[Portofino]

The maximum speed of any machine the difference between the force of its propulsion system and force caused by drag. For a submarine, drag increases dramatically on the surface because the water flowing around the hull meets air. This disrupts the smooth flow of water around the hull of the ships. Causing the bow wave effect

You also have the issue that submarines are normally designed to maximize underwater speed. Since the conning tower provides more drag at the top of the sub, the propulsion system is centered high and/or the hull is designed such that they provide a force to counter the tendency to go nose-up.On the surface, the drag from the conning is gone so the submarine's propeller tends to drive it slighly nose-down. Driving planes need to be angled to counter act this force -- adding more drag.

Propulsion is also lower on the surface since the propeller is less efficient near the surface - where water can not smoothly flow to the propeller, the flow of water around the propeller is greater below the ship than above, and air gets mixed in with the water -- making it less dense causing less force to be applied to the propeller.

 

[whiteoaks7]

Compressible water and submarines

What a fun thread this is

Teardrops are the best shape for underwater vehicles so modern fast submarines tend towards that shape (someone remind me - was it Skipjack that started the trend?).

Water is compressible - it has a finite bulk modulus (it used to create havoc trying to match the modulus of seawater to make cables neutrally bouyant at all depths - and then there's the layers (oh no, not the layers) and salinity variation (oh no, ... )).

Submarine passageways get smaller because the boat is not filled with water so the pressure squeezes it - nothing to do with compressibility of water.

Can we have more pictures of pretty girls demonstrating residual buoyancy and near perfectly matched bulk modulii now?

David Berry

 

[Neil_Y]

Interesting read this and very familiar, I sold the research machines to places like RSRE and if we came up with new techniques or ideas that would benefit their research we could sell a machine, so in at least one case it was the sales team that came up with the idea that increased heat sensing sensitivity of chip based sensors by a huge factor back in the 80's. The idea was so simple but no one had tried it.They wanted to be able to detect the heat signature on the front of a jet coming out of low cloud.

I now supply new technology for some submarines, these are quite interesting (advanced) machines and built by a small team in the west country. Some of the technology on these is way ahead of that used on our own Bae subs. http://www.msubs.com/unmanned-vehicles.html

What I see from MOD is that they often look to academics for technology knowledge when in some areas small rapid prototype operations are way ahead.

 

[Tanqueray]

The single biggest factor affecting dived v surface speed is the complete immersion of the propellor (i.e. the immersion of the top 25-30% of the prop into 'solid' water rather than froth).
The above will give a speed increase in the order of 4:3 (which ties in with the OP's Typhoon figures). The effect is similar (but not the same) for a propulsor as opposed to a propellor.

Benefits from hull submersion are to a large extent offset by the fin and deck appendages (though not completely).

Hard evidence for the above (which is meticulously logged) is easily obtained obtained during trials secured alongside surfaced versus underwater restraint.
The shaft torque meter will not enter the 'red' when surfaced, and water flow is zero when restrained.

Water is compressible - it's particular compressibility at any stage is a matter of great interest when operating a Nuclear reactor.

Steve